WO2017072897A1 - Acceleration sensor system and self-diagnosis method - Google Patents

Acceleration sensor system and self-diagnosis method Download PDF

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Publication number
WO2017072897A1
WO2017072897A1 PCT/JP2015/080488 JP2015080488W WO2017072897A1 WO 2017072897 A1 WO2017072897 A1 WO 2017072897A1 JP 2015080488 W JP2015080488 W JP 2015080488W WO 2017072897 A1 WO2017072897 A1 WO 2017072897A1
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Prior art keywords
signal
self
diagnosis
acceleration sensor
output
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PCT/JP2015/080488
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French (fr)
Japanese (ja)
Inventor
久亮 金井
李　ウェン
山本　昭夫
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株式会社日立製作所
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Priority to JP2016569862A priority Critical patent/JP6218974B2/en
Priority to PCT/JP2015/080488 priority patent/WO2017072897A1/en
Publication of WO2017072897A1 publication Critical patent/WO2017072897A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups

Definitions

  • the present invention relates to an acceleration sensor system and a self-diagnosis method.
  • Patent Document 1 states that “the capacitor has a frequency-capacitance characteristic having a resonance frequency, so that the capacitance of the capacitor is measured with a control signal having a first frequency that is extremely higher or lower than the resonance frequency. The normal measurement is performed, and a self-diagnosis is performed in which the capacitance of the capacitor is measured with a control signal of the second frequency in the vicinity including the resonance frequency.
  • Some capacitive acceleration sensors that require high sensitivity include a movable electrode having a high resonance Q value.
  • a servo capacitive acceleration sensor has a movable electrode having a high Q value.
  • the higher the Q value of the movable electrode the easier it is to generate vibration when a voltage is applied. Therefore, the movable electrode having a high Q value is more likely to remain vibrated after the voltage application is stopped, compared to the movable electrode having a low Q value. This causes a problem that when the application of the voltage for self-diagnosis is stopped, it takes a long time for the movable electrode to be stationary, and normal measurement after the self-diagnosis cannot be started immediately.
  • an object of the present invention is to more accurately control the stop of the vibration of the movable electrode and to shorten the self-diagnosis time.
  • the present application includes a plurality of means for solving at least a part of the above-described problems, and examples thereof are as follows.
  • An acceleration sensor system includes a sensor that outputs an output signal indicating a change in capacitance in accordance with displacement of a movable electrode, and a self-diagnosis signal for diagnosing the sensor.
  • a self-diagnosis unit that outputs the self-diagnosis signal including a displacement signal for displacing the movable electrode, and stops outputting the self-diagnosis signal according to the level of the output signal.
  • the stop of the vibration of the movable electrode can be controlled more accurately, and the self-diagnosis time can be shortened.
  • the servo-type capacitive acceleration sensor includes a movable electrode having a high Q value (for example, higher than 0.5).
  • the acceleration sensor keeps the movable electrode in an equilibrium state by applying an electrostatic force that cancels the force applied to the movable electrode by acceleration.
  • a PWM (Pulse Width Modulation) voltage can be used as a servo signal that generates an electrostatic force.
  • the acceleration sensor system for example, sets the pulse density according to the acceleration so that the pulse density is low when the detected acceleration is large and the pulse density is high when the detected acceleration is small. adjust. This acceleration sensor system can detect acceleration with high sensitivity while reducing mechanical noise.
  • An acceleration sensor system for improving reliability is required to have a self-diagnosis function for detecting the failure.
  • a periodic predetermined voltage is applied between the fixed electrode and the movable electrode included in the acceleration sensor to displace the position of the movable electrode.
  • a method of detecting an abnormality of the acceleration sensor by evaluating whether or not the displacement amount is within a predetermined range can be adopted. In this method, the resonance frequency of the movable electrode is measured, and the acceleration sensor is diagnosed based on the measured resonance frequency.
  • each embodiment of the present invention relates to a servo-type capacitive acceleration sensor (hereinafter also simply referred to as an acceleration sensor) and a system including the acceleration sensor (hereinafter also simply referred to as an acceleration sensor system).
  • an acceleration sensor a servo-type capacitive acceleration sensor
  • an acceleration sensor system a system including the acceleration sensor
  • FIG. 1 is a block diagram showing an example of the configuration of the acceleration sensor system according to the first embodiment of the present invention.
  • the acceleration sensor system includes an acceleration sensor 101, a signal detection unit 102, a servo control unit 110, a detection signal generation unit 120, a self-diagnosis unit 130, an output unit 140, and a mode switching unit 150.
  • the acceleration sensor 101 detects acceleration as an electric signal representing a change in capacitance, and outputs a detected electric signal S1 (hereinafter referred to as an output signal S1) to the signal detection unit 102.
  • the acceleration sensor 101 includes, for example, a capacitance type acceleration detection element mainly composed of an electrode structure. The acceleration sensor 101 will be described in detail later with reference to FIG.
  • the signal detection unit 102 receives the output signal S1 from the acceleration sensor 101, converts the output signal S1 that is the received analog electrical signal into a voltage, amplifies the voltage, converts the voltage signal into a digital signal, and outputs a servo control unit. 110 and the self-diagnosis unit 130.
  • the servo control unit 110 receives the output signal from the signal detection unit 102, generates a servo signal S6 based on the received output signal, and outputs the servo signal S6 to the mode switching unit 150.
  • the servo control unit 110 generates, as a servo signal, a PWM (Pulse ⁇ Width Modulation) voltage signal in which both the pulse density and the level are adjusted according to the magnitude of the change in capacitance corresponding to the acceleration.
  • the servo signal S6 is a voltage signal and is applied to two fixed electrodes (to be described later) of the acceleration sensor 101 via the mode switching unit 150.
  • the servo control unit 110 receives an output signal which is a received digital signal, and generates a servo signal by performing signal processing on the digital signal.
  • PID control Proportional-Integral-Derivative-Control
  • PID control is a method in which control of an input value to a controlled object is performed by a deviation between an output value from the controlled object and a target value, integration and differentiation thereof.
  • the servo control unit 110 derives a value (voltage, digital value, etc.) corresponding to the electrostatic force necessary to maintain the movable electrode of the acceleration sensor 101 in an equilibrium state based on the received digital signal by PID control. It has a function.
  • the detection signal generation unit 120 generates a detection signal S7 and outputs it to the mode switching unit 150.
  • the detection signal S7 is an electric signal that is applied to the acceleration sensor 101 to detect acceleration and causes the acceleration sensor 101 to detect a change in capacitance as an electric signal.
  • the detection signal S ⁇ b> 7 is a voltage signal and is applied to two fixed electrodes (described later) of the acceleration sensor 101 via the mode switching unit 150.
  • the self-diagnosis unit 130 receives an output signal from the signal detection unit 102.
  • the self-diagnosis unit 130 generates a self-diagnosis signal S8 and outputs it to the mode switching unit 150.
  • the self-diagnosis unit 130 determines the stop timing of the self-diagnosis signal S8 based on the output signal from the signal detection unit 102.
  • the self-diagnosis unit 130 includes a diagnostic signal generation unit 131 and an output signal evaluation unit 132.
  • the self-diagnosis unit 130 includes an analysis unit 133.
  • Diagnostic signal generation unit 131 generates a self-diagnosis signal S8 and outputs it to mode switching unit 150 when a self-diagnosis mode to be described later is selected under the control of mode switching unit 150.
  • the self-diagnosis signal S8 is applied to the acceleration sensor 101 for detecting displacement and an electric signal for applying displacement to the movable electrode of the acceleration sensor 101, and causes the acceleration sensor 101 to detect a change in capacitance as an electric signal. Including electrical signals.
  • the self-diagnosis signal S ⁇ b> 8 is a voltage signal and is applied to two fixed electrodes (described later) of the acceleration sensor 101 via the mode switching unit 150.
  • the diagnostic signal generation unit 131 stops generation and output of the self-diagnosis signal S8 when receiving a stop signal described later from the output signal evaluation unit 132.
  • the output signal evaluation unit 132 Based on the signal level of the capacitance indicated by the output signal corresponding to the self-diagnosis signal S8, the output signal evaluation unit 132 sets the signal level to a predetermined value after the application of the self-diagnosis signal S8 and the peak value of the signal level. Measure the cycle time to reach. This predetermined value is desirably set according to the Q value of the movable electrode of the acceleration sensor. The output signal evaluation unit 132 determines whether or not the signal level has reached a predetermined value, and outputs a stop signal to the diagnostic signal generation unit 131 when the signal level reaches the predetermined value, and the peak value of the measured signal level and The cycle time is output to the analysis unit 133.
  • the analysis unit 133 receives the peak value of the signal level and the period time measured from the output signal evaluation unit 132.
  • the analysis unit 133 determines whether or not the capacitance change is normal based on at least one of the received peak value and cycle time, and uses the determination result as the diagnosis result S5, for example, a PC (Persona Computer) or the like.
  • the diagnosis result S5 can take various forms such as a data signal, a data file, and screen data.
  • the self-diagnosis unit 130 will be described in detail later with reference to FIG.
  • the output unit 140 receives the servo signal S6 from the servo control unit 110, and outputs an acceleration based on the received servo signal. In order to implement such a function, the output unit 140 includes an acceleration output unit 141. The output unit 140 includes an analysis unit 142.
  • the acceleration output unit 141 calculates acceleration based on the servo signal S6, generates acceleration information S3 including the acceleration, and outputs it to an external device such as a PC.
  • the acceleration output unit 141 may receive an output signal from the signal detection unit 102, calculate acceleration based on the output signal, generate acceleration information S3 including the acceleration, and output the acceleration information S3 to an external device.
  • the acceleration output unit 141 outputs the calculated acceleration to the analysis unit 142. Since the process for calculating the acceleration based on the servo signal or the output signal can use a general technique, a description thereof will be omitted.
  • the analysis unit 142 receives acceleration from the acceleration output unit 141, performs predetermined analysis processing on the received acceleration, generates analysis information S4 including the analysis result, and outputs the analysis information S4 to an external device such as a PC, for example. . Since a general technique can be used for the analysis process of acceleration, description is abbreviate
  • the analysis information S4 can be in various forms such as a data signal, a data file, and screen data.
  • the mode switching unit 150 receives the servo signal S6 from the servo control unit 110, the detection signal S7 from the detection signal generation unit 120, and the self-diagnosis signal S8 from the self-diagnosis unit 130.
  • the mode switching unit 150 selects one signal corresponding to the selected operation mode from these three types of signals, and outputs the selected signal to the acceleration sensor 101 as a signal S2. That is, the signal S2 includes any one of the servo signal S6, the detection signal S7, and the self-diagnosis signal S8.
  • the signal S2 is a voltage signal and is applied to two fixed electrodes (to be described later) of the acceleration sensor 101.
  • the acceleration sensor system has a servo control mode, a detection mode, and a self-diagnosis mode as three operation modes.
  • the servo control mode (corresponding to the first mode of the present invention) is a mode for executing servo control.
  • the detection mode (corresponding to the first mode of the present invention) is a mode for detecting acceleration.
  • the self-diagnosis mode (corresponding to the second mode of the present invention) is a mode for diagnosing the state of the acceleration sensor 101.
  • the servo signal S6 is selected in the servo control mode.
  • the detection signal S7 is selected in the detection mode.
  • the self-diagnosis signal S8 is selected in the self-diagnosis mode.
  • the mode switching unit 150 basically selects an operation mode by controlling switching of the operation mode based on a preset time division. For example, the mode switching unit 150 alternately switches between the servo control mode and the detection mode based on a predetermined time division.
  • the mode switching unit 150 switches the servo control mode or the detection mode to the self-diagnosis mode at an arbitrary timing. For example, the mode switching unit 150 determines whether or not a normal measurement period (a period including two of the servo control mode and the detection mode) has passed a predetermined time, and when the predetermined period has elapsed, the mode switching unit 150 selects the servo control mode or the detection mode. Switch to self-diagnosis mode. For example, the mode switching unit 150 acquires values such as environmental temperature and environmental humidity measured by another sensor (not shown), and performs self-diagnosis when the value exceeds or falls below a predetermined threshold. You may switch to the mode.
  • the mode switching unit 150 determines whether or not the self-diagnosis signal S8 from the self-diagnosis unit 130 has stopped, and if so, the self-diagnosis mode is normally measured (servo control mode or detection). Mode).
  • FIG. 2 is a diagram for explaining an example of the structure of the acceleration sensor according to the first embodiment.
  • FIG. 2 shows the X direction and the Z direction as directions for explanation.
  • the X direction is a direction in which the main surface of the electrode extends, and corresponds to the left-right direction in FIG.
  • the Z direction is a direction in which the electrodes overlap each other at a distance, and corresponds to the vertical direction in FIG.
  • the acceleration sensor 101 includes a pair of fixed electrodes 1011a and 1011b, and one movable electrode 1013. These two fixed electrodes are connected to the mode switching unit 150 through signal lines.
  • the movable electrode 1013 is connected to the signal detection unit 102 through a signal line.
  • the movable electrode 1013 has a wide main surface in the X direction.
  • the fixed electrode 1011a and the fixed electrode 1011b include a surface region that overlaps the main surface of the movable electrode 1013 when viewed in plan in the Z direction in order to generate an electrostatic force on the movable electrode 1013.
  • the surface area of the fixed electrode 1011a and the surface area of the fixed electrode 1011b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the movable electrode 1013, respectively.
  • the signal lines of the fixed electrode 1011a and the fixed electrode 1011b transmit a signal S2 (servo signal S6, detection signal S7, or self-diagnosis signal S8) corresponding to the operation mode.
  • the servo signal S6 includes a servo signal S6a applied to the fixed electrode 1011a and a servo signal S6b applied to the fixed electrode 1011b.
  • the servo signal S6a is, for example, a voltage signal generated by repeating rectangular wave pulses.
  • the servo signal S6b is a voltage signal inverted with respect to the servo signal S6a.
  • the detection signal S7 includes a detection signal S7a applied to the fixed electrode 1011a and a detection signal S7b applied to the fixed electrode 1011b.
  • the detection signal S7a is, for example, a voltage signal generated by repeating rectangular wave pulses.
  • the detection signal S7b is a voltage signal inverted with respect to the detection signal S7a.
  • the self-diagnosis signal S8 includes a self-diagnosis signal S8a applied to the fixed electrode 1011a and a self-diagnosis signal S8b applied to the fixed electrode 1011b.
  • the self-diagnosis signal S8a includes a displacement signal S8c (not shown) for displacing the movable electrode 1013 and a detection signal S8e (not shown) for detecting a change in capacitance.
  • Self-diagnosis signal S8b includes a displacement signal S8d (not shown) corresponding to displacement signal S8c and a detection signal S8f (not shown) corresponding to detection signal S8e.
  • the displacement signal S8c and the displacement signal S8d are adjusted so that the movable electrode 1013 is displaced.
  • the displacement signal S8c is set to the same voltage as the movable electrode voltage and the displacement signal S8d is set to a voltage different from the movable electrode voltage
  • an electrostatic force is generated between the fixed electrode 1011b and the movable electrode 1013, and the movable electrode 1013 is generated. Is displaced toward the fixed electrode 1011b.
  • the detection signal S8e is, for example, a voltage signal generated by repeating rectangular wave pulses.
  • the detection signal S8f is a voltage signal inverted with respect to the detection signal S8e.
  • the signal line of the movable electrode 1013 transmits the output signal S1.
  • the change in the position of the movable electrode 1013 in the Z direction according to the acceleration (d in the figure) changes the capacitance between the fixed electrode 1011a and the fixed electrode 1011b and the movable electrode 1013.
  • the capacitance between the fixed electrode 1011a and the movable electrode 1013 is represented as C1
  • the capacitance between the fixed electrode 1011b and the movable electrode 1013 is represented as C2.
  • the output signal S1 is a voltage signal representing a change in capacitance including the capacitance difference deltaC.
  • the output signal S1 at a certain point in time represents the capacitance difference deltaC corresponding to the displacement state of the movable electrode 1013.
  • the output signal S1 at two points in time represents a change with time in the capacitance difference deltaC.
  • FIG. 3 is a timing chart showing an example of the timing of the input signal to the acceleration sensor and the output signal from the acceleration sensor in the first embodiment.
  • the servo control mode and the detection mode are alternately switched as described above. Specifically, the servo signal S6 and the detection signal S7 are repeatedly applied to the acceleration sensor 101 alternately. As a result, the position of the movable electrode is maintained in an equilibrium state, and a signal corresponding to the change in capacitance is output. Since the position of the movable electrode is held in an equilibrium state or a state close to equilibrium by servo control, the output signal S1 is 0 or a value close to 0.
  • the self-diagnosis mode starts when selected by the mode switching unit 150 as described above. Specifically, in the self-diagnosis mode, the diagnostic signal generator 131 outputs the displacement signal S8c, the displacement signal S8d, the detection signal S8e, and the detection signal S8f alternately and repeatedly to the acceleration sensor 101. That is, the self-diagnosis period includes a displacement period P1 in which the movable electrode is displaced by the displacement signal, and a detection period P2 in which the change in capacitance is detected by the detection signal. In the displacement period P1, a voltage is applied between the fixed electrode and the movable electrode in order to displace the movable electrode. This voltage is mainly a DC voltage.
  • a signal having the same frequency and voltage as the detection signal S7 is applied to the fixed electrode.
  • the lengths of the displacement period P1 and the detection period P2 are set in advance. As a result, the position of the movable electrode is displaced and a signal corresponding to the change in capacitance is output.
  • the Q value of the movable electrode When the Q value of the movable electrode is higher than 0.5, the position of the movable electrode is gradually displaced away from the equilibrium state (T 1 to T 2 ) when a DC voltage is applied during the movable electrode displacement period P1. Then, after reaching the peak (T 2 ), it gradually displaces so as to gradually return to the equilibrium state (T 2 to T 3 ). This change corresponds to the first period of a phenomenon called ringing. The higher the Q value of the movable electrode, the larger the displacement amount returning to the equilibrium state after the peak. When the Q value of the movable electrode is 0.5 or less, ringing does not occur.
  • the vibration of the movable electrode remains and normal measurement is performed until the vibration stops. Cannot resume. For example, if the self-diagnosis signal is stopped prior to T 3, the vibration of the movable electrode is left later than T 3.
  • the output signal evaluation unit 132 repeatedly measures the displacement level D (n) from the equilibrium state of the movable electrode based on the output signal output in each detection period P2. Further, the output signal evaluation unit 132 determines whether or not each measured displacement level D (n) is below a predetermined threshold value Dth.
  • the threshold value Dth is a value for determining an equilibrium state (including a state close to the equilibrium state), and is set in advance. The threshold value Dth is set smaller as the Q value is higher. The set value of the threshold value Dth may be changed based on an instruction from an external device.
  • the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 131.
  • the self-diagnosis signal is stopped at the timing when the movable electrode returns to the equilibrium state, the subsequent vibration of the movable electrode is completely or smallly suppressed, and the time until stationary is shortened.
  • the self-diagnosis signal is stopped by the displacement level D (n) is equal to or greater than the threshold value Dth timing, vibration subsequent movable electrode remains later than T 3, the time until stationary prolonged.
  • FIG. 4 is a flowchart showing an example of self-diagnosis processing according to the first embodiment.
  • FIG. 7 shows a case where the self-diagnosis mode is started.
  • the initial value of n is “0”.
  • the initial value of Dpeak is “0”.
  • the value of D (0) may be set, for example, by the output signal evaluation unit 132 acquiring and setting the output signal level immediately before the start of the flowchart of this figure, or by setting a predetermined value, for example, “0”. Good. After the output signal evaluation unit 132 starts the flowchart of this figure, the elapsed time is measured.
  • the diagnostic signal generation unit 131 increments n by 1 (step S100).
  • the diagnostic signal generator 131 outputs a displacement signal during the displacement period P1 (step S101).
  • the diagnostic signal generation unit 131 outputs a detection signal during the detection period P2 after the displacement period P1 (step S102).
  • the output signal evaluation unit 132 acquires the output signal level D (n) output from the acceleration sensor 101 via the signal detection unit 102 in accordance with the detection signal in step S102 (step S103).
  • step S103 the output signal evaluation unit 132 acquires the time when the output signal level D (n) is acquired, that is, the elapsed time t (n).
  • the output signal evaluation unit 132 determines whether or not the output signal level D (n) acquired in step S103 is equal to or lower than the output signal level D (n ⁇ 1) acquired last time (step S104). If the output signal evaluation unit 132 determines that the output signal level D (n) exceeds the output signal level D (n ⁇ 1) (no in step S104), the process returns to step S100.
  • step S104 When the output signal evaluation unit 132 determines that the output signal level D (n) is equal to or lower than the output signal level D (n ⁇ 1) (yes in step S104), whether the output signal level peak value Dpeak is 0 or not. It is determined whether or not (step S105). When the output signal evaluation unit 132 determines that the peak value Dpeak of the output signal level is 0 (yes in step S105), the output signal evaluation unit 132 sets the output signal level D (n ⁇ 1) to the peak value Dpeak (step S106).
  • step S105 When the output signal evaluation unit 132 determines that the peak value Dpeak of the output signal level is not 0 (no in step S105), or after executing the process of step S106, the output signal level D (n) is greater than the threshold value Dth. It is determined whether it is small (step S107). If the output signal evaluation unit 132 determines that the output signal level D (n) is greater than or equal to the threshold value Dth (no in step S107), the process returns to step S100.
  • step S107 When the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the elapsed time t (n) of the output signal level D (n) acquired in step S103 is obtained. The cycle time ts is set (step S108).
  • the analysis unit 133 determines whether or not the peak value Dpeak of the output signal level is included in the normal range (from the minimum value Dmin to the maximum value Dmax) (step S109).
  • the peak value Dpeak has a correlation with the sensitivity of the acceleration sensor 101. If the analysis unit 133 determines that the peak value Dpeak is included in the normal range (yes in step S109), the analysis unit 133 determines whether the cycle time ts is included in the normal range (from the minimum value tmin to the maximum value tmax). (Step S110).
  • the period time ts has a correlation with the resonance frequency of the acceleration sensor 101.
  • the analysis unit 133 determines that the peak value Dpeak is not included in the normal range (no in step S109). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5.
  • the diagnosis result S5 may include a peak value Dpeak.
  • the analyzing unit 133 determines that the cycle time ts is not included in the normal range (no in step S110). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5.
  • the diagnosis result S5 may include a cycle time ts.
  • the analysis unit 133 determines that the cycle time ts is included in the normal range (yes in step S110), the analysis unit 133 determines that the acceleration sensor 101 is normal (step S112). For example, the analysis unit 133 outputs information indicating that the sensor is normal to the external device as the diagnosis result S5.
  • the diagnosis result S5 may include a peak value Dpeak and a cycle time ts. The analysis unit 133 may not output the diagnosis result S5. And the analysis part 133 complete
  • the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 131. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
  • the acceleration sensor system determines whether or not the output signal level has fallen below a predetermined value after the start of the self-diagnosis mode. In addition, the acceleration sensor system stops the self-diagnosis signal when the output signal level falls below a predetermined value. Thereby, the acceleration sensor system stops the self-diagnosis signal at the timing when the movable electrode returns to the equilibrium state or the vicinity thereof, more accurately controls the stop of the vibration of the movable electrode, and shortens the self-diagnosis time. be able to. The acceleration sensor system stops the self-diagnosis signal when the output signal level exceeds the peak value and the output signal level falls below a predetermined value.
  • the acceleration sensor system displaces the movable electrode by a period as close as possible to T 0 corresponding to one period of the resonance frequency f 0 (period T 1 to T 3 in the example of FIG. 3), and performs self-diagnosis in a short period. It can be carried out.
  • the acceleration sensor system does not require a large-scale logic circuit such as a frequency sweep function or a peak frequency detection function, power consumption can be reduced.
  • the acceleration sensor of the second embodiment is different in electrode structure from the acceleration sensor of the first embodiment. A description will be given centering on differences from the first embodiment.
  • FIG. 5 is a block diagram showing an example of the configuration of the acceleration sensor system according to the second embodiment of the present invention.
  • the acceleration sensor system includes an acceleration sensor 201, a signal detection unit 102, a servo control unit 110, a detection signal generation unit 220, a self-diagnosis unit 130, an output unit 140, and a mode switching unit 250.
  • the acceleration sensor 201 outputs an output signal S1 indicating a change in capacitance to the signal detection unit 102.
  • the acceleration sensor 201 will be described in detail later with reference to FIG.
  • the detection signal generation unit 220 generates a detection signal S7 and outputs it to the acceleration sensor 201.
  • the detection signal S7 is applied to one set of fixed electrodes of two sets of fixed electrodes described later of the acceleration sensor 201.
  • the self-diagnosis unit 130 includes a diagnostic signal generation unit 231 and an output signal evaluation unit 132. In addition, the self-diagnosis unit 130 includes an analysis unit 133.
  • the diagnostic signal generation unit 231 When the self-diagnosis mode is selected by the control of the mode switching unit 250, the diagnostic signal generation unit 231 generates a self-diagnosis signal S8 and outputs the self-diagnosis signal S8 to the mode switching unit 250.
  • the self-diagnosis signal S8 includes a displacement signal and does not include a detection signal.
  • the mode switching unit 250 receives the servo signal S6 from the servo control unit 110 and the self-diagnosis signal S8 from the self-diagnosis unit 130.
  • the mode switching unit 250 selects one signal corresponding to the selected operation mode from these two types of signals, and outputs the selected signal to the acceleration sensor 201 as a signal S2. That is, the signal S2 includes any one of the servo signal S6 and the self-diagnosis signal S8.
  • the signal S ⁇ b> 2 is applied to the other set of fixed electrodes of the acceleration sensor 201, which will be described later.
  • the acceleration sensor system of the second embodiment has two operation modes: a servo control mode (corresponding to the first mode of the present invention) and a self-diagnosis mode (corresponding to the second mode of the present invention).
  • a servo control mode corresponding to the first mode of the present invention
  • a self-diagnosis mode corresponding to the second mode of the present invention.
  • the servo signal S6 is selected in the servo control mode.
  • the self-diagnosis signal S8 is selected in the self-diagnosis mode.
  • the detection signal S7 is output to the acceleration sensor 201 regardless of which operation mode is selected.
  • the mode switching unit 250 switches the servo control mode to the self-diagnosis mode at an arbitrary timing.
  • the mode switching unit 250 can determine, for example, whether or not the normal measurement period (period including the servo control mode) exceeds a predetermined time, and can switch the servo control mode to the self-diagnosis mode when it exceeds.
  • the mode switching unit 250 acquires values such as environmental temperature and environmental humidity measured by other sensors (not shown), and performs self-diagnosis when the value exceeds or falls below a predetermined threshold value. You may switch to the mode.
  • the mode switching unit 250 determines whether or not the self-diagnosis signal S8 from the self-diagnosis unit 130 has stopped, and if so, the self-diagnosis mode is changed to normal measurement (servo control mode). Switch.
  • FIG. 6 is a diagram illustrating an example of the structure of the acceleration sensor according to the second embodiment.
  • FIG. 6 shows the X direction (left-right direction) and the Z direction (up-down direction) as directions for explanation.
  • the acceleration sensor 201 includes a pair of fixed electrodes 2011a and 2011b, a pair of fixed electrodes 2012a and 2012b, and one movable electrode 2013.
  • the fixed electrode 2011a and the fixed electrode 2011b are connected to the detection signal generation unit 220 through a signal line.
  • the fixed electrode 2012a and the fixed electrode 2012b are connected to the mode switching unit 250 through a signal line.
  • the movable electrode 2013 is connected to the signal detection unit 102 through a signal line.
  • the movable electrode 2013 has a wide main surface in the X direction.
  • the fixed electrode 2011a and the fixed electrode 2011b include a surface region that overlaps a part of the main surface of the movable electrode 2013 (one end in the X direction) when viewed in plan in the Z direction.
  • the surface area of the fixed electrode 2011a and the surface area of the fixed electrode 2011b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the one end of the movable electrode 2013, respectively.
  • the fixed electrode 2012a and the fixed electrode 2012b include a surface region that overlaps a part of the main surface of the movable electrode 2013 (the other end in the X direction) when viewed in plan in the Z direction.
  • the surface area of the fixed electrode 2012a and the surface area of the fixed electrode 2012b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the other end of the movable electrode 2013, respectively. ing.
  • the signal lines of the fixed electrode 2011a and the fixed electrode 2011b transmit the detection signal S7.
  • the signal lines of the fixed electrode 2012a and the fixed electrode 2012b transmit a signal S2 (servo signal S6 or self-diagnosis signal S8) corresponding to the operation mode.
  • the detection signal S7 includes a detection signal S7a applied to the fixed electrode 2011a and a detection signal S7b applied to the fixed electrode 2011b.
  • the servo signal S6 includes a servo signal S6a applied to the fixed electrode 2012a and a servo signal S6b applied to the fixed electrode 2012b.
  • the self-diagnosis signal S8 includes a self-diagnosis signal S8a applied to the fixed electrode 2012a and a self-diagnosis signal S8b applied to the fixed electrode 2012b.
  • the self-diagnosis signal S8a includes a displacement signal S8c (not shown) for displacing the movable electrode 2013.
  • Self-diagnosis signal S8b includes a displacement signal S8d (not shown) corresponding to displacement signal S8c.
  • the signal line of the movable electrode 2013 transmits the output signal S1.
  • a change in the position of the movable electrode 2013 in the Z direction according to the acceleration (d in the figure) changes the capacitances C1 and C2 between the fixed electrode 2011a and the fixed electrode 2011b and the movable electrode 2013.
  • the output signal S1 is a voltage signal representing a change in capacitance including the capacitance difference deltaC.
  • the servo signal S6 and the self-diagnosis signal S8 are switched in a time division manner and the detection signal S7 is always applied to the acceleration sensor 201. Thereby, the displacement of the movable electrode 2013 can be continuously measured regardless of the operation mode.
  • FIG. 7 is a timing chart showing an example of the timing of the input signal to the acceleration sensor and the output signal from the acceleration sensor in the second embodiment.
  • the servo control mode is selected as described above. Specifically, the servo signal S6 is applied to the acceleration sensor 201. The detection signal S7 is also applied to the acceleration sensor 201. As a result, the position of the movable electrode is maintained in an equilibrium state, and a signal corresponding to the change in capacitance is output.
  • the self-diagnosis mode is started by being selected by the mode switching unit 250 as described above. Specifically, in the self-diagnosis mode, the diagnostic signal generation unit 231 outputs the displacement signal S8c and the displacement signal S8d to the acceleration sensor 201. The detection signal S7 is also applied to the acceleration sensor 201. As a result, the position of the movable electrode is displaced and a signal corresponding to the change in capacitance is output.
  • the output signal evaluation unit 132 repeatedly measures the displacement level D (n) from the equilibrium state of the movable electrode based on the output signal output during the self-diagnosis mode. Further, the output signal evaluation unit 132 determines whether or not each measured displacement level D (n) is less than the threshold value Dth. When the displacement level D (n) falls below the threshold value Dth, the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 231.
  • FIG. 8 is a flowchart showing an example of self-diagnosis processing according to the second embodiment.
  • FIG. 8 shows a case where the self-diagnosis mode is started. A description will be given centering on differences from FIG.
  • the diagnostic signal generator 231 starts outputting a displacement signal (step S201).
  • the diagnostic signal generation unit 231 increments n by 1 (step S202).
  • the output signal evaluation unit 132 acquires the output signal level D (n) output from the acceleration sensor 201 via the signal detection unit 102 in accordance with the detection signal (step S203).
  • the output signal evaluation unit 132 acquires the time when the output signal level D (n) is acquired, that is, the elapsed time t (n).
  • steps S104 to S112 The processing in steps S104 to S112 is the same as in FIG.
  • the process returns to step S202.
  • the output signal evaluation unit 132 determines that the output signal level D (n) is equal to or higher than the threshold value Dth (no in step S107)
  • the process returns to step S202.
  • the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107)
  • the elapsed time t (n) of the output signal level D (n) acquired in step S203 is determined. , And set to the cycle time ts.
  • the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 231. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
  • the second embodiment of the present invention has been described above.
  • the acceleration sensor system according to the second embodiment can obtain the following effects in addition to the same effects as those of the first embodiment.
  • the acceleration sensor system continuously applies a displacement signal to the movable electrode after the start of the self-diagnosis mode and continuously measures the displacement of the movable electrode. Thereby, the evaluation accuracy and diagnosis accuracy of sensor characteristics such as peak value and cycle time can be improved.
  • the displacement period and the detection period are time-divided, and the displacement of the movable electrode is intermittently detected.
  • the acceleration sensor system performs self-diagnosis using characteristics (peak value and cycle time) related to the resonance frequency.
  • the Q value is measured as a characteristic related to the resonance frequency, and self-diagnosis is performed using the measured Q value, thereby improving the diagnostic accuracy of the acceleration sensor.
  • the description will focus on the differences from the first and second embodiments.
  • FIG. 9 is a diagram for explaining an example of the displacement of the movable electrode when a diagnostic signal is applied.
  • the movable electrode displacement x (t) varies according to, for example, the equation (1).
  • f 0 represents the resonance frequency of the acceleration sensor
  • Q represents the Q value of the movable electrode
  • t represents the elapsed time from the start of application of the self-diagnosis signal S8, and
  • x 0 represents the proportionality constant.
  • the movable electrode displacement x is zero.
  • the movable electrode displacement x reaches a peak.
  • t 2 and the movable electrode displacement x are expressed by, for example, Expression (2) and Expression (3), respectively.
  • the movable electrode displacement x starts to return toward zero.
  • the movable electrode displacement x is closest to the position 0 at the self-diagnosis starting.
  • T 3 and the movable electrode displacement x at this time are respectively represented by, for example, equations (4) and (5).
  • t 3 varies according to f 0 and Q. However, t 3 is approximately equal to the reciprocal of the resonance frequency f 0 when Q is 5 or more. Based on such a relationship, the resonance frequency f 0 can be derived from the time t 3 . Further, as can be seen from the equation (5), the movable electrode displacement x at t 3 changes according to Q. Based on this relationship, you are possible to derive the Q value from the movable electrode displacement x in t 3.
  • step S107 the output signal evaluation unit 132 determines whether or not the movable electrode displacement x has reached a minimum. For example, the output signal evaluation unit 132 calculates a differential value of the output signal level D (n) and determines whether or not the differential value is zero. Alternatively, the output signal evaluation unit 132 determines whether the differential value of the previous output signal level D (n ⁇ 1) is a negative value and the differential value of the current output signal level D (n) is a positive value. It may be determined. If the output signal evaluation unit 132 determines that the differential value of the output signal level D (n) is 0, or the previous differential value is negative and the current differential value is positive, the process proceeds to step S108. In other cases, the process returns to step S100 or step S202.
  • the output signal evaluation unit 132 sets the elapsed time t (n) of the movable electrode displacement x determined to have reached the minimum in step S108 as the cycle time ts. ts corresponds to t 3 in the above equation (5). D (n) corresponds to the movable electrode displacement x (t 3 ) in the above equation (5). Further, the output signal evaluation unit 132 calculates the Q value. For example, the output signal evaluation unit 132 calculates Q by substituting the movable electrode displacement x at t 3 calculated by the output signal evaluation unit 132 into the above equation (5).
  • the output signal evaluation unit 132 determines that the movable electrode displacement x has reached a minimum, the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
  • the analysis unit 133 determines whether or not the Q value calculated as described above is included in the normal range in addition to steps S109 and S110. When determining that the Q value is not included in the normal range, the analysis unit 133 determines that the acceleration sensor is abnormal (failed). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5.
  • the diagnosis result S5 may include a Q value.
  • the analysis unit 133 determines that the peak value, the cycle time, and the Q value are all included in the corresponding normal range, for example, as the diagnosis result S5, the analysis unit 133 outputs information indicating that the sensor is normal to the external device.
  • the diagnosis result S5 may include a Q value. The analysis unit 133 may not output the diagnosis result S5.
  • the third embodiment of the present invention has been described above.
  • the acceleration sensor system according to the third embodiment stops the self-diagnosis signal when the displacement of the movable electrode reaches a minimum after the start of the self-diagnosis mode.
  • the timing at which the movable electrode returns to the equilibrium state or its vicinity is determined with higher accuracy. It is possible to more accurately control the stop of vibration and to shorten the time for self-diagnosis.
  • the acceleration sensor system measures the Q value in addition to the peak value and the period time as the characteristic relating to the resonance frequency, and performs self-diagnosis using this. Thereby, the diagnostic accuracy of the acceleration sensor can be improved.
  • the acceleration sensor system of each embodiment described above measures one period of resonance of the movable electrode and performs diagnosis based on characteristics such as a peak value of the one period.
  • the acceleration sensor system may measure characteristics such as a peak value of the movable electrode in N cycles (N is an integer greater than 1). In this case, the self-diagnosis time becomes longer, but the characteristics can be measured more accurately.
  • the acceleration sensor system of the third embodiment described above does not have to calculate the Q value while determining whether or not the movable electrode displacement x has reached a minimum.
  • the acceleration sensor system according to the third embodiment may evaluate at least one of the peak value, the period time, and the Q value.
  • the acceleration sensor system according to the first embodiment and the second embodiment may evaluate at least one of a peak value and a cycle time.
  • the acceleration sensor system of each embodiment described above includes one acceleration sensor.
  • the acceleration sensor system may include a plurality of acceleration sensors.
  • the acceleration sensor system may perform self-diagnosis for a plurality of acceleration sensors.
  • the plurality of acceleration sensors may be divided into a plurality of groups, and the acceleration sensor system may execute self-diagnosis at different timings for each group by time division. In this way, acceleration can be measured without stopping the entire system.
  • the processing units of the flowcharts shown in FIGS. 4 and 8 are divided according to the main processing contents in order to make the self-diagnosis processing easy to understand.
  • the present invention is not limited by the way of dividing the processing unit or the name.
  • the self-diagnosis process can be divided into more processing units according to the processing content. Moreover, it can also divide
  • the processing order of the above flowchart is not limited to the illustrated example as long as the object and effect of the present invention can be achieved.
  • the present invention is not limited to the above-described embodiment, and includes various modifications.
  • each of the above-described embodiments has been described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to the one provided with all the constituent elements described.
  • a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.
  • the above-described configurations, functions, processing units, processing means, and the like may be realized in hardware by designing a part or all of them, for example, with an integrated circuit.
  • Each of the above-described configurations, functions, and the like may be realized by software by the processor interpreting and executing a program that realizes each function.
  • Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.
  • the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

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Abstract

To more accurately perform a control to stop vibration of a movable electrode, and shorten a self-diagnosis time. This acceleration sensor system has: a sensor that outputs an output signal that indicates a capacitance change corresponding to displacement of a movable electrode; and a self-diagnosis unit that outputs to the sensor a self-diagnostic signal for diagnosing the sensor. The self-diagnosis unit outputs the self-diagnostic signal including a displacement signal for displacing the movable electrode, and stops, according to the level of the output signal, the output of the self-diagnostic signal.

Description

加速度センサシステム、及び自己診断方法Acceleration sensor system and self-diagnosis method
　本発明は、加速度センサシステム、及び自己診断方法に関する。 The present invention relates to an acceleration sensor system and a self-diagnosis method.
　特許文献１には、「コンデンサが共振周波数を有する周波数－静電容量特性を有しているため、共振周波数より極めて大きい、または、極めて小さい第１周波数の制御信号でコンデンサの静電容量を測定する通常測定が行われ、共振周波数を含むその近傍の第２周波数の制御信号でコンデンサの静電容量を測定する自己診断が行われる」と記載されている。 Patent Document 1 states that “the capacitor has a frequency-capacitance characteristic having a resonance frequency, so that the capacitance of the capacitor is measured with a control signal having a first frequency that is extremely higher or lower than the resonance frequency. The normal measurement is performed, and a self-diagnosis is performed in which the capacitance of the capacitor is measured with a control signal of the second frequency in the vicinity including the resonance frequency.
特許第５２２２４５７号Patent No. 5222457
　高い感度が求められる静電容量型加速度センサには、共振のＱ値が高い可動電極を有するものがある。例えば、サーボ式の静電容量型加速度センサは、Ｑ値が高い可動電極を有する。可動電極は、Ｑ値が高いほど、電圧を印加した際の振動が発生し易い。そのため、Ｑ値が高い可動電極は、Ｑ値が低い可動電極と比べると、電圧の印加を停止した後に振動が残り易い。これは、自己診断のための電圧の印加が停止された場合に、可動電極が静止するために掛かる時間が長くなり、自己診断後の通常測定を直ぐに開始できない、という問題を引き起こす。 Some capacitive acceleration sensors that require high sensitivity include a movable electrode having a high resonance Q value. For example, a servo capacitive acceleration sensor has a movable electrode having a high Q value. The higher the Q value of the movable electrode, the easier it is to generate vibration when a voltage is applied. Therefore, the movable electrode having a high Q value is more likely to remain vibrated after the voltage application is stopped, compared to the movable electrode having a low Q value. This causes a problem that when the application of the voltage for self-diagnosis is stopped, it takes a long time for the movable electrode to be stationary, and normal measurement after the self-diagnosis cannot be started immediately.
　そこで、本発明は、可動電極の振動の停止をより正確に制御し、かつ、自己診断の時間を短縮することを目的とする。 Therefore, an object of the present invention is to more accurately control the stop of the vibration of the movable electrode and to shorten the self-diagnosis time.
　本願は、上記課題の少なくとも一部を解決する手段を複数含んでいるが、その例を挙げるならば、以下のとおりである。 The present application includes a plurality of means for solving at least a part of the above-described problems, and examples thereof are as follows.
　本発明の一態様に係る加速度センサシステムは、可動電極の変位に応じて静電容量変化を表す出力信号を出力するセンサと、前記センサを診断するための自己診断信号を前記センサに出力する自己診断部と、を有し、前記自己診断部は、前記可動電極を変位させるための変位信号を含む前記自己診断信号を出力し、前記出力信号のレベルに応じて前記自己診断信号の出力を停止する。 An acceleration sensor system according to an aspect of the present invention includes a sensor that outputs an output signal indicating a change in capacitance in accordance with displacement of a movable electrode, and a self-diagnosis signal for diagnosing the sensor. A self-diagnosis unit that outputs the self-diagnosis signal including a displacement signal for displacing the movable electrode, and stops outputting the self-diagnosis signal according to the level of the output signal. To do.
　本発明によれば、可動電極の振動の停止をより正確に制御し、かつ、自己診断の時間を短縮することができる。 According to the present invention, the stop of the vibration of the movable electrode can be controlled more accurately, and the self-diagnosis time can be shortened.
　上記した以外の課題、構成及び効果は、以下の実施形態の説明により明らかにされる。 Issues, configurations, and effects other than those described above will be clarified by the following description of the embodiments.
本発明の第１実施形態に係る加速度センサシステムの構成の一例を示すブロック図である。It is a block diagram showing an example of composition of an acceleration sensor system concerning a 1st embodiment of the present invention. 第１実施形態おける加速度センサの構造の一例を説明する図である。It is a figure explaining an example of the structure of the acceleration sensor in 1st Embodiment. 第１実施形態における加速度センサへの入力信号及び加速度センサからの出力信号のタイミングの一例を示すタイミングチャートである。It is a timing chart which shows an example of the timing of the input signal to the acceleration sensor in the 1st embodiment, and the output signal from the acceleration sensor. 第１実施形態に係る自己診断処理の一例を示すフローチャートである。It is a flowchart which shows an example of the self-diagnosis process which concerns on 1st Embodiment. 本発明の第２実施形態に係る加速度センサシステムの構成の一例を示すブロック図である。It is a block diagram which shows an example of a structure of the acceleration sensor system which concerns on 2nd Embodiment of this invention. 第２実施形態における加速度センサの構造の一例を説明する図である。It is a figure explaining an example of the structure of the acceleration sensor in 2nd Embodiment. 第２実施形態における加速度センサへの入力信号及び加速度センサからの出力信号のタイミングの一例を示すタイミングチャートである。It is a timing chart which shows an example of the timing of the input signal to the acceleration sensor in the 2nd embodiment, and the output signal from an acceleration sensor. 第２実施形態に係る自己診断処理の一例を示すフローチャートである。It is a flowchart which shows an example of the self-diagnosis process which concerns on 2nd Embodiment. 診断信号を印加した場合の可動電極の変位の一例を説明する図である。It is a figure explaining an example of the displacement of a movable electrode at the time of applying a diagnostic signal.
　本発明の各実施形態を説明する前に、サーボ式の静電容量型加速度センサ、及び当該加速度センサを含む加速度センサシステムについて補足的に説明する。 Before describing each embodiment of the present invention, a servo-type capacitive acceleration sensor and an acceleration sensor system including the acceleration sensor will be supplementarily described.
　サーボ式の静電容量型加速度センサは、高いＱ値（例えば、０．５より高い）を有する可動電極を備える。この加速度センサは、加速度により可動電極に加わる力を相殺する静電気力が印加されることにより、可動電極を平衡状態に保つ。静電気力を発生させるサーボ信号には、ＰＷＭ（Pulse Width Modulation）電圧を用いることができる。加速度センサシステムは、例えば、検出される加速度が大きい場合はパルス密度を低密度になるように、検出される加速度が小さい場合はパルス密度を高密度になるように、加速度に応じてパルス密度を調整する。この加速度センサシステムは、機械的雑音を低減しつつ、高感度に加速度を検出することができる。 The servo-type capacitive acceleration sensor includes a movable electrode having a high Q value (for example, higher than 0.5). The acceleration sensor keeps the movable electrode in an equilibrium state by applying an electrostatic force that cancels the force applied to the movable electrode by acceleration. A PWM (Pulse Width Modulation) voltage can be used as a servo signal that generates an electrostatic force. The acceleration sensor system, for example, sets the pulse density according to the acceleration so that the pulse density is low when the detected acceleration is large and the pulse density is high when the detected acceleration is small. adjust. This acceleration sensor system can detect acceleration with high sensitivity while reducing mechanical noise.
　近年では、加速度センサシステムは、性能の向上に伴い、更なる高信頼性と省電力化が要求されている。信頼性を向上するための加速度センサシステムは、その故障を検知するための自己診断機能を備えることが要求される。上記のサーボ式の加速度センサシステムに自己診断機能を実装する場合、例えば、加速度センサが備える固定電極と可動電極の間に、周期的な所定の電圧を印加して可動電極の位置を変位させ、その変位量が所定の範囲にあるかどうかを評価することにより加速度センサの異常を検知する方法を採用することができる。この方法は、可動電極の共振周波数を測定し、測定した共振周波数に基づいて、加速度センサの診断を行う。 In recent years, accelerometer systems are required to have higher reliability and power saving as performance is improved. An acceleration sensor system for improving reliability is required to have a self-diagnosis function for detecting the failure. When implementing the self-diagnosis function in the servo-type acceleration sensor system described above, for example, a periodic predetermined voltage is applied between the fixed electrode and the movable electrode included in the acceleration sensor to displace the position of the movable electrode, A method of detecting an abnormality of the acceleration sensor by evaluating whether or not the displacement amount is within a predetermined range can be adopted. In this method, the resonance frequency of the movable electrode is measured, and the acceleration sensor is diagnosed based on the measured resonance frequency.
　しかし、上述の方法においては、可動電極が共振周波数近辺で振動することにより、可動電極の振動が静止するまで通常測定を開始できないため、診断時間が長期化する。また、上記の方法では、共振周波数を測定するために所定の周波数を掃引するために、周波数掃引機能やピーク周波数検出機能などの大規模な論理回路を設ける必要があり、これは消費電力を増大させる。 However, in the above-described method, since the movable electrode vibrates in the vicinity of the resonance frequency, the normal measurement cannot be started until the vibration of the movable electrode stops, so that the diagnosis time is prolonged. In the above method, it is necessary to provide a large-scale logic circuit such as a frequency sweep function and a peak frequency detection function in order to sweep a predetermined frequency in order to measure the resonance frequency, which increases power consumption. Let
　以下、本発明の各実施形態について、図面を参照しながら説明する。各実施形態は、サーボ式の静電容量型加速度センサ（以下、単に加速度センサともいう）、及び当該加速度センサを含むシステム（以下、単に加速度センサシステムともいう）に関する。なお、各実施形態を説明するための全図において同一部には原則として同一符号を付し、その繰り返しの説明は省略する。 Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Each embodiment relates to a servo-type capacitive acceleration sensor (hereinafter also simply referred to as an acceleration sensor) and a system including the acceleration sensor (hereinafter also simply referred to as an acceleration sensor system). Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.
［第１実施形態］
　図１は、本発明の第１実施形態に係る加速度センサシステムの構成の一例を示すブロック図である。加速度センサシステムは、加速度センサ１０１と、信号検出部１０２と、サーボ制御部１１０と、検出信号生成部１２０と、自己診断部１３０と、出力部１４０と、モード切替部１５０とを含む。 [First Embodiment]
FIG. 1 is a block diagram showing an example of the configuration of the acceleration sensor system according to the first embodiment of the present invention. The acceleration sensor system includes an acceleration sensor 101, a signal detection unit 102, a servo control unit 110, a detection signal generation unit 120, a self-diagnosis unit 130, an output unit 140, and a mode switching unit 150.
　加速度センサ１０１は、静電容量の変化を表す電気信号として加速度を検出し、検出した電気信号Ｓ１（以下、出力信号Ｓ１という）を信号検出部１０２に出力する。加速度センサ１０１は、例えば、主に電極構造物により構成された静電容量型の加速度検出素子を含む。加速度センサ１０１については図２を参照して後に詳述する。 The acceleration sensor 101 detects acceleration as an electric signal representing a change in capacitance, and outputs a detected electric signal S1 (hereinafter referred to as an output signal S1) to the signal detection unit 102. The acceleration sensor 101 includes, for example, a capacitance type acceleration detection element mainly composed of an electrode structure. The acceleration sensor 101 will be described in detail later with reference to FIG.
　信号検出部１０２は、加速度センサ１０１から出力信号Ｓ１を受信し、受信したアナログ電気信号である出力信号Ｓ１を電圧に変換して増幅し、その電圧信号をディジタル信号に変換して、サーボ制御部１１０及び自己診断部１３０に出力する。 The signal detection unit 102 receives the output signal S1 from the acceleration sensor 101, converts the output signal S1 that is the received analog electrical signal into a voltage, amplifies the voltage, converts the voltage signal into a digital signal, and outputs a servo control unit. 110 and the self-diagnosis unit 130.
　サーボ制御部１１０は、信号検出部１０２から出力信号を受信し、受信した出力信号に基づいてサーボ信号Ｓ６を生成し、モード切替部１５０に出力する。例えば、サーボ制御部１１０は、加速度に対応した静電容量の変化の大きさに応じて、パルス密度及びレベルの両方を調整したＰＷＭ（Pulse Width Modulation）電圧信号をサーボ信号として生成する。本実施形態では、サーボ信号Ｓ６は、電圧信号であり、モード切替部１５０を介して加速度センサ１０１の後述する２つの固定電極に印加される。 The servo control unit 110 receives the output signal from the signal detection unit 102, generates a servo signal S6 based on the received output signal, and outputs the servo signal S6 to the mode switching unit 150. For example, the servo control unit 110 generates, as a servo signal, a PWM (Pulse 信号 Width Modulation) voltage signal in which both the pulse density and the level are adjusted according to the magnitude of the change in capacitance corresponding to the acceleration. In the present embodiment, the servo signal S6 is a voltage signal and is applied to two fixed electrodes (to be described later) of the acceleration sensor 101 via the mode switching unit 150.
　サーボ制御部１１０は、受信したディジタル信号である出力信号を受信し、当該ディジタル信号を信号処理することによりサーボ信号を生成する。サーボ信号を生成する信号処理の一例として、ＰＩＤ制御（Proportional-Integral-Derivative Control）を用いることができる。ＰＩＤ制御は、制御対象への入力値の制御を、制御対象からの出力値と目標値との偏差、その積分及び微分によって行う方式である。サーボ制御部１１０は、ＰＩＤ制御により、受信したディジタル信号に基づいて、加速度センサ１０１の可動電極を平衡状態に維持するために必要な静電気力に相当する値（電圧、ディジタル値など）を導出する機能を有する。 The servo control unit 110 receives an output signal which is a received digital signal, and generates a servo signal by performing signal processing on the digital signal. As an example of signal processing for generating a servo signal, PID control (Proportional-Integral-Derivative-Control) can be used. PID control is a method in which control of an input value to a controlled object is performed by a deviation between an output value from the controlled object and a target value, integration and differentiation thereof. The servo control unit 110 derives a value (voltage, digital value, etc.) corresponding to the electrostatic force necessary to maintain the movable electrode of the acceleration sensor 101 in an equilibrium state based on the received digital signal by PID control. It has a function.
　検出信号生成部１２０は、検出信号Ｓ７を生成し、モード切替部１５０に出力する。検出信号Ｓ７は、加速度の検出のために加速度センサ１０１に印加され、加速度センサ１０１に静電容量変化を電気信号として検出させるための電気信号である。本実施形態では、検出信号Ｓ７は、電圧信号であり、モード切替部１５０を介して加速度センサ１０１の後述する２つの固定電極に印加される。 The detection signal generation unit 120 generates a detection signal S7 and outputs it to the mode switching unit 150. The detection signal S7 is an electric signal that is applied to the acceleration sensor 101 to detect acceleration and causes the acceleration sensor 101 to detect a change in capacitance as an electric signal. In the present embodiment, the detection signal S <b> 7 is a voltage signal and is applied to two fixed electrodes (described later) of the acceleration sensor 101 via the mode switching unit 150.
　自己診断部１３０は、信号検出部１０２から出力信号を受信する。自己診断部１３０は、自己診断信号Ｓ８を生成し、モード切替部１５０に出力する。自己診断部１３０は、信号検出部１０２から出力信号に基づいて、自己診断信号Ｓ８の停止タイミングを判定する。このような機能を実装するため、自己診断部１３０は、診断信号生成部１３１と、出力信号評価部１３２とを含む。また、自己診断部１３０は、解析部１３３を含む。 The self-diagnosis unit 130 receives an output signal from the signal detection unit 102. The self-diagnosis unit 130 generates a self-diagnosis signal S8 and outputs it to the mode switching unit 150. The self-diagnosis unit 130 determines the stop timing of the self-diagnosis signal S8 based on the output signal from the signal detection unit 102. In order to implement such a function, the self-diagnosis unit 130 includes a diagnostic signal generation unit 131 and an output signal evaluation unit 132. In addition, the self-diagnosis unit 130 includes an analysis unit 133.
　診断信号生成部１３１は、モード切替部１５０の制御により後述する自己診断モードが選択されると、自己診断信号Ｓ８を生成し、モード切替部１５０に出力する。自己診断信号Ｓ８は、加速度センサ１０１の可動電極に変位を与えるための電気信号と、加速度の検出のために加速度センサ１０１に印加され、加速度センサ１０１に静電容量変化を電気信号として検出させるための電気信号とを含む。本実施形態では、自己診断信号Ｓ８は、電圧信号であり、モード切替部１５０を介して加速度センサ１０１の後述する２つの固定電極に印加される。診断信号生成部１３１は、出力信号評価部１３２から後述する停止信号を受信した場合に、自己診断信号Ｓ８の生成及び出力を停止する。 Diagnostic signal generation unit 131 generates a self-diagnosis signal S8 and outputs it to mode switching unit 150 when a self-diagnosis mode to be described later is selected under the control of mode switching unit 150. The self-diagnosis signal S8 is applied to the acceleration sensor 101 for detecting displacement and an electric signal for applying displacement to the movable electrode of the acceleration sensor 101, and causes the acceleration sensor 101 to detect a change in capacitance as an electric signal. Including electrical signals. In the present embodiment, the self-diagnosis signal S <b> 8 is a voltage signal and is applied to two fixed electrodes (described later) of the acceleration sensor 101 via the mode switching unit 150. The diagnostic signal generation unit 131 stops generation and output of the self-diagnosis signal S8 when receiving a stop signal described later from the output signal evaluation unit 132.
　出力信号評価部１３２は、自己診断信号Ｓ８に応じた出力信号が示す静電容量の信号レベルに基づいて、信号レベルのピーク値と、自己診断信号Ｓ８の印加の開始後に信号レベルが所定値に達するまでの周期時間を測定する。この所定値は、加速度センサの可動電極のＱ値に応じて設定するのが望ましい。出力信号評価部１３２は、信号レベルが所定値に達したか否かを判定し、所定値に達した場合に停止信号を診断信号生成部１３１に出力するとともに、測定した信号レベルのピーク値及び周期時間を解析部１３３に出力する。 Based on the signal level of the capacitance indicated by the output signal corresponding to the self-diagnosis signal S8, the output signal evaluation unit 132 sets the signal level to a predetermined value after the application of the self-diagnosis signal S8 and the peak value of the signal level. Measure the cycle time to reach. This predetermined value is desirably set according to the Q value of the movable electrode of the acceleration sensor. The output signal evaluation unit 132 determines whether or not the signal level has reached a predetermined value, and outputs a stop signal to the diagnostic signal generation unit 131 when the signal level reaches the predetermined value, and the peak value of the measured signal level and The cycle time is output to the analysis unit 133.
　解析部１３３は、出力信号評価部１３２から測定された信号レベルのピーク値及び周期時間を受信する。解析部１３３は、受信したピーク値及び周期時間の少なくとも一方に基づいて、静電容量変化が正常であるか否かを判定し、その判定結果を診断結果Ｓ５として、例えばＰＣ（Persona Computer）などの外部装置に出力する。診断結果Ｓ５は、データ信号、データファイル、画面データなど、各種の形態とすることができる。 The analysis unit 133 receives the peak value of the signal level and the period time measured from the output signal evaluation unit 132. The analysis unit 133 determines whether or not the capacitance change is normal based on at least one of the received peak value and cycle time, and uses the determination result as the diagnosis result S5, for example, a PC (Persona Computer) or the like. To the external device. The diagnosis result S5 can take various forms such as a data signal, a data file, and screen data.
　自己診断部１３０については図３を参照して後に詳述する。 The self-diagnosis unit 130 will be described in detail later with reference to FIG.
　出力部１４０は、サーボ制御部１１０からサーボ信号Ｓ６を受信し、受信したサーボ信号に基づいて加速度を出力する。このような機能を実装するため、出力部１４０は、加速度出力部１４１を含む。また、出力部１４０は、解析部１４２を含む。 The output unit 140 receives the servo signal S6 from the servo control unit 110, and outputs an acceleration based on the received servo signal. In order to implement such a function, the output unit 140 includes an acceleration output unit 141. The output unit 140 includes an analysis unit 142.
　加速度出力部１４１は、サーボ信号Ｓ６に基づいて加速度を計算し、その加速度を含む加速度情報Ｓ３を生成し、例えばＰＣなどの外部装置に出力する。加速度出力部１４１は、信号検出部１０２から出力信号を受信して、出力信号に基づいて加速度を計算し、その加速度を含む加速度情報Ｓ３を生成し、外部装置に出力してもよい。加速度出力部１４１は、計算した加速度を解析部１４２に出力する。サーボ信号あるいは出力信号に基づいて加速度を計算する処理は、一般的な技術を用いることができるため、説明を省略する。 The acceleration output unit 141 calculates acceleration based on the servo signal S6, generates acceleration information S3 including the acceleration, and outputs it to an external device such as a PC. The acceleration output unit 141 may receive an output signal from the signal detection unit 102, calculate acceleration based on the output signal, generate acceleration information S3 including the acceleration, and output the acceleration information S3 to an external device. The acceleration output unit 141 outputs the calculated acceleration to the analysis unit 142. Since the process for calculating the acceleration based on the servo signal or the output signal can use a general technique, a description thereof will be omitted.
　解析部１４２は、加速度出力部１４１から加速度を受信し、受信した加速度に対して所定の解析処理を実施し、その解析結果を含む解析情報Ｓ４を生成し、例えばＰＣなどの外部装置に出力する。加速度の解析処理は、一般的な技術を用いることができるため、説明を省略する。解析情報Ｓ４は、データ信号、データファイル、画面データなど、各種の形態とすることができる。 The analysis unit 142 receives acceleration from the acceleration output unit 141, performs predetermined analysis processing on the received acceleration, generates analysis information S4 including the analysis result, and outputs the analysis information S4 to an external device such as a PC, for example. . Since a general technique can be used for the analysis process of acceleration, description is abbreviate | omitted. The analysis information S4 can be in various forms such as a data signal, a data file, and screen data.
　モード切替部１５０は、サーボ制御部１１０からのサーボ信号Ｓ６と、検出信号生成部１２０からの検出信号Ｓ７と、自己診断部１３０からの自己診断信号Ｓ８とを受信する。モード切替部１５０は、これらの３種類の信号の中から、選択した動作モードに対応する１つの信号を選択し、選択した信号を信号Ｓ２として加速度センサ１０１に出力する。すなわち、信号Ｓ２は、サーボ信号Ｓ６、検出信号Ｓ７、及び自己診断信号Ｓ８のいずれか１つからなる。信号Ｓ２は、電圧信号であり、加速度センサ１０１の後述する２つの固定電極に印加される。 The mode switching unit 150 receives the servo signal S6 from the servo control unit 110, the detection signal S7 from the detection signal generation unit 120, and the self-diagnosis signal S8 from the self-diagnosis unit 130. The mode switching unit 150 selects one signal corresponding to the selected operation mode from these three types of signals, and outputs the selected signal to the acceleration sensor 101 as a signal S2. That is, the signal S2 includes any one of the servo signal S6, the detection signal S7, and the self-diagnosis signal S8. The signal S2 is a voltage signal and is applied to two fixed electrodes (to be described later) of the acceleration sensor 101.
　加速度センサシステムは、３つの動作モードとして、サーボ制御モードと、検出モードと、自己診断モードとを有する。サーボ制御モード（本発明の第１のモードに相当する）は、サーボ制御を実行するモードである。検出モード（本発明の第１のモードに相当する）は、加速度を検出するモードである。自己診断モード（本発明の第２のモードに相当する）は、加速度センサ１０１の状態を診断するモードである。サーボ信号Ｓ６は、サーボ制御モードにおいて選択される。検出信号Ｓ７は、検出モードにおいて選択される。自己診断信号Ｓ８は、自己診断モードにおいて選択される。 The acceleration sensor system has a servo control mode, a detection mode, and a self-diagnosis mode as three operation modes. The servo control mode (corresponding to the first mode of the present invention) is a mode for executing servo control. The detection mode (corresponding to the first mode of the present invention) is a mode for detecting acceleration. The self-diagnosis mode (corresponding to the second mode of the present invention) is a mode for diagnosing the state of the acceleration sensor 101. The servo signal S6 is selected in the servo control mode. The detection signal S7 is selected in the detection mode. The self-diagnosis signal S8 is selected in the self-diagnosis mode.
　モード切替部１５０は、基本的には予め設定された時分割に基づいて動作モードの切り替えを制御することにより、動作モードを選択する。モード切替部１５０は、例えば、予め定めた時分割に基づいて、サーボ制御モードと検出モードとを交互に切り替える。モード切替部１５０は、任意のタイミングでサーボ制御モード又は検出モードを自己診断モードに切り替える。モード切替部１５０は、例えば、通常測定期間（サーボ制御モード及び検出モードの２つを含む期間）が所定の時間を経過したか否かを判定し、経過した場合にサーボ制御モード又は検出モードを自己診断モードに切り替えることができる。また、モード切替部１５０は、例えば、他のセンサ（図示せず）により計測された環境温度や環境湿度などの値を取得し、当該値が所定の閾値を超えた又は下回った場合に自己診断モードに切り替えてもよい。 The mode switching unit 150 basically selects an operation mode by controlling switching of the operation mode based on a preset time division. For example, the mode switching unit 150 alternately switches between the servo control mode and the detection mode based on a predetermined time division. The mode switching unit 150 switches the servo control mode or the detection mode to the self-diagnosis mode at an arbitrary timing. For example, the mode switching unit 150 determines whether or not a normal measurement period (a period including two of the servo control mode and the detection mode) has passed a predetermined time, and when the predetermined period has elapsed, the mode switching unit 150 selects the servo control mode or the detection mode. Switch to self-diagnosis mode. For example, the mode switching unit 150 acquires values such as environmental temperature and environmental humidity measured by another sensor (not shown), and performs self-diagnosis when the value exceeds or falls below a predetermined threshold. You may switch to the mode.
　モード切替部１５０は、自己診断モードを選択した後、自己診断部１３０からの自己診断信号Ｓ８が停止したか否かを判定し、停止した場合、自己診断モードを通常測定（サーボ制御モード又は検出モード）に切り替える。 After selecting the self-diagnosis mode, the mode switching unit 150 determines whether or not the self-diagnosis signal S8 from the self-diagnosis unit 130 has stopped, and if so, the self-diagnosis mode is normally measured (servo control mode or detection). Mode).
　図２は、第１実施形態おける加速度センサの構造の一例を説明する図である。図２は、説明のための方向として、Ｘ方向及びＺ方向を示す。Ｘ方向は、電極の主面が延在する方向であり、図２の左右方向に対応する。Ｚ方向は、電極同士が距離を置いて重なる方向であり、図２の上下方向に対応する。 FIG. 2 is a diagram for explaining an example of the structure of the acceleration sensor according to the first embodiment. FIG. 2 shows the X direction and the Z direction as directions for explanation. The X direction is a direction in which the main surface of the electrode extends, and corresponds to the left-right direction in FIG. The Z direction is a direction in which the electrodes overlap each other at a distance, and corresponds to the vertical direction in FIG.
　加速度センサ１０１は、一対の固定電極１０１１ａ及び固定電極１０１１ｂと、１つの可動電極１０１３とを備える。これらの２つの固定電極は、信号線を通じてモード切替部１５０に接続されている。可動電極１０１３は、信号線を通じて信号検出部１０２に接続されている。 The acceleration sensor 101 includes a pair of fixed electrodes 1011a and 1011b, and one movable electrode 1013. These two fixed electrodes are connected to the mode switching unit 150 through signal lines. The movable electrode 1013 is connected to the signal detection unit 102 through a signal line.
　可動電極１０１３は、Ｘ方向において広い主面を有する。固定電極１０１１ａ及び固定電極１０１１ｂは、可動電極１０１３に静電気力を発生させるために、Ｚ方向で平面視した場合に可動電極１０１３の主面に対して重なる面領域を含む。固定電極１０１１ａの面領域及び固定電極１０１１ｂの面領域は、それぞれ、可動電極１０１３の両側の対応する主面に対して面するように、Ｚ方向に所定の距離を置いて配置されている。 The movable electrode 1013 has a wide main surface in the X direction. The fixed electrode 1011a and the fixed electrode 1011b include a surface region that overlaps the main surface of the movable electrode 1013 when viewed in plan in the Z direction in order to generate an electrostatic force on the movable electrode 1013. The surface area of the fixed electrode 1011a and the surface area of the fixed electrode 1011b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the movable electrode 1013, respectively.
　固定電極１０１１ａ及び固定電極１０１１ｂの信号線は、動作モードに応じた信号Ｓ２（サーボ信号Ｓ６、検出信号Ｓ７、又は自己診断信号Ｓ８）を伝送する。 The signal lines of the fixed electrode 1011a and the fixed electrode 1011b transmit a signal S2 (servo signal S6, detection signal S7, or self-diagnosis signal S8) corresponding to the operation mode.
　サーボ信号Ｓ６は、詳細には、固定電極１０１１ａに印加されるサーボ信号Ｓ６ａと、固定電極１０１１ｂに印加されるサーボ信号Ｓ６ｂとから成る。サーボ信号Ｓ６ａは、例えば、矩形波パルスの繰り返しによる電圧信号である。サーボ信号Ｓ６ｂは、サーボ信号Ｓ６ａに対して反転された電圧信号である。 Specifically, the servo signal S6 includes a servo signal S6a applied to the fixed electrode 1011a and a servo signal S6b applied to the fixed electrode 1011b. The servo signal S6a is, for example, a voltage signal generated by repeating rectangular wave pulses. The servo signal S6b is a voltage signal inverted with respect to the servo signal S6a.
　検出信号Ｓ７は、詳細には、固定電極１０１１ａに印加される検出信号Ｓ７ａと、固定電極１０１１ｂに印加される検出信号Ｓ７ｂとから成る。検出信号Ｓ７ａは、例えば、矩形波パルスの繰り返しによる電圧信号である。検出信号Ｓ７ｂは、検出信号Ｓ７ａに対して反転された電圧信号である。 Specifically, the detection signal S7 includes a detection signal S7a applied to the fixed electrode 1011a and a detection signal S7b applied to the fixed electrode 1011b. The detection signal S7a is, for example, a voltage signal generated by repeating rectangular wave pulses. The detection signal S7b is a voltage signal inverted with respect to the detection signal S7a.
　自己診断信号Ｓ８は、詳細には、固定電極１０１１ａに印加される自己診断信号Ｓ８ａと、固定電極１０１１ｂに印加される自己診断信号Ｓ８ｂとから成る。また、自己診断信号Ｓ８ａは、可動電極１０１３を変位させるための変位信号Ｓ８ｃ（図示せず）と、静電容量変化を検出する検出信号Ｓ８ｅ（図示せず）を含む。自己診断信号Ｓ８ｂは、変位信号Ｓ８ｃに対応する変位信号Ｓ８ｄ（図示せず）と、検出信号Ｓ８ｅに対応する検出信号Ｓ８ｆ（図示せず）とを含む。変位信号Ｓ８ｃ及び変位信号Ｓ８ｄは、可動電極１０１３が変位するように調整される。例えば、変位信号Ｓ８ｃは、可動電極電圧と同じ電圧とし、変位信号Ｓ８ｄは、可動電極電圧と異なる電圧とすることにより、固定電極１０１１ｂと可動電極１０１３の間に静電気力が発生し、可動電極１０１３が固定電極１０１１ｂ側に変位する。検出信号Ｓ８ｅは、例えば、矩形波パルスの繰り返しによる電圧信号である。検出信号Ｓ８ｆは、検出信号Ｓ８ｅに対して反転された電圧信号である。 The self-diagnosis signal S8 includes a self-diagnosis signal S8a applied to the fixed electrode 1011a and a self-diagnosis signal S8b applied to the fixed electrode 1011b. The self-diagnosis signal S8a includes a displacement signal S8c (not shown) for displacing the movable electrode 1013 and a detection signal S8e (not shown) for detecting a change in capacitance. Self-diagnosis signal S8b includes a displacement signal S8d (not shown) corresponding to displacement signal S8c and a detection signal S8f (not shown) corresponding to detection signal S8e. The displacement signal S8c and the displacement signal S8d are adjusted so that the movable electrode 1013 is displaced. For example, when the displacement signal S8c is set to the same voltage as the movable electrode voltage and the displacement signal S8d is set to a voltage different from the movable electrode voltage, an electrostatic force is generated between the fixed electrode 1011b and the movable electrode 1013, and the movable electrode 1013 is generated. Is displaced toward the fixed electrode 1011b. The detection signal S8e is, for example, a voltage signal generated by repeating rectangular wave pulses. The detection signal S8f is a voltage signal inverted with respect to the detection signal S8e.
　可動電極１０１３の信号線は、出力信号Ｓ１を伝送する。加速度に応じた可動電極１０１３のＺ方向の位置の変化（図中のｄ）は、固定電極１０１１ａ及び固定電極１０１１ｂと可動電極１０１３との間の静電容量を変化させる。詳細には、例えば、固定電極１０１１ａと可動電極１０１３との間の静電容量をＣ１と表し、固定電極１０１１ｂと可動電極１０１３との間の静電容量をＣ２と表す。これらの静電容量の静電容量差ｄｅｌｔａＣは、例えばｄｅｌｔａＣ＝Ｃ１－Ｃ２と計算することができる。出力信号Ｓ１は、静電容量差ｄｅｌｔａＣを含む静電容量変化を表す電圧信号である。ある時点の出力信号Ｓ１は、可動電極１０１３の変位の状態に応じた静電容量差ｄｅｌｔａＣを表している。２つの時点の出力信号Ｓ１は、静電容量差ｄｅｌｔａＣの時間変化を表している。 The signal line of the movable electrode 1013 transmits the output signal S1. The change in the position of the movable electrode 1013 in the Z direction according to the acceleration (d in the figure) changes the capacitance between the fixed electrode 1011a and the fixed electrode 1011b and the movable electrode 1013. Specifically, for example, the capacitance between the fixed electrode 1011a and the movable electrode 1013 is represented as C1, and the capacitance between the fixed electrode 1011b and the movable electrode 1013 is represented as C2. The capacitance difference deltaC between these capacitances can be calculated as, for example, deltaC = C1−C2. The output signal S1 is a voltage signal representing a change in capacitance including the capacitance difference deltaC. The output signal S1 at a certain point in time represents the capacitance difference deltaC corresponding to the displacement state of the movable electrode 1013. The output signal S1 at two points in time represents a change with time in the capacitance difference deltaC.
　図３は、第１実施形態における加速度センサへの入力信号及び加速度センサからの出力信号のタイミングの一例を示すタイミングチャートである。 FIG. 3 is a timing chart showing an example of the timing of the input signal to the acceleration sensor and the output signal from the acceleration sensor in the first embodiment.
　通常測定の期間では、上述したように、サーボ制御モードと検出モードとが交互に切り替えられる。具体的には、サーボ信号Ｓ６と検出信号Ｓ７とが交互に繰り返し加速度センサ１０１に印加される。これにより、可動電極の位置が平衡状態に維持されるとともに静電容量変化に応じた信号が出力される。サーボ制御により可動電極の位置が平衡状態又は平衡に近い状態に保持されるため、出力信号Ｓ１は、０又は０に近い値である。 In the normal measurement period, the servo control mode and the detection mode are alternately switched as described above. Specifically, the servo signal S6 and the detection signal S7 are repeatedly applied to the acceleration sensor 101 alternately. As a result, the position of the movable electrode is maintained in an equilibrium state, and a signal corresponding to the change in capacitance is output. Since the position of the movable electrode is held in an equilibrium state or a state close to equilibrium by servo control, the output signal S1 is 0 or a value close to 0.
　自己診断モードは、上述したように、モード切替部１５０により選択されることで開始する。具体的には、自己診断モードでは、診断信号生成部１３１は、変位信号Ｓ８ｃ及び変位信号Ｓ８ｄと検出信号Ｓ８ｅ及び検出信号Ｓ８ｆとを、交互に繰り返し加速度センサ１０１に出力する。すなわち、自己診断の期間は、変位信号により可動電極を変位させる変位期間Ｐ１と、検出信号により静電容量変化を検出する検出期間Ｐ２とを含む。変位期間Ｐ１では、可動電極を変位させるために固定電極と可動電極間に電圧が印加される。この電圧は主に直流電圧である。検出期間Ｐ２では、検出信号Ｓ７と同じ周波数及び電圧の信号が固定電極に印加される。変位期間Ｐ１及び検出期間Ｐ２の長さは、予め設定される。これにより、可動電極の位置が変位するとともに静電容量変化に応じた信号が出力される。 The self-diagnosis mode starts when selected by the mode switching unit 150 as described above. Specifically, in the self-diagnosis mode, the diagnostic signal generator 131 outputs the displacement signal S8c, the displacement signal S8d, the detection signal S8e, and the detection signal S8f alternately and repeatedly to the acceleration sensor 101. That is, the self-diagnosis period includes a displacement period P1 in which the movable electrode is displaced by the displacement signal, and a detection period P2 in which the change in capacitance is detected by the detection signal. In the displacement period P1, a voltage is applied between the fixed electrode and the movable electrode in order to displace the movable electrode. This voltage is mainly a DC voltage. In the detection period P2, a signal having the same frequency and voltage as the detection signal S7 is applied to the fixed electrode. The lengths of the displacement period P1 and the detection period P2 are set in advance. As a result, the position of the movable electrode is displaced and a signal corresponding to the change in capacitance is output.
　可動電極のＱ値が０．５よりも高い場合、この可動電極の位置は、可動電極変位期間Ｐ１に直流電圧を印加すると、平衡状態から離れるように徐々に変位し（Ｔ１からＴ２）、ピーク（Ｔ２）に達した後、徐々に平衡状態に戻るように徐々に変位する（Ｔ２からＴ３）。この変化は、リンギングと呼ばれる現象の最初の１周期に相当する。可動電極のＱ値が高いほど、ピーク後に平衡状態に向かって戻る変位量は大きい。可動電極のＱ値が０．５以下である場合、リンギングは発生しない。さらに、Ｑ値が０．５よりも高い可動電極の場合、自己診断モードが終了する（自己診断信号Ｓ８が停止する）タイミングによっては、可動電極の振動が残り、振動が静止するまで通常測定を再開できない。例えば、Ｔ３より前に自己診断信号が停止した場合、可動電極の振動がＴ３よりも後に残る。 When the Q value of the movable electrode is higher than 0.5, the position of the movable electrode is gradually displaced away from the equilibrium state (T 1 to T 2 ) when a DC voltage is applied during the movable electrode displacement period P1. Then, after reaching the peak (T 2 ), it gradually displaces so as to gradually return to the equilibrium state (T 2 to T 3 ). This change corresponds to the first period of a phenomenon called ringing. The higher the Q value of the movable electrode, the larger the displacement amount returning to the equilibrium state after the peak. When the Q value of the movable electrode is 0.5 or less, ringing does not occur. Furthermore, in the case of a movable electrode having a Q value higher than 0.5, depending on the timing at which the self-diagnosis mode ends (self-diagnosis signal S8 stops), the vibration of the movable electrode remains and normal measurement is performed until the vibration stops. Cannot resume. For example, if the self-diagnosis signal is stopped prior to T 3, the vibration of the movable electrode is left later than T 3.
　本実施形態では、出力信号評価部１３２は、各検出期間Ｐ２に出力される出力信号に基づいて、可動電極の平衡状態からの変位レベルＤ（ｎ）を繰り返し測定する。また、出力信号評価部１３２は、測定した各変位レベルＤ（ｎ）について、所定の閾値Ｄｔｈを下回ったか否かを判定する。閾値Ｄｔｈは、平衡状態（平衡状態に近い状態を含む）を判定するための値であり、予め設定されている。閾値Ｄｔｈは、Ｑ値が高いほど小さく設定される。閾値Ｄｔｈの設定値は、外部装置からの指示に基づいて変更できてもよい。変位レベルＤ（ｎ）が閾値Ｄｔｈを下回った場合、出力信号評価部１３２は、停止信号を診断信号生成部１３１に出力する。このようにすることで、可動電極が平衡状態に戻ったタイミングで自己診断信号が停止され、その後の可動電極の振動が完全に或いは小さく抑制され、静止までの時間が短縮される。一方、仮に、変位レベルＤ（ｎ）が閾値Ｄｔｈ以上のタイミングで自己診断信号が停止された場合は、その後の可動電極の振動がＴ３よりも後に残り、静止までの時間が長期化する。 In the present embodiment, the output signal evaluation unit 132 repeatedly measures the displacement level D (n) from the equilibrium state of the movable electrode based on the output signal output in each detection period P2. Further, the output signal evaluation unit 132 determines whether or not each measured displacement level D (n) is below a predetermined threshold value Dth. The threshold value Dth is a value for determining an equilibrium state (including a state close to the equilibrium state), and is set in advance. The threshold value Dth is set smaller as the Q value is higher. The set value of the threshold value Dth may be changed based on an instruction from an external device. When the displacement level D (n) falls below the threshold value Dth, the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 131. By doing so, the self-diagnosis signal is stopped at the timing when the movable electrode returns to the equilibrium state, the subsequent vibration of the movable electrode is completely or smallly suppressed, and the time until stationary is shortened. On the other hand, if, when the self-diagnosis signal is stopped by the displacement level D (n) is equal to or greater than the threshold value Dth timing, vibration subsequent movable electrode remains later than T 3, the time until stationary prolonged.
　図４は、第１実施形態に係る自己診断処理の一例を示すフローチャートである。図７は、自己診断モードが開始された場合を示している。 FIG. 4 is a flowchart showing an example of self-diagnosis processing according to the first embodiment. FIG. 7 shows a case where the self-diagnosis mode is started.
　ｎの初期値は、「０」である。Ｄｐｅａｋの初期値は、「０」である。Ｄ（０）の値は、例えば、本図のフローチャートの開始直前の出力信号レベルを出力信号評価部１３２が取得して設定してもよいし、所定値、例えば「０」を設定してもよい。出力信号評価部１３２、本図のフローチャートの開始後、経過時間を計測する。 The initial value of n is “0”. The initial value of Dpeak is “0”. The value of D (0) may be set, for example, by the output signal evaluation unit 132 acquiring and setting the output signal level immediately before the start of the flowchart of this figure, or by setting a predetermined value, for example, “0”. Good. After the output signal evaluation unit 132 starts the flowchart of this figure, the elapsed time is measured.
　まず、診断信号生成部１３１は、ｎを１インクリメントする（ステップＳ１００）。次に、診断信号生成部１３１は、変位期間Ｐ１の間、変位信号を出力する（ステップＳ１０１）。次に、診断信号生成部１３１は、変位期間Ｐ１の後、検出期間Ｐ２の間、検出信号を出力する（ステップＳ１０２）。次に、出力信号評価部１３２は、ステップＳ１０２の検出信号に応じて加速度センサ１０１から信号検出部１０２を介して出力された出力信号レベルＤ（ｎ）を取得する（ステップＳ１０３）。ステップＳ１０３では、出力信号評価部１３２は、出力信号レベルＤ（ｎ）を取得した時刻、すなわち経過時間ｔ（ｎ）を取得する。 First, the diagnostic signal generation unit 131 increments n by 1 (step S100). Next, the diagnostic signal generator 131 outputs a displacement signal during the displacement period P1 (step S101). Next, the diagnostic signal generation unit 131 outputs a detection signal during the detection period P2 after the displacement period P1 (step S102). Next, the output signal evaluation unit 132 acquires the output signal level D (n) output from the acceleration sensor 101 via the signal detection unit 102 in accordance with the detection signal in step S102 (step S103). In step S103, the output signal evaluation unit 132 acquires the time when the output signal level D (n) is acquired, that is, the elapsed time t (n).
　次に、出力信号評価部１３２は、ステップＳ１０３で取得した出力信号レベルＤ（ｎ）が、前回取得した出力信号レベルＤ（ｎ－１）以下であるか否かを判定する（ステップＳ１０４）。出力信号評価部１３２は、出力信号レベルＤ（ｎ）が出力信号レベルＤ（ｎ－１）を超えると判定した場合（ステップＳ１０４でｎｏ）、処理をステップＳ１００に戻す。 Next, the output signal evaluation unit 132 determines whether or not the output signal level D (n) acquired in step S103 is equal to or lower than the output signal level D (n−1) acquired last time (step S104). If the output signal evaluation unit 132 determines that the output signal level D (n) exceeds the output signal level D (n−1) (no in step S104), the process returns to step S100.
　出力信号評価部１３２は、出力信号レベルＤ（ｎ）が出力信号レベルＤ（ｎ－１）以下であると判定した場合（ステップＳ１０４でｙｅｓ）、出力信号レベルのピーク値Ｄｐｅａｋが０であるか否かを判定する（ステップＳ１０５）。出力信号評価部１３２は、出力信号レベルのピーク値Ｄｐｅａｋが０であると判定した場合（ステップＳ１０５でｙｅｓ）、ピーク値Ｄｐｅａｋに出力信号レベルＤ（ｎ－１）を設定する（ステップＳ１０６）。 When the output signal evaluation unit 132 determines that the output signal level D (n) is equal to or lower than the output signal level D (n−1) (yes in step S104), whether the output signal level peak value Dpeak is 0 or not. It is determined whether or not (step S105). When the output signal evaluation unit 132 determines that the peak value Dpeak of the output signal level is 0 (yes in step S105), the output signal evaluation unit 132 sets the output signal level D (n−1) to the peak value Dpeak (step S106).
　出力信号評価部１３２は、出力信号レベルのピーク値Ｄｐｅａｋが０でないと判定した場合（ステップＳ１０５でｎｏ）、又は、ステップＳ１０６の処理を実行した後、出力信号レベルＤ（ｎ）が閾値Ｄｔｈより小さいか否かを判定する（ステップＳ１０７）。出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈ以上であると判定した場合（ステップＳ１０７でｎｏ）、処理をステップＳ１００に戻す。 When the output signal evaluation unit 132 determines that the peak value Dpeak of the output signal level is not 0 (no in step S105), or after executing the process of step S106, the output signal level D (n) is greater than the threshold value Dth. It is determined whether it is small (step S107). If the output signal evaluation unit 132 determines that the output signal level D (n) is greater than or equal to the threshold value Dth (no in step S107), the process returns to step S100.
　出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈより小さいと判定した場合（ステップＳ１０７でｙｅｓ）、ステップＳ１０３で取得した出力信号レベルＤ（ｎ）の経過時間ｔ（ｎ）を、周期時間ｔｓに設定する（ステップＳ１０８）。 When the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the elapsed time t (n) of the output signal level D (n) acquired in step S103 is obtained. The cycle time ts is set (step S108).
　次に、解析部１３３は、出力信号レベルのピーク値Ｄｐｅａｋが、正常範囲（最小値Ｄｍｉｎから最大値Ｄｍａｘまで）に含まれるか否かを判定する（ステップＳ１０９）。ピーク値Ｄｐｅａｋは、加速度センサ１０１の感度と相関を有する。解析部１３３は、ピーク値Ｄｐｅａｋが正常範囲に含まれると判定した場合（ステップＳ１０９でｙｅｓ）、周期時間ｔｓが正常範囲（最小値ｔｍｉｎから最大値ｔｍａｘまで）に含まれるか否かを判定する（ステップＳ１１０）。周期時間ｔｓは、加速度センサ１０１の共振周波数と相関がある。 Next, the analysis unit 133 determines whether or not the peak value Dpeak of the output signal level is included in the normal range (from the minimum value Dmin to the maximum value Dmax) (step S109). The peak value Dpeak has a correlation with the sensitivity of the acceleration sensor 101. If the analysis unit 133 determines that the peak value Dpeak is included in the normal range (yes in step S109), the analysis unit 133 determines whether the cycle time ts is included in the normal range (from the minimum value tmin to the maximum value tmax). (Step S110). The period time ts has a correlation with the resonance frequency of the acceleration sensor 101.
　解析部１３３は、ピーク値Ｄｐｅａｋが正常範囲に含まれないと判定した場合（ステップＳ１０９でｎｏ）、加速度センサ１０１が異常である（故障している）と判定する（ステップＳ１１１）。解析部１３３は、例えば、診断結果Ｓ５として、センサが故障していることを示す情報を外部装置に出力する。診断結果Ｓ５は、ピーク値Ｄｐｅａｋを含んでいてもよい。 If the analysis unit 133 determines that the peak value Dpeak is not included in the normal range (no in step S109), the analysis unit 133 determines that the acceleration sensor 101 is abnormal (failed) (step S111). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5. The diagnosis result S5 may include a peak value Dpeak.
　解析部１３３は、周期時間ｔｓが正常範囲に含まれないと判定した場合（ステップＳ１１０でｎｏ）、加速度センサ１０１が異常である（故障している）と判定する（ステップＳ１１１）。解析部１３３は、例えば、診断結果Ｓ５として、センサが故障していることを示す情報を外部装置に出力する。診断結果Ｓ５は、周期時間ｔｓを含んでいてもよい。 If the analyzing unit 133 determines that the cycle time ts is not included in the normal range (no in step S110), the analyzing unit 133 determines that the acceleration sensor 101 is abnormal (failed) (step S111). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5. The diagnosis result S5 may include a cycle time ts.
　解析部１３３は、周期時間ｔｓが正常範囲に含まれると判定した場合（ステップＳ１１０でｙｅｓ）、加速度センサ１０１は正常であると判定する（ステップＳ１１２）。解析部１３３は、例えば、診断結果Ｓ５として、センサが正常であることを示す情報を外部装置に出力する。診断結果Ｓ５は、ピーク値Ｄｐｅａｋ及び周期時間ｔｓを含んでいてもよい。解析部１３３は、診断結果Ｓ５を出力しなくてもよい。そして、解析部１３３は、本フローチャートに示す処理を終了する。 If the analysis unit 133 determines that the cycle time ts is included in the normal range (yes in step S110), the analysis unit 133 determines that the acceleration sensor 101 is normal (step S112). For example, the analysis unit 133 outputs information indicating that the sensor is normal to the external device as the diagnosis result S5. The diagnosis result S5 may include a peak value Dpeak and a cycle time ts. The analysis unit 133 may not output the diagnosis result S5. And the analysis part 133 complete | finishes the process shown to this flowchart.
　なお、出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈより小さいと判定した場合（ステップＳ１０７でｙｅｓ）、停止信号を診断信号生成部１３１に出力する。このタイミングに限定されず、出力信号評価部１３２は、Ｓ１０７から本フローチャートの終了までの間に停止信号を出力すればよい。 If the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 131. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
　以上、本発明の第１実施形態について説明した。第１実施形態に係る加速度センサシステムは、自己診断モードの開始後、出力信号レベルが所定値を下回ったか否かを判定する。また、加速度センサシステムは、出力信号レベルが所定値を下回った場合に、自己診断信号を停止する。これにより、加速度センサシステムは、可動電極が平衡状態又はその近辺に戻ったタイミングで自己診断信号を停止させ、可動電極の振動の停止をより正確に制御し、かつ、自己診断の時間を短縮することができる。また、加速度センサシステムは、出力信号レベルがピーク値を過ぎ、且つ、出力信号レベルが所定値を下回った場合に、自己診断信号を停止する。これにより、加速度センサシステムは、可動電極をその共振周波数ｆ０の１周期分Ｔ０にできる限り近い期間（図３の例ではＴ１～Ｔ３の期間）変位させ、短い期間で自己診断を行うことができる。また、加速度センサシステムは、周波数掃引機能やピーク周波数検出機能などの大規模な論理回路を設ける必要がないため、消費電力を低減できる。 The first embodiment of the present invention has been described above. The acceleration sensor system according to the first embodiment determines whether or not the output signal level has fallen below a predetermined value after the start of the self-diagnosis mode. In addition, the acceleration sensor system stops the self-diagnosis signal when the output signal level falls below a predetermined value. Thereby, the acceleration sensor system stops the self-diagnosis signal at the timing when the movable electrode returns to the equilibrium state or the vicinity thereof, more accurately controls the stop of the vibration of the movable electrode, and shortens the self-diagnosis time. be able to. The acceleration sensor system stops the self-diagnosis signal when the output signal level exceeds the peak value and the output signal level falls below a predetermined value. As a result, the acceleration sensor system displaces the movable electrode by a period as close as possible to T 0 corresponding to one period of the resonance frequency f 0 (period T 1 to T 3 in the example of FIG. 3), and performs self-diagnosis in a short period. It can be carried out. In addition, since the acceleration sensor system does not require a large-scale logic circuit such as a frequency sweep function or a peak frequency detection function, power consumption can be reduced.
［第２実施形態］
　第２実施形態の加速度センサは、第１実施形態の加速度センサと電極構造が異なる。第１実施形態と異なる点を中心に説明する。 [Second Embodiment]
The acceleration sensor of the second embodiment is different in electrode structure from the acceleration sensor of the first embodiment. A description will be given centering on differences from the first embodiment.
　図５は、本発明の第２実施形態に係る加速度センサシステムの構成の一例を示すブロック図である。加速度センサシステムは、加速度センサ２０１と、信号検出部１０２と、サーボ制御部１１０と、検出信号生成部２２０と、自己診断部１３０と、出力部１４０と、モード切替部２５０とを含む。 FIG. 5 is a block diagram showing an example of the configuration of the acceleration sensor system according to the second embodiment of the present invention. The acceleration sensor system includes an acceleration sensor 201, a signal detection unit 102, a servo control unit 110, a detection signal generation unit 220, a self-diagnosis unit 130, an output unit 140, and a mode switching unit 250.
　加速度センサ２０１は、静電容量の変化を表す出力信号Ｓ１を信号検出部１０２に出力する。加速度センサ２０１については図６を参照して後に詳述する。 The acceleration sensor 201 outputs an output signal S1 indicating a change in capacitance to the signal detection unit 102. The acceleration sensor 201 will be described in detail later with reference to FIG.
　検出信号生成部２２０は、検出信号Ｓ７を生成し、加速度センサ２０１に出力する。検出信号Ｓ７は、加速度センサ２０１の後述する２組の固定電極のうち一方の組の固定電極に印加される。 The detection signal generation unit 220 generates a detection signal S7 and outputs it to the acceleration sensor 201. The detection signal S7 is applied to one set of fixed electrodes of two sets of fixed electrodes described later of the acceleration sensor 201.
　自己診断部１３０は、診断信号生成部２３１と、出力信号評価部１３２とを含む。また、自己診断部１３０は、解析部１３３を含む。診断信号生成部２３１は、モード切替部２５０の制御により自己診断モードが選択されると、自己診断信号Ｓ８を生成し、モード切替部２５０に出力する。自己診断信号Ｓ８は、変位信号を含み、検出信号を含まない。 The self-diagnosis unit 130 includes a diagnostic signal generation unit 231 and an output signal evaluation unit 132. In addition, the self-diagnosis unit 130 includes an analysis unit 133. When the self-diagnosis mode is selected by the control of the mode switching unit 250, the diagnostic signal generation unit 231 generates a self-diagnosis signal S8 and outputs the self-diagnosis signal S8 to the mode switching unit 250. The self-diagnosis signal S8 includes a displacement signal and does not include a detection signal.
　モード切替部２５０は、サーボ制御部１１０からのサーボ信号Ｓ６と、自己診断部１３０からの自己診断信号Ｓ８とを受信する。モード切替部２５０は、これらの２種類の信号の中から、選択した動作モードに対応する１つの信号を選択し、選択した信号を信号Ｓ２として加速度センサ２０１に出力する。すなわち、信号Ｓ２は、サーボ信号Ｓ６、及び自己診断信号Ｓ８のいずれか１つからなる。信号Ｓ２は、加速度センサ２０１の後述する２組の固定電極のうち他方の組の固定電極に印加される。 The mode switching unit 250 receives the servo signal S6 from the servo control unit 110 and the self-diagnosis signal S8 from the self-diagnosis unit 130. The mode switching unit 250 selects one signal corresponding to the selected operation mode from these two types of signals, and outputs the selected signal to the acceleration sensor 201 as a signal S2. That is, the signal S2 includes any one of the servo signal S6 and the self-diagnosis signal S8. The signal S <b> 2 is applied to the other set of fixed electrodes of the acceleration sensor 201, which will be described later.
　第２実施形態の加速度センサシステムは、２つの動作モードとして、サーボ制御モード（本発明の第１のモードに相当する）と、自己診断モード（本発明の第２のモードに相当する）とを有する。サーボ信号Ｓ６は、サーボ制御モードにおいて選択される。自己診断信号Ｓ８は、自己診断モードにおいて選択される。検出信号Ｓ７は、いずれの動作モードが選択されていても、加速度センサ２０１に出力される。 The acceleration sensor system of the second embodiment has two operation modes: a servo control mode (corresponding to the first mode of the present invention) and a self-diagnosis mode (corresponding to the second mode of the present invention). Have. The servo signal S6 is selected in the servo control mode. The self-diagnosis signal S8 is selected in the self-diagnosis mode. The detection signal S7 is output to the acceleration sensor 201 regardless of which operation mode is selected.
　モード切替部２５０は、任意のタイミングでサーボ制御モードを自己診断モードに切り替える。モード切替部２５０は、例えば、通常測定期間（サーボ制御モード含む期間）が所定の時間を超えたか否かを判定し、超えた場合にサーボ制御モードを自己診断モードに切り替えることができる。また、モード切替部２５０は、例えば、他のセンサ（図示せず）により計測された環境温度や環境湿度などの値を取得し、当該値が所定の閾値を超えた又は下回った場合に自己診断モードに切り替えてもよい。 The mode switching unit 250 switches the servo control mode to the self-diagnosis mode at an arbitrary timing. The mode switching unit 250 can determine, for example, whether or not the normal measurement period (period including the servo control mode) exceeds a predetermined time, and can switch the servo control mode to the self-diagnosis mode when it exceeds. For example, the mode switching unit 250 acquires values such as environmental temperature and environmental humidity measured by other sensors (not shown), and performs self-diagnosis when the value exceeds or falls below a predetermined threshold value. You may switch to the mode.
　モード切替部２５０は、自己診断モードを選択した後、自己診断部１３０からの自己診断信号Ｓ８が停止したか否かを判定し、停止した場合、自己診断モードを通常測定（サーボ制御モード）に切り替える。 After selecting the self-diagnosis mode, the mode switching unit 250 determines whether or not the self-diagnosis signal S8 from the self-diagnosis unit 130 has stopped, and if so, the self-diagnosis mode is changed to normal measurement (servo control mode). Switch.
　図６は、第２実施形態おける加速度センサの構造の一例を説明する図である。図６は、説明のための方向として、Ｘ方向（左右方向）及びＺ方向（上下方向）を示す。 FIG. 6 is a diagram illustrating an example of the structure of the acceleration sensor according to the second embodiment. FIG. 6 shows the X direction (left-right direction) and the Z direction (up-down direction) as directions for explanation.
　加速度センサ２０１は、一対の固定電極２０１１ａ及び固定電極２０１１ｂと、一対の固定電極２０１２ａ及び固定電極２０１２ｂと、１つの可動電極２０１３とを備える。固定電極２０１１ａ及び固定電極２０１１ｂは、信号線を通じて、検出信号生成部２２０に接続されている。固定電極２０１２ａ及び固定電極２０１２ｂは、信号線を通じて、モード切替部２５０に接続されている。可動電極２０１３は、信号線を通じて信号検出部１０２に接続されている。 The acceleration sensor 201 includes a pair of fixed electrodes 2011a and 2011b, a pair of fixed electrodes 2012a and 2012b, and one movable electrode 2013. The fixed electrode 2011a and the fixed electrode 2011b are connected to the detection signal generation unit 220 through a signal line. The fixed electrode 2012a and the fixed electrode 2012b are connected to the mode switching unit 250 through a signal line. The movable electrode 2013 is connected to the signal detection unit 102 through a signal line.
　可動電極２０１３は、Ｘ方向において広い主面を有する。固定電極２０１１ａ及び固定電極２０１１ｂは、Ｚ方向で平面視した場合に可動電極２０１３の主面の一部（Ｘ方向の一端）に対して重なる面領域を含む。固定電極２０１１ａの面領域及び固定電極２０１１ｂの面領域は、それぞれ、可動電極２０１３の前記一端の両側の対応する主面に対して面するように、Ｚ方向に所定の距離を置いて配置されている。固定電極２０１２ａ及び固定電極２０１２ｂは、Ｚ方向で平面視した場合に可動電極２０１３の主面の一部（Ｘ方向の他端）に対して重なる面領域を含む。固定電極２０１２ａの面領域及び固定電極２０１２ｂの面領域は、それぞれ、可動電極２０１３の前記他端の両側の対応する主面に対して面するように、Ｚ方向に所定の距離を置いて配置されている。 The movable electrode 2013 has a wide main surface in the X direction. The fixed electrode 2011a and the fixed electrode 2011b include a surface region that overlaps a part of the main surface of the movable electrode 2013 (one end in the X direction) when viewed in plan in the Z direction. The surface area of the fixed electrode 2011a and the surface area of the fixed electrode 2011b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the one end of the movable electrode 2013, respectively. Yes. The fixed electrode 2012a and the fixed electrode 2012b include a surface region that overlaps a part of the main surface of the movable electrode 2013 (the other end in the X direction) when viewed in plan in the Z direction. The surface area of the fixed electrode 2012a and the surface area of the fixed electrode 2012b are arranged at a predetermined distance in the Z direction so as to face the corresponding main surfaces on both sides of the other end of the movable electrode 2013, respectively. ing.
　固定電極２０１１ａ及び固定電極２０１１ｂの信号線は、検出信号Ｓ７を伝送する。固定電極２０１２ａ及び固定電極２０１２ｂの信号線は、動作モードに応じた信号Ｓ２（サーボ信号Ｓ６、又は自己診断信号Ｓ８）を伝送する。 The signal lines of the fixed electrode 2011a and the fixed electrode 2011b transmit the detection signal S7. The signal lines of the fixed electrode 2012a and the fixed electrode 2012b transmit a signal S2 (servo signal S6 or self-diagnosis signal S8) corresponding to the operation mode.
　検出信号Ｓ７は、詳細には、固定電極２０１１ａに印加される検出信号Ｓ７ａと、固定電極２０１１ｂに印加される検出信号Ｓ７ｂとから成る。 Specifically, the detection signal S7 includes a detection signal S7a applied to the fixed electrode 2011a and a detection signal S7b applied to the fixed electrode 2011b.
　サーボ信号Ｓ６は、詳細には、固定電極２０１２ａに印加されるサーボ信号Ｓ６ａと、固定電極２０１２ｂに印加されるサーボ信号Ｓ６ｂとから成る。 Specifically, the servo signal S6 includes a servo signal S6a applied to the fixed electrode 2012a and a servo signal S6b applied to the fixed electrode 2012b.
　自己診断信号Ｓ８は、詳細には、固定電極２０１２ａに印加される自己診断信号Ｓ８ａと、固定電極２０１２ｂに印加される自己診断信号Ｓ８ｂとから成る。また、自己診断信号Ｓ８ａは、可動電極２０１３を変位させるための変位信号Ｓ８ｃ（図示せず）を含む。自己診断信号Ｓ８ｂは、変位信号Ｓ８ｃに対応する変位信号Ｓ８ｄ（図示せず）を含む。 The self-diagnosis signal S8 includes a self-diagnosis signal S8a applied to the fixed electrode 2012a and a self-diagnosis signal S8b applied to the fixed electrode 2012b. The self-diagnosis signal S8a includes a displacement signal S8c (not shown) for displacing the movable electrode 2013. Self-diagnosis signal S8b includes a displacement signal S8d (not shown) corresponding to displacement signal S8c.
　可動電極２０１３の信号線は、出力信号Ｓ１を伝送する。加速度に応じた可動電極２０１３のＺ方向の位置の変化（図中のｄ）は、固定電極２０１１ａ及び固定電極２０１１ｂと可動電極２０１３との間の静電容量Ｃ１及びＣ２を変化させる。出力信号Ｓ１は、静電容量差ｄｅｌｔａＣを含む静電容量変化を表す電圧信号である。 The signal line of the movable electrode 2013 transmits the output signal S1. A change in the position of the movable electrode 2013 in the Z direction according to the acceleration (d in the figure) changes the capacitances C1 and C2 between the fixed electrode 2011a and the fixed electrode 2011b and the movable electrode 2013. The output signal S1 is a voltage signal representing a change in capacitance including the capacitance difference deltaC.
　上記の加速度センサ２０１の電極構造は、サーボ信号Ｓ６及び自己診断信号Ｓ８が時分割で切り替えて印加されると共に、検出信号Ｓ７が常に加速度センサ２０１に印加される。これにより、可動電極２０１３の変位を動作モードに関わらず継続的に測定することができる。 In the electrode structure of the acceleration sensor 201, the servo signal S6 and the self-diagnosis signal S8 are switched in a time division manner and the detection signal S7 is always applied to the acceleration sensor 201. Thereby, the displacement of the movable electrode 2013 can be continuously measured regardless of the operation mode.
　図７は、第２実施形態における加速度センサへの入力信号及び加速度センサからの出力信号のタイミングの一例を示すタイミングチャートである。 FIG. 7 is a timing chart showing an example of the timing of the input signal to the acceleration sensor and the output signal from the acceleration sensor in the second embodiment.
　通常測定の期間では、上述したように、サーボ制御モードが選択される。具体的には、サーボ信号Ｓ６が加速度センサ２０１に印加される。検出信号Ｓ７も、加速度センサ２０１に印加される。これにより、可動電極の位置が平衡状態に維持されるとともに静電容量変化に応じた信号が出力される。 In the normal measurement period, the servo control mode is selected as described above. Specifically, the servo signal S6 is applied to the acceleration sensor 201. The detection signal S7 is also applied to the acceleration sensor 201. As a result, the position of the movable electrode is maintained in an equilibrium state, and a signal corresponding to the change in capacitance is output.
　自己診断モードは、上述したように、モード切替部２５０により選択されることで開始される。具体的には、自己診断モードでは、診断信号生成部２３１は、変位信号Ｓ８ｃ及び変位信号Ｓ８ｄを加速度センサ２０１に出力する。検出信号Ｓ７も、加速度センサ２０１に印加される。これにより、可動電極の位置が変位するとともに静電容量変化に応じた信号が出力される。 The self-diagnosis mode is started by being selected by the mode switching unit 250 as described above. Specifically, in the self-diagnosis mode, the diagnostic signal generation unit 231 outputs the displacement signal S8c and the displacement signal S8d to the acceleration sensor 201. The detection signal S7 is also applied to the acceleration sensor 201. As a result, the position of the movable electrode is displaced and a signal corresponding to the change in capacitance is output.
　可動電極のＱ値が０．５よりも高い場合、この可動電極の位置は、直流電圧を印加すると、平衡状態から離れるように徐々に変位し（Ｔ１からＴ２）、ピーク（Ｔ２）に達した後、徐々に平衡状態に戻るように徐々に変位する（Ｔ２からＴ３）。 When the Q value of the movable electrode is higher than 0.5, when the DC voltage is applied, the position of the movable electrode is gradually displaced away from the equilibrium state (T 1 to T 2 ), and the peak (T 2 ). After reaching the value, it is gradually displaced so as to gradually return to the equilibrium state (T 2 to T 3 ).
　第１実施形態と同様に、出力信号評価部１３２は、自己診断モードの期間に出力される出力信号に基づいて、可動電極の平衡状態からの変位レベルＤ（ｎ）を繰り返し測定する。また、出力信号評価部１３２は、測定した各変位レベルＤ（ｎ）について、閾値Ｄｔｈを下回ったか否かを判定する。変位レベルＤ（ｎ）が閾値Ｄｔｈを下回った場合、出力信号評価部１３２は、停止信号を診断信号生成部２３１に出力する。 As in the first embodiment, the output signal evaluation unit 132 repeatedly measures the displacement level D (n) from the equilibrium state of the movable electrode based on the output signal output during the self-diagnosis mode. Further, the output signal evaluation unit 132 determines whether or not each measured displacement level D (n) is less than the threshold value Dth. When the displacement level D (n) falls below the threshold value Dth, the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 231.
　図８は、第２実施形態に係る自己診断処理の一例を示すフローチャートである。図８は、自己診断モードが開始された場合を示している。図４と異なる点を中心に説明する。 FIG. 8 is a flowchart showing an example of self-diagnosis processing according to the second embodiment. FIG. 8 shows a case where the self-diagnosis mode is started. A description will be given centering on differences from FIG.
　まず、診断信号生成部２３１は、変位信号の出力を開始する（ステップＳ２０１）。次に、診断信号生成部２３１は、ｎを１インクリメントする（ステップＳ２０２）。次に、出力信号評価部１３２は、検出信号に応じて加速度センサ２０１から信号検出部１０２を介して出力された出力信号レベルＤ（ｎ）を取得する（ステップＳ２０３）。ステップＳ２０３では、出力信号評価部１３２は、出力信号レベルＤ（ｎ）を取得した時刻、すなわち経過時間ｔ（ｎ）を取得する。 First, the diagnostic signal generator 231 starts outputting a displacement signal (step S201). Next, the diagnostic signal generation unit 231 increments n by 1 (step S202). Next, the output signal evaluation unit 132 acquires the output signal level D (n) output from the acceleration sensor 201 via the signal detection unit 102 in accordance with the detection signal (step S203). In step S203, the output signal evaluation unit 132 acquires the time when the output signal level D (n) is acquired, that is, the elapsed time t (n).
　ステップＳ１０４～Ｓ１１２の処理は、図４と同様である。なお、出力信号評価部１３２は、出力信号レベルＤ（ｎ）が出力信号レベルＤ（ｎ－１）を超えると判定した場合（ステップＳ１０４でｎｏ）、処理をステップＳ２０２に戻す。出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈ以上であると判定した場合（ステップＳ１０７でｎｏ）、処理をステップＳ２０２に戻す。出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈより小さいと判定した場合（ステップＳ１０７でｙｅｓ）、ステップＳ２０３で取得した出力信号レベルＤ（ｎ）の経過時間ｔ（ｎ）を、周期時間ｔｓに設定する。出力信号評価部１３２は、出力信号レベルＤ（ｎ）が閾値Ｄｔｈより小さいと判定した場合（ステップＳ１０７でｙｅｓ）、停止信号を診断信号生成部２３１に出力する。このタイミングに限定されず、出力信号評価部１３２は、Ｓ１０７から本フローチャートの終了までの間に停止信号を出力すればよい。 The processing in steps S104 to S112 is the same as in FIG. When the output signal evaluation unit 132 determines that the output signal level D (n) exceeds the output signal level D (n−1) (no in step S104), the process returns to step S202. When the output signal evaluation unit 132 determines that the output signal level D (n) is equal to or higher than the threshold value Dth (no in step S107), the process returns to step S202. When the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the elapsed time t (n) of the output signal level D (n) acquired in step S203 is determined. , And set to the cycle time ts. When the output signal evaluation unit 132 determines that the output signal level D (n) is smaller than the threshold value Dth (yes in step S107), the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit 231. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
　以上、本発明の第２実施形態について説明した。第２実施形態に係る加速度センサシステムは、第１実施形態と同様の効果に加え、次の効果を得ることができる。加速度センサシステムは、自己診断モードの開始後、変位信号を連続的に可動電極に印加するとともに、可動電極の変位を連続的に測定する。これにより、ピーク値や周期時間などのセンサ特性の評価精度及び診断精度を向上することができる。第１実施形態の加速度センサシステムでは、自己診断モードにおいて、変位期間と検出期間が時分割され、可動電極の変位が間欠的に検出される。 The second embodiment of the present invention has been described above. The acceleration sensor system according to the second embodiment can obtain the following effects in addition to the same effects as those of the first embodiment. The acceleration sensor system continuously applies a displacement signal to the movable electrode after the start of the self-diagnosis mode and continuously measures the displacement of the movable electrode. Thereby, the evaluation accuracy and diagnosis accuracy of sensor characteristics such as peak value and cycle time can be improved. In the acceleration sensor system of the first embodiment, in the self-diagnosis mode, the displacement period and the detection period are time-divided, and the displacement of the movable electrode is intermittently detected.
［第３実施形態］
　第１実施形態及び第２実施形態の加速度センサシステムは、共振周波数に係る特性（ピーク値及び周期時間）を使って自己診断を行う。第３実施形態は、共振周波数に係る特性としてＱ値を測定して、これを用いて自己診断を行うことで、加速度センサの診断精度を向上する。第１実施形態及び第２実施形態と異なる点を中心に説明する。 [Third Embodiment]
The acceleration sensor system according to the first embodiment and the second embodiment performs self-diagnosis using characteristics (peak value and cycle time) related to the resonance frequency. In the third embodiment, the Q value is measured as a characteristic related to the resonance frequency, and self-diagnosis is performed using the measured Q value, thereby improving the diagnostic accuracy of the acceleration sensor. The description will focus on the differences from the first and second embodiments.
　まず、Ｑ値の導出方法について説明する。図９は、診断信号を印加した場合の可動電極の変位の一例を説明する図である。 First, a method for deriving the Q value will be described. FIG. 9 is a diagram for explaining an example of the displacement of the movable electrode when a diagnostic signal is applied.
　可動電極変位ｘ（ｔ）は、例えば式（１）に従って変化する。ｆ０は加速度センサの共振周波数を表し、Ｑは可動電極のＱ値を表し、ｔは自己診断信号Ｓ８の印加の開始からの経過時間を表し、ｘ０は比例定数を表す。ｔ１（＝０）では、可動電極変位ｘは０である。 The movable electrode displacement x (t) varies according to, for example, the equation (1). f 0 represents the resonance frequency of the acceleration sensor, Q represents the Q value of the movable electrode, t represents the elapsed time from the start of application of the self-diagnosis signal S8, and x 0 represents the proportionality constant. At t 1 (= 0), the movable electrode displacement x is zero.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
　ｔ２では、可動電極変位ｘはピークに達する。このときのｔ２及び可動電極変位ｘは、それぞれ、例えば式（２）及び式（３）で表される。 In t 2, the movable electrode displacement x reaches a peak. At this time, t 2 and the movable electrode displacement x are expressed by, for example, Expression (2) and Expression (3), respectively.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　さらに時間が経過すると、可動電極変位ｘは０に向かって戻り始める。ｔ３では、可動電極変位ｘは、自己診断開始時の位置０に最も近づく。このときのｔ３及び可動電極変位ｘは、それぞれ、例えば式（４）及び式（５）で表される。 As time further elapses, the movable electrode displacement x starts to return toward zero. In t 3, the movable electrode displacement x is closest to the position 0 at the self-diagnosis starting. T 3 and the movable electrode displacement x at this time are respectively represented by, for example, equations (4) and (5).
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
　式（４）から分かるように、ｔ３は，ｆ０およびＱに応じて変化する。ただし、ｔ３は、Ｑが５以上のとき、ほぼ共振周波数ｆ０の逆数に等しくなる。このような関係に基づいて、時間ｔ３から共振周波数ｆ０を導出することができる。また、式（５）から分かるように、ｔ３における可動電極変位ｘは、Ｑに応じて変化する。このような関係に基づいて、ｔ３における可動電極変位ｘからＱ値を導出することができる。 As can be seen from equation (4), t 3 varies according to f 0 and Q. However, t 3 is approximately equal to the reciprocal of the resonance frequency f 0 when Q is 5 or more. Based on such a relationship, the resonance frequency f 0 can be derived from the time t 3 . Further, as can be seen from the equation (5), the movable electrode displacement x at t 3 changes according to Q. Based on this relationship, you are possible to derive the Q value from the movable electrode displacement x in t 3.
　図４又は図８を参照しながら、自己診断部１３０の処理を説明する。 The processing of the self-diagnosis unit 130 will be described with reference to FIG. 4 or FIG.
　出力信号評価部１３２は、ステップＳ１０７において、可動電極変位ｘが極小に達したか否かを判定する。例えば、出力信号評価部１３２は、出力信号レベルＤ（ｎ）の微分値を算出し、微分値が０であるか否かを判定する。あるいは、出力信号評価部１３２は、前回の出力信号レベルＤ（ｎ－１）の微分値が負の値であり且つ今回の出力信号レベルＤ（ｎ）の微分値が正の値であるか否かを判定してもよい。出力信号評価部１３２は、出力信号レベルＤ（ｎ）の微分値が０である、又は前回の微分値が負であり且つ今回の微分値が正であると判定した場合、処理をステップＳ１０８に進め、この場合以外は、処理をステップＳ１００又はステップＳ２０２に戻す。 In step S107, the output signal evaluation unit 132 determines whether or not the movable electrode displacement x has reached a minimum. For example, the output signal evaluation unit 132 calculates a differential value of the output signal level D (n) and determines whether or not the differential value is zero. Alternatively, the output signal evaluation unit 132 determines whether the differential value of the previous output signal level D (n−1) is a negative value and the differential value of the current output signal level D (n) is a positive value. It may be determined. If the output signal evaluation unit 132 determines that the differential value of the output signal level D (n) is 0, or the previous differential value is negative and the current differential value is positive, the process proceeds to step S108. In other cases, the process returns to step S100 or step S202.
　出力信号評価部１３２は、ステップＳ１０８において、極小に達したと判定した可動電極変位ｘの経過時間ｔ（ｎ）を、周期時間ｔｓに設定する。ｔｓは、上述の式（５）におけるｔ３に相当する。Ｄ（ｎ）は、上述の式（５）における可動電極変位ｘ（ｔ３）に相当する。また、出力信号評価部１３２は、Ｑ値を算出する。出力信号評価部１３２は、例えば、出力信号評価部１３２により算出されたｔ３における可動電極変位ｘを上述の式（５）に代入して、Ｑを算出する。 The output signal evaluation unit 132 sets the elapsed time t (n) of the movable electrode displacement x determined to have reached the minimum in step S108 as the cycle time ts. ts corresponds to t 3 in the above equation (5). D (n) corresponds to the movable electrode displacement x (t 3 ) in the above equation (5). Further, the output signal evaluation unit 132 calculates the Q value. For example, the output signal evaluation unit 132 calculates Q by substituting the movable electrode displacement x at t 3 calculated by the output signal evaluation unit 132 into the above equation (5).
　なお、出力信号評価部１３２は、可動電極変位ｘが極小に達したと判定した場合、停止信号を診断信号生成部に出力する。このタイミングに限定されず、出力信号評価部１３２は、Ｓ１０７から本フローチャートの終了までの間に停止信号を出力すればよい。 When the output signal evaluation unit 132 determines that the movable electrode displacement x has reached a minimum, the output signal evaluation unit 132 outputs a stop signal to the diagnostic signal generation unit. Without being limited to this timing, the output signal evaluation unit 132 may output a stop signal between S107 and the end of this flowchart.
　解析部１３３は、ステップＳ１０９及びＳ１１０に加えて、上述のように算出されたＱ値が、正常範囲に含まれるか否かを判定する。解析部１３３は、Ｑ値が正常範囲に含まれないと判定した場合、加速度センサが異常である（故障している）と判定する。解析部１３３は、例えば、診断結果Ｓ５として、センサが故障していることを示す情報を外部装置に出力する。診断結果Ｓ５は、Ｑ値を含んでいてもよい。解析部１３３は、ピーク値、周期時間、及びＱ値が全て対応する正常範囲に含まれる判定した場合、例えば、診断結果Ｓ５として、センサが正常であることを示す情報を外部装置に出力する。診断結果Ｓ５は、Ｑ値を含んでいてもよい。解析部１３３は、診断結果Ｓ５を出力しなくてもよい。 The analysis unit 133 determines whether or not the Q value calculated as described above is included in the normal range in addition to steps S109 and S110. When determining that the Q value is not included in the normal range, the analysis unit 133 determines that the acceleration sensor is abnormal (failed). For example, the analysis unit 133 outputs information indicating that the sensor has failed to the external device as the diagnosis result S5. The diagnosis result S5 may include a Q value. When the analysis unit 133 determines that the peak value, the cycle time, and the Q value are all included in the corresponding normal range, for example, as the diagnosis result S5, the analysis unit 133 outputs information indicating that the sensor is normal to the external device. The diagnosis result S5 may include a Q value. The analysis unit 133 may not output the diagnosis result S5.
　以上、本発明の第３実施形態について説明した。第３実施形態に係る加速度センサシステムは、自己診断モードの開始後、可動電極の変位が極小に達した場合に、自己診断信号を停止する。これにより、第１実施形態及び第２実施形態のように出力信号レベルと所定値を比較する場合と比べて、可動電極が平衡状態又はその近辺に戻ったタイミングをより精度よく判定し、可動電極の振動の停止をより正確に制御し、かつ、自己診断の時間を短縮することができる。また、加速度センサシステムは、共振周波数に係る特性として、ピーク値及び周期時間に加えてＱ値を測定して、これを用いて自己診断を行う。これにより、加速度センサの診断精度を向上することができる。 The third embodiment of the present invention has been described above. The acceleration sensor system according to the third embodiment stops the self-diagnosis signal when the displacement of the movable electrode reaches a minimum after the start of the self-diagnosis mode. Thereby, compared with the case where the output signal level is compared with the predetermined value as in the first embodiment and the second embodiment, the timing at which the movable electrode returns to the equilibrium state or its vicinity is determined with higher accuracy. It is possible to more accurately control the stop of vibration and to shorten the time for self-diagnosis. Further, the acceleration sensor system measures the Q value in addition to the peak value and the period time as the characteristic relating to the resonance frequency, and performs self-diagnosis using this. Thereby, the diagnostic accuracy of the acceleration sensor can be improved.
　本発明は、上述の実施形態に限定されず、本発明の要旨の範囲内で種々の変形実施が可能である。 The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the present invention.
　上述の各実施形態の加速度センサシステムは、可動電極の共振の１周期を測定し、その１周期のピーク値等の特性に基づいて診断を行う。もちろん、加速度センサシステムは、Ｎ周期（Ｎは１より大きい整数）における可動電極のピーク値等の特性を測定してもよい。この場合、自己診断時間は長くなるが、特性をより正確に測定することができる。 The acceleration sensor system of each embodiment described above measures one period of resonance of the movable electrode and performs diagnosis based on characteristics such as a peak value of the one period. Of course, the acceleration sensor system may measure characteristics such as a peak value of the movable electrode in N cycles (N is an integer greater than 1). In this case, the self-diagnosis time becomes longer, but the characteristics can be measured more accurately.
　上述の第３実施形態の加速度センサシステムは、可動電極変位ｘが極小に達したか否かを判定する一方で、Ｑ値を算出しなくてもよい。また、第３実施形態の加速度センサシステムは、ピーク値、周期時間、及びＱ値のうち少なくとも１つを評価してもよい。第１実施形態及び第２実施形態の加速度センサシステムは、ピーク値、及び周期時間の少なくとも１つを評価してもよい。 The acceleration sensor system of the third embodiment described above does not have to calculate the Q value while determining whether or not the movable electrode displacement x has reached a minimum. The acceleration sensor system according to the third embodiment may evaluate at least one of the peak value, the period time, and the Q value. The acceleration sensor system according to the first embodiment and the second embodiment may evaluate at least one of a peak value and a cycle time.
　上述の各実施形態の加速度センサシステムは、１つの加速度センサを含む。もちろん、加速度センサシステムは、複数の加速度センサを含んでもよい。この場合、加速度センサシステムは、複数の加速度センサについて自己診断を行えばよい。また、複数の加速度センサを複数のグループに分け、加速度センサシステムは、時分割により各グループに対して異なるタイミングで自己診断を実行してもよい。このようにすれば、システム全体を停止することなく加速度を計測することができる。 The acceleration sensor system of each embodiment described above includes one acceleration sensor. Of course, the acceleration sensor system may include a plurality of acceleration sensors. In this case, the acceleration sensor system may perform self-diagnosis for a plurality of acceleration sensors. Further, the plurality of acceleration sensors may be divided into a plurality of groups, and the acceleration sensor system may execute self-diagnosis at different timings for each group by time division. In this way, acceleration can be measured without stopping the entire system.
　図４及び図８で示したフローチャートの処理単位は、自己診断処理を理解容易にするために、主な処理内容に応じて分割したものである。処理単位の分割の仕方や名称によって、本願発明が制限されることはない。自己診断処理は、処理内容に応じて、さらに多くの処理単位に分割することもできる。また、１つの処理単位がさらに多くの処理を含むように分割することもできる。さらに、本発明の目的及び効果を達成できるのであれば、上記のフローチャートの処理順序も、図示した例に限られるものではない。 The processing units of the flowcharts shown in FIGS. 4 and 8 are divided according to the main processing contents in order to make the self-diagnosis processing easy to understand. The present invention is not limited by the way of dividing the processing unit or the name. The self-diagnosis process can be divided into more processing units according to the processing content. Moreover, it can also divide | segment so that one process unit may contain many processes. Furthermore, the processing order of the above flowchart is not limited to the illustrated example as long as the object and effect of the present invention can be achieved.
　本発明は、上記した実施形態に限定されるものではなく、様々な変形例が含まれる。例えば、上記した各実施形態は、本発明を分かりやすく説明するために詳細に説明したものであり、本発明が、必ずしも説明した全ての構成要素を備えるものに限定されるものではない。また、ある実施形態の構成の一部を、他の実施形態の構成に置き換えることが可能であり、ある実施形態の構成に、他の実施形態の構成を加えることも可能である。また、各実施形態の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 The present invention is not limited to the above-described embodiment, and includes various modifications. For example, each of the above-described embodiments has been described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to the one provided with all the constituent elements described. In addition, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
　上記した各構成、機能、処理部、処理手段等は、それらの一部または全部を、例えば集積回路で設計する等によりハードウェアで実現してもよい。また、上記の各構成、機能等は、プロセッサがそれぞれの機能を実現するプログラムを解釈し、実行することによりソフトウェアで実現されてもよい。各機能を実現するプログラム、テーブル、ファイル等の情報は、メモリーや、ハードディスク、SSD(Solid State Drive)等の記録装置、または、ＩＣカード、ＳＤカード、ＤＶＤ等の記録媒体に置くことができる。また、制御線や情報線は説明上必要と考えられるものを示しており、製品上必ずしも全ての制御線や情報線を示しているとは限らない。実際には殆ど全ての構成が相互に接続されていると考えてもよい。 The above-described configurations, functions, processing units, processing means, and the like may be realized in hardware by designing a part or all of them, for example, with an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by the processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.
１０１…加速度センサ、１０２…信号検出部、１１０…サーボ制御部、１２０…検出信号生成部、１３０…自己診断部、１３１…診断信号生成部、１３２…出力信号評価部、１３３…解析部、１４０…出力部、１４１…加速度出力部、１４２…解析部、１５０…モード切替部、２０１…加速度センサ、２２０…検出信号生成部、２３１…診断信号生成部、２５０…モード切替部、１０１１ａ…固定電極、１０１１ｂ…固定電極、１０１３…可動電極、２０１１ａ…固定電極、２０１１ｂ…固定電極、２０１２ａ…固定電極、２０１２ｂ…固定電極、２０１３…可動電極、Ｓ１…出力信号、Ｓ２…信号、Ｓ３…加速度情報、Ｓ４…解析情報、Ｓ５…診断結果、Ｓ６…サーボ信号、Ｓ６ａ…サーボ信号、Ｓ６ｂ…サーボ信号、Ｓ７…検出信号、Ｓ７ａ…検出信号、Ｓ７ｂ…検出信号、Ｓ８…自己診断信号、Ｓ８ａ…自己診断信号、Ｓ８ｂ…自己診断信号、Ｓ８ｃ…変位信号、Ｓ８ｄ…変位信号、Ｓ８ｅ…検出信号、Ｓ８ｆ…検出信号 DESCRIPTION OF SYMBOLS 101 ... Acceleration sensor 102 ... Signal detection part 110 ... Servo control part 120 ... Detection signal generation part 130 ... Self-diagnosis part 131 ... Diagnosis signal generation part 132 ... Output signal evaluation part 133 ... Analysis part 140 DESCRIPTION OF SYMBOLS ... Output part 141 ... Acceleration output part 142 ... Analysis part 150 ... Mode switching part 201 ... Acceleration sensor 220 ... Detection signal generation part 231 ... Diagnostic signal generation part 250 ... Mode switching part 1011a ... Fixed electrode 1011b ... fixed electrode, 1013 ... movable electrode, 2011a ... fixed electrode, 2011b ... fixed electrode, 2012a ... fixed electrode, 2012b ... fixed electrode, 2013 ... movable electrode, S1 ... output signal, S2 ... signal, S3 ... acceleration information, S4 ... analysis information, S5 ... diagnosis result, S6 ... servo signal, S6a ... servo signal, S6b ... servo signal, S7 ... detection signal, S a ... detection signal, S7b ... detection signal, S8 ... self signal, S8a ... self signal, S8b ... self signal, S8c ... displacement signal, S8d ... displacement signal, S8e ... detection signal, S8f ... detection signal

Claims (11)

  1. 　加速度センサシステムであって、
    　可動電極の変位に応じて静電容量変化を表す出力信号を出力するセンサと、
    　前記センサを診断するための自己診断信号を前記センサに出力する自己診断部と、を有し、
    　前記自己診断部は、前記可動電極を変位させるための変位信号を含む前記自己診断信号を出力し、前記出力信号のレベルに応じて前記自己診断信号の出力を停止する
    加速度センサシステム。     An acceleration sensor system,
    A sensor that outputs an output signal indicating a change in capacitance according to the displacement of the movable electrode;
    A self-diagnosis unit that outputs a self-diagnosis signal for diagnosing the sensor to the sensor,
    The self-diagnosis unit outputs the self-diagnosis signal including a displacement signal for displacing the movable electrode, and stops outputting the self-diagnosis signal according to the level of the output signal.
  2. 　請求項１に記載の加速度センサシステムであって、
    　前記自己診断部は、前記出力信号のレベルを複数回測定し、前記レベルが所定の閾値に達したか否かを判定し、前記レベルが前記所定の閾値に達した場合に、前記自己診断信号の出力を停止する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    The self-diagnosis unit measures the level of the output signal a plurality of times, determines whether the level has reached a predetermined threshold value, and when the level has reached the predetermined threshold value, the self-diagnosis signal Acceleration sensor system that stops the output of.
  3. 　請求項２に記載の加速度センサシステムであって、
    　前記自己診断部は、前記レベルがピーク値に達した後、前記レベルが前記所定の閾値に達した場合に、前記自己診断信号の出力を停止する
    加速度センサシステム。     The acceleration sensor system according to claim 2,
    The self-diagnosis unit is an acceleration sensor system that stops outputting the self-diagnosis signal when the level reaches the predetermined threshold after the level reaches a peak value.
  4. 　請求項２又は３に記載の加速度センサシステムであって、
    　前記所定の閾値は、前記レベルの極小値である
    加速度センサシステム。     The acceleration sensor system according to claim 2 or 3,
    The acceleration sensor system, wherein the predetermined threshold is a minimum value of the level.
  5. 　請求項１に記載の加速度センサシステムであって、
    　加速度の測定を行うための第１のモードと、
    　自己診断を行うための第２のモードと、
    　前記第１のモードと前記第２のモードとを相互に切り替えるモード切替部と、を有し、
    　前記モード切替部は、前記自己診断信号の出力が停止した場合に、前記第２モードを前記第１のモードに切り替える
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    A first mode for measuring acceleration;
    A second mode for self-diagnosis;
    A mode switching unit that switches between the first mode and the second mode;
    The mode switching unit is an acceleration sensor system that switches the second mode to the first mode when the output of the self-diagnosis signal is stopped.
  6. 　請求項１に記載の加速度センサシステムであって、
    　前記出力信号を得るための検出信号を前記センサに出力する検出信号生成部と、
    　サーボ制御のためのサーボ信号を前記センサに出力するサーボ制御部と、
    　前記検出信号及び前記サーボ信号が出力される第１のモードと、
    　前記自己診断信号が出力される第２のモードと、を有し、
    　前記自己診断部は、前記第２のモードにおいて、
    　前記変位信号と前記検出信号とを交互に含む前記自己診断信号を出力し、
    　前記検出信号に応じて得られた前記出力信号のレベルに応じて、前記自己診断信号の出力を停止する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    A detection signal generator for outputting a detection signal for obtaining the output signal to the sensor;
    A servo control unit for outputting a servo signal for servo control to the sensor;
    A first mode in which the detection signal and the servo signal are output;
    A second mode in which the self-diagnosis signal is output,
    In the second mode, the self-diagnosis unit is
    Outputting the self-diagnosis signal including the displacement signal and the detection signal alternately;
    An acceleration sensor system that stops the output of the self-diagnosis signal according to the level of the output signal obtained according to the detection signal.
  7. 　請求項１に記載の加速度センサシステムであって、
    　前記出力信号を得るための検出信号を前記センサに出力する検出信号生成部と、
    　サーボ制御のためのサーボ信号を前記センサに出力するサーボ信号生成部と、
    　前記検出信号及び前記サーボ信号が出力される第１のモードと、
    　前記検出信号及び前記自己診断信号が出力される第２のモードと、を有し、
    　前記自己診断部は、前記第２のモードにおいて、
    　前記検出信号に応じて得られた前記出力信号のレベルに応じて、前記自己診断信号の出力を停止する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    A detection signal generator for outputting a detection signal for obtaining the output signal to the sensor;
    A servo signal generator for outputting a servo signal for servo control to the sensor;
    A first mode in which the detection signal and the servo signal are output;
    A second mode in which the detection signal and the self-diagnosis signal are output;
    In the second mode, the self-diagnosis unit is
    An acceleration sensor system that stops the output of the self-diagnosis signal according to the level of the output signal obtained according to the detection signal.
  8. 　請求項１に記載の加速度センサシステムであって、
    　前記自己診断部は、
    　前記出力信号のレベルを複数回測定し、前記レベルが所定の閾値に達したか否かを判定し、前記レベルが前記所定の閾値に達した場合に、前記自己診断信号の出力を停止し、
    　前記自己診断信号の出力の開始後、前記レベルが前記所定の閾値に達するまでの時間を測定し、前記測定した時間と所定の時間範囲とを比較することにより、前記センサが正常か否かを判定する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    The self-diagnosis unit
    Measure the level of the output signal multiple times, determine whether the level has reached a predetermined threshold, and when the level has reached the predetermined threshold, stop outputting the self-diagnosis signal,
    After starting the output of the self-diagnosis signal, the time until the level reaches the predetermined threshold is measured, and the measured time is compared with a predetermined time range to determine whether the sensor is normal. Judgment acceleration sensor system.
  9. 　請求項１に記載の加速度センサシステムであって、
    　前記自己診断部は、
    　前記出力信号のレベルを複数回測定し、前記レベルが所定の閾値に達したか否かを判定し、前記レベルが前記所定の閾値に達した場合に、前記自己診断信号の出力を停止し、
    　前記自己診断信号の出力の開始後、前記レベルのピーク値を測定し、前記ピーク値と所定の値範囲とを比較することにより、前記センサが正常か否かを判定する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    The self-diagnosis unit
    Measure the level of the output signal multiple times, determine whether the level has reached a predetermined threshold, and when the level has reached the predetermined threshold, stop outputting the self-diagnosis signal,
    An acceleration sensor system that determines whether or not the sensor is normal by measuring a peak value of the level after the output of the self-diagnosis signal and comparing the peak value with a predetermined value range.
  10. 　請求項１に記載の加速度センサシステムであって、
    　前記自己診断部は、
    　前記出力信号のレベルを複数回測定し、前記レベルが所定の閾値に達したか否かを判定し、前記レベルが前記所定の閾値に達した場合に、前記自己診断信号の出力を停止し、
    　前記自己診断信号の出力の開始後、前記レベルが前記所定の閾値に達するまでの時間を測定し、前記測定した時間に基づいて前記センサのＱ値を算出し、前記Ｑ値と所定の値範囲とを比較することにより、前記センサが正常か否かを判定する
    加速度センサシステム。     The acceleration sensor system according to claim 1,
    The self-diagnosis unit
    Measure the level of the output signal multiple times, determine whether the level has reached a predetermined threshold, and when the level has reached the predetermined threshold, stop outputting the self-diagnosis signal,
    After the output of the self-diagnosis signal is started, a time until the level reaches the predetermined threshold is measured, a Q value of the sensor is calculated based on the measured time, and the Q value and a predetermined value range An acceleration sensor system that determines whether or not the sensor is normal by comparing
  11. 　可動電極の変位に応じて静電容量変化を表す出力信号を出力する加速度センサの自己診断方法であって、
    　前記加速度センサを診断するための自己診断信号を前記加速度センサに出力する自己診断工程を含み、
    　前記自己診断工程では、前記可動電極を変位させるための変位信号を含む前記自己診断信号が出力され、前記出力信号のレベルに応じて前記自己診断信号の出力が停止される
    自己診断方法。     A method of self-diagnosis of an acceleration sensor that outputs an output signal representing a change in capacitance according to displacement of a movable electrode,
    A self-diagnosis step of outputting a self-diagnosis signal for diagnosing the acceleration sensor to the acceleration sensor;
    In the self-diagnosis step, the self-diagnosis signal including a displacement signal for displacing the movable electrode is output, and the output of the self-diagnosis signal is stopped according to the level of the output signal.
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