JP2006292577A - Inertial sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the accuracy of measurement by inhibiting the migration of ions inside of a case 12 to remove destabilizing factor. <P>SOLUTION: The inertial sensor device equipped with a conductive rotor 11, an electric insulating case 12 a plurality of control electrodes 13 are formed, and a sensor circuit 20 calculating acceleration A, while making a control electrode 13 to produce electrostatic attraction to cancel the fluctuation by detecting those relative displacement, and generating the complementary voltage of both the positive and negative as control voltage to apply to adjacent electrodes 3a and 3b, includes a bias circuit 32 generating the complementary, constant bias voltage ±Vof of both the positive and negative capable of receiving transmitted electricity during shutdown of feeding to the sensor circuit 20 and a switching circuit 31 applying the bias voltage to the adjacent electrodes 3a and 3b instead of the control voltage during shutdown of feeding to the sensor circuit 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inertial sensor device having a movable body (movable part) driven by an electrostatic force (electrostatic attractive force), and is particularly suitable for an inertial sensor device manufactured by micromachine technology.

Conventionally, as this kind of inertial sensor device, a micro sensor that detects acceleration in only one direction (see, for example, Patent Document 1) or an electrostatic levitation gyro device that performs multi-directional acceleration detection (see, for example, Patent Documents 2 to 4). These are all known to have a conductive movable part, an electrically insulating fixed part having an electrode formed on the surface facing it, and a relative displacement of the movable part relative to the fixed part. And a sensor circuit that detects and calculates a measurement value such as acceleration calculation.
Among them, in the microsensor (Patent Document 1), a movable electrode as a movable portion is elastically supported by a cantilever in the middle of a fixed electrode formed on an opposing surface of a parallel insulating substrate which is a fixed portion. In the case of an electrostatic servo type sensor, it is a control electrode, and a control voltage that generates an electrostatic attractive force that eliminates the fluctuation of the relative displacement of the movable part is applied to the control electrode.

  Moreover, in the electrostatic levitation type gyro apparatus (Patent Documents 2 to 4), the gyro rotor as a movable part is formed in a disk shape (Patent Document 2) or an annular shape (Patent Documents 3 to 4), and is fixed. It is mounted in the vacuum space of the gyro case that is the part. The case is made of an electrically insulating member, and a large number of control electrodes are formed on the inner surface of the case that forms the rotor facing surface. Further, an electronic circuit as a sensor circuit is attached to the gyro mechanism portion constituted by them, and thereby, a relative displacement of the rotor with respect to the case is detected, and a control voltage that generates an electrostatic attractive force that eliminates the fluctuation is detected. Is applied to the control electrode, and measurement value calculation such as acceleration calculation is performed based on the detection result of relative displacement. In the case of the electrostatic levitation gyro apparatus, in addition to the attitude control control electrode, an electrode for rotationally driving the rotor and a detection electrode for detecting relative displacement are also provided on the inner surface of the case. As for the relative displacement detection method, there are a method of flowing a displacement detection signal from the control electrode to the detection electrode (Patent Documents 2 to 3), and a flow of the displacement detection signal from the detection electrode to the control electrode (patents). Reference 4).

  Among these, a specific example useful for explaining the present invention is an annular rotor type electrostatic levitation gyro device in which a sense circuit is mainly composed of a digital processor and a displacement detection signal is passed from the control electrode to the detection electrode. Is illustrated. 1A is a longitudinal end view of a gyro mechanism, FIG. 1B is a perspective view showing an electrode arrangement in the gyro mechanism, and FIG. 1C is a block diagram of a sensor circuit and the like. FIG. 2A is an example of a control voltage waveform when the sensor is operating, and FIG. 2B is an example of an applied voltage waveform when the sensor is stopped. In the illustration of the electrode arrangement, the control electrode for posture control and the detection electrode for displacement detection are specified, but the electrode for rotation drive is not necessary for the description of the present invention, and is omitted for the sake of simplicity.

  An annular rotor-type gyro mechanism 10 (see FIGS. 1A and 1B) includes an annular rotor 11 that is built in a case 12 in a state where it can electrostatically float and rotate. The case 12 is configured by combining an upper bottom member made of an insulator such as glass, a lower bottom member, and a spacer, and an annular vacuum space is formed therein. The rotor 11 is made of a conductor such as silicon and is formed in an annular shape so as to rotate stably around one spin axis. In order to apply an electrostatic attractive force from the case 12 to the rotor 11, a large number of electrodes 13 and 14 made of a metal film pattern or the like are formed on the inner surface of the case 12. The electrodes 13 and 14 are arranged so as to satisfy a predetermined relationship such as a distance to the rotor 11 and a pitch according to their roles.

  The electrodes 13 and 14 of the case 12 connected to the sensor circuit 20 will be described in detail. The electrodes 13 and 14 are divided into a plurality of pairs arranged opposite to each other with the rotor 11 interposed therebetween. In particular, the control electrode 13 for electrostatic support is further divided into pairs arranged adjacent to each other. For example, in the illustrated case, the adjacent control electrodes 3a and 3b in the upper bottom member form an adjacent pair, the adjacent control electrodes 3c and 3d in the lower bottom member also form an adjacent pair, and the adjacent electrodes 3a and 3b and the adjacent electrode 3c. , 3d form an opposing pair. The same applies to the other control electrodes 13. In this specification, when distinguishing individual electrodes in consideration of the adjacent state of the control electrodes, reference numerals such as 3a and 3b are given, and when all the control electrodes are described without regard to individual electrodes, 13 is used. The symbol is attached.

  In order to explain the specific role of these control electrodes 13, the three axes orthogonal to each other in the space are defined as the X axis, the Y axis, and the Z axis, respectively, and in FIG. The Y axis is placed in a direction penetrating the paper surface, the Z axis is placed in the vertical direction of the paper surface, the rotation around the X axis is φ, and the rotation around the Y axis is θ. Then, the control electrode 13 formed on the spacer in the case 12 and arranged in the X-axis direction is applied with a control voltage to generate an electrostatic attractive force in the X direction according to the applied voltage, and according to the displacement of the rotor 11 in the X direction. The capacitance with the rotor 11 is changed. The control electrode 13 formed in the spacer in the case 12 and arranged in the Y-axis direction performs the same function in the Y direction, and is formed in the upper bottom member and the lower bottom member in the case 12 and arranged in the Y-axis direction. The control electrode 13 exhibits the same function in the ± Z ± φ direction, and the control electrode 13 formed on the upper bottom member and the lower bottom member of the case 12 and arranged in the X-axis direction is related to the ± Z ± θ direction. The same function is demonstrated. Further subdividing, for example, the adjacent electrodes 3a and 3b are related to the + Z + φ direction, and the adjacent electrodes 3c and 3d are related to the −Z−φ direction.

  The sensor circuit 20 (see FIG. 1C) is connected to the control electrode 13 and the detection electrode 14 of the gyro case 12 and constitutes an electrostatic levitation type gyro together with the gyro mechanism unit 10 to detect displacement. A plurality of signals that can be discriminated in frequency are used as the signal for use, and these signals are superimposed on each control voltage, applied to the control electrode 13, and detected by the detection amplifier 21 from the detection electrode 14. The arithmetic unit 22 is digitized using a digital processor 24 composed of a digital signal processor or a microprocessor, and an A / D conversion circuit 23 (analog-digital conversion circuit) is provided on the input side of the output of the detection amplifier 21. A D / A conversion circuit 25 (digital-analog conversion circuit) is attached to the output side of the control amount that regulates the control voltage. Then, the relative displacement of the rotor 11 with respect to the case 12 is calculated from the detection value of the displacement detection signal, and the acceleration A is calculated from the relative displacement. The acceleration A is a typical example of a measurement value obtained by the inertial sensor device, and the measurement value may be a speed or a position.

  The calculation unit 22 is also configured to calculate a control amount for eliminating the fluctuation based on the detection result of the relative displacement, and the control amount is output via the D / A conversion circuit 25 to the output amplifier 26. , The corresponding control voltage is applied from the output amplifier 26 to the control electrode 13, thereby generating an electrostatic attractive force between the control electrode 13 forming portion of the case 12 and the portion facing the rotor 11. 11 and 12 are kept constant. Generation of such control voltage and calculation of acceleration A for gyro output (refer to Patent Document 2, FIG. 7, Patent Document 3, FIG. 9, Patent Document 4, FIG. 9 and the like), in the case of a gyro, five directions X, Y, First, the displacement in each direction is calculated from the detection signal for displacement detection (eg, ΔX, ΔY, ΔZ, Δθ, Δφ in FIG. 7 of Patent Document 2), and PID calculation is performed on it. After the necessary levitation force is calculated (for example, fX, fY, fZ, fθ, fφ in FIG. 7 of Patent Document 2), this is performed.

A control voltage for posture control is generated by distributing the calculated levitation force to each electrode in accordance with the arrangement and capacity of the control electrode 13 (for example, ± V1A to ± V4A in FIG. 7 of Patent Document 2), The acceleration for gyro output is calculated by converting the levitation force into external force acceleration according to the mass of the rotor 11 (for example, αX, αY, αZ, dθ in FIG. 7 of Patent Document 2). / Dt, dφ / dt).
The effective component of such a control voltage is approximately several tens of kHz or less for moving the rotor 11, whereas the displacement detection signal for measuring the relative displacement without affecting the movement of the rotor 11 is The frequency is sufficiently high, for example, a signal on the order of MHz, and the displacement detection signal generation circuit 27 has, for example, five frequency components, and is superimposed on the control voltage on the input side of the output amplifier 26. .

  Further, when generating each control voltage, the calculation unit 22 generates complementary voltages having different positive and negative for those applied to the control electrode forming the opposing pair and the control electrode forming the adjacent pair. ing. As a specific example, for the opposed pair of the adjacent electrodes 3a, 3b and the adjacent electrodes 3c, 3d among the six pairs of control electrodes 13 of the annular rotor type (see FIG. 1C), the control voltage The application state will be described in detail (see FIG. 2A). A constant offset voltage applied to the control electrode 13 when the rotor 11 is stationary at the neutral position apart from the rotation about the Z-axis is Vof, and is calculated and changed in the ± Z ± θ direction for posture control. When the control voltage component is Vx, the main component of the applied voltage V3a is −Vof−Vx, the main component of the applied voltage V3b is + Vof + Vx, the main component of the applied voltage V3c is −Vof + Vx, and the main component of the applied voltage V3d is The component is set to + Vof-Vx.

These applied voltages are affected by the fact that the high-frequency displacement detection signal is superimposed, but if the in-phase superimposed components at this high frequency are ignored, the applied voltages V3a and V3b of the adjacent electrodes 3a and 3b are reversed in polarity. The applied voltages V3c and V3d of the adjacent electrodes 3c and 3d are also complementary with waveforms having positive and negative inversions.
However, such a control voltage is applied when the operating power is supplied to the sensor circuit 20 and the sensor circuit 20 is operating normally. The power supply to the sensor circuit 20 is stopped and the sensor circuit 20 is stopped. When is not operating, the applied voltage V3a and the like of the control electrode 13 is 0 V (see FIG. 2B).

JP-A-5-172846 Japanese Patent Laid-Open No. 08-320231 JP 2001-235329 A JP 2004-191296 A

[Patent Document 5] Japanese Patent Application No. 2004-363704 The invention disclosed therein is an improvement of the above-described electrostatic levitation gyro apparatus (Patent Documents 2 to 4), and superimposes a displacement detection signal on each control voltage. At this time, the superimposition destination is time-divided, and the control voltage output is removed from the electrode to which the displacement detection signal is being applied. In addition, the measurement value calculation such as the acceleration calculation is not performed immediately from the detection result of the relative displacement, but the measurement value calculation such as the acceleration calculation is performed based on the control voltage for canceling the relative displacement. Therefore, the calculation of acceleration and the like lowers the operation speed with priority on accuracy, and the calculation of control amount and the like lowers the accuracy with priority on operation speed, thereby making the sensor circuit small and inexpensive.

  In short, in such an undisclosed inertial sensor device and the conventional inertial sensor device described above, the control voltage and the sense voltage (voltage of the displacement detection signal) are applied to the electrodes corresponding to each axis in a time-sharing or superimposed manner. Is done. The polarity of the sense voltage is reversed according to the direction of the coordinates. A charge having an amplitude corresponding to the position (relative displacement) of the rotor appears on the position detection electrode (detection electrode). This is converted into a voltage signal, and a control voltage is calculated. The control voltage is applied only during a period in which the sense voltage is not applied in the time division method, and is applied together with the sense voltage in the superposition method. The force applied to the rotor is calculated from the voltage applied to the electrodes or from the detected position (relative displacement) of the rotor, and as a result, it can be operated as an inertial sensor device. If the rotor is rotated, it can be operated as a gyro device.

[Problems to be solved by the invention]
However, both the conventional inertial sensor device and the undisclosed inertial sensor device generate complementary voltages having different positive and negative as control voltages and apply them to adjacent electrodes among the control electrodes. As a result, it has been speculated that the measurement accuracy hindering factor is caused. That is, as a result of long-term experiments and observations, the distribution state of ions existing inside the fixed part such as an insulator case changes slowly but seems to have a negligible effect on measurement accuracy over time. It turns out that it becomes.

  FIG. 3 is a partially enlarged schematic view of the mechanism section for explaining such a problem. (A) is an ion distribution immediately after the start of the sensor operation, and (b) is an ion distribution after the sensor operation is continued. Show. Ions are illustrated by “+” and “−” in a round white area that is an image of an ion trap, but are distributed in a substantially uniform state inside the case 12 before an electric field is applied. Since the case 12 is an insulator, even if a control voltage is applied to the control electrode 13, the uniform distribution state is maintained for at least a while (see FIG. 3A). In addition, electrostatic attraction works as expected at the time of design. However, when the inertial sensor device is continuously operated for a long time of several hours to several tens of hours or more, ions inside the insulator move inside the insulator, specifically, (see FIG. 3B), “+” Ions are unevenly distributed on the electrode 3a side to which the negative control voltage (−Vof−Vx) is applied, and “−” ions are unevenly distributed on the electrode 3b side to which the positive control voltage (+ Vof + Vx) is applied. The electric field with respect to the rotor 11 is changed by the electric field generated by these unevenly distributed ions.

This partially cancels the electric field applied to the rotor 11 (see the dotted line portion in FIG. 3B), so that a part of the electrostatic attraction is lost, so that the static electricity as designed between the case 12 and the rotor 11 is lost. Since no attractive force is generated and the electrostatic force is insufficient, not only the attitude control ability is degraded, but also the acceleration measurement becomes unstable. As a result, the measurement accuracy of the inertial sensor device is deteriorated. In addition, after ions in the insulator are unevenly distributed due to long-term operation, if the operation is stopped by turning off the power supply to the sense circuit, the ions inside the insulator are dispersed over a long period of time. The instability factor is restored.
Therefore, it is a technical problem to improve the measurement accuracy by removing the unstable factor of the measurement accuracy by suppressing the movement of ions inside the insulator (fixed portion).

  The inertial sensor device of the present invention (Solution 1) has been invented in order to solve such a problem, and has a conductive movable part and a plurality of control electrodes formed on a surface facing this. Detecting the relative displacement of the electrically insulating fixed portion and the movable portion with respect to the fixed portion, and applying a control voltage to the control electrode to generate an electrostatic attractive force that eliminates the fluctuation, and detecting the relative displacement A sensor circuit that performs measurement value calculation such as acceleration calculation based on the result or the control voltage, and generates complementary voltages having different positive and negative as the control voltage and uses them as adjacent electrodes among the control electrodes In the inertial sensor device to be applied to the sensor circuit, a bias circuit provided where power can be received even when power supply to the sensor circuit is stopped, and generating a complementary constant bias voltage with different positive and negative, and the sensor circuit The power feeding is stopped to characterized by comprising a switching circuit for applying to the electrode in adjacent one of said control electrode of said bias voltage in place of the control voltage.

  The inertial sensor device according to the present invention (solving means 2) is the inertial sensor apparatus according to the above-described solving means 1, wherein the bias voltage is an average voltage of the control voltage.

  Furthermore, the inertial sensor device of the present invention (Solution means 3) includes a conductive movable part, an electrically insulating fixed part having a plurality of control electrodes formed on a surface facing the conductive movable part, and the above-described fixed part. A control voltage that detects the relative displacement of the movable part and generates an electrostatic attractive force that eliminates the fluctuation is applied to the control electrode, and a measurement value such as an acceleration calculation based on the detection result of the relative displacement or the control voltage An inertial sensor device that generates a complementary voltage with different positive and negative as the control voltage, and applies them to adjacent electrodes of the control electrode, wherein A plurality of bias electrodes formed on a portion other than the surface facing the movable portion and a complementary constant bias voltage having different positive and negative polarity provided where power can be received even when power supply to the sensor circuit is stopped. Form, characterized by comprising a bias circuit for applying to the bias electrode.

  Further, the inertial sensor device of the present invention (Solution means 4) is the inertial sensor device of Solution means 3, wherein the bias circuit receives power from a battery and uses the voltage as the bias voltage. And

In such an inertial sensor device of the present invention (Solution 1), after the power supply to the sensor circuit is cut off and the sensor circuit stops operating, the positive and negative complementary voltages generated by the bias circuit are different. A constant bias voltage is applied to the adjacent electrodes among the control electrodes in place of complementary control voltages having different positive and negative values through the switching circuit.
As a result, the ions inside the electrically insulating fixed part are unevenly distributed in the vicinity of the control electrode both when the sensor circuit is in operation and when it is not in operation, so that the movement of ions is suppressed, so that the ion distribution state is stable. As a result, the unstable factor of measurement accuracy is eliminated.

In addition, since the bias voltage is static, the power consumed by the bias circuit and the switching circuit is very small, and it is supplied by using a small dedicated battery, a rechargeable backup power source, or the continuous use of a battery as in the embodiments described later. Is possible.
Therefore, according to the present invention, it is possible to realize an inertial sensor device with high measurement accuracy over a long period of time by positively distributing ions in the vicinity of the control electrode to the vicinity of the control electrode.

  In the inertial sensor device of the present invention (solution 2), since the bias voltage is set to the average voltage of the control voltage, the uneven distribution state of ions inside the electrically insulating fixed portion is determined when the sensor circuit operates. Therefore, both controllability and measurement accuracy are most stable.

Further, in the inertial sensor device of the present invention (Solution means 3), the complementary constant bias voltages having different positive and negative values generated by the bias circuit are always applied to the bias electrode regardless of whether the sensor circuit is powered. To be applied. Since the bias electrode is formed in a portion of the fixed portion other than the surface facing the movable portion, the bias electrode is attracted to the surface and the ions are separated from the surface facing the movable portion.
As a result, the ions inside the electrically insulating fixing part are unevenly distributed in the remote part of the control electrode both when the sensor circuit is in operation and when it is not in operation. Stable and eliminates unstable factors of measurement accuracy.

In this case as well, since the bias voltage is static, the power consumed by the bias circuit and the switching circuit is very small, and a small dedicated battery, a rechargeable backup power source, or a battery such as the embodiment described later is continued. It can be supplied by use.
Therefore, according to the present invention, it is possible to realize an inertial sensor device with high measurement accuracy over a long period of time by positively distributing ions inside the electrically insulating fixing portion far away from the control electrode. .

  Moreover, in the inertial sensor device of the present invention (solution 4), the bias circuit is the simplest wiring-based one by directly using the voltage received from the battery as the bias voltage. Here, the circuit mainly composed of wiring includes not only a circuit only for wiring but also a combination of a semi-wiring member such as a connector and a combination of auxiliary members such as a surge absorber.

About the inertial sensor apparatus of such this invention, the concrete form for implementing this is demonstrated by the following Examples 1-3.
The embodiment 1 shown in FIG. 4 embodies the above-described solving means 1 and 2 (claims 1 and 2 as originally filed), and the embodiment 2 of FIG. 5 is a modification thereof. The third embodiment shown in FIG. 6 embodies the above-described solving means 3 to 4 (claims 3 to 4 at the beginning of the application).
In the drawings, the same reference numerals are given to the same components as those in the prior art, and therefore, repeated explanations are omitted. Hereinafter, the differences from the prior art will be mainly described. Also in the description of the following embodiments, as in the description of the conventional example, the description of the electrodes and control means for driving the gyro rotor is omitted.

  A specific configuration of the inertial sensor device according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 4A is a block diagram of the sensor circuit 20 and the like of an electrostatic levitation gyro device that is a typical example of an inertial sensor device.

The electrostatic levitation gyro apparatus of FIG. 4A is different from the conventional example of FIG. 1 described above in that a bias means 30 is added. The gyro mechanism 10 and the sensor circuit 20 are taken over in the same state.
The bias means 30 is the same as the above-described offset voltage ± Vof as the bias voltage, and the switching circuit 31 inserted and connected to the control voltage transmission line extending from the output amplifier 26 of the sensor circuit 20 to the control electrode 13 of the gyro mechanism unit 10. A bias circuit 32 that generates a constant voltage and sends it to the switching circuit 31, and a switch 33 that performs / stops power supply to the sensor circuit 20 in response to an operation command B given from an external operation member, for example. .

This electrostatic levitation type gyro device is of a battery drive type that operates by receiving power supply from a battery 34 that generates positive and negative power supply voltages ± Vcc. Power supply from the battery 34 to the sensor circuit 20 is performed by a switch 33. However, power supply from the battery 34 to the bias circuit 32 is always performed.
The bias circuit 32 may be a resistance voltage dividing circuit, but a step-down circuit such as a step-down circuit including a switched capacitor circuit is employed to reduce power consumption.

  The switching circuit 31 is composed of a low power consumption analog switch made of, for example, a MOS-FET, and is provided for each line of the control voltage. Then, the operation is switched according to the operation command B, and when the operation command B instructs the power supply from the battery 34 to the sensor circuit 20, the control voltage from the output amplifier 26 is selected and output to the control electrode 13 to operate. When the command B instructs to stop power supply from the battery 34 to the sensor circuit 20, the bias voltage (+ Vof or −Vof) from the bias circuit 32 is selected and output to the control electrode 13.

  With respect to the electrostatic levitation gyro apparatus (inertial sensor apparatus) of the first embodiment, its usage and operation will be described with reference to the drawings. FIG. 4B shows an example of an applied voltage waveform when the sensor is stopped, and is compared with FIG. 2B of the conventional example.

  When the operation command B instructs execution of power supply, operating power is supplied from the battery 34 to the sensor circuit 20 via the switch 33, and the bias circuit 32 is disconnected from the control electrode 13 by the switching circuit 31 and output amplifier. The control voltage output from 26 is applied to the control electrode 13 as in the prior art (see FIG. 2A). At the same time, a displacement detection signal is also applied from the displacement detection signal generation circuit 27 to the control electrode 13, and the displacement detection signal is detected by the detection amplifier 21 via the detection electrode 14, so that the relative displacement of the rotor 11 with respect to the case 12 is detected. Is calculated by the calculation unit 22. Further, the calculation unit 22 calculates the acceleration A from the relative displacement, and also calculates a control amount for canceling the acceleration A from the relative displacement, and this control amount passes through the D / A conversion circuit 25 and the output amplifier 26 to obtain the control voltage. Thus, this control voltage is applied to the control electrode 13. Thus, as in the prior art, posture control and acceleration detection using electrostatic levitation force are appropriately performed.

  On the other hand, when the operation command B instructs the power supply stop, unlike the conventional case (see FIG. 2B), the power supply from the battery 34 to the sensor circuit 20 is stopped by the switch 33 and the switching circuit. The sensor circuit 20 is disconnected from the control electrode 13 by 31 and the bias voltage output from the bias circuit 32 is applied to the control electrode 13 instead (see FIG. 4B). The control electrodes 13 to which the negative control voltage has been applied when the sensor circuit 20 is operated, for example, the applied voltages V3a and V3c to the electrodes 3a and 3c become a bias voltage −Vof corresponding to the average voltage, and the sensor circuit 20 operates. The applied voltage V3b, V3d, etc. to the control electrode 13, for example, the electrodes 3b, 3d, etc., to which a positive control voltage has been applied at times, becomes a bias voltage + Vof corresponding to the average voltage. For this reason, even when the sensor circuit 20 is not operating, a voltage corresponding to the operating time is continuously applied to each control electrode 13.

Then, the ions in the case 12 are always unevenly distributed in the vicinity of the control electrode 13 (see FIG. 3B), and the state is stably maintained. Therefore, regardless of the operation / non-operation of the sensor circuit 20, at any time, The control voltage applied to the control electrode 13 and the electrostatic attractive force generated between the rotor 11 and the case 12 have a stable and constant relationship over a long period of time.
Therefore, according to this embodiment, since the voltage applied to the control electrode is substantially the same when the sensor circuit 20 is not operating and when the sensor circuit 20 is operating, the ions inside the case 12 made of an insulator remain substantially in place. As a result, it is possible to prevent fluctuation of the acceleration A measurement value of the inertial sensor due to the movement of ions inside the insulator.

  The electrostatic levitation type gyro apparatus (inertia sensor apparatus) of the present invention whose block diagram is shown in FIG. 5 is different from that of the first embodiment described above in that the time division means 28 (TDM ) Is added, and the two-input switching circuit 31 is extended to the three-input switching circuit 35 in order to share the time division function.

  The time division means 28 time-divides the superposition destination when superimposing the displacement detection signal on each control voltage, and removes the control voltage output from the electrode to which the displacement detection signal is being applied (see Patent Document 5). The time division signal C and other timing signals are generated and sent to the digital processor 24 and the switching circuit 35. Here, a circuit separate from the digital processor 24 is shown, but it may be embodied by a program of the digital processor 24. In any case, the control voltage (± Vof ± Vx) output from the D / A conversion circuit 25 and the displacement detection signal output from the displacement detection signal generation circuit 27 can be selected without being directly superimposed. A time-division signal C that can be selected automatically is generated and sent to the switching circuit 35. The frequency of the time division signal C is higher than the control voltage of several tens kHz, lower than the MHz order of the displacement detection signal, and is in the middle, for example, several hundred kHz. The displacement detection signal and the control voltage are eliminated from each other with respect to the voltage amplitude, and the signal level is increased, for example, to near the power supply voltage ± Vcc.

  Similarly to the switching circuit 31, the switching circuit 35 is also composed of an analog switch with low power consumption, and is provided for each line of the control voltage. The switching circuit 35 is switched according to the operation command B, and the operation command B is transferred from the battery 34 to the sensor circuit 20. Is instructed to stop power supply to the bias circuit 32, the bias voltage (+ Vof or −Vof) from the bias circuit 32 is selected and output to the control electrode 13. On the other hand, when the operation command B instructs execution of power supply from the battery 34 to the sensor circuit 20, the switching is further performed in accordance with the time division signal C in order to exhibit the extended function of the switching circuit 31, and the displacement detection signal generation circuit 27. The displacement detection signal from the output amplifier 26 and the control voltage from the output amplifier 26 are alternately selected and output to the control electrode 13. The selection output of the displacement detection signal is performed by a time difference formula so that the plurality of control electrodes 13 do not overlap.

  In this case, when power is supplied to the sensor circuit 20 and the sensor circuit 20 is operating, the control electrode 13 corresponding to each axis ± X, ± Y, ± Z, ± Z ± θ, ± Z ± φ A control voltage and a sense voltage (displacement detection signal) are alternately applied in the division. The polarity of the sense voltage is reversed corresponding to the direction of coordinates (± of each axis). For example, an in-phase sense voltage is applied to the adjacent electrodes 3a and 3b of the control electrode 13, and an in-phase sense voltage is also applied to the adjacent electrodes 3c and 3d, but the counter electrodes 3a and 3c and the counter electrodes 3b and 3d are also applied. For, the sense voltage is out of phase. Then, charges having an amplitude corresponding to the position of the rotor 11 (relative displacement of the rotor 11 with respect to the case 12) appear on the detection electrode 14.

This is detected by the detection amplifier 21 and input to the calculation unit 22 and distributed to each axis in accordance with the timing signal of the time division means 28. In this case as well, displacement calculation and the like are performed appropriately, and static It operates properly as an electrolevitation type gyro device (see Patent Document 5).
Further, when the power supply to the sensor circuit 20 is cut off and the sensor circuit 20 stops operating, the average voltage applied to the control electrodes during the operation of the sensor circuit 20 is the same as in the first embodiment. Since the equal bias voltage is applied to each control electrode 13, the control voltage and the electrostatic attraction force are in a stable and constant relationship over a long period of time, so that the ions inside the case 12 made of an insulator are As a result, it is possible to prevent fluctuations in the measured acceleration A of the inertial sensor due to the movement of ions inside the insulator.

  Not only the time division of the displacement detection signal and the control voltage but also the extension related to the measurement value calculation can be used together with the present invention although the illustration is omitted. That is, (see Patent Document 5), instead of immediately calculating a measured value such as acceleration A from the detection result of the relative displacement, the measured value is calculated based on a control voltage for canceling the relative displacement. May be. Specifically, the acceleration calculation program is uninstalled from the digital processor 24 that is required to operate at high speed in order to calculate the control amount, and the program is ported to another low-speed and inexpensive processor, and D / A conversion is performed. The effective component of the control voltage is extracted from the output of the circuit 25 and the output of the output amplifier 26 by a low-pass filter, and the acceleration A is calculated based on the extracted component. Even in this case, the force applied to the rotor 11 can be obtained by calculation from the control voltage applied to the control electrode 13, and an appropriate acceleration A is calculated. Thereby, the sensor circuit 20 can be made small and inexpensive.

  A specific configuration of an electrostatic levitation gyro device as a third embodiment of the inertial sensor device of the present invention will be described with reference to the drawings. 6A is a longitudinal end view of the gyro mechanism, FIG. 6B is a plan view of the gyro mechanism, and FIG. 6C is a block diagram of a sensor circuit and the like.

  This electrostatic levitation type gyro apparatus is different from those of the first and second embodiments described above in that a plurality of bias electrodes 42 are added to the gyro mechanism part 10 and a bias means 40 obtained by modifying the bias means 30. The bias voltage is applied to the bias electrode 42 instead of the control electrode 13.

  The bias electrode 42 is an electrode dedicated to ion movement control, and is provided in a part different from the control electrode 13 and the detection electrode 14 on the surface of the case 12 facing the rotor 11. Specifically, in the case 12 (fixed part) of the gyro mechanism part 10, it is formed not on the inner surface facing the rotor 11 (movable part) but on the outer surface of the case 12 spaced from the rotor 11 (illustrated). In the example, two are formed in a semicircular shape). For example, when the rotor diameter is 1 mm, the separation distance between the rotor 11 and the control electrode 13 is about several tens of μm, whereas the separation distance between the rotor 11 and the bias electrode 42 is about 500 μm. It differs by an order of magnitude depending on the seed electrode.

  The bias means 40 is composed of a bias circuit realized only by wiring connecting the output terminal of the battery 34 and the bias electrode 42. The battery 34 is connected in front of the switch 33 and can receive power even when power supply to the sensor circuit 20 is stopped. Further, the positive power supply voltage + Vcc output from the battery 34 is applied to the bias electrode 42 at the diagonal position (see 24 with + in FIG. 6A), and the negative power supply voltage −Vcc output from the battery 34 is applied to the other. When applied to the bias electrode 42 at the diagonal position (see -24 in FIG. 6A), a complementary constant bias voltage ± Vcc of different positive and negative is applied to the adjacent bias electrode 42. It has become.

In this case, a complementary bias voltage ± Vcc is always applied to the bias electrode 42 via the bias means 40 regardless of the power supply state to the sensor circuit 20. Since the bias electrode 42 is formed on the outer surface of the case 12, the ions inside the case 12 are pulled away from the control electrode 13 and are unevenly distributed in the vicinity of the bias electrode 42.
As a result, the ions in the case 12 continue to be unevenly distributed in the vicinity of the bias electrode 42, that is, in the remote portion of the control electrode 13, and the state is stably maintained. Therefore, the control can be performed at any time regardless of the operation / non-operation of the sensor circuit 20. The control voltage applied to the electrode 13 and the electrostatic attractive force generated between the rotor 11 and the case 12 have a stable and constant relationship over a long period of time.

Even if the application of the bias voltage to the bias electrode 42 is continued during the operation of the sensor circuit 20, the distance to the rotor 11 is orders of magnitude greater than that of the control electrode 13. The electrostatic attractive force between the two is not undesirably impaired.
Therefore, according to this embodiment, the ions inside the case 12 made of an insulator remain almost in a fixed position regardless of the operating state of the sensor circuit 20, and as a result, the inertial sensor caused by the movement of ions inside the insulator. It is possible to prevent fluctuations in the measured value of acceleration A. Further, the power consumed by the bias means 40 is very small because it is only due to the leakage current from the insulating portion.

[Others]
In the above embodiment, the electrostatic levitation type gyro device is used as the inertial sensor device, but the application of the present invention is not limited thereto. For example, even the above-described cantilever-supported microsensor is an electrostatic servo type sensor, and when complementary control voltages having different positive and negative are applied to adjacent control electrodes, The present invention can be applied.

(A) is a longitudinal end view of a mechanism part, (b) is a perspective view showing electrode arrangement in the mechanism part, and (c) is a block diagram of a sensor circuit, etc., for a conventional inertial sensor device. (A) is an example of a control voltage waveform when the sensor is operating, and (b) is an example of an applied voltage waveform when the sensor is stopped. It is a mechanism part longitudinal cross-section partial enlarged schematic diagram for problem description, (a) shows the ion distribution immediately after the start of the sensor operation, and (b) shows the ion distribution after the sensor operation is continued. (A) is a block diagram of a sensor circuit etc. about the inertial sensor apparatus of Example 1 of this invention, (b) is an example of the applied voltage waveform at the time of a sensor stop. It is a block diagram of a sensor circuit etc. about Example 2 of an inertial sensor device of the present invention. In Embodiment 3 of the inertial sensor device of the present invention, (a) is a longitudinal end view of a mechanism part, (b) is a plan view of the mechanism part, and (c) is a block diagram of a sensor circuit and the like.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Gyro mechanism part, 11 ... Rotor (movable part), 12 ... Case (fixed part),
13 ... Control electrode, 3a, 3b, 3c, 3d ... Adjacent electrode, 14 ... Detection electrode,
20 ... sensor circuit, 21 ... detection amplifier, 22 ... calculation unit,
23 ... A / D conversion circuit, 24 ... digital processor, 25 ... D / A conversion circuit,
26... Output amplifier, 27... Displacement detection signal generation circuit, 28.
30 ... bias means, 31 ... switching circuit, 32 ... bias circuit, 33 ... switch,
40 ... bias means, 41 ... gyro mechanism, 42 ... bias electrode,
A: Acceleration (measured value), B: Operation command, C: Time division signal, Vcc: Power supply voltage,
Vof: Offset voltage, V3a, V3b, V3c, V3d ... Applied voltage

Claims (5)

  A conductive movable part, an electrically insulating fixed part having a plurality of control electrodes formed on the surface facing the conductive movable part, and a relative displacement of the movable part with respect to the fixed part are detected, and the fluctuation is eliminated. A sensor circuit that applies a control voltage that generates electrostatic attraction to the control electrode, and calculates a measurement value such as acceleration calculation based on the detection result of the relative displacement or the control voltage, and the control voltage is positive or negative. In an inertial sensor device that generates different complementary voltages and applies them to adjacent electrodes among the control electrodes, the complementary sensors are provided where power can be received even when power supply to the sensor circuit is stopped. A bias circuit that generates a constant bias voltage, and when the power supply to the sensor circuit is stopped, the bias voltage is replaced with the adjacent voltage among the control electrodes instead of the control voltage. Inertial sensor device being characterized in that includes a switching circuit for applying to the. The inertial sensor device according to claim 1, wherein the bias voltage is an average voltage of the control voltage.   A conductive movable part, an electrically insulating fixed part having a plurality of control electrodes formed on the surface facing the conductive movable part, and a relative displacement of the movable part with respect to the fixed part are detected, and the fluctuation is eliminated. A sensor circuit that applies a control voltage that generates electrostatic attraction to the control electrode, and calculates a measurement value such as acceleration calculation based on the detection result of the relative displacement or the control voltage, and the control voltage is positive or negative. In the inertial sensor device that generates different complementary voltages and applies them to the adjacent electrodes of the control electrodes, a plurality of the fixed portions formed on a portion other than the surface facing the movable portion. A bias circuit, which is provided in a place where power can be received even when power supply to the sensor circuit is stopped, and which generates a complementary constant bias voltage having different positive and negative voltages and applies the bias voltage to the bias electrode; Inertial sensor device, characterized in that equipped. 4. The inertial sensor device according to claim 3, wherein the bias circuit receives power from a battery and uses the voltage as the bias voltage.   The inertial sensor device according to any one of claims 1 to 4, wherein the inertial sensor device is an electrostatic levitation type gyro device having the movable portion as a rotor and the fixed portion as a case.

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