JP3254257B2 - Vibrating gyro sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyro sensor which is used for judging a turning of an automobile and detects a rotational angular velocity, and more particularly to a regular triangular prism shaped sound piece type vibration gyro sensor.

[0002]

2. Description of the Related Art A vibration gyro sensor can directly and accurately detect a rotational angular velocity applied to the sensor, so that when mounted on a vehicle, a turning direction of the vehicle and a yaw rate at the time of turning can be detected. Becomes These detection results are very useful for navigation devices, four-wheel steering devices, anti-lock brake control devices, etc.
Examination of adoption is being actively conducted.

[0003] However, for example, in the case of the regular triangular prism-shaped vibrating gyro sensor, a piezoelectric element such as so-called PZT is attached to a regular triangular prism-shaped vibrator made of a constant elastic material. Therefore, there are many mechanical parts, and due to variations in materials and manufacturing tolerances,
After the signal processing, it is necessary to correct the zero point voltage which is an intermediate value of the fluctuation range of the sensor output voltage and which is the output voltage when the rotation angular velocity is not input. In addition, there is a problem that a drift occurs due to a change with time or an environmental change due to a temperature or the like due to a difference in thermoelastic coefficient of the component.

In order to correct such drift, for example, the following method has been proposed.

When mounted on a vehicle, it is possible to determine whether or not the vehicle is traveling normally by other sensors, so that the sensor output during steady traveling is corrected by software processing.

A high-speed analog / digital conversion of a sensor signal is performed, and the frequency component of the sensor signal is analyzed by a so-called FFT method or the like, so that a low-frequency sensor output component and an extremely low-frequency drift component are discriminated. Only components are removed by operation.

[0007] The sensor signal is AC-coupled to block a DC component, and an extremely low frequency drift component is electrically removed.

[0008]

In the above-mentioned method, it is necessary to input detection results from a steering sensor, left and right wheel speed sensors, and the like to the correction circuit, which requires a large-scale configuration and requires software processing. So,
The versatility of the gyro sensor alone is extremely poor. Further, when the drift is large, the zero point voltage greatly deviates from the center of the dynamic range of the sensor, and there is a problem that the dynamic range of the sensor cannot be fully utilized.

In the above-mentioned method, a digital signal processor having a high-speed operation function is required, so that the configuration becomes large and the sensor lacks versatility.

In the above method, the structure is relatively simple, and therefore, such a drift correction circuit can be built in the sensor, and it is excellent in versatility. However, if a constant rotational angular velocity is continuously input,
The sensor output changes to the zero point voltage, which is the output when the rotational angular velocity is not input, and even though the rotational angular velocity is applied, only the same output as when no rotational angular velocity is applied can be obtained. Problem.

An object of the present invention is to provide a vibration gyro sensor capable of correcting drift due to aging and environmental changes with a simple and versatile configuration.

[0012]

[0013]

According to the present invention, there is provided a vibrating gyroscope having a signal processing circuit for deriving an output voltage corresponding to a rotational angular velocity from a component due to a Coriolis force among output voltages of a piezoelectric element formed on a side surface of a vibrator. A sensor for determining whether or not the output voltage is in a steady state based on a change amount per predetermined time, and outputting a correction permission signal when the sensor is in the steady state; In response to the signal, the output voltage at the time when it is determined to be in the steady state is stored as a target voltage, and during the period of the steady state, the correction voltage is such that the output voltage is equal to the target voltage. A correction voltage generating means for applying the correction voltage to the signal processing circuit and for holding the correction voltage when the signal processing circuit enters an unsteady state and applying the correction voltage to the signal processing circuit. Is Rosensa.

[0014]

[0015]

[0016]

[0017]

According to the present invention, the signal processing circuit for processing the output voltage of the piezoelectric element is provided with drift correction means including steady state determination means and correction voltage generation means. The steady state determining means determines whether the output voltage of the piezoelectric element is in a steady state based on a change amount per predetermined time, that is, a change rate of the output voltage, and is in a steady state in which the rotational angular velocity is not changed. Sometimes, a correction permission signal is output to the correction voltage generating means.

When the correction permission signal is input, the correction voltage generation means stores the output voltage of the piezoelectric element at that time as a target voltage, and stores the output voltage during a period in which the steady state continues. A correction voltage equal to the set target voltage is supplied to the signal processing circuit. Further, when an unsteady state occurs, the correction voltage immediately before the unsteady state is held and applied to the signal processing circuit. The signal processing circuit adds the correction voltage to the output voltage of the piezoelectric element and derives it as an output signal of the vibration gyro sensor. Therefore, drift correction can be performed with a simple configuration without providing a special sensor or the like for steady state determination.

[0019]

[0020]

[0021]

[0022]

FIG. 1 is a block diagram showing an electrical configuration of a vibration gyro sensor 22 having a drift correction circuit 21 according to one embodiment of the present invention. This vibration gyro sensor 22
Uses a right triangular prism-shaped vibrator 1 having left and right piezoelectric elements 2 and 3 for driving on two sides of the vibrator 1 and a feedback side on the remaining one side. A piezoelectric element 4 is provided. A drive signal of, for example, 8 kHz from the oscillation circuit 5 is applied to the piezoelectric elements 2 and 3 via the phase correction circuit 6 in a state where the phases are shifted by 90 ° to excite the vibrator 1. When the vibrator 1 is rotated in the direction indicated by the arrow 7 in this state, the voltage generated by the Coriolis force proportional to the rotational angular velocity is superimposed on the drive signal, and the output indicated by reference numerals 8a and 9a appears on lines 8 and 9, respectively. A voltage is derived. Note that the output voltage includes a drift component.

The output voltages from the piezoelectric elements 2 and 3 are subjected to amplitude correction by an amplitude correction circuit 10 and output from a differential amplifier circuit 1.
When the differential amplification is performed in step 1, the drive signal from the phase correction circuit 6 is canceled, and only the voltage component due to the Coriolis force and the drift is extracted from the differential amplification circuit 11 to the line 12 as indicated by reference numeral 12a. can do. When the output from the differential amplifier circuit 11 is subjected to half-wave rectification in the synchronous detection circuit 13 in synchronization with the drive signal from the oscillation circuit 5,
Reference numeral 14a indicates to the DC amplification circuit 15 through the line 14.
Is provided. The output is smoothed by the DC amplifier circuit 15, so that an output proportional to the rotational angular velocity as indicated by reference numeral 16 a is derived to the line 16.

The output from the DC amplifying circuit 15 is given as a sensor output of the vibration gyro sensor 22 to a navigation device, an antilock brake control device, and the like, and is used for turning determination and yaw rate calculation. This sensor output is also supplied to a drift correction circuit 21 from which a drift correction voltage generated as described later is output to a line 17.
, And the sensor output from the DC amplification circuit 15 becomes an output voltage corresponding to only the rotational angular velocity from which the drift component has been removed.

The drift correction circuit 21 is supplied with a high-level voltage Vcc via a line 24 from a power supply circuit 23 for supplying power to the circuits 5, 11, 13 and the like. The reference voltage Vref, which is の of the voltage Vcc, is applied thereto. In addition, a drive signal from the oscillation circuit 5 is given via a line 26.

FIG. 2 is a block diagram showing an electrical configuration of the drift correction circuit 21. When the ignition key switch of the automobile is turned on to the Acc or IG contact, power supply from the power supply circuit 23 to each part of the vibration gyro sensor 22 is started. As a result, the reset circuit 31 outputs a first correction permission signal to the target voltage setting circuit 33 via the line 32 at the rising timing of the voltage Vcc. In response to this, the target voltage setting circuit 33
Derives a reference voltage Vref input from the power supply circuit 23 via the line 25 to a line 34 as a target voltage, and the level shift circuit 35
The drift correction voltage is fed back to the DC amplifier 15 via the line 17.

On the other hand, the sensor output from the DC amplifier circuit 15 via the line 16 is supplied from the follower circuit 36 via the switches SW1 and SW2 to the two hold circuits 37 and 37.
38 respectively. The switch SW1 outputs the timing from the timing signal generation circuit 41 during a period in which the second correction permission signal from the later-described steady state determination circuit 39 is inverted by the inversion buffer 40 and the second correction permission signal is not output. Signal is AND gate 4
2 to perform a switching operation.

A drive signal from the oscillation circuit 5 via the line 26 is supplied to the timing signal generation circuit 41 by a frequency dividing circuit 43 realized by a so-called gate IC.
For example, it is input after being divided by 256. Therefore, in response to the drive signal of 8 kHz, the timing signal shown in FIG. 3C is derived from the timing signal generation circuit 41 to the switch SW1 every 128 msec, and the hold value of the hold circuit 37 is updated. The timing signal generation circuit 41 deviates from the timing signal of the switch SW1 by a half cycle, that is, 64 ms.
The timing signal shown in FIG. 3D is derived to the switch SW2 with a shift of ec. Therefore, when the second correction permission signal is not derived from the steady state determination circuit 39, the two hold circuits 37 and 38 are shifted from each other by a half cycle to update and hold the sensor output from the DC amplifier circuit 15. ing.

The hold values of the hold circuits 37 and 38 are determined by the differential amplification and comparison circuit 4 of the steady state determination circuit 39.
4 and the differential amplification and comparison circuit 44
When the amount of change in the hold values of the two hold circuits 37 and 38 is, for example, within ± 5 [mV] per 64 msec, the vehicle is in a steady state, that is, the vehicle is stopped or running straight, or turning at a constant rotational angular velocity. Is determined, and the signal is supplied to the line 18,
19, the second correction permission signal is output. The filter circuit 45 prevents an erroneous steady-state determination when the hold values of the hold circuits 37 and 38 that fluctuate in an unsteady state accidentally fall within the voltage 5 [mV] even for a moment. For example, about 2 seconds.

When the second correction permission signal is derived, the timing signal from the timing signal generation circuit 41 to the switch SW1 is blocked by the AND gate 42, and the hold value of the hold circuit 37 is changed to an unsteady state. Is held at the value immediately before The second correction permission signal is also supplied to the target voltage setting circuit 33, and the target voltage setting circuit 33 also receives a second correction permission signal via a line 46 when the second correction permission signal is input. Is set to the target voltage and is led out to the level shift circuit 35 via the line 34.

The first and second parts shown in FIG.
The correction permission signal is also supplied to the switch SW3 via the OR gate 47. This switch SW3 supplies the output of the follower circuit 36 to the integration circuit 48 during the period in which the first and second correction permission signals are derived. The integration circuit 48 is also supplied with a target voltage from the target voltage setting circuit 33. Therefore, a correction voltage is generated from the integration circuit 48 so that the output of the follower circuit 36 approaches the target voltage. The drift correction voltage is fed back from the line 17 to the DC amplification circuit 15 via the level shift circuit 35, and thus drift correction is performed.

Therefore, when the power supply is started from time t1 in FIG. 3 and the sensor output for which drift correction is not performed changes as indicated by reference numeral α1 in FIG. 3 (1), drift correction is performed. And a sensor output indicated by reference symbol α2.

FIG. 4 is an electric circuit diagram showing a specific configuration of the drift correction circuit 21, and portions corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals. The frequency dividing circuit 43
Is configured to include an integrated circuit 43a for frequency division,
The parallel output from the integrated circuit 43a is supplied to the gate ICs 41a and 41b in the timing signal generating circuit 41, respectively. The driving signal is divided by 256 as described above, and the switches SW1 and SW2 are alternately switched every 64 msec. A signal is output.

The differential amplifying and comparing circuit 44 of the steady state judging circuit 39 includes a differential amplifier 44a and a window comparator 44b, and the differential amplifier 44a holds the hold values of the hold circuits 37 and 38. The output corresponding to the difference is amplified by, for example, a gain of 20 times and is derived to the window comparator 44b. The window comparator 44b includes a pair of comparators 44m and 44n and voltage dividing resistors R1 to R3.
3 is a line 24 for the voltage Vcc and a line 49 for the ground level.
Are interposed in series. Therefore, the output voltage of the differential amplifier 44a is equal to the voltage Vref ± 100 [mV] created by the voltage division of these resistors R1 to R3.
Are within the two reference voltages V1 and V2, a high-level output is derived from the comparators 44m and 44n to the filter circuit 45.

The filter circuit 45 includes two differential amplifiers 4
5a and 45b and a capacitor C3. The inverting input terminals of the differential amplifiers 45a and 45b
From the line 25 to the reference voltage Vref via the line 53
Is given. The differential amplifier 45a derives an output corresponding to the difference between the differential amplifier 44a and the reference voltage of the window comparator 44b, and charges and discharges the capacitor C3. The differential amplifier 45b receives the charging voltage of the capacitor C3 and the reference voltage Vr from the line 25 to the line 53.
ef, and when the charging voltage of the capacitor C3 is high, that is, when there is no change in the input to the hold circuits 37 and 38, the second correction permission signal is output to the lines 18 and 19.

The reset circuit 31 includes a capacitor C4
And two inverting buffers 31a and 31b. When the power is turned on as described above, the charging of the capacitor C4 starts, and the voltage drop between the terminals of the capacitor C4 becomes a predetermined level. Up to the switch SW from the inversion buffers 31a and 31b via the line 32.
3, a high-level first correction permission signal is derived. The switch SW3 is also turned on by the second correction permission signal via the line 19. While the switch SW3 is conducting as described above, the integration circuit 48
Derives an output to the level shift circuit 35 such that the deviation between the sensor output input via the switch SW3 and the target voltage input via the line 34 from the target voltage setting circuit 33 becomes zero. .

On the other hand, in the target value setting circuit 33, when the second correction permission signal is input from the line 19, the switch SW5 is turned on, and the switch SW4 is turned off via the inversion buffer 51. Is input as a target voltage after the hold value of the hold circuit 37 via the line 46 is corrected as described later. When the high-level first correction permission signal is derived from the reset circuit 31 via the line 52, the switch S
W5 is turned off, switch SW4 is turned on, and line 2 is turned off.
5 is input to the integrating circuit 48 as a target voltage.

However, when the target voltage is switched as described above, the integrating circuit 48 corresponds to the difference between the target voltages.
Output also shifts. Therefore, in the level shift circuit 35 which is a compensation circuit, when the switch SW4 is conductive, the switch SW7 is conductive and the line 5
After the output voltage of the integrator circuit 48 is added to the reference voltage Vref through 3, it is amplified by the differential amplifier 35 a to generate the drift correction voltage. On the other hand, switch S
When W5 is conducting, the voltage of the integrating circuit 48 is added to the voltage obtained by amplifying the difference between the reference voltage Vref and the output voltage of the target value setting circuit 33 by the differential amplifier 35b, and then the operational amplifier 35b is turned on. , A drift correction voltage is generated. In this way, it is possible to absorb the output transition of the integrating circuit 48 when the target voltage is switched.

Further, the sensor output input via the line 16 is held by the hold circuit 37,
6 may slightly differ from the voltage VA led to 6 due to the offset of the follower circuit 36 and the hold circuit 37 and the like. Therefore, if drift correction is performed with this deviation occurring, a deviation will occur in the sensor output. Therefore, if the steady state and the unsteady state are repeated, the deviation will accumulate.

In this embodiment, a correction circuit 55 is provided in the target voltage setting circuit 33 in order to solve such a problem. The correction circuit 55 includes two differential amplifiers 55a and 55b. When the hold value VA of the hold circuit 37 is higher than the reference voltage Vref, the voltage Vc at the point 56 is slightly determined by the resistor RA. Voltage Vr. Therefore, the comparator 5
5, the output voltage VB becomes VA-Vr. On the other hand, when voltage VA is smaller than reference voltage Vref, V
B = VA + Vr. The correction circuit 55 may be deleted when the offset values of the follower circuit 36 and the hold circuit 37 are matched.

As described above, in the drift correction circuit 21 according to the present invention, the zero point voltage can be set to the reference voltage Vref when the power is turned on, so that the adjustment of the mark at the time of manufacturing the vibration gyro sensor 22 becomes unnecessary, and the process is simplified. can do. Further, not only a change over time due to the correction of the zero point voltage but also an environmental change such as a temperature change is corrected in accordance with the sensor output in a steady state, so that drift correction can be performed with a simple configuration without using software processing. It can be performed. Furthermore, even if the material does not have excellent temperature characteristics, it can be used with priority given to mechanical strength, and reliability such as impact resistance can be improved. Furthermore, the drift correction circuit 21 according to the present invention is composed of a collection of basic circuits such as a gate IC, a differential amplifier circuit, and an analog switch.
It is easy to reduce the size to C, and the size and cost can be reduced. In addition, the versatility can be improved by being integrated with the sensor.

[0042]

As described above, according to the present invention, variations in transducers and piezoelectric elements and drift caused by aging or environmental changes thereof are corrected by a simple configuration without using software processing. be able to. Therefore, versatility can be improved by integrating these correction circuits on the sensor side. In addition, the adjustment at the time of manufacturing can be simplified, and a component having good mechanical strength can be used even if the temperature characteristics are not necessarily good, and reliability such as impact resistance can be improved. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a vibration gyro sensor 22 including a drift correction circuit 21 according to one embodiment of the present invention.

FIG. 2 is a block diagram illustrating an electrical configuration of a drift correction circuit 21.

FIG. 3 is a waveform chart for explaining the operation of the drift correction circuit 21.

FIG. 4 is an electric circuit diagram showing a specific configuration of the drift correction circuit 21.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillator 2-4 Piezoelectric element 21 Drift correction circuit 22 Vibration gyro sensor 31 Reset circuit 33 Target voltage setting circuit 35 Level shift circuit 36 Follower circuit 37, 38 Hold circuit 39 Steady state determination circuit 44 Differential amplification and comparison circuit 45 Filter circuit 48 Integrator

Continuation of the front page (56) References JP-A-4-235310 (JP, A) JP-A-3-199972 (JP, A) JP-A-3-4215 (JP, U) JP-A-4-38512 (JP , U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 19/00-19/72 G01P 9/00-9/04 G01C 21/00-21/36

Claims (1)

(57) [Claims] 1. A vibrating gyroscope having a signal processing circuit for deriving an output voltage corresponding to a rotational angular velocity from a component due to Coriolis force among output voltages of a piezoelectric element formed on a side surface of a vibrator, A steady state determining unit that determines whether or not the vehicle is in a steady state from a change amount per set time, and outputs a correction permission signal when the vehicle is in a steady state. The output voltage at the point in time when it is determined to be stored is stored as a target voltage, and during the period of the steady state, a correction voltage such that the output voltage is equal to the target voltage is supplied to the signal processing circuit. A vibrating gyro sensor, comprising: a correction voltage generating means for holding the correction voltage and supplying the correction voltage to the signal processing circuit in a steady state.