JP3412092B2 - Gyro drift cancellation device on vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyro drift canceling device on a vehicle, and more particularly, though not intended to limit the invention, to the present invention. No. 191189
The present invention relates to an improvement of a drift cancellation device presented in Japanese Patent Application Laid-Open No. 7-43165 . 2. Description of the Related Art Some types of sensors, such as a piezoelectric vibrating gyroscope, output a signal containing a DC component, and the DC level generally varies according to temperature and humidity. The DC level drift of this type of signal becomes significant when the gain of the amplifier for amplifying the signal is increased to increase the detection sensitivity, thereby increasing the detection error. [0003] In order to suppress the occurrence of errors due to such fluctuations in the DC level, a capacitor coupling circuit that cuts off the DC component is conventionally provided at the output of the sensor. Since no DC component appears at the output of the capacitor coupling circuit, a signal from which drift has been removed is obtained. [0004] However, since the capacitor coupling circuit attenuates not only the DC component but also the AC component having a low frequency, the capacitor coupling circuit may be used when the signal contains an AC component having a very low frequency. , A part of the signal to be detected is missing or attenuated. For example, when using a piezoelectric vibrating gyroscope to detect a changing angular velocity in the traveling direction of a car, if the traveling direction of the car changes slowly, the output of the piezoelectric vibrating gyroscope will have a very low frequency alternating current. Ingredients appear. Therefore, in order to correctly detect a slow change in the traveling direction, it is necessary to directly refer to the output signal of the piezoelectric vibrating gyroscope without using a capacitor coupling circuit, so that the DC level drift becomes a problem. . If the time constant of the capacitor coupling circuit is increased, the attenuation of the low-frequency AC component can be reduced, but there is a limit in increasing the time constant. That is, since the capacity of the capacitor becomes large, the circuit becomes large. In a circuit having a large time constant, a large voltage fluctuation occurs even if the leakage current of the capacitor is small, and a new DC level drift occurs in the output of the amplifier. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to cancel a drift of a DC level of a gyro on a vehicle and output an accurate signal, and to prevent a signal component having a low frequency from being attenuated or missing. [0007] In order to solve the above-mentioned problems, a drift cancel apparatus for a gyro on a vehicle according to the present invention is provided.
A gyro (11) on a vehicle for outputting a detection signal including a DC component and an AC component; amplification means (15) for inputting and amplifying the detection signal to generate an output signal; A base signal generating means for outputting (16); a synthesizing means (1B) for adding or subtracting the base signal to or from an input of the amplifying means; refer to the level of the detection signal and the level of the base signal. And the difference between them is a predetermined first
First discriminating means (24, 25) for discriminating whether or not the difference is larger than a first threshold value; when a state in which the difference is larger than the first threshold value has continued for a first time or more, First average calculating means (23b, 27, 28a) for calculating the average level (Vb) of the detection signal; changing the level of the base signal output by the base signal generating means according to the average level Base level changing means (28b);
Threshold value setting means (30) for setting a second threshold value (Vw) which is large at a low speed and small at a high speed corresponding to the speed of the vehicle; the level (VS2) of the output signal of the amplifying means
And a second identification means (2A, 2B) for identifying whether or not the difference between the level of the signal and a predetermined zero level (Vc) of the signal is within a second threshold (Vw). Repeatedly referring to the level of the output signal within a second time, and only when the difference between the level of the output signal and a predetermined zero level of the signal is within a second threshold value, Averaging means (2C, 2F) for calculating the average (Mc) of a plurality of levels sampled within a second time; the average calculated by the second averaging means and the zero The difference (ΔVd) from the level is a predetermined value (Vt
If it is h) above, modifying the zero level on the basis of the average, the zero level adjusting means (2J, 2K); and to output a signal corresponding to the difference between the level and the zero level of the output signal signal output means (22); Ru equipped with. The symbols shown in the parentheses indicate the reference numerals of the corresponding elements in the embodiments described later for reference, but each component of the present invention is a specific element in the embodiments. It is not limited to only. The drift cancellation of the gyro on the vehicle according to the present invention.
According to the apparatus , the amplifying means amplifies a signal obtained by adding or subtracting the detection signal and the base signal. A state in which the difference between the level of the detection signal and the level of the base signal is larger than the first threshold value (ΔV) is for a long time (for example, 25 seconds).
When (sec) continues, the first average calculating means calculates the average level of the detection signal within that time, and the level of the base signal is automatically changed in accordance with the average level. The signal output means outputs a signal corresponding to the difference between the level of the output signal and the zero level. This zero level is automatically adjusted by the zero level adjusting means. That is, the level of the output signal is repeatedly referred to within a predetermined time (for example, 15 seconds), and a number of levels sampled when the difference between the level of the output signal and the zero level is within the second threshold value (Vw). If the difference between the average (Mc) of (VS2) and the zero level is equal to or greater than a predetermined value, the zero level is corrected based on the average (Mc). Since the position change speed of the vehicle is proportional to the vehicle speed, even if the direction changes at the same angular speed, the change speed of the position and direction differs in proportion to the vehicle speed. It is preferable that fluctuation (level change of the angular velocity signal) can be extracted. Therefore , the drift of the gyro on the vehicle according to the present invention.
Cancellation device, as described above, comprises a threshold value setting means (30), for setting a small threshold (Vw) is greater high speed at a low speed corresponding to the speed of the vehicle (V). Thus, at a high speed, a minute output fluctuation (a level change of the angular velocity signal) of the piezoelectric vibrating gyroscope is extracted. In the case of a high speed, the turning time of the vehicle is short, and a change in the drift level during this period is practically inconceivable. Therefore, there is substantially no possibility of erroneously extracting the drift as an angular velocity signal at a high speed.
In the case of low speed, the extraction sensitivity of the angular velocity signal is relatively slightly lower than in the case of high speed, but since it is low speed, the vehicle position change speed and the direction change speed due to the vehicle speed and angular speed (turn speed) are slow. However, the vehicle position recognition error is negligible. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings. FIG. 1 shows a configuration example of an apparatus for carrying out the present invention. The apparatus shown in FIG. 1 is an azimuth measuring apparatus which can be mounted on a vehicle and used. Referring to FIG. 1, a piezoelectric vibrating gyroscope 11, a reference voltage source 12, a buffer 13, amplifiers 14, 15, a D / A converter 16, an A / D converter 17,
Microcomputer 18, subtractors 19 and 1B, adders 1A and 1C, antenna ANT, GPS receivers 1D and G
A PS demodulator 1E is provided. The piezoelectric vibrating gyroscope 11 used in this embodiment is a model ENC-05 manufactured by Murata Manufacturing Co., Ltd.
S, which has a reference voltage input terminal R, a signal output terminal S, a power supply terminal Vcc, and an earth terminal G. The piezoelectric vibrating gyroscope 11 outputs a voltage proportional to the angular velocity of rotation about one axis to a signal output terminal S. In this embodiment, in order to detect the azimuth, the piezoelectric vibrating gyroscope 11 is arranged with the axis of rotation directed vertically. The rotation angle of the piezoelectric vibrating gyroscope 11 (ie, the rotation angle of the vehicle) is obtained by integrating the detected angular velocity.
The azimuth (traveling direction) of the vehicle can be obtained based on the rotation angle obtained from the angular velocity. In this embodiment, the GPS positioning is performed by using the GPS receiver 1D and the GPS demodulator 1E, and an accurate reference direction is detected.
However, since it takes a relatively long time to perform the GPS positioning, it is not possible to detect the azimuth that changes every moment in real time only by performing the GPS positioning. Therefore, in this embodiment, real-time azimuth detection is realized by combining detection of a reference azimuth by GPS positioning and detection of a rotation angle using the piezoelectric vibrating gyroscope 11. According to the specifications, the piezoelectric vibrating gyroscope 11 outputs a DC voltage Vo within the range of Vref ± 500 mV to the output terminal S when there is no rotation, and a voltage of Vo + 72 mV when rotating at the maximum angular velocity. Is output.
Also, since a relatively large drift occurs in the output voltage,
It is standard practice to cut out the DC component via a capacitor coupling circuit and extract the signal at the output terminal S. However, when a capacitor coupling circuit is used, a signal component having a very low frequency is greatly attenuated or lost. Therefore, in a case where a signal component that changes slowly, such as an angular velocity of an automobile, is also required, it is convenient. Is bad. Therefore, in this embodiment, a special control is performed using the microcomputer 18 to cancel the drift of the output level of the piezoelectric vibrating gyroscope 11 without providing a capacitor coupling circuit. The signal Vin output from the signal output terminal S of the piezoelectric vibrating gyroscope 11 passes through the buffer 13 and is applied to the subtracters 19 and 1B, respectively. In the subtracter 19, a voltage obtained by subtracting a constant reference voltage (DC voltage) Vref output from the reference voltage source 12 from the signal Vin is input to the amplifier 14 and amplified. Further, in the subtractor 1B, the signal V
A voltage obtained by subtracting the base signal Vbase output from the D / A converter 16 from in is input to the amplifier 15 and amplified. In this example, the gain A1 of the amplifier 14 is 1.8 and the gain A2 of the amplifier 15 is 28.6. Adder 1A
, The result of adding the output signal of the amplifier 14 and the reference voltage Vref becomes a signal VS1, and the result of adding the output signal of the amplifier 15 and the reference voltage Vref becomes a signal VS2. These signals VS1 and VS2 are respectively A /
The data is input to the microcomputer 18 via the D converter 17. The reference voltage Vref is 2.5 V in this example. Originally, the signal Vin has the same voltage as Vref when there is no rotation as shown at the top of FIG. 7, and the voltage increases when the angular velocity in the forward direction is detected, and increases when the angular velocity in the reverse direction is detected. Decrease. However, in practice, drift occurs, so that the voltage of the signal Vin when there is no rotation is displaced from the reference voltage Vref as shown in the middle and lower parts of FIG. 7, and the amount of displacement changes over time. . Therefore, for example, after (Vin-Vref) is amplified by A1 times,
When ref is added, as shown in FIG. 7, the static level of the amplified voltage (the level at the time of non-rotation) fluctuates greatly with the drift of the voltage of the signal Vin. The signal reaches the saturation level and the correct level cannot be detected. In any case, if the static level of the signal fluctuates, the correspondence between the voltage of the signal and the rotational angular velocity shifts, and a rotational angular velocity detection error occurs. Therefore, in this embodiment, first, even if the static level of the signal Vin fluctuates, the actual static level of the signal Vin is controlled so that the level of the signal VS2 obtained at the output of the amplifier 15 having a large amplification degree does not saturate. Is generated, and the offset of the amplifier 15 is automatically adjusted using the base signal Vbase. As a result, even when the quiescent level of the signal Vin greatly deviates from the reference voltage Vref as shown in FIG. 8, the level of the signal having a large amplitude can be prevented from being saturated. In this embodiment, in order to detect the static level of the signal Vin, the signal VS1 obtained by amplifying the signal Vin by the amplifier 14 is referred to. However, the level of the signal Vin may be directly referred to. The operation of the microcomputer 18 is shown in FIGS. FIG. 3 shows the main routine, and FIG. 2 shows the routine of the timer interrupt 1. When the power of the apparatus is turned on, in step 31, initialization is first performed, in which a pulse interrupt (FIG. 4A) and a timer interrupt 2 for calculating a vehicle speed V in response to a vehicle speed synchronization pulse are performed. ((B) of FIG. 4 is permitted. Next, the GPS positioning calculation is executed,
Clear the output invalid flag and enable timer interrupt 1 (Fig. 2). The microcomputer 18 is supplied with one vehicle speed synchronizing pulse for a predetermined small angle rotation of the axle, and when pulse interruption and timer interruption 2 are permitted,
The computer 18 executes the interrupt processing shown in FIG. 4A every time one vehicle speed synchronizing pulse arrives. That is, the pulse count register RVC is incremented by one (the data of the register is updated to one which is incremented by one) (41). When the timer interrupt 2 is permitted, the microcomputer 18 starts the interrupt timer 2 (program timer). When the time of the interrupt timer 2 is over, the microcomputer 18 responds thereto. Is restarted, and FIG.
The timer interrupt 2 shown in FIG. That is, the vehicle speed V is obtained from the data RVC of the pulse count register RVC.
Is calculated and written in the vehicle speed register V (42), and the pulse count register RVC is cleared (43). If the time limit value of the interrupt timer 2 is Tt2, the vehicle speed V becomes
It is proportional to the number of generated vehicle speed synchronization pulses (RVC) during t2. Based on this relationship, the vehicle speed V is calculated in step 42 and written into the vehicle speed register V. This update write is T
Since the processing is performed at t2, the latest vehicle speed is always secured in the vehicle speed register V. Referring again to FIG. 3, in the GPS positioning calculation, information received from three or more satellites is transmitted to the GPS receiver 1.
D and input via the GPS demodulator 1E, and based on the information, perform a predetermined calculation to determine the azimuth in the traveling direction, and set the azimuth obtained here as the reference azimuth ψref. When the timer interrupt 1 is permitted in step 31, the routine of the timer interrupt 1 of FIG. 2 is executed every time a request for the timer interrupt 1 occurs. In this embodiment, the request for timer interrupt 1 is 2
It occurs periodically every 0 msec. Referring to FIG. 2, the routine of timer interrupt 1 will be described. In step 21, two signals VS1 and V
S2 is sampled by the A / D converter 17 and A2
/ D conversion result is input. In step 22, the result obtained by subtracting the zero level Vc from the value of the sampled signal VS2, that is, the value corresponding to the rotational angular velocity ω is stored in the register Rω.
Store in In the next step 23a, the register Rr
And the contents of the register Rω are added, and the result is stored in the register Rr. In the next step 23b, the contents of the register Rt and the value of the sampled signal VS1 are added, and the result is stored in the register Rt. That is, the integrated value of the rotational angular velocity ω is held in the register Rr, and the integrated value of the signal VS1 is held in the register Rt. In the following step 24, the value of the sampled signal VS1 is compared with the upper threshold level Vbase + ΔV, and in step 25, the value of the signal VS1 is compared with the lower threshold level Vbase−ΔV. The threshold ΔV is
In this example, it is set to 56 mV. Then, the signal VS1
If the value is within the upper and lower threshold values, the process proceeds to step 26. If the value is out of the range, the process proceeds to step 27. That is, the value of the signal VS1 and the base signal Vbase
When the values are substantially equal, the process proceeds to step 26, and when the difference between the two is large, the process proceeds to step 27. In step 27, after adding 1 to the contents of the register Tbase, the contents of Tbase are referred to and
Identify whether it is seconds or more. Timer interrupt cycle is 20 ms
c, and the content of Tbase increases by 1 every 20 msec.
(= 50 × 25). If the content of Tbase is less than 25 seconds, the process proceeds to step 2A. If the content of Tbase is 25 seconds or more, the process proceeds to steps 2a, 2b, and 29, and then proceeds to step 2A. If the value of the signal VS1 falls within the upper and lower threshold values before 25 seconds elapse, the register Tbase is set in step 26.
And Rt are cleared. That is, when the value of the signal VS1 is out of the range of the upper and lower threshold values continuously for 25 seconds, the process proceeds to step 28a. In step 28a, the signal VS sampled for 25 seconds held in the register Rt is output.
The integration value of 1 is sampled by the number of samplings N25 (= 1250)
The result, that is, the average value Vb of the signal VS1 for 25 seconds is obtained, and the value obtained by converting the average value Vb to the average level of the input signal Vin is stored in the register Vb2. In the next step 28b, the contents of the register Vb2 are stored in the D / A
Output to the converter 16. As a result, the base signal Vba
The voltage of se is updated. That is, the average value of the signal Vin for 25 seconds becomes the new voltage of Vbase. For example, as shown in FIG. 8, the quiescent level of the signal Vin shifts from the reference voltage Vref due to the drift of the signal Vin, but the average value of the signal VS1 is changed to the base signal Vba.
output as se, and every time the deviation increases, the base signal Vba
By successively updating se, the voltage of the base signal Vbase can be brought close to the quiescent level of the signal Vin (and VS1), whereby only the signal whose DC component has been removed from the signal Vin is amplified by the amplifier 15. Therefore, the quiescent level of the signal VS2 approaches the reference voltage Vref. Therefore, even when the amplitude of the signal Vin is large (the angular velocity is large), the saturation of the voltage as shown in FIG.
It is unlikely to occur in S2. Referring again to FIG. Step 2
8b, when the base signal Vbase is updated, the output invalid flag is set in the next step 29, and the registers Rr,
Clear the contents of Rt and Tbase. That is, the base signal V
When the base changes, the quiescent level of the signal VS2 greatly changes in a stepwise manner, and the data before updating the base signal Vbase is likely to include a relatively large error. Invalidate the affected data. In step 30, a threshold value Vw corresponding to the vehicle speed V is calculated and set. The vehicle speed V is the vehicle speed register V
The threshold value Vw is calculated by an operation according to a calculation formula Vw = Vwo- (Vwo-a) V / Vv set on the program, and is written into the threshold value register Vw. FIG. 5 shows the relationship between the vehicle speed V and the threshold value Vw according to this calculation formula. In step 2A, the value of the signal VS2 is compared with the threshold level Vc + Vw, and in the next step 2B,
The value of the signal VS2 is compared with the threshold level Vc-Vw.
Vw is a value indicated by the data of the register Vw. VS2> V
If c + Vw, the process proceeds from step 2A to 2D, where VS2> V
If it is c-Vw, the process proceeds from step 2B to 2D. VS2
Is within the range between the threshold levels Vc-Vw and Vc + Vw, the process proceeds to step 2C. The threshold value Vw is set to 7.3 mV in this example. In step 2C, first, the register Rt2
Is added to the content of the sampled signal VS2, the result is stored in the register Rt2, and 1 is added to the content of the register Cs. The register Rt2 holds the integrated value of the value of the signal VS2, and the register Cs holds the data number of VS2 integrated into Rt2. In the next step 2D1, 1 is added to the contents of the register Tw. In the next step 2D2, the number of samples is verified. This is shown in FIG. Here, first, 1 is added to the content of the reference count register Cso (4
4). Then, a ratio Cs / Cso of the number of times of sampling Cs of the register Cs to the number of times of reference Cso of the register Cso is calculated, and it is checked whether this is 56.2% or more (4).
5). If so, the number of samples for the zero level calibration is sufficient, so the process proceeds to the next check 2D3 (FIG. 2).
If it is less than 56.2%, for example, the high level VS2 to be extracted shown in FIG.
(A level exceeding Vc + Vw), the reference count register Cso is counting up during that time, but the sample count register Cs has stopped counting, so the number of zero-level samples (extraction of a level less than Vc + Vw in FIG. 9). Since the number of times is too small, the current 15-second time count section and the data therein are canceled to start a new 15-second time count and data collection. Cs, Cso and Tw are cleared (46), and the process returns to the main routine. Now, in the above verification (2D2), Cs / C
If so is 56.2% or more, the content of the register Tw is compared with 15 seconds in the next step 2D3 in FIG. Actually, the content of Tw is compared with 750 (= 50 × 15). If Tw ≧ 15 seconds, then step 2E
Proceed to. In step 2E, the contents of the register Cs and 422 are compared. That is, during the 15 seconds, the register Rt
422 is compared with the data number of VS2 integrated to 2.
If Cs> 422, the process proceeds to step 2F; otherwise, the process proceeds to step 2G. In step 2F, the content of the register Rt2 is divided by the content of the register Cs, and as a result, Cs data sampled in 15 seconds is obtained.
The average value of the data is stored in the register Mc. In the next step 2H, it is checked whether or not valid data exists in the register Mp. When there is data, the flow proceeds to step 2I, and if not, the flow proceeds to step 2L. In step 2L, the value of the register Mc is stored in the register Mp. In step 2I, the absolute value of the difference between the content of the register Mc (current average value) and the content of the register Mp (previous average value) is set to ΔVd, and the next step 2J
Then, the difference ΔVd obtained in step 2I is set to the threshold value Vth
Compare with The threshold value Vth is 2.44 m in this example.
V. ΔVd> Vth, that is, 1 of signal VS2
If the average value of the data within the range of Vc ± Vw for 5 seconds has changed by Vth or more from the previous value, step 2K is executed next. In step 2K, the content of the register Mc, that is, the current average value is set as a new zero level Vc and stored in the register Mp. Further, the registers Rt2, C
Clear the contents of s, Cso, Tw. The data (VS2) integrated in the register Rt2 in step 2C has a zero level V as shown in FIG.
c is in a very narrow range (± Vw), and when the signal component of the angular velocity appears, the level of the signal VS2 becomes Vc
Since the value is out of the range of ± Vw, the average value (Mc) obtained in step 2F is the average level when the signal VS2 is at the static level for 15 seconds. By drift
For example, if the static level increases or decreases over time,
The difference (ΔVd) between the current average value (Mc) and the previous average value (Mp) becomes larger than the threshold value Vth, and the zero level Vc is automatically updated in step 2K. Therefore, the zero level Vc is always adjusted so as to approach the actual stationary level. Therefore, the data stored in the register Rω in step 22 is the rotational angular velocity detected by the piezoelectric vibrating gyroscope 11. A description will be given with reference to FIG. When the output invalid flag is not set, step 34 is executed. In step 34, the integrated value of the rotational angular velocity, that is, the rotational angle held in the register Rr, is added to the reference azimuth ψref obtained by the GPS positioning calculation, and the result is used as the current azimuth data. The azimuth data is output to the outside. When the difference between the stationary level and the base signal Vbase increases due to the drift of the signal Vin and the output invalid flag is set, step 33 is executed. In step 33, first, the interrupt is prohibited, the contents of various registers are cleared, the GPS positioning operation is executed, the zero level Vc is initialized, the output invalid flag is cleared, and the interrupt is permitted. The rotation angle (Rr content) is cleared,
A new reference direction ψref is detected by the GPS positioning calculation. FIG. 10 shows the results of measuring the change in the detected azimuth when the zero level Vc is sequentially corrected by detecting the drift and when the Vc is not updated by the apparatus of the above embodiment. In this experiment, the apparatus was set in a stationary state, and the experiment was performed under the condition that only the influence of the drift appears as a change. Referring to FIG. 10, the apparatus according to the embodiment sufficiently suppresses the influence of the drift and provides an accurate rotation angle (azimuth).
Can be detected. In the above-described embodiment, the case where the direction of travel of the vehicle is detected by using the piezoelectric vibrating gyroscope has been described. The present invention can be carried out in the same manner as in the above-described embodiment when processing the signal of the device. Although the amplifier 14 shown in FIG. 1 may be omitted and the signal Vin may be referred to instead of the signal VS1, the control error of the base signal Vbase slightly increases. As described above, according to the present invention, the DC level drift of the detector output is canceled without installing a capacitor coupling circuit, so that a slow signal change other than the drift is lost. The signal can be read accurately by preventing the signal from attenuating or attenuating. A threshold setting means (30) for setting a large threshold value (Vw) at a low speed and a small threshold value at a high speed corresponding to the speed (V) of the vehicle is included. Thereby, at high speed, a minute output fluctuation (level change of the angular velocity signal) of the piezoelectric vibrating gyroscope is extracted. The turning time of the vehicle is short at high speed,
Since the change in the drift level during this period is substantially unthinkable, there is substantially no possibility that the drift will be erroneously detected as an angular velocity signal at high speed. In the case of low speed, the extraction sensitivity of the angular velocity signal is
Although the speed is relatively low compared to the high speed, the speed is low and the vehicle position change speed and the direction change speed due to the vehicle speed and the angular speed (turn speed) are low.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a configuration of an apparatus according to an embodiment. FIG. 2 shows a timer interrupt 1 of the microcomputer of FIG.
Is a flowchart showing the contents of the above. FIG. 3 is a flowchart showing a main routine of the microcomputer of FIG. 1; 4A is a flowchart showing the contents of a pulse interrupt of the microcomputer of FIG. 1, and FIG. 4B is a flowchart showing the contents of a timer interrupt 2. . FIG. 5 is a diagram showing a V calculated by “Calculate Vw” 30 shown in FIG.
5 is a graph showing a relationship between w and a vehicle speed V. FIG. 6 is a flowchart showing the contents of “verification of sample number” 2D2 shown in FIG. 2; 7 is a waveform diagram showing an example of a signal output from the piezoelectric vibrating gyroscope 11 shown in FIG. 1 and a signal obtained by amplifying the signal. 8 is a waveform chart showing the levels of signals Vin and VS2 and a base signal of the apparatus of FIG. 9 is a waveform diagram showing signals VS2, zero level Vc, and threshold levels of the device of FIG. FIG. 10 is a graph showing measurement results of drift of the apparatus of FIG. 1; [Description of Signs] 11: Piezoelectric vibration gyro 12: Reference voltage source 13: Buffer 14, 15: Amplifier 16: D / A converter 17: A / D converter 18: Microcomputer 19, 1B: Subtractor 1A , 1C: adder 1D: GPS receiver 1E: GPS demodulator VS1, VS2: signal Vref: reference voltage Vbase: base signal Vc: zero level

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-191812 (JP, A) JP-A-4-62419 (JP, A) JP-A-3-279809 (JP, A) JP-A-2- 38916 (JP, A) JP-A-7-43165 (JP, A) JP-A-63-182519 (JP, A) JP-A-60-183518 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 19/00-19/72 G01P 9/04 G01C 21/00

Claims (1)

(57) [Claim 1] A gyro on a vehicle for outputting a detection signal including a DC component and an AC component; Amplifying means for receiving and amplifying the detection signal to generate an output signal; DC level A base signal generating means for outputting a base signal; a synthesizing means for adding or subtracting the base signal to or from an input of the amplifying means; and a level of the detection signal and a level of the base signal. And first identification means for identifying whether or not the difference is greater than a predetermined first threshold value; when the state in which the difference is greater than the first threshold value has continued for a first time or more. First average calculating means for calculating an average level of the detection signal within the time; changing a level of a base signal output by the base signal generating means according to the average level; Level changing means; corresponding to the speed of the vehicle Threshold setting means for setting a second threshold value which is large at low speeds and small at high speeds; a difference between the level of the output signal of the amplifying means and a predetermined zero level of the signal is referred to Second identification means for identifying whether or not is within a second threshold value; repeatedly referring to the level of the output signal within a second time, and determining the output signal level and the predetermined zero level of the signal; Second average calculating means for sampling the level of the detection signal only when the difference between the two is within a second threshold value and calculating the average of a plurality of levels sampled within a second time; When the difference in the average calculating means and average is calculated with the zero level of is at a predetermined or higher, modifying the zero level on the basis of the average, the zero level adjusting means; and, level with the zero level of the output signal Signal according to the difference Vehicle on gyro drift canceling apparatus comprising; output signal output means.