JPH06294652A - Drift correction system for gyro - Google Patents

Abstract

PURPOSE:To provide a drift correction system which can correct drift even when a vehicle is running. CONSTITUTION:A CPU3 makes a decision whether the output from a gyro, when a vehicle is running, comes between the upper and lower limits when the vehicle is running straight. If it comes between the upper and lower limits, the CPU3 operates a moving average value which is then subtracted from the output of a gyro sensor 1 by means of the subtractor 5 and the difference is fed to a navigation system 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gyro drift correction device.

[0002]

2. Description of the Related Art Although a gyro is widely used in a car navigation system or the like, the gyro has a problem that an error called a drift occurs. FIG. 4 is an output characteristic diagram of a piezoelectric ceramic gyro, for example. As shown in FIG. 4, the output voltage value of the gyro is at a predetermined value when the angular velocity is 0. There is a case where it shifts to the negative side, and this is called drift. Such drift correction is performed by stopping the vehicle for a certain period of time, measuring the static voltage at that time, and using this voltage as a correction value.

[0003]

However, according to the conventional correction method, the vehicle needs to be stopped for a long time, and the vehicle is hardly stopped during traveling on a highway or the like, so that the drift is not corrected. was there. Therefore, the drift increases with time, and this is measured as an angle change, and as a result, the position estimation in the navigation operation is not normally performed, which causes a navigation error. The present invention aims to solve the above-mentioned problems of the prior art.

[0004]

In order to achieve the above object, the present invention provides a gyro drift correction apparatus which is provided in a vehicle and detects a change in angular velocity of the vehicle. An output level determination means for determining whether or not the output upper limit value and the lower limit value of the gyro estimated to be traveling in a straight line are present, and the output of the gyro while the vehicle is traveling is the output upper limit value and the lower limit value. When it is within the range, the moving average value calculating means for calculating the moving average value of the output and the correcting means for correcting the gyro drift based on the moving average value are provided.

[0005]

The output level determining means determines whether the output of the gyro while the vehicle is traveling is within the range of the upper and lower limits of the output of the gyro which is estimated that the vehicle is traveling straight. When the output of the gyro while the vehicle is traveling is within the range of the output upper limit value and the lower limit value, it can be estimated that the angular velocity is almost 0. Therefore, the moving average value of the gyro at this time is calculated by the moving average value calculating means. The calculated gyro drift is corrected based on the calculated moving average value.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the output of the vibration gyro sensor 1 using a piezoelectric ceramic is converted into a digital amount by the A / D converter 2 and input to the CPU 3, where the gyro sensor 1
It is adapted to determine whether the output from the output is within a predetermined range. The range is a range in which it is estimated that the vehicle is traveling in a straight line, in other words, a range that can be regarded as a static voltage. FIG. 2 is an explanatory diagram of the output voltage of the gyro sensor 1 and the traveling state of the vehicle. The output voltage of the gyro sensor 1 is within a predetermined range when the vehicle is traveling straight ahead. The CPU 3 is configured to calculate the moving average of the output from the gyro sensor 1 when it is determined that the output of the gyro sensor 1 is within this range. The drift voltage can be estimated from this average value. The average value is D /
Converted into an analog quantity by the A converter 4 and subtracted by the subtracter 5
The average value is subtracted from the output from the gyro sensor 1, and the output is given to the vehicle-mounted navigation device 9 as a drift-corrected value.

In this embodiment, the temperature characteristic of the gyro sensor 1 such as a piezoelectric ceramic is taken into consideration when setting the upper limit value and the lower limit value shown in FIG. That is, in a vibrating gyroscope using a piezoelectric ceramic, the temperature change is large and the range between the upper limit value and the lower limit value is large.
It is difficult to correct the drift as it is. Therefore, in this embodiment, the temperature coefficient ROM 8 is provided, and the upper limit value and the lower limit value corresponding to the temperature are stored therein as shown in Table 1, and the upper limit value and the lower limit value corresponding to the temperature measured by the temperature sensor 6 are stored. The value is used to determine whether or not the value is within a predetermined range. Reference numeral 7 is an A / D converter.

[Table 1] The data in Table 1 shows that the gyro sensor 1 and the temperature sensor 6 are put in a thermostatic chamber and the temperature is changed from -20 ° C to + 80 ° C.
It can be obtained by measuring the value of the gyro sensor 1 at that time.

The operation will be described with reference to FIG. Temperature sensor 6
Temperature is measured by (Step 40), and temperature coefficient ROM
The upper limit value and the lower limit value corresponding to the measured temperature are read from 8 (step 41). Then, the output voltage of the gyro sensor 1 is read (step 42), and it is determined whether the voltage is in the range between the upper limit value and the lower limit value (step 4).
3). When the output voltage of the gyro sensor 1 is out of the range, the current drift correction value is held. When the output voltage is within the range, a moving average value of the output voltage is calculated and used as a new drift correction value (step 4).
4). Then, this moving average value is output to the D / A converter 4, the subtracter 5 subtracts it from the output from the gyro sensor 1, and gives this output to the vehicle-mounted navigation device 9 (step 45).

The above-mentioned drift correction device can be incorporated in a gyro or can be incorporated in a navigation device. Further, although the D / A converter 4 and the subtractor 5 are used in the above-described embodiment, it is possible to perform digital processing without using them, which enables a significant cost reduction.

According to the configuration of the embodiment described above, it is possible to correct the drift of the gyro sensor 1 without stopping the vehicle. Further, since the straight traveling state of the vehicle is detected according to the environmental temperature, even the gyro sensor 1 having the temperature characteristic can effectively correct the drift. The gyro is not limited to the piezoelectric ceramic type and may be of any type. Alternatively, all the data shown in Table 1 may not be stored, but only the upper limit value and the lower limit value at the reference temperature may be stored, and the temperature may be corrected using a predetermined function and used.

[0011]

As described above, the present invention is a gyro drift correction device that is provided in a vehicle and detects a change in the angular velocity of the vehicle.
Output level determination means for determining whether or not the vehicle is running straight in the range of the output upper limit value and lower limit value of the gyro, and the output of the gyro while the vehicle is traveling, the output upper limit value and When it is within the range of the lower limit value, a moving average value calculating means for calculating the moving average value of the output and a means for correcting the gyro drift based on the moving average value are provided, so that the vehicle is running. It is possible to correct the drift. Therefore, even when traveling for a long time, accurate navigation calculation can be performed.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the running state of the vehicle and the output voltage of the gyro.

FIG. 3 is a flow chart for explaining the operation of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of drift.

[Explanation of symbols]

1: Gyro sensor, 2: A / D converter, 3: CP
U, 4: D / A converter, 5: subtractor, 6: temperature sensor, 7: A / D converter, 8: temperature coefficient ROM, 9:
In-vehicle navigation device.

Claims (3)

[Claims] 1. A gyro drift correction device provided in a vehicle for detecting a change in angular velocity of the vehicle, wherein the output of the gyro while the vehicle is traveling is an upper limit value of the output of the gyro which is estimated to be traveling linearly. Output level determination means for determining whether or not it is within the range of the lower limit value, and when the output of the gyro while the vehicle is traveling is within the range of the output upper limit value and the lower limit value, the moving average value of the output is calculated. A gyro drift correction device, comprising: a moving average value calculating means for correcting the drift of the gyro based on the moving average value. 2. The gyro drift correction device according to claim 1, further comprising a correction unit that corrects the output upper limit value and the output lower limit value according to temperature. 3. A gyro drift correction device provided in a vehicle for detecting a change in angular velocity of the vehicle, comprising: a temperature detection means; and an output of the gyro that the vehicle is estimated to be traveling in a straight line for each predetermined temperature range. The threshold value storage means for storing the upper limit value and the lower limit value and the output of the gyro while the vehicle is traveling are within the range of the output upper limit value and the lower limit value read from the threshold value storage means according to the temperature. Output level determination means for determining whether or not, and a moving average value calculation means for calculating a moving average value of the output when the output of the gyro while the vehicle is running is within the range of the output upper limit value and the lower limit value. A gyro drift correction device comprising: a correction unit that corrects a gyro drift for each predetermined temperature range based on the moving average value.