JPH06117872A - Method for correcting offset of sensor - Google Patents

Abstract

PURPOSE:To pertinently correct the offset of a sensor used for detecting the state of an object to be controlled when the sensor is restarted after the function of the sensor is once stopped. CONSTITUTION:In case the power supply to a sensor device is instantaneously interrupted while an automobile runs, it is discriminated that the automobile is in a stable state from the steering angle of the vehicle being +5 deg. and the output value of a filter circuit 4, namely, the value Ysd of a detected signal is read at the count time T2 of a timer which is, for example, three seconds after the instantaneous interruption. Then an offset correcting process is performing by gradually making an offset correcting value Yod to become nearer and, finally, coincident with the value Ysd of the detected signal. When it is recognized that the sensor outputs a detecting signal while the stable state of the object to be controlled is discriminated, it can be discriminated that the sensor is offset. Therefore, the offset of the sensor can be accurately corrected even when the object to be controlled is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor offset correction method, and more particularly to a sensor offset correction method for correcting a sensor offset when a sensor device is momentarily disconnected.

[0002]

2. Description of the Related Art Conventionally, there are various types of sensors which detect a state of a detection target and perform a predetermined control based on the detected value. The sensors are, for example, for detecting yaw rate in an automobile. (See Japanese Patent Laid-Open No. 3-253471). Based on the yaw rate detection signal from the yaw rate sensor, for example, the navigation device of the automobile can be controlled.

There is a case where a zero offset occurs in the sensor due to performance deterioration and the like, and when used for control, it is necessary to remove the offset value from the sensor detection signal. For example, it is possible to read the detection signal value of the sensor at the time of starting the device, average the value, and use it as an offset value to correct the sensor detection signal by offset correction. In this case, after starting the device, the sensor is put in a standby state for a predetermined time until the sensor becomes stable, and after the time is up, the sensor detection value is sampled a predetermined number of times (several times) in a predetermined sampling period, The offset correction is performed by using the moving average value of the values as the offset value and then subtracting the offset value from the sensor detection signal value.

However, in the above-mentioned conventional method, when the sensor to be corrected is the sensor for detecting the vehicle state as described above, when the power source of the apparatus is momentarily interrupted for some reason during traveling. At the time of restarting, it was difficult to determine whether the sensor detection signal read at the time of restarting was a signal indicating the vehicle state or a sensor offset value.

[0005]

In view of the above problems of the prior art, the main object of the present invention is to provide a sensor when the sensor for detecting the state of the controlled object is once stopped and then restarted. An object of the present invention is to provide a sensor offset correction method capable of appropriately performing the offset correction of the above.

[0006]

According to the present invention, there is provided a process for detecting that a sensor for detecting a state of a controlled object is once stopped and then restarted, and the restart. A step of reading the detection signal of the sensor later, and a step of correcting the detection signal value of the sensor as its offset value only when a predetermined condition corresponding to the stable state of the controlled object is satisfied after the restart, It is achieved by providing a method of correcting an offset of a sensor, which comprises: In particular, when performing the correction, it is preferable that the correction value obtained as the offset value is obtained by asymptotically matching the detection signal value of the sensor.

[0007]

As described above, when the sensor is once stopped and then restarted, it is determined that the predetermined condition corresponding to the stable state of the controlled object is satisfied after the restart, and the sensor is detected regardless of the stable state. If any detection signal is output from, the detection signal value can be regarded as the sensor offset value, and the detection signal value at that time can be corrected as the sensor offset value. In particular, by gradually performing the offset correction, there is no sudden change in the operation of the control target.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a main portion of a yaw rate sensor correction circuit used in, for example, a navigation device for an automobile as a controlled object to which the present invention is applied. Figure 1
In this case, the detection signal of the yaw rate sensor 1 which is an offset correction target and which is arranged at a proper position of the automobile (not shown) is input to the control circuit (not shown) as a control yaw rate signal via the subtractor 2. Has become.

Further, a part of the detection signal from the yaw rate sensor 1 is branched and taken out from the node of the yaw rate sensor 1 and the subtractor 2, and is subtracted to the subtractor 2 through the limiter 3 and the filter circuit 4 in this order. It is designed to be input as a signal. The filter circuit 4 may be configured by, for example, connecting two-order Butterworth type digital filters in three stages in series. Also, the vehicle speed sensor 5
And the detection signals of the steering angle sensor 6 are transmitted to the filter circuit 4
Is input to the correction processing control unit 7 for controlling the.

FIG. 2 is a schematic block diagram showing a method for offset correction of the detection signal of the yaw rate sensor 1. In step ST1, the yaw rate / offset value Yod stored in the correction processing control unit 7 is checked for abnormality,
In the next step ST2, a timer (not shown) in the correction processing control section 7 is set to 3 seconds, and the process proceeds to step ST3.

In step ST3, it is determined whether or not the vehicle is in the stopped state based on the detection signal from the vehicle speed sensor 5. If it is determined that the vehicle is in the stopped state, the process proceeds to step ST4. In step ST4, a limit check of the detection signal Ysd of the yaw rate sensor 1 is performed, and in the next step ST5, a moving average value Ysm of the detection signal Ysd within a predetermined time is calculated,
In step ST5, the average value Ysm is set as a new yaw rate / offset value Yod. In this way, the offset correction value of the yaw rate detection signal when the present sensor device is activated while the vehicle is stopped is obtained.

When the yaw rate detection signal is generated by the yawing of the automobile during the subsequent traveling, the yaw rate / offset value Yod is subtracted from the detected signal value to correct the offset-corrected control yaw rate. Signal is required.

By the way, when the vehicle starts traveling, the flow chart proceeds from step ST3 to step ST7. Even if the power source of the sensor device is momentarily interrupted for some reason, it is determined in step ST7 whether or not the instantaneous interruption occurs. In the normal state where no instantaneous interruption occurs, the process returns to step ST1 and the above routine is repeated.

When it is determined in step ST7 that the instantaneous interruption has occurred, the process proceeds to step ST8, and the yaw rate / offset value Yod is set to 0 in step ST8. In the next step ST9, it is determined whether or not the vehicle is stopped thereafter. If the vehicle is traveling, the process proceeds to the next step ST10. In step ST10, it is determined whether or not the steering wheel is being operated. In this embodiment, when the vehicle speed sensor 5 determines that the vehicle is traveling, the steering angle sensor 6 detects the steering angle as a predetermined condition for determining that the traveling vehicle is in a stable state. , The steering angle is within ± 5 degrees.

If it is determined in step ST10 that the steering wheel is not operated, or if it is determined in step ST9 that the vehicle is stopped, the process proceeds to step ST11. In step ST11, it is determined whether or not the timer set to 3 seconds has timed out, and if it is not timed out, the process returns to step ST1 and the routine is repeated. Then, if it is determined that the time is up in step ST12 after 3 seconds have passed, the process proceeds to step ST13,
Offset correction processing is performed in step ST13, and the routine is repeated.

When it is determined in step ST10 that the steering wheel is operated so that the steering angle exceeds ± 5 degrees, the timer is set to 3 seconds in step ST14, and the process returns to step ST1. Although not described in the flow chart, the start and stop flags of the offset correction process are set at appropriate places. For example, when the offset correction process is started, steps ST8 to ST12 are avoided in the next routine. I process it.

By the way, a method of obtaining an offset correction value when performing the offset correction processing in step ST13 will be described below with reference to FIG. When the device is once stopped and then restarted during traveling, that is, when a momentary interruption occurs in the power source of the sensor device at timing T1 as shown in the figure, the filter circuit of the sensor device is Four
The output of is gradually increased as shown in the diagram of the yaw rate sensor 1, reaches a certain value, becomes stable, and is output as an offset value.

At this time, as described above, when a momentary interruption occurs during traveling, the steering angle is monitored, and if it is within ± 5 degrees as shown in the figure, the vehicle is traveling straight ahead. It can be determined that yawing has not occurred. When the yaw rate detection signal is output as shown in the figure in spite of such a stable state, it can be determined that the output value is the offset value of the yaw rate sensor 1. The correction process is started after the output value of the filter circuit 4 becomes stable after the momentary interruption, that is, at the timing T2 shown in FIG. 3 after a predetermined time (3 seconds in the embodiment) has elapsed.

In this correction, the offset correction value is made asymptotic to the output value of the filter circuit 4 as a detection value, and if they match, the offset correction processing in step ST13 is completed and the value is set to yaw rate. As the offset value Yod, offset correction processing is performed on the detection signal Ysd. By gradually performing the offset correction in this manner, a sudden change in the operation of the control target does not occur, and the driver does not feel uncomfortable.

In this embodiment, the sensor to be corrected is the yaw rate sensor 1 and the steering angle sensor 6 is used as the other state detection sensor. However, the state detection sensor is not limited to these. Left and right wheel speed sensors for detecting the difference may be used.

[0022]

As described above, according to the present invention, a predetermined condition corresponding to the stable state of the controlled object is satisfied after the restart when the power supply of the apparatus is restarted after the sensor once stops functioning and then restarts. The offset correction process is performed only when the sensor detection signal value at that time is used as the offset value, and the offset correction process of the sensor is performed even when the control target that is originally difficult to perform the offset correction process is operating. Can be done accurately.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a correction circuit of a yaw rate sensor of an automobile to which the present invention is applied.

FIG. 2 is a schematic flowchart of offset correction processing according to the present invention.

FIG. 3 is a timing chart for explaining the present control method.

[Explanation of symbols]

 1 Yaw Rate Sensor 2 Subtractor 3 Limiter 4 Filter Circuit 5 Vehicle Speed Sensor 6 Steering Angle Sensor 7 Correction Processing Control Section

Claims (2)

[Claims] 1. A process for detecting that a sensor for detecting a state of a controlled object is once stopped and then restarted, a process of reading a detection signal of the sensor after the restart, and a process for restarting the sensor after the restart. And a step of correcting the detection signal value of the sensor as its offset value only when a predetermined condition corresponding to the stable state of the controlled object is satisfied. 2. The offset correction method for a sensor according to claim 1, wherein, when performing the correction, a correction value obtained as the offset value is obtained by asymptotically matching the detection signal value of the sensor.