JP2010260430A - Sensor reference point correction method - Google Patents

Abstract

An object of the present invention is to provide a sensor reference point correction method capable of correcting the midpoint of the yaw rate even when the vehicle starts running immediately after the vehicle is started.
According to a sensor reference point correction method for correcting a yaw rate midpoint of a yaw rate sensor when a predetermined time ΔTst has elapsed in a state where the vehicle in a running state has stopped after the vehicle has stopped, When the vehicle V is stopped for a predetermined time ΔTst ′ shorter than the time ΔTst, the yaw rate sensor is tentatively corrected for the midpoint.
[Selection] Figure 2

Description

  The present invention relates to a method for correcting a reference point of a sensor provided in a vehicle.

Vehicles equipped with an electric power steering (EPS) device that reduces a driver's steering force are known. Such vehicles include an EPS ECU (Electronic Control Unit) for controlling the electric power steering device. Is equipped.
In addition, when a vehicle stability assist (VSA) that controls the behavior of the vehicle by combining ABS (Anti Lock Brake System) or TCS (Traction Control System) is provided, the vehicle has a VSA ECU for controlling the behavior of the vehicle. ing.

The EPS ECU controls the electric power steering device in accordance with the behavior of the vehicle such as the vehicle running state (turning, straight traveling) and the vehicle speed, and generates an auxiliary steering force to reduce the steering force of the driver and the steering handle. Reaction force control (control for applying reaction force to the operation of the steering handle) is executed in accordance with the steering angle.
Therefore, some vehicles including an electric power steering device have a vehicle behavior detection system including a sensor that detects the behavior of the vehicle. In order to detect turning of the vehicle, the vehicle behavior detection system includes a yaw rate sensor and a steering angle sensor as sensors for detecting the behavior of the vehicle.

As the rudder angle sensor, a sensor (for example, a rotary encoder) that uses a relative angle change amount of the steering handle as a detection value may be used. In this case, the EPS ECU can calculate the steering angle of the steering handle based on the amount of change in angle from the reference point, for example, when the steering handle is in the neutral position (hereinafter referred to as the steering angle midpoint).
Therefore, EPSECU needs to learn the steering angle midpoint. The yaw rate detected by the yaw rate sensor is used for learning the steering angle midpoint.
In order to improve the learning accuracy of the steering angle midpoint, the yaw rate sensor is required to detect the yaw rate with high accuracy.

  Some yaw rate sensors use semiconductor elements, and such a yaw rate sensor has a characteristic that a variation in a detection value accompanying a change in ambient temperature is large. Since the ambient temperature of the yaw rate sensor sequentially changes as the vehicle travels, it is preferable to appropriately correct the midpoint serving as the reference point in order to accurately detect the yaw rate of the vehicle in the traveling state.

  For example, in Patent Document 1, when the ignition switch is turned on, the provisional neutral position of the steering handle is set, and further, the provisional neutral position is appropriately corrected according to the subsequent traveling state of the vehicle. A steering angle neutral learning device that learns a neutral position (steering angle midpoint) is disclosed.

Japanese Patent No. 3728991

  According to the technique disclosed in Patent Document 1, it is determined that the vehicle is traveling straight on the basis of the detection value of the yaw rate sensor, but there is no description regarding correction of the midpoint of the yaw rate sensor, and the change in the ambient temperature. If the detected value of the yaw rate sensor fluctuates with this, there is a problem that the steering angle midpoint cannot be learned accurately.

In order to solve this problem, a configuration in which the midpoint of the yaw rate sensor is appropriately corrected is preferable.
The yaw rate sensor corrects the midpoint by determining a detected value when no yaw rate is generated in the vehicle as a reference value. Therefore, for example, the midpoint can be corrected by determining the detected value when the vehicle is stopped as the reference value.
At this time, immediately after the traveling vehicle stops, the yaw rate sensor is not stable due to the afterglow of vibration during traveling. Therefore, the midpoint of the yaw rate sensor can be accurately corrected by correcting the detected value when the vehicle is stopped for a predetermined time and the yaw rate sensor is stabilized as the reference value.

  In such a configuration, it is preferable that the vehicle stops for several tens of seconds until the running vehicle stops and the yaw rate sensor becomes stable. Therefore, it takes a time of several tens of seconds from the time when the vehicle in the traveling state stops until the midpoint of the yaw rate sensor is corrected.

  By the way, when the vehicle is started (when the ignition switch is turned on), the yaw rate sensor is stable. Therefore, even if the middle point of the yaw rate sensor is corrected immediately after the vehicle is started, the middle point of the yaw rate sensor is accurately determined. Can be corrected.

  Further, if the configuration is such that the midpoint of the yaw rate sensor is corrected after several tens of seconds from the start of the vehicle, the driver may start running the vehicle before the EPS ECU corrects the midpoint of the yaw rate sensor. . In this case, the vehicle travels in a state where the midpoint of the yaw rate sensor is not corrected.

  As described above, if the middle point of the yaw rate sensor is not corrected, the learning accuracy of the steering angle midpoint of the EPSECU decreases, and the EPSECU cannot accurately control the reaction force. As a result, there is a problem that the driver feels uncomfortable.

  Therefore, an object of the present invention is to provide a sensor reference point correction method that can correct the midpoint of the yaw rate even when the vehicle starts running immediately after the vehicle is started.

  In order to solve the above-mentioned problem, the present invention provides a sensor reference point correction method including a procedure for correcting a sensor reference point when a vehicle state satisfies a predetermined condition. The condition is relaxed and the reference point of the sensor is corrected.

According to the present invention, even when the sensor reference point correction method includes a procedure for correcting the sensor reference point when the vehicle state satisfies a predetermined condition, the condition of the sensor is reduced at the start of the vehicle. The reference point can be corrected.
Therefore, it becomes easy to correct the reference point of the sensor when the vehicle is started.

  Further, according to the present invention, the condition includes that the vehicle is stopped for a predetermined time, and relaxing the condition is shortening the predetermined time. To do.

  According to the present invention, the reference point of the sensor can be corrected in a short time when the vehicle is started.

  Further, according to the present invention, the sensor is a yaw rate sensor, and has a function of learning a middle point of the rudder angle sensor based on a detected value of the rudder angle sensor when the yaw rate detected by the yaw rate sensor is a predetermined value or less. A procedure for correcting a midpoint, which is a reference point of the yaw rate sensor, when the vehicle condition satisfies the condition, and at the start of the vehicle, the condition is relaxed and the midpoint of the yaw rate sensor is corrected The sensor reference point correction method is used.

According to the present invention, even if the sensor reference point correction method includes a procedure for correcting the midpoint of the yaw rate sensor when the vehicle state satisfies a predetermined condition, the condition is relaxed when starting the vehicle. The midpoint of the sensor can be corrected.
Therefore, it becomes easy to correct the middle point of the yaw rate sensor when the vehicle is started.

  According to the present invention, it is possible to provide a sensor reference point correction method capable of correcting the midpoint of the yaw rate even when the vehicle starts running immediately after the vehicle is started.

It is a figure which shows the electric power steering apparatus with which a vehicle is equipped. It is a figure which shows the stop time of a vehicle, and the time which correct | amends a yaw rate midpoint. It is a flowchart which shows the procedure of yaw rate midpoint correction | amendment and steering angle midpoint learning.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the steering mechanism of the vehicle V includes a steering wheel (not shown) on a pinion shaft 22 that rotates together with a pinion gear (not shown) that meshes with a rack of a rack shaft 25 a of a rack and pinion mechanism 25. A steering handle 21 is attached via a shaft.
When the driver steers the steering handle 21, a pinion gear (not shown) rotates integrally with the pinion shaft 22 to move the rack shaft 25a in the left-right direction, and the left and right steered wheels 2R connected to the rack shaft 25a, 2L turns.

The vehicle V is provided with an electric power steering device 1.
The electric power steering device 1 includes an electric motor 23 that generates an auxiliary steering force (auxiliary steering torque) that reduces the steering force when the driver steers the steering handle 21 as an electric force and applies the steering force to the steering mechanism. ing.
The output shaft of the electric motor 23 meshes with the gear of the pinion shaft 22 via a gear (not shown). When the driver steers the steering handle 21, the output shaft of the electric motor 23 rotates to assist the pinion shaft 22. Steering force is reduced by generating steering torque.

Further, the electric power steering apparatus 1 includes an EPS ECU 20 that controls the electric power steering apparatus 1 by driving and controlling the electric motor 23.
The EPS ECU 20 includes a microcomputer (not shown), a microcomputer (ROM) including a ROM (Read Only Memory), a RAM (Random Access Memory), and peripheral circuits. The CPU executes a program stored in the ROM, for example. Thus, the drive of the electric motor 23 is controlled.

The VSA ECU 30 that controls the behavior of the vehicle V includes a microcomputer (not shown), a microcomputer having a ROM, a RAM, and the like, and a peripheral circuit. The CPU executes a program stored in the ROM, for example. To control. For example, the VSA ECU 30 is disposed in the engine room 3.
The EPS ECU 20 and the VSA ECU 30 are connected to each other by, for example, a CAN (Controller Area Network) protocol network (hereinafter referred to as a CAN network) and can exchange data with each other.

  A torque sensor 16 is attached to the pinion shaft 22 to detect a steering torque when the driver steers the steering handle 21 and outputs a torque signal Ts. The torque signal Ts is input to the EPS ECU 20, and the EPS ECU 20 calculates the steering torque generated in the pinion shaft 22.

The yaw rate sensor 18 as a sensor for detecting the behavior of the vehicle is incorporated in, for example, the VSA ECU 30, detects the yaw rate generated in the vehicle V, and outputs the yaw rate signal Ys.
The yaw rate signal Ys is input to the EPS ECU 20 via the CAN network, and the EPS ECU 20 calculates the yaw rate generated in the vehicle V.

Further, a vehicle speed sensor 17 is connected to the EPSECU 20.
The vehicle speed sensor 17 detects the vehicle speed as the number of pulses per unit time, and outputs a vehicle speed signal Vs.
The vehicle speed signal Vs is input to the EPS ECU 20, and the EPS ECU 20 calculates the vehicle speed of the vehicle V.

Further, the vehicle V is provided with a steering angle sensor 24 for detecting the steering angle of the steering handle 21.
The rudder angle sensor 24 is constituted by, for example, a sensor that detects an amount of change in angle when the driver steers the steering handle 21, and outputs an angle signal θs. The angle signal θs is input to the EPSECU 20, and the EPSECU 20 calculates the steering angle of the steering handle 21 based on the angle signal θs.

The EPS ECU 20 sets the auxiliary steering torque output from the electric motor 23 based on the calculated vehicle speed, steering torque, and the like, and supplies the electric motor 23 with a drive current Ic that rotates the electric motor 23 so as to output the set auxiliary steering torque. To do.
In the electric motor 23, the output shaft is rotationally driven by the supplied drive current Ic, and an auxiliary steering torque is applied to the pinion shaft 22 to reduce the steering force.
Further, the EPS ECU 20 executes reaction force control for applying a steering reaction force to the steering handle 21 based on the calculated vehicle speed, steering torque, steering angle, yaw rate, and the like.

  In the present embodiment, the EPS ECU 20 is configured to detect the behavior of the vehicle V based on the detection values of the vehicle speed sensor 17, the steering angle sensor 24, and the yaw rate sensor 18, and the vehicle speed sensor 17, the steering angle sensor 24, and the yaw rate are detected. The vehicle behavior detection system 5 is configured including the sensor 18 and the EPS ECU 20.

  If the steering angle sensor 24 is a sensor that detects the amount of change in the angle of the steering handle 21, the EPS ECU 20 learns that the steering handle 21 is in the neutral position (steering angle midpoint), and from the steering angle midpoint. Based on the angle change amount, the steering angle of the steering handle 21 is calculated. Therefore, EPSECU 20 needs to learn the steering angle midpoint. Hereinafter, learning of the steering angle midpoint by the EPS ECU 20 is referred to as steering angle midpoint learning.

  It is preferable that the EPS ECU 20 periodically learns the steering angle midpoint in order to detect the steering angle of the steering handle 21 with high accuracy.

  Since the vehicle V goes straight when the steering handle 21 is at the rudder angle midpoint, the EPS ECU 20 inputs from the rudder angle sensor 24 when the yaw rate is not generated in the traveling vehicle V in the rudder angle midpoint learning. The rudder angle calculated based on the angle signal θs is determined as the rudder angle midpoint.

For example, the EPS ECU 20 determines that the steering handle 21 is at the steering angle midpoint when the following condition A is satisfied, and learns the steering angle midpoint.
<< Condition A >>
1. The vehicle speed of the vehicle V is equal to or greater than a predetermined value VEL1.
2. The yaw rate generated in the vehicle V is equal to or less than a predetermined value YAW1.
3. The steering torque generated on the pinion shaft 22 is within a predetermined value TRQ1.
4). The fluctuation range of the rudder angle is ΔDEG1 or less.
5.1. ~ 4. The state continues for time TIM1.

As described above, the EPS ECU 20 of the vehicle V has a function of learning the steering angle midpoint based on the detected value of the steering angle sensor 24 when the yaw rate detected by the yaw rate sensor 18 is equal to or less than the predetermined value YAW1.
Further, since the detected value of the yaw rate detected by the yaw rate sensor 18 is used for the steering angle midpoint learning of the EPS ECU 20, the reference of the yaw rate sensor 18 is used in order to improve the accuracy of the detected value of the yaw rate of the yaw rate sensor 18. A configuration in which the points are corrected appropriately is preferable. With this configuration, the accuracy of the steering angle midpoint learning of the EPS ECU 20 can be improved.
Hereinafter, the midpoint (midpoint of the yaw rate sensor) serving as the reference point of the yaw rate sensor 18 is referred to as a yaw rate midpoint. The middle point of the yaw rate is a detection value detected by the yaw rate sensor 18 when no yaw rate is generated in the vehicle V.
Further, correcting the midpoint of the yaw rate is hereinafter referred to as midpoint correction (reference point correction), and correcting the midpoint of the yaw rate sensor is referred to as yaw rate midpoint correction.

For example, the EPS ECU 20 determines the detected value detected by the yaw rate sensor 18 when the following condition B is satisfied as the yaw rate midpoint and corrects the yaw rate midpoint.
<< Condition B >>
When the vehicle V has been stopped for a predetermined time ΔTst and a predetermined time ΔTyaw shorter than the predetermined time ΔTst has elapsed since the vehicle V stopped.

Further, when the vehicle V is traveling, the EPS ECU 20 determines the detected value detected by the yaw rate sensor 18 when the following condition C is satisfied as the yaw rate midpoint, and corrects the yaw rate midpoint.
<< Condition C >>
1. The fluctuation range of the yaw rate is within a predetermined value ΔYAW2.
2. The steering torque generated on the pinion shaft 22 is within a predetermined value TRQ2.
3. The fluctuation range of the steering angle is within a predetermined value Δθ2.
4). The vehicle speed is equal to or higher than a predetermined value VEL2.
5.1. ~ 4. State continues for time TIM2.

The predetermined values (VEL1, YAW1, TRQ1, ΔDEG1, TIM1, ΔYAW2, TRQ2, Δθ2, VEL2, TIM2) of the conditions A and C are the performance required for the vehicle V, the steering angle sensor 24, and the yaw rate sensor 18. What is necessary is just to set suitably based on the sensitivity of this.
The predetermined times ΔTst and ΔTyaw will be described later.

  The EPS ECU 20 corrects the yaw rate midpoint when either of the above-described condition B or condition C is satisfied, and further, when the condition A is satisfied, the steering ECU is adjusting the steering angle based on the detected value of the yaw rate sensor 18 corrected by the yaw rate midpoint. Point learning. Thus, EPSECU 20 can calculate the steering angle of the steering handle 21 with high accuracy by appropriately learning the steering angle midpoint. The EPS ECU 20 can suitably control the reaction force based on the steering angle of the steering handle 21 with high accuracy.

When the EPS ECU 20 corrects the yaw rate midpoint when the traveling vehicle V stops, the vehicle V needs to stop for a predetermined time ΔTst as shown in FIG.
When the predetermined time ΔTst has elapsed with the vehicle V stopped, the EPS ECU 20 determines the yaw rate detected by the yaw rate sensor 18 when the predetermined time ΔTyaw shorter than the predetermined time ΔTst has elapsed since the vehicle V stopped. Determine the midpoint.
Thus, the yaw rate sensor 18 can be stabilized by stopping the vehicle V for a predetermined time ΔTst after the vehicle V in the running state stops. The EPS ECU 20 can accurately correct the yaw rate midpoint by determining the detected value detected when the yaw rate sensor 18 is in a stable state as the yaw rate midpoint.

Therefore, the predetermined time ΔTst may be set in advance through experiments or the like, for example, as the time during which the yaw rate sensor 18 is stabilized.
Further, the predetermined time ΔTyaw is not a limited time, and may be set as appropriate based on the characteristics of the yaw rate sensor 18 such as a half time (ΔTyaw = ΔTst / 2) of the predetermined time ΔTst.
Alternatively, the predetermined time ΔTyaw may be equal to the predetermined time ΔTst.

As described above, the predetermined time ΔTst when the vehicle V stops in order for the EPS ECU 20 to correct the midpoint of the yaw rate is a time required for the yaw rate sensor 18 to be stabilized, and may be set to a time of several tens of seconds. . For this reason, if the driver turns on an ignition switch (not shown) and starts the vehicle V, then the yaw rate midpoint correction is performed when the predetermined time ΔTst shown in FIG. There is a case where the vehicle V is caused to travel before the time ΔTst elapses.
Then, after the vehicle V is started, if the vehicle V enters a traveling state before the predetermined time ΔTst has elapsed, the vehicle V travels without the EPS ECU 20 correcting the yaw rate midpoint.

Thereafter, EPSECU 20 cannot correct the yaw rate midpoint until vehicle V satisfies either condition B or condition C, and consequently cannot learn the steering angle midpoint.
Accordingly, the EPS ECU 20 cannot calculate the steering angle of the steering handle 21 with high accuracy, and cannot suitably control the steering handle 21 for reaction force. As a result, the driver may feel uncomfortable.

Therefore, in the present embodiment, when the EPS ECU 20 is not learning the steering angle midpoint, such as immediately after the vehicle V is started, the execution condition for the yaw rate midpoint correction is relaxed.
Specifically, when performing the yaw rate midpoint correction, EPSECU 20 significantly shortens the predetermined time ΔTst of the stop of vehicle V shown in FIG.
With this configuration, the EPS ECU 20 can correct the yaw rate midpoint in a short stoppage time, and further can learn the steering angle midpoint based on the detected value of the yaw rate sensor 18 that has been corrected for the yaw rate midpoint.

For example, the EPSECU 20 determines that the yaw rate sensor 18 is turned on when a predetermined time ΔTyaw ′ shorter than the stop time ΔTst ′ elapses when the vehicle V immediately after starting has stopped for a stop time ΔTst ′ shorter than the stop time ΔTst. The detected value detected is determined as the yaw rate midpoint (temporary midpoint) of the yaw rate sensor 18, and the yaw rate sensor 18 is provisionally corrected to the midpoint. Such midpoint correction of the provisional yaw rate sensor 18 is referred to as provisional midpoint correction.
That is, EPSECU 20 tentatively corrects the yaw rate sensor 18 after the vehicle V is started.

  For example, when the driver can turn on an ignition switch (not shown) and start the vehicle V, and the vehicle V can start running in about 10 seconds, the stop time ΔTst ′ that is shorter than 10 seconds (for example, 5 seconds). Is set in advance, and the predetermined time ΔTyaw ′ is set to a time shorter than the stop time ΔTst ′. That is, the EPS ECU 20 relaxes the conditions for learning the yaw rate midpoint and corrects the temporary midpoint.

With this configuration, EPSECU 20 can always tentatively correct the midpoint of yaw rate sensor 18 after vehicle V is started.
The EPS ECU 20 can learn the steering angle midpoint based on the detected value of the yaw rate sensor 18 that has been subjected to the provisional midpoint correction when the above-described condition A is satisfied.

With reference to FIG. 3, the procedure by which the EPS ECU 20 performs the yaw rate midpoint correction and the steering angle midpoint learning will be described (see FIGS. 1 and 2 as appropriate).
As shown in FIG. 3, when the vehicle V starts, EPS ECU 20 corrects the yaw rate sensor 18 for a temporary midpoint (step S1).

The EPS ECU 20 performs the steering angle midpoint learning based on the detected value of the yaw rate sensor 18 that has been subjected to the provisional midpoint correction when the steering angle midpoint learning condition is satisfied after the provisional midpoint correction of the yaw rate sensor 18 (step S2 → Yes). (Step S3).
The EPS ECU 20 assumes that the steering angle midpoint learning condition is satisfied when the above-described condition A is satisfied, and that the steering angle midpoint learning condition is not satisfied when the condition A is not satisfied.

Thereafter, while the yaw rate midpoint correction condition is not satisfied (step S4 → No), the EPS ECU 20 returns the process to step S2 and does not perform the yaw rate midpoint correction, but when the yaw rate midpoint correction condition is satisfied (step S4 → Yes). ) EPSECU 20 corrects the yaw rate midpoint (step S5).
The EPS ECU 20 determines that the yaw rate midpoint correction condition is satisfied when either the above-described condition B or condition C is satisfied, and the yaw rate midpoint correction is performed when neither the condition B nor the condition C is satisfied. Assume that the condition is not satisfied.
The yaw rate midpoint correction condition becomes the predetermined condition described in the claims.
Further, the predetermined time ΔTst included in the condition B is the predetermined time described in the claims.

  Returning to step S2, if the yaw rate midpoint correction condition is satisfied (step S4 → Yes) while the steering angle midpoint learning condition is not satisfied (step S2 → No), the EPS ECU 20 can correct the yaw rate midpoint (step S5). ). Therefore, the EPS ECU 20 can learn the steering angle midpoint based on the detection value of the yaw rate sensor 18 corrected for the yaw rate midpoint without using the detection value of the yaw rate sensor 18 corrected for the temporary midpoint.

  Thus, the EPS ECU 20 (see FIG. 1) according to the present embodiment can always correct the temporary midpoint of the yaw rate sensor 18 (see FIG. 1) when the vehicle V (see FIG. 1) is started. The steering angle midpoint can be learned based on the detected value of the yaw rate sensor 18 subjected to the provisional midpoint correction.

  As described above, the EPS ECU 20 (see FIG. 1) according to the present embodiment sets the stop time required for the vehicle V when correcting the midpoint of the yaw rate immediately after the driver starts the vehicle V (see FIG. 1). As shown in FIG. 2, provisional midpoint correction is performed by shortening ΔTst to ΔTst ′. In other words, the EPS ECU 20 performs midpoint correction (temporary midpoint correction) by relaxing the yaw rate midpoint correction condition.

  With this configuration, even when the driver starts running the vehicle V immediately after starting the vehicle V, the steering angle midpoint learning can be performed based on the detected value of the yaw rate sensor 18 subjected to the provisional midpoint correction. The steering angle of the steering handle 21 (see FIG. 1) can be detected with high accuracy. Therefore, the reaction force control of the steering handle 21 can be suitably executed, and an excellent effect that the driver feels uncomfortable can be preferably suppressed.

The EPS ECU 20 (see FIG. 1) is configured to relax the yaw rate midpoint correction condition immediately after the vehicle V (see FIG. 1) is started. For example, the EPS ECU 20 is not learning the steering angle midpoint. A configuration in which the yaw rate midpoint correction condition is relaxed during the state may be employed.
The EPS ECU 20 is configured to relax the yaw rate midpoint correction condition by shortening the stop time ΔTst required for the vehicle V. For example, ΔYAW2 (variation range of the yaw rate) or TRQ2 (pinion) of the condition C described above is used. The yaw rate midpoint correction condition may be relaxed by relaxing condition C, such as increasing the value of the steering torque generated on the shaft 22.

5 Vehicle Behavior Detection System 17 Vehicle Speed Sensor 17 (Vehicle Behavior Detection System)
18 Yaw rate sensor (sensor, vehicle behavior detection system)
20 EPSECU (control device, vehicle behavior detection system)
24 Rudder angle sensor (vehicle behavior detection system)
ΔTst Predetermined time V Vehicle

Claims (3)

A sensor reference point correction method comprising a procedure for correcting a sensor reference point when a vehicle condition satisfies a predetermined condition,
A sensor reference point correction method, wherein the sensor reference point is corrected by relaxing the condition when the vehicle is started. The condition includes that the vehicle is stopped for a predetermined time,
The method for correcting a reference point of a sensor according to claim 1, wherein relaxing the condition is shortening the predetermined time. The sensor is a yaw rate sensor,
When the yaw rate detected by the yaw rate sensor is equal to or less than a predetermined value, the vehicle state having a function of learning a middle point of the rudder angle sensor based on the detected value of the rudder angle sensor satisfies the condition. It has a procedure to correct the midpoint as the sensor reference point,
3. The sensor reference point correction method according to claim 1, wherein when the vehicle is started, the condition is relaxed and a midpoint of the yaw rate sensor is corrected. 4.

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