JPH1137774A - Computing method for drift amount of on-vehicle gyro-type yaw rate sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a computing method that can compute the drift amount of a yaw rate sensor precisely even when a vehicle is moved by a movement means such as a ferryboat. SOLUTION: In the computing method for the drift amount of a yaw rate sensor, when the stop state of a vehicle is judged, the drift amount γd of the yaw rate sensor is computed on the basis of the output of the yaw rate sensor. Whether the vehicle is in a stopped state or not is judged (S20). When the vehicle is in the stopped state, a temporary drift amount γdt is computed and stored on the basis of the output γs of the yaw rate sensor in every prescribed time from a point of time in which the state is first judged (S30 to S70). When the running state of the vehicle is judged (S80), the first amount γd is set to a latest preliminary drift amount γdt(n) which is stored just before.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of calculating a drift amount of a yaw rate sensor, and more particularly to a method of calculating a drift amount of a gyro-type yaw rate sensor mounted on a vehicle.

[0002]

2. Description of the Related Art In a yaw rate sensor mounted on a vehicle such as an automobile, a deviation may occur between a yaw rate detected by the yaw rate sensor and an actual yaw rate of the vehicle due to various factors. The deviation is generally called drift. One of the methods for correcting the drift of the yaw rate sensor is disclosed in, for example,
As described in JP-A-26161, it is determined whether or not the vehicle is in a stopped state, and when the stopped state of the vehicle is determined, the drift amount of the yaw rate sensor is calculated based on the output of the yaw rate sensor, and the yaw rate sensor is calculated. A method of subtracting the amount of drift from the output of (i) is conventionally known.

Generally, when the vehicle is stopped, the actual yaw rate of the vehicle is 0, and when the vehicle is stopped, the output of the yaw rate sensor corresponds to the drift amount of the yaw rate sensor. According to the method, the drift of the yaw rate sensor is canceled by the calculated drift amount, whereby the actual yaw rate of the vehicle can be accurately obtained.

[0004]

Generally, the stationary state of a vehicle is determined based on the detection results of on-board sensors such as wheel speed sensors, and the vehicle is stopped based on the detection results of these sensors. However, there is a case where the vehicle is actually yawing with respect to the earth, such as when the vehicle is on a ferry boat or a turntable.

Accordingly, the yaw rate sensor is a gyro-type yaw rate sensor generally used for a vehicle such as an automobile. When the vehicle is moved by a moving means such as a ferry boat, the yaw rate sensor moves the vehicle. The yaw rate of the yaw movement caused by the movement is detected. Therefore, in the conventional drift correction method as described above, the drift amount of the yaw rate sensor is calculated as the sum of the true drift amount and the yaw rate of the actual yaw motion of the vehicle. As a result, the drift amount of the yaw rate sensor is calculated. There is a problem that the calculation cannot be performed accurately and the yaw rate detected by the yaw rate sensor cannot be accurately corrected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in a conventional yaw rate sensor drift correction method for calculating a drift amount of a yaw rate sensor based on an output of the yaw rate sensor when the vehicle is stopped. The main object of the present invention is to calculate the drift amount of the yaw rate sensor based on the output of the yaw rate sensor in a situation where the vehicle does not yaw relative to the earth, so that the vehicle can move the ferry boat. Even in the case where the yaw rate sensor is moved by such a moving means, it is necessary to accurately calculate the drift amount of the yaw rate sensor.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a gyro-type yaw rate control system for calculating a drift amount of a yaw rate sensor based on an output of a yaw rate sensor when a stop state of the vehicle is determined. A method of calculating the drift amount of the sensor, when the vehicle is in a stopped state, calculating and storing a provisional drift amount based on the output of the yaw rate sensor at predetermined time intervals from the time when the stopped state is first determined, Setting the drift amount to the latest provisional drift amount stored immediately before when it is determined that the vehicle is stopped from being stopped, and a drift correction method for the vehicle-mounted gyro-type yaw rate sensor. 1) or an output of a wheel speed sensor that detects a wheel speed based on a pulse generated at a frequency proportional to the rotation speed of the wheel. The vehicle stopped state is determined by the method of calculating the drift amount of the vehicle-mounted gyro-type yaw rate sensor that calculates the drift amount of the yaw rate sensor based on the output of the yaw rate sensor when the vehicle stopped state is determined. When the vehicle is stopped, the temporary drift amount is calculated and stored at predetermined time intervals based on the output of the yaw rate sensor from the time when the stop state is first determined, and the stop time is determined when the release of the vehicle stop state is determined. Calculating the drift amount to the latest provisional drift amount stored immediately before when the stop time is less than the reference value, and setting the drift amount to the latest provisional drift amount when the stop time is equal to or more than the reference value. Setting the vehicle to the provisional drift amount stored immediately before the vehicle. It is achieved by the drift amount calculating method (the second aspect).

In general, even when a vehicle is on a ferry boat, the ferry boat is in a stopped state immediately before the vehicle starts running, so that the vehicle is stationary with respect to the earth immediately before the vehicle starts running. The actual yaw rate of the vehicle is therefore considered to be zero.

According to the configuration of the first aspect, when the vehicle is in a stopped state, the provisional drift amount is calculated and stored at predetermined time intervals based on the output of the yaw rate sensor from the time when the stopped state is first determined. When it is determined that the vehicle is stopped, the drift amount is set to the latest provisional drift amount stored immediately before. Therefore, even when the vehicle is moved by a moving means such as a ferry boat, the latest provisional drift amount is determined immediately before the release of the stopped state of the vehicle is determined, that is, in a situation where both the moving means and the vehicle are stopped. Since it is the calculated drift amount, the drift amount of the yaw rate sensor can be accurately obtained.

Generally, a wheel speed sensor detects a wheel speed based on a pulse generated at a frequency proportional to the rotation speed of the wheel. When the rotation speed of the wheel is low, the wheel speed sensor detects the wheel speed. Can not. Therefore, if the vehicle accelerates while slowly turning left or right after stopping at the intersection, the stop state of the vehicle is determined based on the output of the wheel speed sensor, and then the stop state is determined. However, since the vehicle is actually performing yaw movement, the yaw rate sensor detects the yaw rate of the yaw movement. Therefore, if the provisional drift amount immediately before the stop state is determined to be released is set as the drift amount of the sensor, the drift amount is the sum of the true drift amount and the yaw rate of the actual yaw motion of the vehicle.

According to the second aspect of the present invention, when the stop time of the vehicle is shorter than the reference value, the drift amount is set to the latest provisional drift amount stored immediately before, and when the stop time is longer than the reference value, the drift amount is set. Is set to the provisional drift amount stored immediately before the latest provisional drift amount.For example, when the vehicle is stopped and the vehicle slowly accelerates while turning, the drift amount is set to The drift amount of the yaw rate sensor is accurately calculated by setting the provisional drift amount calculated in (1).

[0012]

According to a preferred aspect of the present invention, there is provided the above-mentioned claim 1 or 2,
The provisional drift amount is configured to be calculated as an average value of the output of the yaw rate sensor at the predetermined time (preferred mode 1).

According to another preferred aspect of the present invention, in the configuration according to the first aspect, the vehicle is released from the stopped state within the predetermined time from the time when the stopped state of the vehicle is first determined. Is determined, the calculation of the provisional drift amount is stopped, and the previously set drift amount is maintained (preferred mode 2).

According to another preferred aspect of the present invention, in the configuration according to the second aspect, when the stop time is shorter than the predetermined time, the calculation of the provisional drift amount is stopped and the previously set drift amount is set. It is configured to maintain the drift amount obtained (preferred embodiment 3).

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic structural view showing a vehicle on which a method for calculating a drift amount of a yaw rate sensor according to the present invention is executed.

In FIG. 1, 10fl and 10fr denote left and right front wheels of the vehicle 12, respectively, and 10rl and 10rr denote left and right rear wheels of the vehicle, respectively. Each of these wheels is provided with a wheel speed sensor 14fl, 14fr, 14rl, 14rr for detecting a wheel speed Vwi (i = fl, fr, rl, rr). Each wheel speed sensor includes a magnetic gear fixed to a corresponding axle and an electromagnetic pickup fixed to a wheel support member, and generates an output pulse at a frequency proportional to the rotation speed of the wheel.

The vehicle 12 is provided with a gyro-type yaw rate sensor 16 and a shift position sensor 18. The yaw rate sensor 16 detects a yaw rate γ of the vehicle, and the shift position sensor 18 detects a shift position of an automatic transmission (not shown).

As shown, the wheel speed sensors 14fl to 14fl
A signal indicating the wheel speed Vwi detected by rr, a signal indicating the yaw rate γs detected by the yaw rate sensor 16, and a signal indicating the shift position detected by the shift position sensor 18 are input to the electric control device 20. Although not shown in detail in the drawing, the electric control device 20 has, for example, a general configuration in which a CPU, a ROM, a RAM, and an input / output port device are connected to each other by a bidirectional common bus. Microcomputer.

The electric control device 20 controls the wheel speed Vwi in accordance with the flowcharts shown in FIGS.
The vehicle stop state is determined based on the following equation, and when the vehicle stop state is determined, the drift amount γd of the yaw rate sensor 16 is calculated, and the drift amount γd is further subtracted from the output γs of the yaw rate sensor to reduce the yaw rate sensor drift. to correct.

Next, a routine for calculating the drift amount of the yaw rate sensor and the yaw rate correction routine in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 10, each signal is read, and in step 20, the vehicle is stopped for a predetermined time Tsc (for example, 10 seconds) in accordance with the flowchart shown in FIG. It is determined whether or not the operation has continued. If a negative determination is made, the process proceeds to step 80, and if an affirmative determination is made, the count values Ta and Tb of the timer are set to ΔT (eg, A positive constant corresponding to the cycle time in the flowchart shown in FIG. 2) is incremented, and the output γs of the yaw rate sensor 16 is integrated in step 40 to calculate the integrated value Σγs of the yaw rate.

In step 50, it is determined whether or not the count value Ta of the timer is equal to or greater than a reference value Tac (eg, a positive constant of about 5 seconds). If a negative determination is made, step 160 is executed. When the determination is affirmative, in step 60, the provisional drift amount γdt of the yaw rate sensor is calculated in accordance with the following equation 1, where N is a positive integer equal to Tac / ΔT.

Γdt = Σγs / N

In step 70, the provisional drift amount γdt calculated in step 60 is updated to its latest value γ
updated by being stored in RAM as d (n),
Also, the previous value of the provisional drift γd (n-1) is
In addition to being updated to the provisional drift amount calculated at 0, the count value Ta of the timer and the integrated value of the yaw rate Σ
After γs is reset to 0, the routine proceeds to step 160.

In step 80, for example, the maximum value Vwmax of the wheel speeds Vwi of the four wheels is set to the reference value Vwo.
It is determined whether or not the vehicle is running by determining whether or not the value is (positive constant) or more. If the determination is affirmative, the process proceeds to step 90. In step 90, it is determined whether or not the count value Tb of the timer is smaller than the reference value Tac. If a negative determination is made, the process proceeds to step 100. If a negative determination is made in step 80 and an affirmative determination is made in step 90, the process proceeds to step 150.

In step 100, it is determined whether or not the count value Tb of the timer is equal to or larger than a reference value Tbc (eg, a positive constant larger than Tac such as 2Tac).
If a negative determination is made, the drift amount γd of the yaw rate sensor is set to the tentative drift amount γdt (n) calculated and stored immediately before in step 110, and if a positive determination is made, the yaw rate The drift amount γd of the sensor is set to the provisional drift amount γdt (n-1) calculated and stored one time before γdt (n).

In step 130, the filter coefficient R is set to a positive constant of, for example, 0.5 or more and less than 1, and γd
(n) is the value of the drift amount set in step 110 or 120, and γd (n-1) is the previous value of the drift amount, and the filtering process of the drift amount γd of the yaw rate sensor is performed according to the following equation 2. In step 140, the drift amount γd is stored in the RAM.

## EQU2 ## γd = R ・ γd (n) + (1−R) ・ γd (n-1)

In step 150, the count values Ta and Tb of the timer are reset to 0, respectively, and the integrated value ヨ ー γs of the yaw rate is reset to 0. In step 160, the yaw rate is calculated according to the following equation (3). The corrected yaw rate γ is calculated by subtracting the output γs of the sensor 16 by the drift amount γd.

Γ = γs−γd

Next, the subroutine for determining the vehicle stop state in the above-mentioned step 20 will be described with reference to the flowchart shown in FIG.

First, in step 21, it is determined whether or not the maximum value Vwmax of the wheel speeds Vwi of the four wheels is less than a reference value Vwo (positive constant), and a negative determination is made. If so, the process proceeds to step 24, and if a positive determination is made, the process proceeds to step 22.

In step 22, it is determined whether or not the shift position of the automatic transmission detected by the shift position sensor is in the P range. When the count value Ts is incremented by ΔTs (positive constant) and a negative determination is made, the count value Ts of the timer is reset to 0, and then the routine proceeds to step 80.

In step 25, it is determined whether or not the count value Ts of the timer is equal to or greater than a reference value Tsc (positive constant).
If the determination is negative, the routine proceeds to step 80.

Thus, according to the illustrated embodiment, when it is determined in step 20 that the vehicle has been stopped for a predetermined time Tsc or more, steps 30 to 70 are performed.
, A provisional drift amount γdt is calculated for each Tac time. If a negative determination is made in step 20 and the running state of the vehicle is determined in step 80, it is determined in step 100 whether or not the stop time of the vehicle is longer than the Tbc time. .

When the stop time of the vehicle is shorter than the Tbc time, a negative determination is made in step 100, and the yaw rate sensor 16 is turned on in step 110.
Is set to the latest provisional drift amount γdt (n), the filtered value γd is calculated in step 130, and the value is stored as the yaw rate sensor drift amount γd in step 140. You.

For example, as shown in FIG.
If the vehicle is stopped at time t1, or if the ignition switch is closed at time t1 while the vehicle is stopped, affirmative determination is made at step t2 at time t2 after the elapse of Tsc. As a result of the determination, the calculation of the integrated value ヨ ー γs of the yaw rate is started, and the provisional drift amount γdt is calculated at time t3 when the time Tac has elapsed from time t2. When the vehicle enters the running state at time t4, which is before time t5 when the time Tac elapses from time t3, a negative determination is made in step 20, a positive determination is made in step 80, and a positive determination is made in step 80. A negative determination is made in step 100, whereby the drift amount γd of the yaw rate sensor is set to the latest provisional drift amount γdt (n) in step 110.

When the stop time of the vehicle is equal to or longer than the Tbc time, an affirmative determination is made in step 100, and in step 120, the drift amount γd of the yaw rate sensor 16 becomes the latest provisional drift amount γdt (n )
Tentative drift amount γdt (n-1) calculated and stored just before
Is calculated in step 130, and the filtered value γd is calculated in step 130. In step 140, the value is stored as the drift amount γd of the yaw rate sensor.

For example, as shown in FIG.
At the time point t3 after the elapse of the Tac time, the provisional drift amount γdt is calculated and stored as the provisional drift amount γdt (n). At time t4 when Tac time has elapsed from time t3.
, The provisional drift amount γdt is calculated and stored as the latest provisional drift amount γdt (n), and the previous provisional drift amount γdt is updated to the previous value γdt (n-1). And time t
Time point t5 before time point t6 when Tac time elapses from 4
When the vehicle is in a running state in step S1, a negative determination is made in step S20, an affirmative determination is made in step S80, and a negative determination is made in step S100. The drift amount γd of the yaw rate sensor is set to a value γdt (n-1) immediately before the latest provisional drift amount γdt (n).

When the stop time of the vehicle is too short to calculate the provisional drift amount γdt, that is, as shown in FIG. 6, the stop time of the vehicle is less than Tsc + Tac, and the time t
The time t3 before the time t4 when the Tac time elapses from 2
In step 50, when the vehicle starts running,
In steps 80 and 90, the affirmative determination is made without performing the affirmative determination, so that the provisional drift amount γdt is not calculated, and the yaw rate sensor drift amount γdt is calculated.
d is maintained at a previously computed and stored value.

Therefore, according to the illustrated embodiment, when the stop time of the vehicle is relatively short, for example, 15 seconds or more and less than 20 seconds, the drift amount γd of the yaw rate sensor 16 is calculated immediately before the vehicle starts running. Is set to the latest provisional drift amount γdt (n), so that even if the vehicle is moved by a moving means such as a free boat, the moving means is in a stopped state and the vehicle is also stopped with respect to the moving means. The drift amount γd of the yaw rate sensor can be accurately obtained as the drift amount at a certain time, whereby the detection value of the yaw rate sensor can be accurately corrected and the yaw rate of the vehicle can be accurately detected.

In the conventional drift correction method for a yaw rate sensor described in Japanese Patent Application Laid-Open No. 64-26161, the time for calculating the drift amount of the yaw rate changes depending on the stop time of the vehicle. According to the illustrated embodiment, the provisional drift amount of the yaw rate sensor is always calculated at regular intervals, so that the drift amount can always be obtained under constant conditions.

According to the illustrated embodiment, when the vehicle stop time is long, for example, 20 seconds or more, the drift amount γd of the yaw rate sensor 16 becomes the latest provisional drift amount γ.
Since the provisional drift amount γdt (n-1) immediately before dt (n) is set, even if the vehicle accelerates while turning slowly after stopping at the intersection, the vehicle actually stops. The drift amount γd of the yaw rate sensor can be accurately obtained as the drift amount when the vehicle is running, whereby the detection value of the yaw rate sensor can be accurately corrected and the yaw rate of the vehicle can be accurately detected.

Further, the above-mentioned conventional drift correction method for the yaw rate sensor has a problem that the drift amount of the yaw rate sensor cannot be accurately obtained when the vehicle stops and then slowly turns and accelerates. In order to solve this problem, the time between the end of the calculation of the drift amount and the time of the determination of the start of traveling of the vehicle must be set long, in which case the stopping time of the vehicle is relatively short. In this case, the drift amount of the yaw rate sensor cannot be calculated.

On the other hand, according to the illustrated embodiment, the provisional drift amount of the yaw rate sensor is calculated every predetermined time, so that the drift amount of the yaw rate sensor can be reduced even when the vehicle stops for a relatively short time. Can be reliably calculated, thereby preventing the frequency of calculating the drift amount from being excessively reduced.

Further, according to the illustrated embodiment, when the stop time of the vehicle is very short, for example, less than 15 seconds, the provisional drift amount of the yaw rate sensor is not calculated, and the drift amount calculated before that is not calculated. Since γd is maintained,
It is possible to reduce a possibility that the drift amount is incorrectly calculated based on a specific detection value of the yaw rate sensor generated during a very short stop time of the vehicle.

In particular, according to the illustrated embodiment, step 1
In step 30, the drift amount γd is calculated as a filtered value based on the current value γd (n) of the drift amount of the yaw rate sensor 16 and its previous value γd (n-1). It is possible to reduce a possibility that the drift amount is incorrectly calculated based on the detected value.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to the above embodiment, and various other embodiments are included in the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the above-described embodiment, in step 130, the filtering process is performed based on the current value γd (n) of the drift amount and the previous value γd (n-1). The filtering process may be performed based on three or more recent drift amounts, and the filtering process in step 130 may be omitted.

In the above-described embodiment, the drift amount γd calculated in step 130 is the same as that in step 1
Before the step 130 or before the step 140, the magnitude of the deviation between the current value γd (n) of the drift amount and the previous value γd (n-1) is determined. It is determined whether or not the value is less than the reference value (positive constant). If an affirmative determination is made, the process proceeds to step 150 without executing steps 130, 140, and 140, respectively. Good.

[0049]

As is apparent from the above description, according to the first aspect of the present invention, even when the vehicle is moved by a moving means such as a ferry boat, the latest provisional drift amount of the vehicle is maintained. Immediately before it is determined that the vehicle is stopped,
That is, since the drift amount is calculated when both the moving means and the vehicle are stopped, the drift amount of the yaw rate sensor can be accurately obtained.

According to the second aspect of the present invention, the drift amount is set to the tentative drift amount calculated when the vehicle is stopped even when the vehicle accelerates while turning slowly after stopping. Thus, the drift amount of the yaw rate sensor can be accurately calculated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a vehicle on which a method for calculating a drift amount of a yaw rate sensor according to the present invention is executed.

FIG. 2 is a flowchart illustrating a drift amount calculation and a yaw rate correction routine of a yaw rate sensor according to the embodiment.

FIG. 3 is a flowchart illustrating a subroutine for determining a vehicle stop state in the embodiment.

FIG. 4 is a time chart showing the operation of the illustrated embodiment in a case where the vehicle enters a running state before a time Tbc elapses from the time when the vehicle stopped state is determined.

FIG. 5 is a time chart showing the operation of the illustrated embodiment in a case where the vehicle enters a running state after a lapse of Tbc time from the time when the vehicle stopped state is determined.

FIG. 6 is a time chart showing the operation of the illustrated embodiment in a case where the vehicle enters a running state before a time Tac elapses from the time when the vehicle stopped state is determined.

[Explanation of symbols]

 12 ... vehicle 14 fl-14 rr ... wheel speed sensor 16 ... yaw rate sensor 18 ... shift position sensor 20 ... electric control device

Claims (2)

[Claims] A method for calculating a drift amount of a vehicle-mounted gyro-type yaw rate sensor that calculates a drift amount of a yaw rate sensor based on an output of a yaw rate sensor when a stop state of the vehicle is determined. A step of calculating and storing a provisional drift amount based on the output of the yaw rate sensor at predetermined time intervals from the time when the stop state is first determined; and storing the drift amount immediately before the release of the stop state of the vehicle is determined. Setting the drift amount to the latest provisional drift amount that has been set. 2. A stopped state of a vehicle is determined based on an output of a wheel speed sensor that detects a wheel speed based on a pulse generated at a frequency proportional to a rotation speed of the wheel. When the stopped state of the vehicle is determined. A method for calculating the drift amount of an in-vehicle gyro-type yaw rate sensor that calculates the drift amount of the yaw rate sensor based on the output of the yaw rate sensor. When the vehicle is in a stopped state, every predetermined time from when the stopped state is first determined. Calculating and storing a provisional drift amount based on the output of the yaw rate sensor, obtaining a stop time when it is determined that the vehicle is stopped, and immediately determining the drift amount when the stop time is less than a reference value. Is set to the latest provisional drift amount, and when the stop time is equal to or longer than the reference value, the drift amount is set to the latest provisional drift amount. Drift amount calculation method for onboard gyroscopic yaw rate sensor, characterized in that it contains a step of setting the provisional drift amount stored immediately before.