JP3186104B2 - Sensor characteristic correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compensating a sensor characteristic used in a vehicle-mounted electronic control device using a vehicle sensor.

[0002]

2. Description of the Related Art In automobile sensors, IG-ON
After the ignition switch is turned on, it takes time for the sensor output characteristics to stabilize, and there is a case where drift occurs due to environmental conditions such as temperature. If such a sensor is used, the sensor output characteristics after IG-ON , And control is started only after the reference signal value is obtained, and thereafter, the control is performed using the sensor value at the time when the condition for obtaining the reference signal is satisfied as the reference signal value.

For example, an angular velocity sensor (hereinafter, referred to as a yaw rate sensor) for measuring a rotational angular velocity (hereinafter, referred to as a yaw) of a vehicle used for four-wheel steering control is an IG-type sensor.
After turning on, wait for the sensor output characteristics to stabilize, and then the vehicle is stopped, the steering wheel is not turned even during running, or the state where no disturbance is received continues for a certain period of time This is detected to determine a reference signal value (sensor output value in a state where yaw does not occur), and the output value of the sensor is obtained based on the signal value.

That is, as shown in FIG. 4, the rising characteristic of the yaw rate sensor at the time of IG-ON when the yaw does not occur has a characteristic that converges to a constant value with time. Could not be used. After that, the value was used as the reference output value of the sensor only when the state became stable.

For this purpose, the steering ratio (θs) for determining the steering angle of the rear wheel with respect to the steering angle is controlled by the following equation, where V is the vehicle speed, θH is the steering angle, and 舵 is the yaw rate. When the reference signal value of the yaw rate sensor is obtained, θs = f (V) + f (θH) + f (ψ) (1) When the reference signal value of the yaw rate sensor is not obtained, θs = f '(V) (2) This conventional control flow will be described with reference to FIG. First, in step 71, it is determined whether or not a fixed time has elapsed since the IG-ON in order to determine whether the output of the sensor is stabilized. Control not using the yaw rate sensor shown in the equation. If the predetermined time has elapsed, it is determined in step 73 whether the vehicle is stopped or the steering wheel is turned during running in step 73, and the reference output value of the yaw rate sensor is determined in 74.

If the reference output value of the yaw rate sensor has been determined in step 75, control using the yaw rate sensor shown in the above equation (1) can be performed in the process of step 77. Therefore, when the reference output value of the yaw rate sensor has not been determined, the processing in step 76 is always performed, so that control using only the vehicle speed (V) without using the yaw rate sensor as shown in the above equation (2) is performed. Do.

[0007]

However, in the above conventional control method, when the reference signal value is not obtained, the control by the sensor is not performed and the control by another sensor is substituted, or the control itself is replaced. Had stopped. Therefore, there is a problem that the originally intended control cannot be performed and the performance of the system is significantly reduced.

Further, since drift occurs due to environmental changes such as temperature even after the reference signal value is obtained, a condition (for example, when the vehicle is stopped) for periodically obtaining the reference signal value is detected. It is necessary to update and control the value at that time as a reference signal value, and when a condition for obtaining the reference signal value cannot be detected, there is a problem that the reference signal value cannot be updated even if drift occurs.

The present invention solves such a conventional problem. Even if the conditions for obtaining the reference signal of the sensor do not occur after IG-ON, or an error occurs in the reference signal due to drift of the sensor. There and to provide a good sensor characteristics correction method as possible out control using the sensor accurately be generated.

[0010]

In order to achieve the above object, the present invention provides a condition that an output value of a sensor indicates a reference signal value,
For example, a means for determining that the vehicle is stopped or a means for determining that the vehicle is traveling straight while traveling, a means for learning by averaging the temporal output characteristics of the sensor, and a storage interval of the learning value After the IG-ON, the time is shortened within a predetermined time and then lengthened thereafter, and a means for storing the value in the backup RAM as time elapses, and turning on the power if the condition that the output value of the sensor indicates the reference signal value is not satisfied. (I
G-ON) Backup RA
A means for interpolating and calculating a learning value stored in M to obtain a reference signal value of the sensor, and a configuration using the learning value as a reference signal value when a condition that the output value of the sensor indicates the reference signal value is satisfied. And

[0011]

According to the present invention, therefore, after IG-ON,
Even when the condition that the vehicle is stopped or the condition that the vehicle is traveling straight while traveling is not satisfied, the control using the sensor can be performed by the learning value stored in the backup RAM, and even after the condition is satisfied. Since the learning value is used instead of using the instantaneous value of the sensor as the reference signal value, there is an effect that highly accurate control corresponding to the temporal drift characteristic can be performed. Further, there is also an effect that the learning function can absorb variations of individual sensors.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, an angular velocity sensor (hereinafter referred to as a yaw rate sensor) used for four-wheel steering control will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a four-wheel steering system. In FIG. 1, reference numeral 1 denotes a yaw rate sensor that measures a rotational angular velocity (hereinafter, referred to as yaw) of a vehicle, 2 denotes a vehicle speed sensor that measures the speed of the vehicle, and 3 denotes a steering angle sensor that measures a steering angle of a steering wheel. It is. Reference numeral 4 denotes a control unit, and a yaw rate sensor 1
Signals from the vehicle speed sensor 2 and the steering wheel angle sensor 3 are input, and a signal for determining a steering angle ratio of the rear wheels to the steering wheel angle, that is, a steering ratio is output to the steering ratio control mechanism 5. A rear wheel drive mechanism 6 drives the rear wheels under the control of the steering ratio control mechanism 5.

FIG. 2 shows the configuration of the control unit 4. In FIG. 2, reference numeral 41 denotes an input interface circuit to which signals from the yaw rate sensor 1, the vehicle speed sensor 2, and the steering angle sensor 3 are input.
Reference numeral 42 denotes a CPU having a built-in backup RAM 43, which calculates a steering ratio from an input signal or data in the backup RAM 43, and outputs a steering ratio control signal 45 through an output interface circuit 44.

The operation of the embodiment constructed as described above will be described with reference to the flowchart shown in FIG. In FIG. 3, it is determined whether or not the vehicle is stopped in step 31 and whether or not the steering wheel is not turned during running in step 32.
The process of step 33 is performed only when the condition for learning the reference output value is satisfied.

That is, as shown in FIG. 4, the characteristic of the reference output value of the yaw rate sensor 1 when no yaw is generated is such that the reference signal value is not changed until times t1, t2,. It changes relatively quickly and stabilizes at a certain value. However, after tm, drift gradually occurs due to a change in environment such as temperature. Therefore, by increasing the time interval of the characteristic value as compared with the above, the backup RAM 43 provided in the microcomputer 42 shown in FIG.
As shown in Table 1, the elapsed time tn and the reference output value of the yaw rate sensor 1 at that time are updated and stored in the table as a learning value.

[0017]

[Table 1]

In this learning method, if the learning value of the elapsed time tn after IG-ON is Vn and the output value of the yaw rate sensor 1 is ψ, Vn can be expressed by the following equation.

Vn = ψ × C / 256 + (256−C) × (previous Vn) / 256 where C: constant n = 1, 2, 3,..., Which is a so-called first-order low-pass filter Therefore, unnecessary components such as noise are removed, and a more accurate learning value Vn can be obtained. After IG-ON by such a method, the reference signal output value of the yaw rate sensor 1 is averaged and learned.

Next, in FIG. 3, it is determined in step 34 whether a predetermined time (time tm shown in FIG. 4) has elapsed,
In step 35, the learning value is set to tm immediately after IG-ON.
Up to this point, the learning value storage interval is shortened because the rate of change of the reference signal value of the sensor is high, and after a certain time (tm) elapses, the interval is lengthened and the learning value is stored in the table of the backup RAM 43. (However, the learning interval is considerably faster than the storage interval.) Then, in step 36, the learning value Vn is used as the reference signal value of the yaw rate sensor 1 when no yaw is generated. Further, if the condition for learning the reference signal value of the post-IG-ON sensor is not satisfied in step 37, the value learned in the past and stored in the backup RAM 43 in step 38 is calculated from the elapsed time after IG-ON. A reference signal value of the yaw rate sensor 1 is obtained by interpolation calculation.

Therefore, since the reference signal value of the yaw rate sensor 1 is obtained in steps 36 and 38, the yaw rate sensor 1 is used in step 39 as shown in the above equation (1) using this value as a reference value. Then, control is performed based on the vehicle speed (V), the steering angle (θH), and the yaw rate (行 う). That is, as shown in FIG.
Even when the yaw has occurred immediately afterward, or even when the reference signal value of the yaw rate sensor 1 changes due to drift, the value obtained in step 38 is used as the reference value, and the yaw rate sensor 1 shown in the above equation (1) is used. Perform control.

As described above, according to the above embodiment, the IG-O of the yaw rate sensor 1 when no yaw is generated
By learning by averaging the temporal output characteristics from the time N and updating and storing the learning value of the yaw rate sensor 1 at that time in the table of the backup RAM 43 with the passage of time, the learning value is used. Immediately after IG-ON, four-wheel steering control using the reference signal output value of the yaw rate sensor 1 can be performed, and the above learning value is used instead of using the instantaneous value of the yaw rate sensor 1 as the reference signal value. Therefore, it is possible to control the drift characteristic with time due to the environmental temperature or the like with high accuracy.

Further, by learning the reference signal output values of the individual yaw rate sensors 1, it is possible to absorb variations in the individual sensors in mass production. Further, by updating and storing the learning value in the backup RAM 43, it is possible to control the secular change with high accuracy.

[0024]

As is clear from the above embodiment, the present invention averages and learns the temporal output characteristics from the time of IG-ON of the sensor and learns them in the backup RAM table.
Since the learning value of the sensor at that time is updated and stored with time, control using the reference signal output value of the sensor can be performed immediately after IG-ON.
Until the characteristics of the sensor become stable after the IG-ON or until the reference output value of the sensor is obtained, it is possible to prevent the control using the sensor from being performed and the system performance from being lowered. Has an effect.

Also, with respect to drift or aging of the sensor due to a change in environment such as temperature, the learning value of the reference output value of the sensor is backed up as time passes.
By updating and storing in the table of M and using this, there is an excellent effect that the control can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of a four-wheel steering system according to an embodiment of the present invention.

FIG. 2 is a flowchart of control using the yaw rate sensor.

FIG. 3 is a block diagram of the control unit.

FIG. 4 is an output voltage characteristic diagram at the time of IG-ON when yaw does not occur.

FIG. 5 is an output voltage characteristic diagram at the time of IG-ON when yaw is occurring.

FIG. 6 is a flowchart of control using a conventional yaw rate sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Yaw rate sensor 2 Vehicle speed sensor 3 Steering angle sensor 4 Control unit 5 Steering ratio control mechanism 6 Rear wheel drive mechanism 43 Backup RAM

Claims (8)

(57) [Claims] An on-vehicle electronic control device to which a microcomputer is applied, which is a sensor for detecting a change in the state of a vehicle, requires a certain period of time after the IG-ON until the output characteristics of the sensor become stable, and For example, in a system for controlling the vehicle based on the calculation result based on the output of the sensor that causes a drift in output characteristics due to environmental conditions, a condition in which the sensor does not detect a change in the state of the vehicle is set. Learning the sensor characteristics,
A method for correcting sensor characteristics, wherein the value is used as a reference signal value when there is no change in the state of the vehicle. 2. A low-pass filter for an output value of said sensor.
Calculate the learning value of the reference signal of the sensor.
Sensor characteristic correction method according to claim 1, wherein the determining the. 3. The method according to claim 1, wherein the sensor learning value is stored in a backup RA.
Sensor characteristic correction method according to claim 1 or claim 2, wherein the storing the M. 4. The storage of the sensor learning value is performed by IG-ON.
The method according to any one of claims 1 to 3, wherein the time interval is shortened immediately afterward, and is lengthened after a certain time has elapsed. 5. A state change of the vehicle is detected after IG-ON .
If the reference signal value of the sensor is not found, the learning value stored in the backup RAM is interpolated and calculated based on the elapsed time after IG-ON, and the value is not detected by the sensor to detect a change in the state of the vehicle. A sensor characteristic correction method characterized by using as a time value. 6. After the IG-ON, a change in the state of the vehicle is detected.
A method of correcting sensor characteristics, wherein learning is started from a point in time when a condition that a sensor does not detect a state change is satisfied and a reference signal value is obtained, and the learned value is used as a reference signal value of the sensor. 7. A sensor for detecting and outputting a change in the state of a vehicle.
And the sensor does not detect a change in the state of the vehicle.
Storage means for storing the output of the sensor under conditions
When the stored output does not change in the state of the vehicle.
To correct the output of the sensor as the reference output of
Estimating means for estimating a state change of the vehicle.
State estimation device. 8. A storage device according to claim 1, wherein said storage means stores a predetermined time until a predetermined time.
The output is stored at a time interval of
Storing the output at a different time interval from the predetermined time interval
The state estimation device according to claim 7, wherein: