JPH0544562A - Sensor characteristic correcting method - Google Patents

Abstract

PURPOSE:To perform control by using a sensor from a time right after IG-ON even when it takes a lot of time until the output characteristics of a sensor is stabilized during IG-ON. CONSTITUTION:A yaw rate sensor 1 to measure the rotation angular velocity of a vehicle, a car speed sensor 2, a handle steering angel sensor 3, and a control unit 4 to which signals therefrom are inputted are provided. From a time right after IG-ON, the rise characteristics of the yaw rate sensor 1 are learnt, and a learning value is stored in a backup RAM together with a time. During a time in which output characteristics are stabilized during IG-ON, control by using the yaw rate sensor 1 is practicable from a time right after IG-ON by using the learning value stored in the backup RAM as a reference signal value.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art IG-ON for automobile sensors
In some cases, it takes a certain period of time from (ignition switch ON) until the output characteristics of the sensor become stable. When such a sensor is used, control is started after the output characteristics become stable.

It takes a long time to stabilize particularly. For example, in an angular velocity sensor (hereinafter referred to as yaw rate sensor) for measuring a rotational angular velocity (hereinafter referred to as yaw) of a vehicle used for four-wheel steering control, IG- O
After N, it is detected that the vehicle is stopped, or the steering wheel is not turned even during running, or that there is no disturbance or the like for a certain period of time, and the reference signal value (yaw occurs The sensor output value) was determined and the sensor output value was calculated based on the signal value.

That is, as shown in FIG. 4, the rising characteristic of the yaw rate sensor when the yaw rate sensor is IG-ON has a characteristic that it converges to a constant value with time. Was not available. After that, the value was used as the reference output value of the sensor until it became stable.

For this reason, the steering ratio (θs) that determines the steering angle of the rear wheels with respect to the steering angle has been controlled by the following equation, where V is the vehicle speed, θH is the steering angle, and ψ 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, in order to determine that the output of the sensor is stable, it is determined whether or not a certain time has elapsed after the IG-ON. If the certain time has not elapsed, the above (2) is executed in step 76. The control does not use the yaw rate sensor shown in the formula. When a certain period of time has passed, in step 72, it is determined in step 73 whether the vehicle is stopped or the steering wheel is turned while traveling, and the reference output value of the yaw rate sensor is determined in 74.

Here, when the reference output value of the yaw rate sensor is determined in step 75, the 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 is not determined, the processing of step 76 is always performed, and therefore the yaw rate sensor is not used as shown in the above equation (2), and control is performed only by the vehicle speed (V). To do.

[0007]

However, in the above-mentioned conventional control method, when the reference signal value of the sensor is not obtained, the control by the sensor is not performed and the control by another sensor is used instead. Or the control itself was stopped. Therefore, there is a problem that the originally intended control cannot be performed and the system performance is significantly reduced.

The present invention solves such a conventional problem, in a state where the characteristics of the sensor are not stable,
Alternatively, the IG-O can be used even if the condition for determining stability is not generated.
An object of the present invention is to provide an excellent sensor characteristic correction method capable of performing control using the sensor from N hours.

[0009]

In order to achieve the above object, the present invention has a condition that an output value of a sensor indicates a reference signal value,
For example, a means for discriminating that the vehicle is stopped, or a means for discriminating that the vehicle is traveling straight while traveling,
Means for learning the temporal output characteristics of the sensor from G-ON (ignition switch ON), means for storing the learned value with the passage of time, and interpolation calculation of the learned value according to the passage of time after IG-ON. And a means for obtaining a reference signal value of the sensor, and a value stored in the backup RAM is used as a reference signal value for the time until the output characteristics of the sensor become stable after the IG-ON.

[0010]

Therefore, according to the present invention, the rising characteristics of the sensor are always learned within a certain time after the IG-ON when the vehicle is stopped or when the condition that the vehicle is traveling straight is satisfied. However, even if the condition is not satisfied, the learning value stored in the backup RAM is used, so that the control using the output value of the sensor can be performed immediately after the IG-ON.

[0011]

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

FIG. 1 shows the construction of a four-wheel steering system. In FIG. 1, 1 is a yaw rate sensor that measures the rotational angular velocity of the vehicle (hereinafter referred to as yaw), 2 is a vehicle speed sensor that measures the speed of the vehicle, and 3 is a steering wheel steering angle sensor that measures the steering angle of the steering wheel. Is. 4 is a control unit, which is a yaw rate sensor 1,
The signals of the vehicle speed sensor 2 and the steering wheel steering angle sensor 3 are input, and a signal for determining the steering angle ratio of the rear wheels with respect to the steering wheel steering angle, that is, the 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 turning ratio control mechanism 5.

FIG. 2 shows the structure of the control unit 4. In FIG. 2, reference numeral 41 is an input interface circuit to which signals from the yaw rate sensor 1, the vehicle speed sensor 2 and the steering wheel 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 above embodiment constructed as described above will be described with reference to the flow chart shown in FIG. In FIG. 3, it is determined in step 31 whether or not a certain time has elapsed after the IG-ON. If not, the vehicle is stopped in step 32, or the steering wheel is turned while running in step 33. It is determined whether or not there is, and the process of step 34 is performed only when the condition for learning the reference output value of the yaw rate sensor 1 is met.

That is, as shown in FIG. 4, when yaw does not occur, the rising characteristic of the reference output value of the yaw rate sensor 1 at the time of IG-ON has a characteristic that it converges to a constant value with time. .. The reference signal value gradually changes until time t1, t2, ... Tn after IG-ON, and then stabilizes at a constant value. This characteristic value is updated at fixed time intervals in the table of the backup RAM 43 provided in the micro computer 42 shown in FIG. 2 as the learning value of the elapsed time tn and the reference output value of the yaw rate sensor 1 at that time as shown in Table 1. Then store.

[0016]

[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, ..., This is a so-called first-order low-pass filter. Since unnecessary components such as noise are removed, a more accurate learning value Vn can be obtained.

By this method, step 34 shown in FIG.
In, the reference signal output value is learned at regular time intervals after the IG-ON until the output voltage of the yaw rate sensor 1 stabilizes. After that, in step 35, the reference signal output of the yaw rate sensor 1 at that time is calculated by interpolating the learning time stored in the table of the backup RAM and the time t after IG-ON based on the value learned in step 34. The value is obtained, and in step 36, control is performed by the vehicle speed (V), the steering wheel steering angle (θH), and the yaw rate (ψ) by the reference signal output value of the yaw rate sensor 1, as shown in the above-mentioned formula (1). Further, as shown in FIG. 5, even when yaw occurs immediately after IG-ON, the value obtained in step 35 is used as a reference value,
The control using the yaw rate sensor 1 shown in the above-mentioned formula (1) is performed.

As described above, according to the above embodiment, the IG-O of the yaw rate sensor 1 when yaw is not generated.
Backup RA by learning the rising characteristic value at N
The learning value of the yaw rate sensor 1 at that time is updated and stored in the table of M43 with the lapse of time, so that the reference signal output value of the yaw rate sensor 1 is used immediately after IG-ON by using this learning value. Wheel steering control can be performed.

Further, by learning the reference signal output value of each yaw rate sensor 1, it is possible to absorb the variation of each sensor in the case of mass production. Furthermore, by updating and storing the learning value in the backup RAM 43, it is possible to control with high accuracy even with age.

It should be noted that the learning time tn is to secure a time until the sensor signal becomes sufficiently stable in consideration of variations among the sensors, and thereafter, the output voltage Vn of the sensor at tn is used as a reference signal.

[0023]

As is apparent from the above embodiment, the present invention learns the rising characteristic value of the sensor when the sensor is IG-ON and updates the learning value of the sensor at that time in the backup RAM table with the passage of time. By storing it, the control using the reference signal output value of the sensor can be performed immediately after the IG-ON, so that the reference output value of the sensor can be obtained until the characteristics of the sensor become stable after the IG-ON. Until then, it has an excellent effect that it is possible to prevent the system performance from being deteriorated because the control using the sensor cannot be performed.

[Brief description of 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 during IG-ON when yaw does not occur.

FIG. 5 is an output voltage characteristic diagram during IG-ON when yaw is occurring.

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

[Explanation of symbols]

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

Claims (4)

[Claims] 1. A vehicle-mounted electronic control device to which a microcomputer is applied, which is a sensor for detecting a change in vehicle state, and which is based on the output of the sensor whose output characteristics require more time to stabilize than when power is supplied. In a system for performing a calculation and controlling the vehicle based on the calculation result, when the vehicle is IG-ON, a condition is set in which the sensor does not detect a change in the state of the vehicle. A method for correcting a sensor characteristic, which is controlled based on a learned value by using an output value of the sensor from the time of IG-ON. 2. A value obtained after a certain period of time of the learning characteristic of the rising characteristic of the sensor is used as a value when the sensor has not detected a change in the vehicle state after a certain period of time has elapsed since the IG-ON. The sensor characteristic correction method according to claim 1, characterized in that 3. The sensor characteristic correction method according to claim 1 or 2, wherein the sensor learning value is stored in a backup RAM at regular intervals. 4. The sensor characteristic correction method according to claim 1, wherein the sensor learning value is calculated by interpolation.