JPH08542B2 - Steering sensor zero point correction method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting the zero point position of a steering sensor that detects a steering angle of a vehicle.

(Prior Art and Problems Thereof) Since a steering angle of a vehicle is detected and required electronic control such as power steering is performed, a steering sensor may be conventionally provided in the vehicle.
This steering sensor is first installed in the vehicle by aligning its zero point with the neutral position of the steering wheel (steering angle = 0 °), but it may contain some errors due to variations in adjustment, and In some cases, the position of the zero point adjusted at the time of assembling is slightly deviated with the passage of time, and an error occurs in the detection output subsequently. In such a case, if readjustment is performed, an accurate detection output can be obtained again, but it is necessary to periodically check whether the zero point position is displaced, and when the zero point position is displaced, It is very troublesome because the readjustment work must be done through acquisition.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems of the prior art,
It is an object of the present invention to provide a steering sensor zero-point correction method capable of automatically correcting the steering sensor zero-point position.

(Means for Achieving the Object) In order to achieve the above object, in the zero point correction method of the steering sensor according to the present invention, the steering output from the steering sensor when the vehicle is traveling and the steering wheel is near the neutral position. Data is sampled and a value representative of the distribution of the sampling data is obtained to obtain a 0-point correction value of the steering sensor, and the steering data is corrected by the correction value.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a 0-point correction method for a steering sensor according to the present invention. The output signal of the steering sensor 1 for detecting the steering angle (voltage value signal corresponding to the steering angle) is A /
An analog signal is converted into a digital signal by the D converter 2 and is taken into the central control unit (CPU) 3. On the other hand, the output signal of the vehicle speed sensor 4 for detecting the vehicle speed (a pulse signal having a repetition frequency corresponding to the vehicle speed) is frequency-voltage converted by the F / V converter 5, and further converted from an analog signal to a digital signal by the A / D converter 2. Converted to signal, CP
Captured by U3. A memory 6 and a display 7 are connected to the CPU 3, and the CPU 3 uses the memory 6 to perform arithmetic processing for zero-point correction as described in detail below based on the above-mentioned captured signal. Then, the processing result is displayed on the display 7 and is output to a required place.

FIG. 2 is a flowchart showing in detail an example of the processing procedure of the 0-point correction processing in the CPU 3 of FIG. When the processing is started, initialization such as clearing of the memory contents is first performed in step S1, and then in step S2, the current x and v are set.
Is entered. Here, x is steering data from the steering sensor 1, and v is vehicle speed data from the vehicle speed sensor 4.

Next, in step S3, the input steering data x at the present time is corrected by the zero point correction value c (described later) at the present time, and x-c is output as the corrected steering data. Then, in step S4, whether v ≠ 0,
That is, it is determined whether or not the current vehicle speed is 0 (in other words, whether or not the vehicle is traveling), and step S5
In step S6, it is determined whether or not the preset sampling time T _S has elapsed, and in step S6, dX / dt
It is determined whether or not <K _X, that is, whether the time change rate of the steering data x is smaller than a predetermined value K _X. When the determinations in steps S4, S5, S6 are all "Yes", that is, the vehicle is traveling, the sampling time T _S has elapsed, and the time change rate of the steering data x is higher than the predetermined value K _X. Only when it is smaller, the process proceeds to the next step S7. In other cases, the process returns to step S2 and the above process is repeated. Where dx / d
t represents the steepness of the steering wheel operation, and a large value thereof generally means that the steering wheel is largely operated from its neutral position. That is, the steepness of the steering wheel operation tends to be relatively small near the neutral position and increase as the distance from the neutral position increases. dx / d
The process is advanced from step S6 only when t <K _X is to eliminate the data greatly deviated from the neutral position and perform the zero point correction only on the data near the neutral position to improve the reliability of the process as much as possible. This is because.

In step S7, it is determined whether m> n. Here, m means the number of times of sampling at the present time (that is, equivalent to the number of data sampled up to the present time), and n means a preset number of sampling data (for example, n = 25).
6 may be set). Since m <n within the fixed time after the processing is started, the determination in step S7 is "No", and at this time the processing proceeds to step S8. In step S8, the steering data x and the vehicle speed data v input in step S2 are stored in the memory 6 in association with each other as sampling data. Then, the process returns to step S2 again to repeat the above-described process, and the sampling data is accumulated in the memory 6.

When the number of times of sampling m exceeds the set value n after a while, the determination in step S7 becomes "Yes", and the process proceeds from step S7 to step S9. In step S9, of the sampling data accumulated in the memory 6, the sampling data when the vehicle speed is the lowest (that is, the vehicle speed data v is the smallest) is erased. And step S10
Instead of the erased sampling data, the current steering data x and the vehicle speed data v (that is, input in the immediately preceding step S2) are stored in the memory 6 as sampling data in association with each other.

By the way, generally, the frequency of the steering angle of the running vehicle has a normal distribution or a distribution close to a normal distribution as shown by the solid line in FIG. In FIG. 3, the vertical axis represents frequency, the horizontal axis represents steering angle (°), and the center is the neutral position of the steering wheel (steering angle = 0 °). Assuming that there is no error in the steering sensor 1, the actual steering angle and the detected angle of the steering sensor 1 match, so the set of steering data x obtained by sampling the output of the steering sensor 1 is actually Similarly to the steering angle, the normal distribution is obtained as shown by the solid line in FIG. However, when there is an error in the steering sensor 1, the actual steering angle and the detected angle of the steering sensor 1 are always deviated by an error. Therefore, the set of steering data x obtained by sampling the output of the steering sensor 1 is As shown by the dotted line in FIG. 3, the central portion of the distribution is shifted by an error amount to form a normal distribution. That is, the error of the steering sensor 1 can be known by obtaining the central portion of the distribution (in other words, the representative value of the set).

As the representative value of the set, there are an average value, a median value, a mode value, etc. (these distributions all have the same value in the normal distribution), but in this embodiment, the central part of the distribution is obtained by the average value. . In step S11, for this purpose,
The average value of the set of steering data x accumulated in the memory 6 as described above is calculated. Then, in the following step S12, this is registered as the 0-point correction value c. Then, the process returns to step S2, the current steering data x and the vehicle speed data v are input, and then the process proceeds to step S3, where the steering data x just input by the 0-point correction value c registered in step S12 is input. Correct to obtain error-free steering data.

In the above embodiment, after the sampling data accumulated in the memory 6 reaches the predetermined number n, the sampling data having the lowest vehicle speed is sequentially erased in step S9. Sampling data will remain. In general, the steering angle is small during high-speed running, and therefore, the data remaining in the memory 6 becomes closer to the center of the normal distribution as time passes. The state of the distribution at this time is shown in FIG. In this way, as the time elapses, the variation between the steering data, which is the basis of error detection, becomes smaller, so that the error can be detected more accurately.

FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 is a flow chart showing the processing procedure of the CPU 3 in this embodiment. This embodiment is basically the same as the embodiment shown in FIG. 1, but an acceleration sensor 8 is newly provided in order to know whether or not the steering wheel is near the neutral position, and the acceleration sensor 8 acts on the vehicle body. The horizontal acceleration is detected and the output signal is taken into the CPU 3 via the A / D converter 2. Acceleration sensor 8
As such, for example, a pendulum type in which acceleration is detected from a swing position of a swingable pendulum is known.

The lateral acceleration data y from the acceleration sensor 8 is the sixth
In step S2 'in the figure, the steering data x and the vehicle speed data v are input together. And step S
At 6 ', it is judged if dy / dt <K _y, that is, if the temporal change rate of the lateral acceleration is smaller than a predetermined value K _y . dy / dt represents the steepness of the lateral acceleration change of the vehicle, and a large value thereof generally means that the steering wheel is largely operated from its neutral position. That is, the steepness of the change in the lateral acceleration tends to be relatively small in the vicinity of the neutral position of the steering wheel and increase as the distance from the neutral position increases. Only when dy / dt <K _y is the second step to proceed from step S6 ′.
This is to improve the processing reliability by eliminating the data largely deviated from the neutral position and performing the zero point correction only on the data near the neutral position, as in step S6 in the figure. By the way, although data near the neutral position can be obtained by collecting only steering data when the absolute value of the lateral acceleration is within the predetermined range, the data obtained when there is an error in the acceleration sensor It is not preferable because it is not distributed around the neutral position. Note that, in FIG. 6, the processes other than steps S2 'and S6' are the same as those in FIG.

In the above embodiment, whether the steering wheel is in the vicinity of the neutral position is known from the time change rate of the steering angle and the time change rate of the lateral acceleration acting on the vehicle. It is also possible to make a judgment, and it is also possible to make a judgment by combining a plurality of parameters.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize a steering sensor zero point correction method capable of automatically correcting the steering sensor zero point position. Furthermore, since the zero point correction is performed using only the data when the steering wheel is near the neutral position, it is possible to perform highly reliable correction.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a flow chart showing a processing procedure according to the present invention, FIGS. 3 and 4 are diagrams showing data distribution, and FIG. 5 is another diagram of the present invention. FIG. 6 is a block diagram showing an embodiment, and FIG. 6 is a flow chart showing the processing procedure. 1 ... Steering sensor 3 ... CPU 4 ... Vehicle speed sensor 8 ... Acceleration sensor

Claims (5)

[Claims] 1. A method for correcting a zero point position of a steering sensor for detecting a steering angle of a vehicle, which is output from the steering sensor while the vehicle is traveling and the steering wheel is near a neutral position. A steering sensor is characterized in that the steering data is sampled and a value representative of a distribution of the sampling data is obtained to obtain a 0-point correction value of the steering sensor, and the steering data is corrected by the correction value. 0 point correction method. 2. The method for correcting a zero point of a steering sensor according to claim 1, wherein the value representative of the distribution of sampling data is an average value. 3. The zero-point correction method for a steering sensor according to claim 2, wherein the steering data used in the averaging is a predetermined number in order from the vehicle speed at the time of sampling. 4. The method according to claim 1, wherein whether or not the steering wheel is near the neutral position is determined by whether or not the rate of change of the steering data is equal to or less than a certain value.
The 0 point correction method of the steering sensor according to the item. 5. An acceleration sensor is provided for knowing a lateral acceleration acting on a vehicle, and whether or not a steering wheel is near a neutral position is determined by whether a rate of change of input data from the acceleration sensor is a certain value or less. The zero point correction method for the steering sensor according to claim 1, wherein