JPH0420122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a steering angle detection device for detecting a steering angle of a steering wheel.

<Prior Art> In recent years, microcomputers have been used to control the steering force of a power steering device according to vehicle speed, steering wheel rotation angle, and the like. In this case, the sensor used to detect the steering wheel rotation angle is an encoder that sends out a pulse signal every time the steering shaft rotates by a unit angle. It will be advantageous.

<Problems to be Solved by the Invention> However, since the steering angle detection device using an encoder cannot obtain the absolute steering angle, the steering angle stored in the memory is lost when the ignition switch is turned off. If this occurs, the next time the power is turned on, only the relative rotation angle with the position of the steering wheel in the stopped state as the origin can be detected, and the neutral position (straight-ahead state) of the steering wheel cannot be recognized.

One way to solve this problem is to back up the microcomputer with a low-consumption constant voltage circuit so that the contents of the memory will not be lost even when the ignition switch is turned off. Even in this case, if the battery runs out, it is difficult to do anything about it, and it cannot be a fundamental solution.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned problems of the conventional art. It is equipped with a neutral position detection means for recording the frequency of angles and detecting the rotation angle with the maximum frequency as the neutral position, and a rotation angle calculation means for calculating the rotation angle into a rotation angle starting from the neutral position.

<Function> With the above configuration, the rotation angles stored in the counting means that input and count the output of the encoder are input and counted every time the car travels a unit distance or unit time, and the frequency of these rotation angles is recorded. By detecting the maximum rotation angle as the neutral position and calculating the rotation angle from the neutral position, the steering wheel rotation angle, that is, the steering angle, from the neutral position of the steering wheel is detected.

<Examples> Examples of the present invention will be described below based on the drawings. In FIG. 1, 10 is an encoder, 11 is a waveform shaping circuit, and 12 is a computer. ing.

In FIG. 2, 20 indicates a steering shaft, one end of which is connected to a steering wheel, and the other end is connected to a power steering wheel. A rotary plate 21 is installed on the steering shaft 20,
A large number of slits 22 are formed on the circumference of the rotating plate 21 at equal angular intervals. On the circumference of the rotary plate 21, there are phase A detection sensors 23 and B phase detection sensors consisting of a light emitting element and a light receiving element facing each other with the rotary plate 21 in between.
Phase detection sensors 24 are arranged with a phase difference of 1/4 period, and these sensors 23 and 24 are fixed to a fixed part such as a steering column. Each sensor 2
3 and 24 are pulse signals that receive the light passing through the slit 22 and are shifted by 1/4 period each time the steering shaft 20 rotates by a unit angle, as shown in FIG.
Generates SS1 and SS2. The rotary plate 21 and the sensors 23 and 24 constitute the encoder 10.

As shown in FIG. 3, the steering direction determining means 13 uses a combination of two pulse signals SS1 and SS2 generated by the encoder 10 and shifted by 1/4 period to determine one period of the pulse signal from "0" to "0". 3” of 4
The steering direction of the steering wheel is determined based on the current area signal and the previous area signal. As for the area signal, when the signals SS1 and SS2 are both low level, S becomes "0", and when the signal SS1 is low level, SS2 becomes "0".
When is at a high level, S becomes "1", and the signal SS
When 1 is high level and SS2 is low level, S is classified as "2", and when both signals SS1 and SS2 are high level, S is classified as "3".

Next, the steering direction determining means 13 and the counting means 14 will be explained with reference to the flowchart shown in FIG. Note that S in Figure 4 indicates the current area signal,
shall indicate the previous area signal. First, in step 30, it is determined whether S and OS are the same, and if YES, the program returns with the assumption that the steering wheel is stopped. If NO, proceed to steps 31 and onwards, and in step 31 check whether S is "0" or not.
In step 32, it is determined whether S is "1", and in step 33, it is determined whether S is "2". If neither of these is the case, in step 34, S is recognized as "3". Ru. If S is determined to be "0" in step 31, the process proceeds to step 35, where it is determined whether OS is "1". If NO, it is determined that the direction of rotation of the steering wheel is normal (clockwise), and in step 39, 1 is added to the rotation angle θ stored in the memory of the computer 12. Also step 35
If the determination result is YES, it is determined that the rotation direction of the steering wheel is reverse (counterclockwise), and in step 40, 1 is subtracted from the rotation angle θ stored in the memory. Similarly, if S is determined to be "1" in step 32,
In step 36, it is determined whether the OS is "0", and if it is determined in the step 33 that S is "2", in step 37 it is determined whether the OS is "0", If S is recognized as "3" in step 34, step 38
It is determined whether the OS is "1" or not, and depending on the result of the determination, the contents of the rotation angle .theta. stored in the memory are added or subtracted in step 39 or step 40 as described above.

The neutral position detection means 15 detects the neutral position of steering based on the frequency of the rotation angle θ detected as described above, and the memory of the computer 12 is provided with a large number of buffer areas. The number i of such buffer areas is expressed by i=2×θ1/N, where θ1 is the total angle from the steering wheel to the lock, and N is the unit angle of the encoder 10. For example, the total angle from the steering wheel to the lock is 3 rotations and the unit angle of the encoder 10 is 3 degrees, then i becomes 720.

Next, the neutral position detection means 15 and rotation angle calculation means 16 will be explained according to the flowchart shown in FIG. When a pulse signal is output by a vehicle speed sensor (not shown) which outputs a pulse signal every time the car travels a unit distance, an interrupt signal is sent and the program is started by this interrupt signal. First, in step 50, the rotation angle θ stored in the counting means 14 is read, and in step 51, 1 is added to the buffer area BF(θ) corresponding to the rotation angle θ. Next, in step 52, buffer area BF
It is determined whether the content of (θ) is larger than the set value BFLIM, and if NO, the first buffer area BF (θMIN) of all buffer areas is addressed. Thereafter, in a loop from step 54 to step 57, the maximum value of each buffer area is determined, and the number i of that buffer area is stored in the register. That is, in step 54, it is determined whether the content of the addressed buffer area is larger than the maximum value up to now, and if YES, in step 55, the number i of that buffer area is stored in the register CNTR that stores the maximum value. stored and then the next buffer area is addressed in step 56.
If the determination result in step 54 is NO, the process jumps to step 56. In this way, the contents of all buffer areas are compared to find the number i of the buffer area with the largest content, and in step 57, the final buffer area BF is
When (θMAX) is determined, the process moves to step 58. In step 58, i is subtracted from the rotation angle .theta. obtained as described above, and the result is output as the steering angle A.

Note that the determination result in step 52 is YES.
When this happens, the contents of all buffer areas are corrected to 1/2 in steps 60 to 63 to prevent buffer area overflow.

In this way, every time the car travels a unit distance, the rotation angle θ
By reading the rotation angle θ and adding 1 to the buffer area corresponding to the rotation angle θ to find the rotation angle θ corresponding to the buffer area with the maximum content, it is possible to recognize the neutral position of the steering, and therefore, the rotation angle θ can be determined by By calculating the rotation angle with the neutral position as the starting point, the steering angle A can be accurately determined.

That is, when the vehicle is stopped when the ignition switch is turned on, the direction of the steering wheel is not constant, and therefore the rotation angle θ obtained by the output of the encoder 10 is the same as that of the steering wheel when the power is turned on. The position is the starting point.

For example, if the ignition switch is turned on and the car is driven with the steering wheel turned almost fully to the left at P1 as shown in Figure 6, the frequency distribution of the rotation angle θ will be as shown by the solid line. The frequency is highest at the rotation angle θX corresponding to the neutral position of steering. Along with this, buffer area i (θX) corresponding to the rotation angle θX
Therefore, by subtracting i from θ, the rotation angle can be corrected to the rotation angle with the maximum frequency position (steering neutral position) as the starting point.

In the above embodiment, an example has been described in which the rotation angle θ is sampled every time the car travels a unit distance, but the rotation angle θ may be sampled every time the vehicle travels for a unit time.

Further, in the above embodiment, an example was described in which the number of buffer areas is twice as many as the rotation angle of the steering wheel, considering that the power is turned off when the steering wheel is turned all the way to the left or right. However, it is sufficient to find at least the frequency near neutral steering, and therefore the number of buffer areas can be reduced by almost half.

<Effects of the Invention> As described above, the present invention has a configuration in which the neutral position is determined from the frequency of the relative rotation angle obtained by the encoder and the steering angle is calculated. Even if the contents of the angle are erased, the steering angle can be accurately detected depending on the driving situation after the power is turned on.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a control circuit diagram of a steering angle detection device, FIG. 2 is a diagram showing an encoder, FIG. 3 is an output waveform diagram thereof, and FIGS. 4 and 5. 6 is a diagram showing a flowchart, and FIG. 6 is a diagram for explaining the operation. 10... Encoder, 12... Computer,
13... Steering direction determining means, 14... Counting means,
15... Neutral position detection means, 16... Rotation angle calculation means.

Claims (1)

[Claims] 1. An encoder that has a rotary plate that rotates in synchronization with the steering shaft and sends out a pulse signal for each unit angle of the rotary plate, and an encoder that inputs the pulse signal from this encoder and counts up according to the steering direction. Alternatively, there is a counter that counts down, and a neutral position that reads the rotation angles stored in the counter every unit travel distance or unit time, records the frequency of these rotation angles, and detects the rotation angle with the highest frequency as the neutral position. A steering angle detection device comprising a detection means and a rotation angle calculation means for calculating the rotation angle into a rotation angle starting from a neutral position. 2. The neutral position detection means detects one buffer area in the buffer area corresponding to the rotation angle each time the rotation angle is read.
2. The steering angle detection device according to claim 1, wherein the rotation angle corresponding to the buffer area of maximum content is detected.