JPH0576564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a steering angle detection device that detects 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 in accordance with 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.

However, a steering angle detection device using an encoder cannot obtain the absolute steering angle, so if the steering angle stored in memory is lost when the ignition switch is turned off, it will stop when the power is turned on next time. There is a problem in that only the relative rotation angle with the position of the steering wheel in the state as the origin can be detected, making it impossible to recognize the neutral position (straight-ahead state) of the steering wheel.

Comprehensively evaluating the above, the neutral position is determined based on the transition of the steering wheel rotation angle in the driving state by taking advantage of the fact that when driving, the vehicle is traveling straight ahead, and the rotation detected by the encoder is A realistic and safe measure is to correct the angle.

<Problems to be Solved by the Invention> The above-mentioned neutral position can be detected by sampling the rotation angle of the steering wheel during driving at regular intervals, for example, and processing these sampling data using software. In particular, when starting to drive after the power is turned on, the steering wheel is often turned significantly at low speeds, and even if the data obtained from this is processed, it is likely to be influenced by chance, resulting in poor detection accuracy and the possibility of correct neutralization. There is a problem that the travel distance or time required to detect the position becomes long.

<Means for Solving the Problems> The present invention has been made to solve the above-mentioned conventional problems, and when the handle rotation speed is high, it is obvious that the handle is not in the neutral position. The handle rotation angle in such a case is removed from the sampling data.

That is, a determining means for determining whether the absolute value of the rotational speed of the handle is larger or smaller than a set value;
Only when the absolute value of the rotation speed is smaller than a set value, multiple rotation angles stored in the counting means are sampled for each unit travel distance or unit time, and these multiple sampling data are statistically processed by software processing. The neutral position is determined using the rotation angle, and the rotation angle is corrected using this neutral position as the starting point.

In addition, instead of detecting the absolute value of the rotational speed of the steering wheel, a means is provided to detect the vehicle speed and determine whether or not this vehicle speed is greater than a set value, and only when the vehicle speed is greater than the set value, the unit mileage is determined. Alternatively, a plurality of rotation angles stored in the counting means may be sampled every unit time, and these multiple sampling data are statistically processed by software processing to obtain a neutral position, and the rotation angle starting from this neutral position is calculated. This is a correction.

<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, which includes a steering direction determining means 13, a counting means 14, a neutral position detecting means 15, a rotation angle calculating means 16, and a rotation speed detecting means. It is constituted by means 17.

In FIG. 2, 20 indicates a steering shaft, one end of which is connected to a handle, and the other end to which is connected a power steering wheel. steering shaft 2
A rotating plate 21 is attached on top of the rotating plate 2.
A large number of slits 22 are formed at equal angular intervals on one circumference. On the circumference of the rotating plate 21, an A-phase detection sensor 23 and a B-phase detection sensor 24, which are composed of a light emitting element and a light receiving element facing each other with the rotating plate 21 in between, are arranged with a 1/4 period phase shift. The sensors 23 and 24 are fixed to a fixed part such as a steering column. Each of the sensors 23 and 24 receives the light passing through the slit 22, and each unit rotation of the steering shaft 20 causes a rotation of 1/2 as shown in FIG.
Pulse signals SS1 and SS2 that are shifted by four periods are generated.
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 that are 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.

The steering direction determining means 13 and counting means 14 will be explained below with reference to the flowchart shown in FIG. First, in step 30, the encoder 1
When a pulse signal is input from 0, it is determined in step 31 whether or not it is a forward rotation, and if NO, it is determined in the next step 32 whether or not it is a reverse rotation.
If this is also NO, it is assumed that the handle is stopped and the program returns. If it is determined in step 31 that the direction of rotation of the handle is normal, the computer 1
1 is added to the rotation angle θ stored in the memory No. 2. Further, if it is determined in step 32 that the direction of rotation of the handle is reverse, step 34 is performed.
1 is subtracted from the rotation angle θ stored in the memory. In this manner, the contents of the rotation angle θ stored in the memory are added or subtracted in step 33 or step 34 depending on the direction of rotation of the handle. Therefore, the count contents of the memory represent the relative rotation angle θ with the steering wheel rotation angle at the time of power-on as the starting point.

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 from 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 40, 1 is added to a memory counter that accumulates the number of times of processing n, and in step 41, the rotation angle .theta. stored in the counting means 14 is read. Next, in step 42, the rotational speed detection means 17
The absolute value θ・ of the rotation speed detected at is the set value θ・
It is determined whether it is smaller than LIM, and if YES, the rotation angle θ is added to a memory counter that accumulates rotation angles for each unit traveling distance in the next step 43. Next, in step 44, the cumulative value θ1 of the rotation angle is
The cumulative number of times n is divided to obtain the average value of the rotation angle θ, and this average value is stored in the memory as CENTER. In step 45, the cumulative number n
It is determined whether or not the rotation angle θ has reached the set value n1. If NO, in step 46 the rotation angle θ is
CENTER is subtracted and the result is output as steering angle SA. In addition, in step 42, the absolute value θ・ of the handle rotation speed becomes the set value θ・
If it is determined that it is larger than LIM, the rotation angle θ
The process jumps to step 45 without performing cumulative addition.

In this way, every time the car travels a unit distance, the rotation angle θ
By reading in and finding CENTER from the average value, and calculating the rotation angle θ to the rotation angle starting from CENTER, the steering angle SA starting from the neutral position can be calculated.
becomes detectable. Moreover, in this case, since the rotation angle θ when the steering wheel rotation speed is high is removed from the data for calculating the neutral position, the travel distance until the correct neutral position is detected can be shortened. FIG. 6 shows the sampling timing for calculating the neutral position with respect to changes in the rotation angle θ.

Note that the determination result in step 45 is
If YES, in step 47 the cumulative number n
is modified to n2 (0<n2<n1), and step 48
In order to correct the cumulative rotation angle θ1 according to the cumulative number of times n2 after correction, the following calculation formula is executed to prevent overflow of θ1.

θ1=θ1−(θ1/n1)×(n1−n2) Next, another embodiment of the present invention will be described based on FIG. In this embodiment, instead of the absolute value θ of the steering wheel rotation speed, the rotation angle θ is sampled only when the vehicle speed V is greater than the set value VLIM, and the rest is the same as the previous embodiment. It's the same.

FIG. 8 shows still another embodiment of the present invention, in which the neutral position is detected based on the frequency of the rotation angle θ. In this embodiment, a large number of buffer areas are provided in the memory of the computer 12, and when the rotation angle θ stored in the counting means 14 is read in step 50, the buffer area BF corresponding to the rotation angle θ is read in step 51. 1 is added to (θ). Next, in step 52, the contents of the buffer area BF (θ) are set to the set value.
It is determined whether it is larger than BFLIM, and if NO, all buffer areas are
The number i of the buffer area with the maximum content is determined from BF(i). Then, in step 54, the number i is subtracted from the rotation angle θ, and the result is output as the steering angle SA. Note that if the content of a certain buffer area is larger than the set value BFLIM, the determination result in step 52 is
YES, and in step 55 the contents of all buffer areas BF(i) are revised to 1/2 to prevent buffer area overflow.

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.

<Effects of the Invention> As described above, the present invention samples a plurality of relative rotation angles obtained by an encoder for each unit traveling distance or unit time, and processes these plural sampling data by averaging processing, frequency distribution processing, etc. Since the configuration uses software processing to determine the neutral position using statistical processing, the steering angle can be detected in a small space using an encoder that does not change over time. Therefore, even if the contents of the steering angle are lost, the steering angle can be accurately detected based on the driving situation after the power is turned on.

Further, according to the present invention, since the relative rotation angle is sampled only when the rotational speed of the steering wheel is smaller than the set value or when the vehicle speed is larger than the set value, the correct neutral position can be reached within a short traveling distance or time. Detectable effects are also produced.

[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, FIG. 6 is a diagram showing sampling timing with respect to changes in rotation angle, and FIGS. 7 and 8 are diagrams showing other embodiments of the present invention. 10... Encoder, 12... Computer,
14... Counting means, 15... Neutral position detection means,
16...Rotation angle calculation means, 17...Rotation speed detection means.

Claims (1)

[Scope of Claims] 1. An encoder that sends out two sets of pulse signals for each unit angle of the steering shaft, a direction determining means that inputs the pulse signals from the encoder and determines the rotation direction, and this direction determining means a counting means for counting up or down a pulse signal from the encoder according to the rotational direction determined by the steering shaft; a means for detecting the absolute value of the rotational speed of the steering shaft; a discriminating means for discriminating whether the rotation speed is large or small; and a sampling means for sampling a plurality of rotation angles stored in the counting means for each unit traveling distance or unit time only when the absolute value of the rotation speed is smaller than a set value; neutral position detection means for statistically processing a plurality of sampled rotation angles through software processing to obtain a neutral position; and rotation angle calculation for calculating the rotation angle stored in the counting means into a rotation angle with the neutral position as a starting point. A steering angle detection device comprising means. 2. An encoder that sends out two sets of pulse signals for each unit angle of the steering shaft, a direction determining means that inputs the pulse signals from the encoder and determines the rotation direction, and a rotation direction determined by the direction determining means. a counting means for counting up or down a pulse signal from the encoder in accordance with the vehicle speed; a means for detecting the vehicle speed; a determining means for determining whether the vehicle speed is greater than or less than a set value; and a means for determining whether the vehicle speed is greater than the set value. sampling means for sampling a plurality of rotation angles stored in the counting means for each unit travel distance or unit time; and a neutral position for calculating a neutral position by statistically processing the plurality of sampled rotation angles by software processing. A steering angle detection device comprising: a detection means; and a rotation angle calculation means for calculating the rotation angle stored in the counting means into a rotation angle starting from a neutral position. 3. The steering angle detection device according to claim 1, wherein the neutral position detection means calculates the average value of a plurality of sampled rotation angles to determine the neutral position. 4. The steering angle detection device according to claim 1, wherein the neutral position detection means determines the neutral position by comparing frequencies of a plurality of sampled rotation angles. 5. The steering angle detection device according to claim 2, wherein the neutral position detection means calculates the average value of a plurality of sampled rotation angles to determine the neutral position. 6. The steering angle detection device according to claim 2, wherein the neutral position detection means determines the neutral position by comparing frequencies of a plurality of sampled rotation angles.