JP3745154B2 - Automatic steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic steering apparatus for detecting, for example, a guidance sign embedded in a road surface and automatically steering a vehicle based on the detected sign.
[0002]
[Prior art]
Research and development of an automatic driving system that realizes automatic driving on an automobile-only road or the like has been conventionally performed. For example, the automatic driving system is configured to detect guidance signs such as magnetic nails embedded in a road at regular intervals, and to automatically steer a vehicle based on the detected signs.
[0003]
FIG. 4 is a block diagram showing an electrical configuration of an automatic driving system that has been conventionally proposed. This automatic driving system obtains a signal from a sensor or the like that detects a guidance sign, and generates a steering angle instruction value at a certain period (for example, 50 msec), and a main ECU 1 And a steering ECU 2 that performs steering angle control of the steering mechanism 3 based on the steering angle instruction value. In addition to these, the automatic driving system includes, for example, a configuration that measures an inter-vehicle distance from a preceding vehicle and controls an engine and a brake so as to keep the inter-vehicle distance constant. In FIG. 4, these illustrations are omitted.
[0004]
[Problems to be solved by the invention]
In the configuration of FIG. 4 described above, the rudder angle control is performed every period in which the main ECU 1 gives a rudder angle instruction, and thus the rudder angle changes in a step shape. Therefore, in particular, when the rudder angle instruction value changes greatly, the rudder angle changes suddenly, and the vehicle exhibits a rattling behavior, which impairs comfort for passengers. Moreover, this tendency becomes more prominent as the steering angle control is performed with high responsiveness and high accuracy, so that it is impossible to achieve both accurate automatic steering and comfortable riding comfort.
[0005]
Although this problem can be solved by shortening the steering angle instruction cycle from the main ECU 1 to the steering ECU 2, the number of communications between the main ECU 1 and the steering ECU 2 increases, so it cannot be said to be a preferable solution. . In particular, when there is a lot of communication between the main ECU 1 and the steering ECU 2, it is extremely difficult to shorten the steering angle instruction cycle.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic steering device that can solve the above technical problems and can realize a comfortable riding comfort of an automobile.
[0007]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, an invention according to claim 1 is directed to an automatic steering apparatus that performs steering angle control of a steering mechanism based on a steering angle instruction value input every predetermined period, and interpolates between steering angle instruction values. The steering rudder angle interpolation means (21) for calculating the target rudder angle value at a time interval shorter than the predetermined cycle, and the steering rudder of the steering mechanism based on the target rudder angle value calculated by the command rudder angle interpolation means. An automatic steering apparatus including steering angle control means (23, 24, 25) for performing angle control. Note that the numbers in parentheses are reference numerals of corresponding components in the embodiments described later.
[0008]
According to the above configuration, the target rudder angle value is calculated at a time interval shorter than the predetermined period by interpolating between the rudder angle instruction values input every predetermined period, and the rudder angle control is performed based on this. Done. Thereby, even if the difference between the steering angle instruction values given one after another is large, the steering angle can be changed smoothly. Therefore, a comfortable riding comfort can be realized without causing the vehicle to rattle. Therefore, it is possible to realize an automatic steering device that has good responsiveness and can achieve both high precision steering angle control and comfortable riding comfort.
[0009]
And since it is not necessary to shorten the input period of a steering angle instruction value, the frequency | count of communication with the process part (main ECU) which generates a steering angle instruction value does not increase.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a configuration of an automatic steering apparatus according to an embodiment of the present invention. The automatic steering device is a device that detects a guide sign such as a magnetic nail embedded in a road by the sign sensor 11 and automatically controls the steering angle of the steering mechanism 30 based on the detected sign. That is, the automatic steering device is a main ECU (electronic control unit) that generates a steering angle instruction value at predetermined intervals (for example, 50 msec) based on output signals from various sensors such as the sign sensor 11 and the vehicle speed sensor 12. 10 and a steering ECU 20 that controls the steering angle of the steering mechanism 30 based on the steering angle instruction value from the main ECU 10. The steering ECU 20 controls the motor M of the steering mechanism 30 based on the steering angle instruction value from the main ECU 10 and the output of the steering angle sensor 37 provided in association with the steering mechanism 30, and in this way, Achieve automatic steering.
[0011]
The steering mechanism 30 is attached to the steering shaft 32 that extends in the vehicle width direction, a cylindrical housing 33 that supports the steering shaft 32 so as to be slidable in the axial direction, and the housing 33. And a motor M composed of a three-phase brushless motor. The steering shaft 32 is coupled to a knuckle arm 35 via a tie rod 34. With this configuration, the rotation of the motor M is converted into sliding in the vehicle width direction of the steering shaft 32, whereby the knuckle arm 35 is pushed and pulled, thereby turning the wheel 40 attached to the knuckle arm 35. Is achieved. The rudder angle sensor 37 can be constituted by, for example, a tie rod displacement detection sensor that detects the displacement of the tie rod 34.
[0012]
The steering ECU 20 includes a microcomputer and executes steering angle control processing for automatic steering mainly by software processing. The software for the rudder angle calculation process interpolates between rudder angle instruction values given at predetermined intervals from the main ECU 10 in cooperation with the microcomputer, and sets the target rudder at a time interval shorter than the predetermined cycle. An interpolation circuit 21 that generates an angle value, a subtraction circuit 22 that calculates a difference between a target steering angle value output by the interpolation circuit 21 and a steering angle value detected by the steering angle sensor 37, and an output of the subtraction circuit 22. A PID control unit 23 that determines a target current value of the motor M by PID control (proportional-plus-integral-plus-derivative control), and a difference between a target current value output from the PID control unit 23 and a current value flowing through the motor M A subtracting circuit 24 for calculating, and a PWM (Pulse Width Modulation) driving circuit 25 for controlling the pulse width of the motor M based on the output of the subtracting circuit 24 are configured. The current value flowing through the motor M is detected by the current detection circuit 26.
[0013]
FIG. 2 is a flowchart for explaining the operation of the interpolation circuit 21. The interpolation circuit 21 divides the cycle T in which the main ECU 10 outputs the steering angle instruction value into N, and generates a target steering angle value that is updated every T / N. That is, the interpolation circuit 21 executes the processing shown in this flowchart for each time represented by this T / N.
The interpolation circuit 21 first sets the number of divisions N (for example, 20) (step S1), and sets the values of N target rudder angle values in the period of the length of the previous cycle T as an array variable SA (i) ( i = 1, 2,..., N) (steps S2, S3, S4). That is, when N is decremented by 1 (step S4) and SA (N-1) is sequentially substituted for SA (N) (step S2), when N becomes 1 (step S3), the array In the variables SA (2) to SA (N), the immediately preceding N target rudder angle values are stored.
[0014]
The initial value of the array variable SA (i) is “0”. Therefore, when the ignition switch is turned on and the interpolation process is performed for the first time, the process branches from step S3 to step S5 with all the values of SA (1) to SA (N) being “0”. Then, the steering angle instruction value MD given from the main ECU 10 is substituted into the array variable SA (1) (step S5).
[0015]
Next, a total sum of N array variables SA (1) to SA (N) is calculated (step S6), and then an average value obtained by dividing the total sum by the division number N is a target steering angle value. (Step S7). Thereafter, the target rudder angle value is substituted into the array variable SA (1) (step S8).
For example, at the start of control, if the steering angle instruction value MD output from the main ECU 10 for the first time is 20 degrees and N = 20, the target steering angle output first by the interpolation circuit 21 is 1 degree (= MD / N).
[0016]
In the interpolation calculation in the next cycle, the values of the array variables SA (1) to SA (N-1) are shifted to the array variables SA (2) to SA (N) by the processing in steps S2 to S4. Therefore, the target rudder angle is 2 MD / N, and increases by MD / N.
Similarly, in a period until the next steering angle instruction value MDn is given from the main ECU 10, the target steering angle value increases by MD / N for every period T / N of the interpolation processing. If the next steering angle instruction value MDn is given, this steering angle instruction value MDn is substituted into the array variable SA (1), and thereafter, MDn / N every interpolation processing cycle T / N. The target rudder angle value increases gradually. In this way, the steering angle instruction value MD input every cycle T is linearly interpolated, and a target steering angle value that smoothly changes every cycle T / N shorter than the cycle T is output.
[0017]
FIG. 3 shows a relationship between a change (solid line) in the steering angle instruction value MD output from the main ECU 10 and a target steering angle value (two-dot chain line) output from the interpolation circuit 21 in response to the input of the steering angle instruction value MD. FIG. It will be understood that the rudder angle command value MD changes stepwise in the period T, whereas the target rudder angle value shows a substantially smooth change.
As described above, in the automatic steering device of this embodiment, the target steering angle value is set at the cycle of T / N by interpolating the steering angle instruction value given from the main ECU 10 every cycle T, and based on this. The steering angle control is performed. As a result, the rudder angle can be changed smoothly, and rattling steering is not performed. Therefore, it is possible to realize automatic steering that improves the ride comfort of the automobile.
[0018]
Furthermore, since it is not necessary to shorten the output cycle of the steering angle instruction value of the main ECU 10, the number of communications between the main ECU 10 and the steering ECU 20 does not increase.
Although the embodiments of the present invention have been described above, the present invention can be implemented in other forms. For example, in the above-described embodiment, the example in which the automatic steering is performed based on the detection result of the guidance sign embedded in the road has been described. However, the present invention is based on, for example, vehicle-to-vehicle communication or road-to-vehicle communication on the steering information of the preceding vehicle. Thus, the present invention can also be applied to an automatic steering system configured to perform automatic steering based on the above.
[0019]
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an automatic steering apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining the operation of the interpolation circuit;
FIG. 3 is a diagram showing a relationship between a change (solid line) in the steering angle instruction value output from the main ECU and a target steering angle value (two-dot chain line) output from the interpolation circuit in response to the input of the steering angle instruction value; It is.
FIG. 4 is a block diagram showing an electrical configuration of a conventionally proposed automatic driving system.
[Explanation of symbols]
21 Interpolation circuit 22 Subtraction circuit 23 PID control unit 24 Subtraction circuit 25 PWM drive circuit 26 Current detection circuit 30 Steering mechanism 37 Steering angle sensor 40 Wheel 10 Main ECU
20 Steering ECU
M motor

Claims (1)

In the automatic steering device that performs the steering angle control of the steering mechanism based on the steering angle instruction value input every predetermined cycle,
Interpolating between steering angle command values, command steering angle interpolation means for calculating a target steering angle value at a time interval shorter than the predetermined cycle;
An automatic steering apparatus comprising: steering angle control means for performing steering angle control of a steering mechanism based on a target steering angle value calculated by the indicated steering angle interpolation means.

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