JP6621179B2 - Automatic steering device - Google Patents

Description

  The present invention relates to an automatic steering apparatus for a vehicle.

  For example, as disclosed in Japanese Patent Application Laid-Open No. 2005-343184, an automatic steering apparatus that automatically recognizes the shape of a road on which the vehicle is traveling and automatically steers the vehicle is known. Further, in an automatic steering device for a vehicle, as disclosed in Japanese Patent Application Laid-Open No. 2005-343184, it is determined whether or not a steering wheel is operated (override operation) by a driver during execution of automatic steering. When it is determined that it has been performed, a technique is known in which automatic steering is stopped to give priority to a driver's operation. If the automatic steering device determines that the override operation has ended, the automatic steering device resumes automatic steering control.

JP 2005-343184 A

  The course of the vehicle at the end of the override operation may be different from the course determined by the automatic steering device. In this case, the automatic steering device may give a relatively large rudder angle to the vehicle to restore the course together with the resumption of the automatic steering control. There is a possibility.

  The present invention solves the above-described problems, and an object of the present invention is to provide an automatic steering device that can reduce discomfort experienced by a driver when automatic steering is resumed after an override operation.

  An automatic steering device according to one aspect of the present invention recognizes the shape of a road on which a torque sensor, an electric power steering device, and a vehicle are running to detect input torque to a steering wheel by a driver, and follows the shape of the road. An automatic steering instruction device that calculates and outputs an instruction steering angle, which is information of a steering angle necessary for the vehicle to travel, and a steering angle control current in a motor included in the electric power steering device according to the instruction steering angle And a steering control unit that executes feedback control for causing the actual steering angle to follow the commanded steering angle, and the steering control unit is configured such that when the feedback control is executed, the input torque is a predetermined first threshold value. The feedback control is temporarily stopped when it is detected that the above is reached, and the input torque becomes less than a predetermined second threshold value that is lower than the first threshold value. The automatic steering apparatus that resumes the feedback control when detecting that the steering control unit detects that the input torque is less than the second threshold after the feedback control is temporarily stopped. During the predetermined period, the upper limit values of the angular speed and angular acceleration of the actual steering angle are set lower than the upper limits of the angular speed and angular acceleration of the actual steering angle outside the predetermined period, and the steering angle control Output current.

  ADVANTAGE OF THE INVENTION According to this invention, the automatic steering device which can reduce the discomfort which a driver | operator receives at the time of automatic steering resumption after override operation can be provided.

It is a block diagram which shows the structure of an automatic steering apparatus. It is a block diagram for demonstrating control of an electric power steering apparatus. It is a block diagram for demonstrating control of the electric power steering apparatus at the time of the automatic steering resumption after an override operation.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings used for the following description, the scale of each component is made different in order to make each component recognizable on the drawing. It is not limited only to the quantity of the component described in (1), the shape of the component, the ratio of the size of the component, and the relative positional relationship of each component.

  An automatic steering apparatus 1 according to this embodiment shown in FIG. 1 is an apparatus that performs steering during an automatic driving operation of a vehicle. The automatic steering device 1 includes an electric power steering device (hereinafter referred to as EPS) 10 having a mechanism for changing the steering angle of the vehicle, and an automatic steering instruction device 2 that gives a steering instruction to the EPS 10 during an automatic driving operation. Prepare.

  The rotation of the steering wheel 9 by the input of the driver of the vehicle is converted into the rotation of the steered wheels 20 in the steered direction via the steered mechanism 15 provided in the EPS 10. In the present embodiment, as an example, the steering mechanism unit 15 has a rack and pinion mechanism. The pinion shaft 15 a provided with the pinion gear of the rack and pinion mechanism of the steering mechanism portion 15 is connected to the steering wheel 9 via a universal joint or the like, and the pinion shaft 15 a rotates together with the steering wheel 9.

  The EPS 10 includes a motor 14 that is an electric actuator, and applies an operation force applied to the steering wheel 9 by the driver by applying torque output from the motor 14 to the pinion shaft 15a in accordance with an input to the steering wheel 9 by the driver. A so-called power assist operation is performed. Further, the EPS 10 rotates the pinion shaft 15a by the motor 14 in response to an instruction output from the automatic steering instruction device 2 independently of an input to the steering wheel 9 by the driver during an automatic driving operation of the vehicle. The steered wheels 20 are rotated in the steered direction. Since the mechanical configuration of the EPS 10 is known, a detailed description thereof will be omitted.

  The automatic steering instruction device 2 includes an external environment recognition device 3 for recognizing the external environment around the vehicle, a navigation device 4 for recognizing the shape of the road on which the vehicle is traveling, and the vehicle traveling speed, longitudinal acceleration, yaw rate, etc. A vehicle behavior detection device 5 for detecting the behavior of the vehicle is provided.

  The external environment recognition device 3 recognizes the shape of the traveling road ahead of the vehicle and the presence of an object existing on and around the traveling road based on information from a sensor that recognizes the external environment of the vehicle. The external environment recognition device 3 includes, for example, a stereo camera that keeps the front of the vehicle in the field of view, and performs known image processing and the like on the image captured by the stereo camera, thereby existing in the shape of the road ahead and the traveling direction. Recognize the position and movement of objects.

  The navigation device 4 includes a positioning device that detects the current position (latitude, longitude) of the vehicle using at least one of a satellite positioning system, an inertial navigation device, and road-to-vehicle communication, a map information storage unit that stores map information, Is provided. The map information includes information indicating the shape of the road such as the curvature of the road, the gradient of the longitudinal section, and the state of intersection with another road. The navigation device 4 recognizes the shape of the road ahead of the vehicle based on the current position of the vehicle detected by the positioning device and the map information stored in the map information storage unit.

  The automatic steering instruction device 2 is based on information such as the shape of the road recognized by the external environment recognition device 3 and the navigation device 4, information on the current behavior of the vehicle, and information on the vehicle motion model. Is calculated for the steering angle θc, which is the angle of the pinion shaft 8a necessary for traveling along the road that is currently traveling, and is output to the EPS 10. Since an automatic steering instruction device using an external environment recognition device such as a stereo camera is known, a detailed description of the configuration is omitted.

  The EPS 10 includes a steering mechanism unit 15, a steering control unit 11, an input torque sensor 12, a pinion shaft angle sensor 13, and a motor 14. The steered mechanism unit 15 has a mechanism that converts a force that rotates the pinion shaft 15a into a force that rotates the steered wheels 20 in the steered direction. A steering mechanism using a rack and pinion mechanism as in this embodiment is a known technique.

  The steering control unit 11 is composed of a computer having a CPU, ROM, RAM, input / output device and the like connected to a bus, and controls the operation of the EPS 10 based on a predetermined program.

  The input torque sensor 12 detects an input torque Tm that is a torque input to the pinion shaft 15a by the driver via the steering wheel 9. The pinion shaft angle sensor 13 detects the rotation angle θ of the pinion shaft 15a.

  The motor 14 is an electric motor that outputs a motor output torque To that is a torque for rotating the pinion shaft 15a around the axis. That is, the input torque Tm input from the driver via the steering wheel 9 and the motor torque To input from the motor 14 are input to the pinion shaft 15a.

  FIG. 2 is a block diagram of the steering control during the automatic driving operation of the EPS 10. As shown in FIG. 2, information on the commanded steering angle θc calculated by the automatic steering commanding device 2 is input to the EPS 10.

  During the automatic driving operation of the vehicle, the steering control unit 11 of the EPS 10 changes the steering angle control current Is applied to the motor 14 with the commanded steering angle θc as a target value, thereby controlling the angle θ of the pinion shaft 15a as a control amount. The feedback control is performed to follow the command steering angle θc.

  The steering control unit 11 of the present embodiment includes a PID control unit 11a that calculates a steering angle control current Is by using general PID control as a feedback control method. The PID control unit 11a can change the values of the proportional gain Kp, the differential gain Kd, and the integral gain Ki for the steering angle control and the steering angular speed control.

  Further, the steering control unit 11 of the EPS 10 calculates the assist current Ia to be given to the motor 14 so that the input torque Tm and the pinion shaft angle θ have a predetermined relationship, and assists the driver in inputting to the steering wheel 9. Execute power assist operation. The steering control unit 11 can change the value of the power assist gain, which is a gain when calculating the assist current value Ia from the input torque Tm.

  As described above, the command current Ic input to the motor 14 during the automatic operation is a value obtained by adding the assist current Ia to the steering angle control current Is. The motor 14 outputs a motor torque To corresponding to the command current Ic.

  If the driver is not applying force to the steering wheel 9, the steering angle control current Is output from the PID control unit 11a and the command current Ic input to the motor 14 are equal. Further, when the driver applies the input torque Tm to the steering wheel 9 during the automatic driving operation, the input torque Tm and the assist current Ia act on the EPS 10 as disturbances. Further, the road surface reaction torque Tr generated with the movement of the steered wheels 20 with respect to the road surface is also input to the pinion shaft 15a.

  Next, the operation of the override determination process during the automatic driving operation of the automatic steering device 1 having the above-described configuration will be described.

  Overriding means that the driver operates the steering wheel 9 during the automatic driving operation of the vehicle. The overriding is performed, for example, when the driver tries to drive the vehicle on a route different from the traveling route of the automatic driving operation. The override determination process is a process for temporarily stopping the automatic driving operation and switching to the manual driving by the driver when the operation of the steering wheel 9 by the driver is detected.

  Schematically, the steering control unit 11 of the automatic steering device 1 according to the present embodiment allows the driver when the input torque Tm detected by the input torque sensor 12 is equal to or greater than a first threshold value Tth1 that is a predetermined value. It is determined that an override operation has been performed. Further, after determining that the driver has performed an override operation, the steering control unit 11 has the second threshold value Tth2 in which the input torque Tm detected by the input torque sensor 12 is a predetermined value lower than the first threshold value Tth1. When it becomes less than, it is determined that the override operation by the driver is finished.

  The steering control unit 11 temporarily stops the feedback control of the steering by the automatic steering device 1 during the period when it is determined that the override operation by the driver is being performed.

  FIG. 3 is a block diagram for explaining the control of the EPS 10 when it is determined that the override operation has ended. As shown in FIG. 3, the control of the EPS 10 at the time when it is determined that the override operation has ended is that the steering angular speed limiter 11b is added to the control of the EPS 10 during the normal automatic driving operation shown in FIG. different.

  Here, as shown in FIG. 3, the period during which the steering angular speed limiter 11b is applied to the control of the EPS 10 is after determining that the override operation has been performed, and the input torque Tm becomes less than the second threshold value Tth2. This is a period from when this is detected until a predetermined time t1 elapses.

  The rudder angular velocity limiter 11b acts on the rudder angle control current Is applied to the motor 14 in the steering feedback control by the automatic steering device 1, and limits the maximum values of the angular velocity and angular acceleration of the pinion shaft 15a, as will be described later.

  In the following description, the elapsed time from when it is determined that the override operation has been performed and the input torque Tm is less than the second threshold value Tth2 is referred to as a post-return time t, and the input torque A time point when it is detected that Tm is less than the second threshold value Tth2 is t = 0 [seconds]. In addition, a period in which the value of the time after return is 0 ≦ t ≦ t1 (period in which the EPS 10 shown in FIG. 3 is controlled) is referred to as a limiter effective period.

  As shown in FIG. 3, the value of the pinion shaft angular velocity ω which is the angular velocity of the pinion shaft 15a and the value of the pinion shaft angular acceleration α which is the angular acceleration of the pinion shaft 15a are input to the rudder angular velocity limiter 11b.

  The pinion shaft angular velocity ω is calculated by differentiating the pinion shaft angle θ detected by the pinion shaft angle sensor 13 with respect to time. The pinion shaft angular acceleration α is calculated by differentiating the pinion shaft angular velocity ω with respect to time.

  Further, the rudder angular velocity limiter 11b stores a limit angular velocity ω1 that is the maximum pinion shaft angular velocity allowed during the limiter effective period and a limit angular acceleration α1 that is the maximum pinion shaft angular acceleration permitted during the limiter effective period. Yes. The values of the critical angular velocity ω1 and critical angular acceleration α1 are set to values lower than the critical angular velocity and critical angular acceleration of the pinion shaft 15a during a normal automatic driving operation that is outside the limiter effective period.

  The steering angular speed limiter 11b has a steering angular speed limiter gain G that is a gain multiplied by the steering angle control current Is. The value of the steering angular speed limiter gain G is variable within the range of 0 to 1. When the value of the steering angular speed limiter gain G is less than 1, the steering angular control current Is decreases in the steering feedback control by the automatic steering device 1 by the action of the steering angular speed limiter 11b.

  The steering angular speed limiter 11b changes the value of the steering angular speed limiter gain G so that the pinion shaft angular speed ω does not exceed the limit angular speed ω1 during the limiter effective period, and acts on the steering angle control current Is.

  Specifically, the value of the steering angular speed limiter gain G is obtained by multiplying three gains G1, G2, and G3 described below. That is, G = G1, G2, and G3. Each of the three gains G1, G2, and G3 is a variable value within a range of 0 to 1.

  The gain G1 is a value that changes according to the change of the pinion shaft angular velocity ω, and decreases as the value of the pinion shaft angular velocity ω approaches the limit angular velocity ω1. In the present embodiment, as an example, G1 = 1− (ω / ω1).

  Due to the presence of the gain G1, during the limiter effective period, the value of the pinion shaft angular velocity ω increases and approaches the limit angular velocity ω1, and the value of the steering angular velocity limiter gain G decreases and the value of the steering angle control current Is decreases. Therefore, in the automatic steering device 1 of the present embodiment, the pinion shaft angular velocity ω does not exceed the limit angular velocity ω1 during the limiter effective period.

  The gain G2 is a value that increases as the post-return time t increases during the limiter effective period, and the value is fixed to 1 outside the limiter effective period. The gain G2 increases with time so that the value is 0 at the time t = 0 after the return and 1 at the time t = t1 after the return. In this embodiment, as an example, G2 = t / t1 during the limiter effective period (0 ≦ t ≦ t1). Further, G2 = 1 outside the limiter effective period (t> t1).

  Due to the presence of the gain G2, during the limiter effective period, the value of the steering angular speed limiter gain G decreases and the value of the steering angle control current Is decreases as the value of the post-return time t decreases. Therefore, immediately after returning to the feedback control after the override operation by the driver, the value of the rudder angular speed limiter gain G becomes almost 0, so that a sudden change in the pinion shaft angle θ is suppressed.

  The gain G3 is a value that changes according to the change of the pinion shaft angular acceleration α, and decreases as the value of the pinion shaft angular acceleration α approaches the limit angular acceleration α1. In this embodiment, as an example, G3 = 1− (α / α1).

  Due to the presence of the gain G3, during the limiter effective period, the value of the pinion shaft angular acceleration α increases, and as the limit angular acceleration α1 is approached, the value of the steering angular velocity limiter gain G decreases and the value of the steering angle control current Is decreases. . Therefore, in the automatic steering device 1 of the present embodiment, the pinion shaft angular acceleration α does not exceed the limit angular acceleration α1 during the limiter effective period.

  As described above, the automatic steering apparatus 1 according to the present embodiment performs feedback control when it is detected that the input torque Tm is equal to or greater than the predetermined first threshold value Tth1 during execution of feedback control for automatic steering. Pause and give priority to steering by the override operation by the driver. Thereafter, when the automatic steering device 1 detects that the input torque Tm is less than a predetermined second threshold value Tth2 lower than the first threshold value Tth1 (t = 0), the override operation by the driver is completed. Determine and restart feedback control of automatic steering.

  During the limiter effective period (0 ≦ t ≦ t1), which is a predetermined period after returning to the automatic steering feedback control execution state after the override operation by the driver, the steering control unit 11 The value of the steering angle control current Is is decreased by the angular velocity limiter 11b so that the pinion shaft angular velocity ω does not exceed the limit angular velocity ω1 and the pinion shaft angular acceleration α does not exceed the limit angular acceleration α1.

  Here, the limit angular velocity ω1 and the limit angular acceleration α1 are set to values lower than the limit angular velocity and the limit angular acceleration of the pinion shaft 15a during the normal automatic driving operation outside the limiter effective period. In the form of the automatic steering device 1, when the automatic steering is resumed after the override operation, a sudden change in the steering angle is suppressed, and the discomfort experienced by the driver can be reduced.

  Further, in the automatic steering device 1 of the present embodiment, the value of the steering angular speed limiter gain G becomes almost 0 immediately after the automatic steering is resumed after the override operation due to the effect of the gain G3. The value of G increases. For this reason, in the automatic steering device 1 of the present embodiment, a sudden change in the pinion shaft angle θ immediately after resuming the automatic steering after the override operation is suppressed, and the discomfort experienced by the driver can be reduced.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. An automatic steering apparatus that includes such a change is also applicable. Moreover, it is included in the technical scope of the present invention.

1 Automatic steering device,
2 automatic steering instruction device,
3 External environment recognition device,
4 navigation devices,
5 Vehicle behavior detection device,
9 Steering wheel,
10 Electric power steering system (EPS)
11 Steering control unit,
11a PID controller,
11b Rudder angular velocity limiter,
12 Input torque sensor,
13 Pinion shaft angle sensor,
14 motor,
15 steering mechanism,
15a pinion shaft,
20 steered wheels.

Claims (1)

A torque sensor that detects the input torque to the steering wheel by the driver,
Electric power steering device,
An automatic steering instruction device that recognizes the shape of a road on which the vehicle is traveling, calculates and outputs an instruction steering angle that is information on a steering angle necessary for the vehicle to travel along the shape of the road, and A steering control unit that outputs a steering angle control current to a motor included in the electric power steering device according to a commanded steering angle, and executes feedback control for causing the actual steering angle to follow the commanded steering angle;
With
The steering control unit temporarily stops the feedback control when detecting that the input torque is equal to or higher than a predetermined first threshold during execution of the feedback control, and the input torque is less than the first threshold. An automatic steering apparatus that resumes the feedback control when it is detected that the value is less than a predetermined second threshold value,
The steering control unit sets an upper limit value of the angular velocity and angular acceleration of the actual steering angle during a predetermined period from the time when the input torque is detected to be less than the second threshold after the feedback control is temporarily stopped. An automatic steering apparatus characterized in that the steering angle control current is set lower than the upper limit values of the angular velocity and angular acceleration of the actual steering angle outside the predetermined period.

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