JP2017030432A - Rear wheel steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear wheel steering control device for performing steering control of left and right rear wheels independently, which can reduce manufacturing costs by simplifying a configuration.SOLUTION: A rear wheel steering control device 13 comprises an electronic control device 15 and a connection switch part 27 for switching the electronic control device 15 alternately between a first connection state where the electronic control device is connected to a steering motor 24L, a rotation angle detector 25L, and an absolute position detector 26L of one actuator 14 L and a second connection state where the electronic control device is connected to a steering motor 24R, a rotation angle detector 25R, and an absolute position detector 26R of the other actuator 14R. The electronic control device 15 has a function of controlling the actuator 14L (14R) in the connection state by using a rotation angle detected by the rotation angle detector and an absolute position detected by the absolute position detector of the actuator 14L (14R) in the connected state according to a steering command value input from an electronic control unit 9.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a rear wheel steering control device used for a vehicle such as an automobile.

  2. Description of the Related Art Conventionally, a rear wheel steering device that steers rear wheels in addition to front wheel steering has been known for the purpose of stabilizing the running performance of a vehicle. The control device for the rear wheel steering device, for example, has a built-in microcomputer, determines an appropriate control amount of the steering angle and toe angle from the values of various sensor groups for constantly monitoring the state of the vehicle, For driving the actuator. The steered device is an important function that affects the running performance of the vehicle. The steered device estimates the optimum steered angle according to the state of the vehicle and the road surface, and performs control to stabilize the vehicle.

(1). In the rear wheel steering control device, when the left and right rear wheels are independently controlled to be steered, it is generally configured by a pair of control devices to control two actuators independently (Japanese Patent Application No. 2014-108081). ).
(2). As another conventional example, a technique has been proposed in which left and right actuators are connected in parallel to a drive circuit and driven by a single control device (Patent Document 1).

Japanese Patent No. 3476972

In the conventional example of (1), since a pair of control devices is required, the manufacturing cost increases.
In the conventional example of the above (2), the manufacturing cost is suppressed by being configured by one control device. However, since the motor is connected in parallel to the common FET bridge circuit, the left and right actuators are independently connected. The steering cannot be controlled.

  An object of the present invention is to provide a rear wheel steering control device capable of reducing the manufacturing cost by simplifying the configuration in a control device for independently steering control of the left and right rear wheels.

The rear wheel steering control device 13 of the present invention is a control device that controls a rear wheel steering device 12 that steers the left and right rear wheels 10 and 11 of a vehicle independently by a pair of actuators 14L and 14R. The actuators 14L and 14R are respectively steered motors 24L and 24R serving as driving sources, rotational angle detectors 25L and 25R for detecting rotational angles of the steered motors 24L and 24R, and absolute values of the actuators 14L and 14R. Absolute position detectors 26L and 26R for detecting positions,
The rear wheel steering control device 13 is
One electronic control unit 15;
The electronic control unit 15 is connected to the steering motor 24L (24R), the rotation angle detector 25L (25R), and the absolute position detector 26L (26R) of one of the pair of actuators 14L and 14R. A first connection state and a second connection state connected to the steering motor 24R (24L), the rotation angle detector 25R (25L), and the absolute position detector 26R (26L) in the other actuator. A connection switching unit 27 that switches alternately;
Have
The electronic control unit 15 detects the rotation angle and the absolute position detected by the rotation angle detector 25L (25R) in the connected actuator according to the steering command value input from the host control means 9. The actuator 26L (26R) has a function of controlling the actuator in the connected state using the absolute position detected by the detector 26L (26R).

  According to this configuration, the connection switching unit 27 of the rear wheel steering control device 13 switches alternately between the first connection state and the second connection state. The electronic control unit 15 detects the rotation angle detected by the rotation angle detector 25L (25R) and the absolute position detector 26L in the actuator in the connected state according to the steering command value input from the host control means 9. The actuator in the connected state is controlled using the absolute position detected at (26R).

  In the first connection state, the one electronic control unit 15 is electrically connected to the steering motor 24L (24R), the rotation angle detector 25L (25R), and the absolute position detector 26L (26R) in one actuator. Connected state. In the second connection state, the one electronic control unit 15 is electrically connected to the steering motor 24R (24L), the rotation angle detector 25R (25L), and the absolute position detector 26R (26L) in the other actuator. Connected state. In this way, by controlling the actuators in the connected state by the connection switching unit 27 among the pair of actuators 14L and 14R by the single electronic control device 15, the manufacturing cost is reduced as compared with the one using the pair of control devices. Can be achieved.

A vehicle speed sensor 7 for detecting a vehicle speed and a yaw rate sensor 8 for detecting a yaw rate acting on the vehicle are provided, and the electronic control unit 15 detects the vehicle speed detected by the vehicle speed sensor 7 and the yaw rate sensor 8. You may have the connection switching control part 22 which instruct | indicates to switch the connection state of the said connection switching part 27 based on either one or both of a yaw rate.
According to this configuration, the connection switching control unit 22 determines the vehicle state during traveling based on the vehicle speed or the yaw rate, and determines the switching timing. The relationship between the vehicle state and the switching timing is determined by, for example, a result of a test or a simulation. The connection switching control unit 22 is realized by, for example, a microprocessor.

When the vehicle is turning, the connection switching control unit 22 commands the switching of the rear wheel actuator 14R (14L) on the outer side of the turn with priority over the actuator 14L (14R) on the rear side of the turn. May be.
When the vehicle is turning, the cornering force sharing ratio of the rear wheels on the inner side when turning is low, and the burden on the rear wheels on the outer side when turning is higher. Therefore, if the optimum rear wheel rudder angle value is given to the outer rear wheel during turning, the turning performance can be obtained even if the following accuracy of the rear wheel rudder angle during turning is low to some extent. Therefore, the connection switching control unit 22 instructs the switching of the rear wheel actuator 14R (14L) on the outer side of the turn with priority over the actuator 14L (14R) of the rear wheel on the inner side of the turn. Turn performance can be obtained.

  The rear wheel steering control device according to the present invention is a control device that controls a rear wheel steering device that independently steers the left and right rear wheels of a vehicle using a pair of actuators, and each of the pair of actuators includes a drive source. A turning motor, a rotation angle detector that detects the rotation angle of the steering motor, and an absolute position detector that detects the absolute position of the actuator. The rear wheel steering control device is connected to one electronic control device, and the electronic control device is connected to the steering motor, the rotation angle detector, and the absolute position detector of one actuator of the pair of actuators. And a connection switching unit that alternately switches between the first connection state and the second connection state connected to the steering motor, the rotation angle detector, and the absolute position detector in the other actuator. The electronic control unit is configured to detect a rotation angle detected by the rotation angle detector and an absolute position detected by the absolute position detector in the actuator in a connected state in accordance with a steering command value input from an upper control unit. Using the position, the actuator has a function of controlling the actuator in the connected state. For this reason, in the control device that controls the left and right rear wheels independently, it is possible to reduce the manufacturing cost by simplifying the configuration.

It is a schematic explanatory drawing of the motor vehicle carrying the rear-wheel steering apparatus which applies the rear-wheel steering control apparatus which concerns on embodiment of this invention. It is a block diagram which shows the conceptual structure of the rear-wheel steering control apparatus. It is a figure which shows an example of the timing chart which switches a connection state using the rear-wheel steering control apparatus. It is a figure which shows the other example of the timing chart which switches a connection state using the rear-wheel steering control apparatus.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic explanatory diagram of an automobile equipped with a rear wheel steering device to which a rear wheel steering control device according to this embodiment is applied. The left and right front wheels 2 and 3 of the automobile 1 that is a vehicle are steered left and right by transmitting the steering angle of the steering wheel 4 to a front wheel steering device 5 that is a main steering device made of, for example, a rack and pinion. . The outputs of the steering angle sensor 6, the vehicle speed sensor 7, and the yaw rate sensor 8 provided with respect to the steering shaft of the steering wheel 4 are input to the electronic control unit 9. The electronic control unit 9 is a main control unit that performs overall cooperative control, overall control, and the like of the automobile 1 and is abbreviated as ECU or VCU.

  The left and right rear wheels 10 and 11 are steered by a rear wheel steering device 12 fixed to a chassis (vehicle body) via knuckle arms Na and Nb corresponding to the tie rods connected to the rear wheel steering device 12. The The rear wheel steering device 12 can steer the left and right rear wheels 10 and 11 independently by a pair of steering motors 24L and 24R. As for the turning angles of the rear wheels 10 and 11, the target turning angles determined by the electronic control unit 9 according to the input of travel information of the automobile 1, such as the steering angle sensor 6, the vehicle speed sensor 7, and the yaw rate sensor 8, are used. The rear wheel steering control device 13 receives the rear wheel steering control device 13 and the left and right rear wheels 10 and 11 are independently controlled by the rear wheel steering control device 13.

  The rear wheel turning device 12 has drive means 14 for turning the rear wheels 10 and 11 in the same phase and in the opposite phase with respect to the front wheel turning angle. This drive means 14 is a linear motion actuator composed of, for example, a slide screw (not shown) without reverse input or a ball screw (not shown) with a reverse input prevention mechanism. The driving means 14 converts a nut (not shown) that is screwed into the linear actuator with a motor via a speed reducer (not shown) to convert it into a linear motion of the linear actuator.

  This linear motion actuator includes a pair of actuators 14L and 14R that drive the left and right rear wheels 10 and 11 independently. Of these actuators 14L and 14R, the first actuator 14L is a drive means for turning the left rear wheel 10, and the second actuator 14R is a drive means for turning the right rear wheel 11. The first actuator 14L detects the absolute position of the steering motor 24L as a drive source, a rotation angle detector 25L (FIG. 2) that detects the rotation angle of the steering motor 24L, and the first actuator 14L. An absolute position detector 26L (FIG. 2). The second actuator 14R detects the absolute position of the steering motor 24R serving as a drive source, a rotation angle detector 25R (FIG. 2) for detecting the rotation angle of the steering motor 24R, and the second actuator 14R. And an absolute position detector 26R (FIG. 2).

FIG. 2 is a block diagram showing a conceptual configuration of a control device 13 (hereinafter referred to as “rear wheel steering control device”) 13 that controls the rear wheel steering device 12 (FIG. 1) having the above-described configuration.
The rear wheel steering control device 13 includes one electronic control device 15 and a connection switching unit 27. The one electronic control unit 15 independently controls the first and second actuators 14L, 14R that steer the left and right rear wheels 10, 11 (FIG. 1).

  The electronic control unit 15 includes a microprocessor 16, a command-side input signal input interface unit 17 obtained from the electronic control unit 9 which is a higher-level control means, a detection obtained from the first actuator 14 </ b> L or the second actuator 14 </ b> R. The input interface unit 18 for the input signal on the side, the output interface unit 19, and the motor drive unit 20 are included. Note that the command-side and detection-side input interface units 17 and 18 may be separate electronic elements or a part of one electronic element.

The microprocessor 16 includes a motor control target value calculation unit 21 and a connection switching control unit 22. The target value of the rear wheel turning angle determined by the electronic control unit 9 is transmitted to the motor control target value calculation unit 21 via the command-side input interface unit 17.
In the microprocessor 16, in order to execute the control of the steered motor (left) 24L and the steered motor (right) 24R, the result calculated by the motor control target value computing unit 21 (in this embodiment, calculated from the steered angle). The motor drive command based on the rotation speed of the steered motor 24L or the steered motor 24R) is transmitted to the motor drive unit 20 via the output interface unit 19. The motor drive unit 20 includes a motor current detection unit 23 described later.

  When, for example, a brushless motor is used as the steered motor (left) 24L and the steered motor (right) 24R, the basic control is torque (current), speed, and position control. Therefore, a control system (not shown) mounted on the microprocessor 16 is a composite control system that constitutes a speed control system and a position control system above the current control system. Therefore, the motor drive command value is calculated from the motor current detection value obtained from the motor current detector 23, the rotation angle detector 25L, or the rotation angle detector 25R, in addition to the calculation result calculated by the command from the electronic control unit 9. Control is performed so as to reach the target steering angle based on a feedback value such as a detected rotation angle detection value.

  The absolute position detectors 26L and 26R monitor the absolute positions of the first and second actuators 14L and 14R, respectively. Specifically, when the steering motor 24L of the first actuator 14L is rotated, the rod Rda moves to the left and right according to the amount of rotation decelerated by the speed reducer, as shown in FIG. The left rear wheel 10 is steered through a ball joint (not shown) fixed to the tip of the rod Rda and a knuckle arm Na. As shown in FIG. 2, the absolute position detector 26L detects the absolute position of the rod Rda (FIG. 1) in the left-right direction using, for example, a magnetic detection type detector. However, it is not limited to a magnetic detection type detector. Similarly, the absolute position detector 26R detects the absolute position of the rod Rdb (FIG. 1) connected to the right rear wheel 11 in the left-right direction.

  The absolute position is detected when the power is turned on, for example, when an ignition (not shown) of the vehicle is turned on, and the subsequent control is performed based on the detected absolute position as a rotation angle detector 25L or a rotation angle detector. Position control is performed at the rotation angle obtained from 25R. These control systems are mounted on the microprocessor 16 so as to perform control by, for example, software calculation.

The connection switching control unit 22 of the microprocessor 16 commands the connection state of the connection switching unit 27 to be switched.
The connection switching unit 27 connects the electronic control unit 15 to the steered motor (left) 24L, the rotation angle detector 25L, and the absolute position detector 26L of the first actuator 14L in the first and second actuators 14L and 14R. The first connection state and the second connection state connected to the turning motor (right) 24R, the rotation angle detector 25R, and the absolute position detector 26R in the second actuator 14R are alternately switched.

  For example, the connection switching control unit 22 instructs the connection switching unit 27 to connect the electronic control device 15 to the first actuator 14L. Thereby, the connection switching unit 27 connects the motor drive unit 20 to the steered motor (left) 24L, and connects the input interface unit 18 to the rotation angle detection unit 25L and the absolute position detector 26L (first connection state). ).

  The connection switching control unit 22 changes the connection state of the connection switching unit 27 from the first connection state to the second based on one or both of the vehicle speed detected by the vehicle speed sensor 7 and the yaw rate detected by the yaw rate sensor 8. Command to switch to the connected state. Thereby, the connection switching unit 27 connects the motor drive unit 20 to the steered motor (right) 24R, and connects the input interface unit 18 to the rotation angle detection unit 25R and the absolute position detector 26R (second connection state). ).

  When the vehicle is turning, the sharing ratio of the cornering force of the inner rear wheel when turning is low, and the burden on the rear wheel when turning is higher. Therefore, if the optimum rear wheel rudder angle value is given to the outer rear wheel during turning, the turning performance can be obtained even if the following accuracy of the rear wheel rudder angle during turning is low to some extent. Therefore, the connection switching control unit 22 preferentially switches the actuator 14R (14L) of the rear rear wheel 11 (10) during turning over the actuator 14L (14R) of the rear rear wheel 10 (11) during turning. To the connection switching unit 27. Thereafter, the connection switching control unit 22 instructs the connection switching unit 27 to switch to the actuator 14L (14R) of the rear wheel 10 (11) on the inner side during turning. Thus, desired turning performance can be obtained by setting the outer and inner rear wheels 11 and 10 to the optimum rear wheel steering angle.

  As another example of preferentially switching the actuator 14R (14L) of the rear rear wheel 11 (10) during turning, the connection switching control unit 22 switches the actuator 14L (14R) of the rear rear wheel 10 (11) during turning. The connection switching unit 27 may be commanded so that only the actuator 14R (14L) of the outer rear wheel 11 (10) can be driven while turning neutral. Thus, the desired turning performance can be obtained by setting the outer rear wheel 11 (10) during turning to the optimum rear wheel steering angle. Note that in the case of only control in which the inner wheel side rear wheel is neutral and only the outer wheel side rear wheel is driven, it is not necessary to periodically (or intermittently) switch the inner wheel side rear wheel. When performing both of the above-described control to give the optimum rear wheel steering angle value to the rear rear wheel at the time of turning, it is necessary to periodically (or intermittently) switch the rear wheel on the inner wheel side so as not to be in reverse phase. is there.

FIG. 3 is a diagram illustrating an example of a timing chart for switching the connection state using the rear wheel steering control device 13. Hereinafter, description will be made with reference to FIGS. 1 and 2 as appropriate.
In the example of FIG. 3, when turning the automobile 1, the connection switching control unit 22 causes the actuator 14 </ b> R (14 </ b> L) (simply “outer wheel”) of the rear wheel 11 (10) to be turned outside before turning the target. And a state instructing to switch to the actuator 14L (14R) (simply referred to as “inner wheel”) of the inner rear wheel 10 (11) when turning. Are switched. In this case, the connection switching control unit 22 determines from the detection value from the steering angle sensor 6 whether the rear wheel 10 (11) is outside or inside when turning.

  The connection switching control unit 22 determines the switching timing by determining the vehicle state using one or both of the vehicle speed detected by the vehicle speed sensor 7 and the yaw rate detected by the yaw rate sensor 8. For example, based on the results obtained through experiments and simulations, a map table for switching timing is created for only the vehicle speed, only the yaw rate, or both.

  At the start of turning, first, switching to the “outer wheel” and then switching to the “inner wheel” are repeated, and the turning is finally completed. When one of the rear wheels 10 (11) is steered, the other rear wheel 11 (10) stops the steering, and when the other rear wheel 11 (10) is steered, the one The rear wheel 10 (11) has stopped turning. In this case, since the “outer wheel” is preferentially driven, the total time t (g) for driving the “outer wheel” is “the inner wheel” until the “outer wheel” is completely turned to the target rudder angle. Is longer than the total time t (i) for driving “. The time ratio per unit time for driving the “outer wheel” and the “inner wheel” is larger for the “outer wheel” than for the “inner wheel”.

  FIG. 4 is a diagram illustrating another example of a timing chart for switching the connection state using the rear wheel steering control device 13. The example of FIG. 4 shows a timing chart in the case of switching to “outside wheels” and then switching to “inside wheels”. In this example, after turning the “outer wheel” to the target rudder angle, the steering is switched to the “inner wheel”. Therefore, the “outer wheel” can be driven preferentially. The switching timing to the “inner wheel” is after the completion of the “outer wheel” steering, and in this case, the total time for driving the “outer wheel” and the “inner wheel” is the same.

The effect will be described.
According to the rear wheel steering control device 13 described above, the connection switching unit 27 switches alternately between the first connection state and the second connection state. In accordance with the steering command value input from the electronic control unit 9, the electronic control unit 15 detects the rotation angle and absolute position detector detected by the rotation angle detector 25L (25R) in the actuator 14L (14R) in the connected state. The actuator 14L (14R) in the connected state is controlled using the absolute position detected by 26L (26R). Of the pair of actuators 14L, 14R, the actuator 14L (14R) in the connected state by the connection switching unit 27 is independently controlled by one electronic control unit 15, thereby reducing the manufacturing cost compared to using the pair of control units. Can be achieved.
The connection switching control unit 22 instructs the actuator 14R (14L) of the rear wheel 11 (10) on the outer side to switch preferentially over the actuator 14L (14R) on the rear wheel 10 (11) on the inner side of the turn. By doing so, a desired turning performance can be obtained.

  As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

7 ... Vehicle speed sensor 8 ... Yaw rate sensor 9 ... Electronic control unit (upper control means)
DESCRIPTION OF SYMBOLS 10, 11 ... Rear wheel 12 ... Rear-wheel steering apparatus 14L, 14R ... A pair of actuator 15 ... Electronic control unit 22 ... Connection switching control part 24L, 24R ... Steering motor 25L, 25R ... Rotation angle detector 26L, 26R ... Absolute Position detector 27 ... Connection switching unit

Claims (3)

A control device that controls a rear wheel steering device that independently steers the left and right rear wheels of a vehicle with a pair of actuators, each of the pair of actuators including a steering motor that serves as a drive source, and the steering A rotation angle detector for detecting the rotation angle of the motor, and an absolute position detector for detecting the absolute position of the actuator;
The control device includes:
One electronic control unit,
The electronic control device is connected to the steering motor of one actuator of the pair of actuators, the rotation angle detector and the absolute position detector, and the steering motor of the other actuator, A connection switching unit that alternately switches to a second connection state connected to the rotation angle detector and the absolute position detector;
Have
The electronic control unit is configured to detect a rotation angle detected by the rotation angle detector and an absolute position detected by the absolute position detector in the actuator in a connected state in accordance with a steering command value input from an upper control unit. A rear wheel steering control device having a function of controlling the actuator in the connected state using a position.   2. The rear wheel steering control device according to claim 1, wherein a vehicle speed sensor for detecting a vehicle speed and a yaw rate sensor for detecting a yaw rate acting on the vehicle are provided, and the electronic control unit is configured to detect a vehicle speed detected by the vehicle speed sensor. And a rear wheel steering control device having a connection switching control unit that instructs to switch the connection state of the connection switching unit based on one or both of the yaw rates detected by the yaw rate sensor.   3. The rear wheel steering control device according to claim 2, wherein when the vehicle is turning, the connection switching control unit preferentially switches an actuator for the rear wheel at the outside of the turn over an actuator for the rear wheel at the time of turning. Rear wheel steering control device that commands as follows.

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