JP2024020770A - steering system - Google Patents

Abstract

To provide a steering system capable of suppressing the decline in driving performance even when an abnormality occurs in one of the left and right steering devices.SOLUTION: A steering system of the invention comprises a left steering device 2A steering a left steering wheel 11, a right steering device 2B steering a right steering wheel 12 independently of the left steering device 2A, a left steering controller 3A controlling the left steering device 2A and a right steering controller 3B controlling the right steering device 2B. The left steering controller 3A can detect an abnormality of the right steering controller 3B and when it detects the abnormality of the right steering controller 3B, it executes the right shutdown control to shut off the supply of control current to the right steering device 2B. The right steering controller 3B can detect an abnormality of the left steering controller 3A and when it detects the abnormality of the left steering controller 3A, it executes the left shutdown control to shut off the supply of control current to the left steering device 2A.SELECTED DRAWING: Figure 1

Description

The present invention relates to a single-wheel independent steering type steering system.

A single-wheel independent steering type steering system is a system that steers the left and right wheels independently. In this steering system, the left steering device that steers the left steered wheels and the right steering device that steers the right steered wheels are controlled based on the operation amount of the operating member in manual driving or the command value in automatic driving. Ru. A single-wheel independent steering type steering system is a steer-by-wire system in which an operating member and a steering device are not mechanically connected. For example, Japanese Patent Application Laid-Open No. 2018-58512 states that when a communication abnormality occurs between a host control device and either the left or right steering control device, the steering wheel corresponding to the steering control device that has experienced the communication abnormality is A vehicle steering device that controls a steering angle to a neutral position is disclosed.

JP 2018-58512 Publication

However, with the above device, one wheel is held in the neutral position, which increases the turning resistance when turning, increases the minimum turning radius, etc., and makes it difficult to maintain driving performance, including straight-line performance and turning performance. There is room for improvement in this respect.
An object of the present invention is to provide a steering system that can suppress a decrease in driving performance even when an abnormality occurs in one of the left and right steering devices.

The steering system of the present invention includes a left steering device that steers a left steered wheel, a right steering device that steers a right steered wheel independently of the left steering device, and a right steering device that controls the left steering device. A single-wheel independent steering type steering system comprising: a left steering controller that controls the right steering controller; and a right steering controller that controls the right steering device; If an abnormality in the right steering controller is detected, the right steering controller executes right cutoff control to cut off the supply of control current to the right steering device, and the right steering controller The controller is configured to be able to detect an abnormality in the rudder controller, and when an abnormality in the left steering controller is detected, a left cutoff control is executed to cut off the supply of control current to the left steering device.

According to the present invention, when an abnormality occurs in one controller, the other controller cuts off the supply of control current to the steering device that is controlled by the one controller. As a result, the control current is not supplied to the steered wheel corresponding to the abnormal controller, and the steered wheel becomes in a free state similar to the driven wheel. The steered wheels that have become free after the abnormality is detected follow the traveling direction ensured by the normal steered wheels, that is, the controlled steered wheels, due to self-aligning torque. Therefore, running resistance is suppressed to a minimum, and deterioration of running performance (straight running/turning performance) is suppressed.

FIG. 1 is a configuration diagram of a steering system according to the present embodiment. It is a perspective view showing the composition of the right steering device of this embodiment. It is a block diagram of the steering controller of this embodiment. 3 is a flowchart illustrating an example of the flow of control according to the present embodiment. FIG. 3 is a conceptual diagram for explaining kingpin offset. It is a conceptual diagram for explaining a caster trail.

EMBODIMENT OF THE INVENTION Hereinafter, as a mode for carrying out the present invention, a steering system 1 which is an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the following embodiments, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

The steering system 1 of this embodiment is a single-wheel independent steering type (left and right independent steering type) and a steer-by-wire type steering system. As shown in FIG. 1, the steering system 1 includes a left steering device 2A, a right steering device 2B, a left steering controller 3A, a right steering controller 3B, an operating device 4, and a reaction force controller 5. , is equipped with. The steering system 1 is a steer-by-wire type steering system in which the left steering device 2A and the right steering device 2B and the operating device 4 are not mechanically connected.

Communication within the vehicle is performed using a CAN (car area network or controllable area network) 100. In the drawings, some communication lines are omitted. In this embodiment, the steered wheels are the front wheels 11 and 12, the left steered wheel is the left front wheel 11, and the right steered wheel is the right front wheel 12. The left steering device 2A is a device that steers the left front wheel 11. The right steering device 2B is a device that steers the right front wheel 12 independently of the left steering device 2A. Since the left steering device 2A and the right steering device 2B have the same configuration, the configuration of the right steering device 2B will be explained, and the description of the configuration of the left steering device 2A will be omitted.

(Steering device)
As shown in FIG. 2, the right steering device 2B includes a steering knuckle 21, a steering actuator 22, and a tie rod 23. The steering knuckle 21 is a member that rotatably holds the right front wheel 12. The steering knuckle 21 is a housing of an in-wheel motor unit 7, which will be described later.

The steering actuator 22 is installed at a portion on the base end side of the lower arm 91. The steering actuator 22 includes a steering motor 221, a reduction gear 222, an actuator arm 223, and a rotation angle sensor 224. The steering motor 221 is an electric motor serving as a drive source. The steering motor 221 is, for example, a brushless DC motor.

The reducer 222 is a gear device that reduces the rotation of the steering motor 221. The actuator arm 223 is an arm member that rotates by rotation of the steering motor 221 via the reducer 222. Actuator arm 223 functions as a pitman arm. The tie rod 23 is a member that connects the knuckle arm 211 provided on the steering knuckle 21 and the actuator arm 223 of the steering actuator 22. One end of the tie rod 23 is connected to the actuator arm 223 via a ball joint 231, and the other end of the tie rod 23 is connected to the knuckle arm 211 via a ball joint 232.

The rotation angle sensor 224 detects the rotation angle of the steering motor 221. There is a specific relationship between the rotation angle of the steering motor 221 and the steering angle of the right front wheel 12. Therefore, each controller can calculate the steering angle of the wheel corresponding to the steering motor 221 based on the rotation angle of the steering motor 221. When the steered angle of the steered wheels changes due to road surface disturbance, the detection result of the corresponding rotation angle sensor 224 also changes accordingly. Road surface disturbance is an external force that the wheels 11 to 14 receive from the road surface, and is caused, for example, by a tire entering a small hole in the road, stepping on a stone, etc., or driving on an uneven road.

The rotation angle sensor 224 of the left steering device 2A corresponds to a left steering angle sensor that detects the steering angle of the left front wheel 11, and the rotation angle sensor 224 of the right steering device 2B detects the steering angle of the right front wheel 12. Corresponds to the right steering angle sensor. Hereinafter, the rotation angle sensor 224 of the left steering device 2A will also be referred to as the "left steering angle sensor 224", and the rotation angle sensor 224 of the right steering device 2B will also be referred to as the "right steering angle sensor 224".

The suspension devices 9 for the front wheels 11 and 12 each include a lower arm 91, a steering knuckle 21, a shock absorber 92, and a suspension spring 93. The suspension device 9 is, for example, a MacPherson strut type suspension device. The lower arm 91 is an L arm, and the base end portions of the lower arm 91 are each rotatably supported by a side member (not shown) of the vehicle body via a bush. The steering knuckle 21 is rotatably connected to the tip of the lower arm 91 via a ball joint 911. The shock absorber 92 is a member whose lower end is fixedly supported by the steering knuckle 21 and whose upper end is rotatably supported by the vehicle body via an upper support 94. The suspension spring 93 is a member whose upper end is rotatably supported by the vehicle body via an upper support 94 and whose lower end is supported by a lower support 95 provided on the shock absorber 92.

The vehicle includes various sensors, such as a yaw rate sensor 61 that detects the yaw rate of the vehicle, a wheel speed sensor 62 that detects the wheel speed of each wheel 11, 12, 13, and 14, and a lateral acceleration sensor 63 that detects lateral acceleration. is installed. Since the vehicle speed is calculated based on the wheel speed of each wheel 11 to 14, it can be said that the vehicle is equipped with a vehicle speed sensor that detects the vehicle speed. The vehicle is also equipped with a plurality of sensors (not shown), such as a longitudinal acceleration sensor, etc.

In this embodiment, the vehicle is equipped with an in-wheel motor unit 7 as a drive device on front wheels 11 and 12, which are steered wheels. The in-wheel motor unit 7 includes a steering knuckle 21 that functions as a housing, a drive motor 71, a reduction gear 72, and an axle hub (not shown). The drive motor 71 is an electric motor built into the steering knuckle 21. The reducer 72 is a gear device that reduces the rotation of the drive motor 71. The axle hub is attached to the wheel of the wheel. The in-wheel motor unit 7 is arranged inside the rim of the wheel. Each in-wheel motor unit 7 is controlled by a drive ECU (not shown).

(operating device)
The operating device 4 has a general structure in a steer-by-wire type steering system. As shown in FIG. 1, the operating device 4 includes a steering wheel 41, a steering sensor 42, and a reaction force applying device 43. The steering wheel 41 is an operating member that is steered by the driver.

The steering sensor 42 is a sensor that detects an operating angle, which is a rotation angle of the steering wheel 41, as the operating position or operating amount of the steering wheel 41. For example, when the position of the steering wheel 41 when the vehicle is traveling straight is defined as a neutral position, the rotation angle in each of the left and right directions from the neutral position is the operation angle of the steering wheel 41.

The reaction force applying device 43 is a device that applies a reaction force (reaction force to an operation) to the steering wheel 41. The reaction force applying device 43 includes a reaction force motor 431 which is an electric motor as a force source, a reduction gear 432 for transmitting the force of the reaction force motor 431 to the steering wheel 41, and an operation torque sensor 433. There is. Although not shown, the operating torque sensor 433 detects operating torque as an operating force applied to the steering wheel 41 by the driver based on the amount of twist of a torsion bar incorporated in the steering shaft. The steering sensor 42 and/or the operation torque sensor 433 can be said to be operation amount sensors that detect the operation amount (value related to operation) of the steering wheel 41. In this embodiment, for the sake of explanation, the detection result of the steering sensor 42 is assumed to be the operation amount of the steering wheel 41.

The reaction force controller 5 is an electronic control unit (ECU) including one or more processors 51 and one or more memories 52. The reaction force controller 5 has the same configuration as a left steering controller 3A and a right steering controller 3B, which will be described later. The reaction force controller 5 calculates a target reaction force based on the detection result of the steering sensor 42 and the vehicle speed. The reaction force controller 5 controls the reaction force motor 431 based on the target reaction force. In other words, the reaction force controller 5 supplies a control current to the reaction force motor 431 based on the target reaction force.

(Steering controller)
The left steering controller 3A and the right steering controller 3B (hereinafter also referred to as "steering controllers 3A, 3B") are electronic control units (ECUs) each including one or more processors 31a and one or more memories 31b. It is. The left steering controller 3A, the right steering controller 3B, and the reaction force controller 5 (hereinafter also referred to as "controllers 3A, 3B, 5") are communicably connected to each other via the CAN 100. Each controller 3A, 3B, 5 obtains detection results from various sensors 61, 62, 63, 224, 42.

As shown in FIG. 3, each steering controller 3A, 3B mainly includes a power supply circuit 30, an MCU 31, a motor drive circuit 32, an input/output protection circuit 33, an input conversion circuit 34, and an inspection circuit 35. It is equipped with. The power supply circuit 30 is connected to a power supply 8 made redundant by, for example, a main power supply (for example, a battery) and a backup power supply. The power source 8 includes, for example, a drive system power source, a DC-DC converter, a battery, a backup power source, and the like. Note that the power source 8 may be configured to include a battery.

The power supply 8 is configured, for example, to individually supply power to each of the controllers 3A, 3B, and 5. The power supply 8 and each power supply circuit 30 are configured to be connected when the ignition (key switch) is turned on and disconnected when the ignition (key switch) is turned off, for example, by operating a system switch 81. The system switch 81 is an example of a switching device that can be turned on and off (connection/cutoff).

The MCU 31 is a microcontroller unit that executes various calculations using a processor 31a. The MCU 31 controls the motor drive circuit 32 based on various sensors or command values. The motor drive circuit 32 supplies a control current to the steering motor 221 to be controlled in accordance with the control of the MCU 31 . The MCU 31 and the motor drive circuit 32 control the rotation angle and rotation speed of the steering motor 221. The input/output protection circuit 33 is a circuit for protecting the MCU 31 mainly during communication between the MCU 31 and the CAN 100. The input conversion circuit 34 is a circuit that converts input signals from various sensors into signals suitable for the MCU.

The inspection circuit 35 is a circuit connected to the power source 8, and is a circuit for inspecting, for example, whether a specified voltage is being applied to the controller when the ignition is turned on. The inspection circuit 35 includes, for example, a relay switch that is turned on when the ignition is turned on and turned off when the ignition is turned off, and a voltmeter that detects the voltage applied to the controller when the relay switch is turned on. . A relay switch is an example of a switching device that can be turned on and off (connection/cutoff). The MCU 31 determines whether the ignition is turned on and the controller is connected to the power source 8 based on the detection result (voltage value) of the inspection circuit 35. For example, the MCU 31 is configured not to start or operate if the detection result of the inspection circuit 35 is less than a threshold voltage (including an undetected state due to the relay switch being turned off).

The left steering controller 3A controls the left steering device 2A based on the detection result of the steering sensor 42. The right steering controller 3B controls the right steering device 2B based on the detection result of the steering sensor 42. Each steering controller 3A, 3B calculates a target steering angle based on the detection result of the steering sensor 42, and calculates a target control current based on the target steering angle. Each steering controller 3A, 3B supplies a control current to the steering motor 221 of the corresponding steering device (left steering device 2A or right steering device 2B) based on the target control current.

More specifically, each steering controller 3A, 3B calculates a target yaw rate of the vehicle based on vehicle speed information, steering angle information, and steering operation amount information acquired from various sensors. Each steering controller 3A, 3B calculates a target steering angle so that the detection result of the yaw rate sensor 61 approaches the target yaw rate. Note that the detection result of the lateral acceleration sensor 63 may be used in calculating the target steering angle.

The left steering controller 3A is configured to be able to detect abnormalities in the right steering controller 3B and the reaction force controller 5. The right steering controller 3B is configured to be able to detect abnormalities in the left steering controller 3A and the reaction force controller 5. The reaction force controller 5 is configured to be able to detect abnormalities in the left steering controller 3A and the right steering controller 3B. In this way, each of the controllers 3A, 3B, and 5 is configured to be able to detect an abnormality in a controller other than itself.

Specifically, each controller 3A, 3B, and 5 sets the target steering angle of both steered wheels, that is, the target steering angle of the left front wheel 11 and the target steering angle of the right front wheel 12, based on the detection result of the steering sensor 42. Calculate angles. Each of the controllers 3A, 3B, and 5 compares the calculation results with each other, and determines whether or not there is an abnormality in the other controller based on the comparison result.

For example, in each of the controllers 3A, 3B, and 5, if the calculation result of only one controller is significantly different from the calculation result of other controllers (if the difference is larger than a predetermined threshold X), the controller 3A, 3B, and 5 may be configured to determine that the error is abnormal. In this case, for example, the target steering angle of the left front wheel 11 calculated by the first controller is 0 degrees, and the target steering angle of the left front wheel 11 calculated by the second and third controllers is 10 degrees. In this case, the second and third controllers determine that the first controller is abnormal (0 degrees < threshold value X < 10 degrees).

Further, each controller 3A, 3B, and 5 calculates the target turning angle relative to the operation amount, for example, based on the relationship between the preset "operation amount of the steering wheel 41" and the "estimated calculation range of the target turning angle." The controller may be configured to determine an assumed calculation range, and determine that a controller that produces a calculation result outside the assumed calculation range is abnormal. Further, each of the controllers 3A, 3B, and 5 is configured to periodically output signals to each other, and for example, a controller that does not output the signal for a certain period of time may be determined to be abnormal. In this way, each of the controllers 3A, 3B, and 5 executes the same calculation and monitors each other's calculation results and signals to determine whether or not there is an abnormality in the controller.

An abnormality in the controller occurs due to, for example, an abnormality in the power supply system, an abnormality in the communication system (such as CAN 100), a disconnection inside the controller, or a malfunction in calculation. For example, an abnormality in one controller can be detected by another controller because the calculation result is abnormal, the calculation result does not reach another controller, or the calculation itself is not performed.

(Shutoff control)
When the left steering controller 3A detects an abnormality in the right steering controller 3B, it executes right cutoff control to cut off the supply of control current to the right steering device 2B. The right cutoff control is a control that cuts off the power supply to the steering motor 221 of the right steering device 2B. The right cutoff control may be, for example, a control that forcibly turns off the system switch 81 between the right steering controller 3B and the power source 8. Further, the right cutoff control may be a control that forcibly turns off the relay switch of the inspection circuit 35 of the right steering controller 3B. Since the voltage applied to the relay switch of the inspection circuit 35 is lower than the voltage applied to the system switch 81, on/off control of the inspection circuit 35 can be executed relatively easily.

The right cutoff control can be said to be a control that cuts off the power supply to the right steering controller 3B and the right steering device 2B even when the ignition is on. In this way, when the left steering controller 3A detects an abnormality in the right steering controller 3B, the steering motor 221 of the right steering device 2B is placed in a non-energized state (uncontrolled state) by executing the right cutoff control. , the right front wheel 12 is brought into a free state. The right cutoff control can also be said to be control that prohibits (stops) the operation of the left steering controller 3A (control of the left steering device 2A by the left steering controller 3A).

Similarly, when detecting an abnormality in the left steering controller 3A, the right steering controller 3B executes left cutoff control to cut off the supply of control current to the left steering device 2A. The left cutoff control is a control that cuts off the power supply to the steering motor 221 of the left steering device 2A. The left cutoff control may be, for example, a control that forcibly turns off the system switch 81 between the left steering controller 3A and the power source 8, or a relay switch of the inspection circuit 35 of the left steering controller 3A. It may also be a control that forcibly turns off. The left cutoff control can be said to be a control that cuts off the power supply to the left steering controller 3A even when the ignition is on. In this way, when the right steering controller 3B detects an abnormality in the left steering controller 3A, it puts the steering motor 221 of the left steering device 2A into a non-energized state (uncontrolled state) by executing the left cutoff control. , the left front wheel 11 is brought into a free state. The left cutoff control can also be said to be control that prohibits (stops) the operation of the right steering controller 3B (control of the right steering device 2B by the right steering controller 3B).

When the reaction force controller 5 detects an abnormality in one of the left steering controller 3A and the right steering controller 3B, the reaction force controller 5 detects an abnormality in one of the left steering controller 3A and the right steering controller 3B. 2B) Execute target cutoff control to cut off the supply of control current to. The target cutoff control is the same control as the left cutoff control when the left steering controller 3A is abnormal, and the same control as the right cutoff control when the right steering controller 3B is abnormal. Hereinafter, the right cutoff control, the left cutoff control, and the target cutoff control may be simply referred to as "cutoff control." The cutoff control is a control performed by a normal controller, and can be said to be a control in which a steered wheel to be controlled by a controller determined to be abnormal is brought into a free state.

If one of the steering controllers 3A, 3B is abnormal, the reaction force controller 5 and the other of the steering controllers 3A, 3B will execute the same cutoff control, but the cutoff control executed first will be It will function effectively. Even if the shutdown control is executed simultaneously by two controllers, the shutdown control functions effectively. Even if some communication line is disconnected, the disconnection control of at least one controller functions effectively, so that the abnormal controller can be brought into a non-energized state.

According to this embodiment, when an abnormality occurs in one controller, the other controller cuts off the supply of control current to the steering device that is controlled by the one controller. As a result, the control current is not supplied to the steered wheel corresponding to the abnormal controller, and the steered wheel becomes in a free state similar to the driven wheel. The steered wheels that have become free after the abnormality is detected follow the traveling direction ensured by the normal steered wheels, that is, the controlled steered wheels, due to self-aligning torque. Therefore, running resistance is suppressed to a minimum, and deterioration of running performance (straight running/turning performance) is suppressed.

(Steering control after cutoff control)
The left steering controller 3A detects the steering operation amount in manual operation or the command value in automatic operation (hereinafter also referred to as "steering request value") and the left steering angle sensor in a state where right cutoff control is executed. 224 and the detection result of the right steering angle sensor 224, the left steering device 2A is controlled. The right steering controller 3B performs right steering based on the steering request value, the detection result of the left steering angle sensor 224, and the detection result of the right steering angle sensor 224 in a state where the left cutoff control is executed. Controls the rudder device 2B. Since the both steering controllers 3A and 3B perform similar control, the control of the left steering controller 3A will be explained as an example.

The left steering controller 3A controls the left steering device 2A based on the steering request value and the detection result of the left steering angle sensor 224 in normal times, that is, when right cutoff control is not being executed. In other words, under normal conditions, the left steering controller 3A determines whether the actual steering angle of the left front wheel 11 (hereinafter also referred to as "actual steering angle") calculated based on the detection result of the left steering angle sensor 224 is The left steering device 2A is controlled so as to approach the target steering angle of the left front wheel 11 based on the requested value.

In the state where the right cutoff control is executed, the right front wheel 12 is in a free state, and there is a possibility that the steering angle changes from the state in which it is driven by the left front wheel 11 due to road surface disturbance. The left steering controller 3A acquires not only the detection result of the left steering angle sensor 224 but also the detection result of the right steering angle sensor 224, and takes into account the change in the steering angle of the right front wheel 12 and adjusts the steering angle of the left front wheel 11. Calculate the target steering angle.

For example, when the vehicle is traveling straight with right cutoff control being executed, if a change occurs in the steering angle of the right front wheel 12 in the free state due to road surface disturbance, the left steering controller 3A cancels the change. In other words, the target turning angle of the left front wheel 11 in the controlled state is changed so that the actual yaw rate (hereinafter also referred to as "actual yaw rate") is maintained at the target yaw rate (0 in the case of straight travel). Hereinafter, such control for calculating the target turning angle of the normally steered wheels based on the change in the steered angle of the steered wheels in the free state will also be referred to as "steered angle correction control".

In steering angle correction control, for example, when the steering angle of the right front wheel 12 changes from 0 degrees to 5 degrees to the right due to road surface disturbance when traveling straight, the left steering controller 3A detects the change and adjusts the actual yaw rate. The target steering angle of the left front wheel 11 is changed from 0 degrees to, for example, 5 degrees to the left so that the target yaw rate is maintained. This makes it possible to respond to unintended steering of the right front wheel 12 (steering not in accordance with the required steering value due to road surface disturbance) at an early stage, for example, before the actual yaw rate changes.

Similarly to the left steering controller 3A, the right steering controller 3B also acquires not only the detection results of the right steering angle sensor 224 but also the detection results of the left steering angle sensor 224, and determines the steering angle of the left front wheel 11. The target steering angle of the right front wheel 12 is calculated in consideration of the change. In this way, each of the steering controllers 3A and 3B is configured to be able to execute steering angle correction control.

The amount of correction of the target turning angle performed in the turning angle correction control can be set based on, for example, the "amount of change in the turning angle" of the steered wheels in the free state and the "vehicle speed." Each steering controller 3A may store a map indicating the relationship between the amount of change in the steering angle and the amount of correction for each vehicle speed (for example, a low speed range map, a medium speed range map, a high speed range map, etc.).

Even if it is a correction control that is performed normally, that is, a control that corrects the target turning angle based on changes in the actual yaw rate (hereinafter also referred to as "yaw rate correction control"), the turning angle of the steered wheels in the free state due to road surface disturbances is can compensate for changes in In the yaw rate correction control, it is possible to change the target turning angle of the normally steered wheels and maintain the traveling direction so that the actual yaw rate is maintained at the target yaw rate in response to a change in the actual yaw rate. Further, as the correction control, control for correcting the target steering angle based on a change in the actual lateral acceleration based on the detection result of the lateral acceleration sensor 63 (hereinafter also referred to as "lateral acceleration correction control") may be performed.

However, yaw rate correction control and lateral acceleration correction control are only executed after the yaw rate or lateral acceleration has actually changed, that is, after the vehicle's behavioral state has changed. It is easy to wander in direction. In this embodiment, before the yaw rate correction control and the lateral acceleration correction control are executed, the turning angle correction control is executed for the normal steered wheels based on the detected turning angle of the steered wheels in the free state. be done. Thereby, it is possible to compensate for unintended changes in the steering angle relatively quickly. Therefore, it is possible to suppress wobbling in the traveling direction of the vehicle due to unintended changes in the steering angle of the steered wheels in the free state. Note that since each of the steering controllers 3A and 3B is configured to execute steering angle correction control, it is also possible to configure the steering controller not to execute yaw rate correction control and lateral acceleration correction control. However, each of the steering controllers 3A and 3B is configured to be able to execute steering angle correction control, yaw rate correction control, and/or lateral acceleration correction control, thereby enabling more precise steering control.

An example of the flow of control will be described. As shown in FIG. 4, the controllers 3A, 3B, and 5 monitor each other's states and determine whether there is an abnormality in the controllers (S1). If one of the steering controllers 3A, 3B is abnormal (S1: Yes), the other of the steering controllers 3A, 3B and/or the reaction force controller 5 executes cutoff control (S2). Hereinafter, one of the steering controllers 3A, 3B in which an abnormality has been detected will be referred to as an "abnormal controller", the steered wheel to be controlled by the abnormal controller will be referred to as an "abnormal wheel", and the other steering controller 3A, 3B that is normal will be referred to as an "abnormal wheel". is referred to as a "normal controller", and the steered wheels to be controlled by the normal controller are referred to as "normal wheels". By the cutoff control, the power to the steering motor 221 that steers the abnormal wheel is cut off, and the abnormal wheel becomes free.

With the cutoff control being executed, the normal controller acquires the detection results of each steering angle sensor 224, and acquires not only the information on the steering angle of the normal wheels but also the information on the steering angle of the abnormal wheels ( S3). The normal controller also acquires the detection results of the steering sensor 42 and the vehicle speed sensor (wheel speed sensor 62) (S4). The normal controller calculates a target yaw rate and a target turning angle of the normal wheels based on the information on the turning angle of the abnormal wheels, the information on the amount of steering operation, and the information on the vehicle speed (S5). The normal controller controls the steering motor 221 that steers the normal wheels based on the target turning angle (S6). In this embodiment, the controller performs feedback control based on the target value and the detected value of the sensor. In this way, by executing control that takes into account the steering angle of the abnormal wheel that is in the free state, control delays are reduced, disturbances in the vehicle's direction of travel are suppressed, and driving performance during abnormal conditions is further improved. do.

(Kingpin offset and caster trail)
The steering system 1 of this embodiment is mounted on a vehicle configured such that the king pin offset δ1 and the caster trail δ2 are zero. In this embodiment, the suspension device 9 is designed so that the kingpin offset δ1 and caster trail δ2 are substantially zero.

As shown in FIG. 2, the kingpin axis KP is a straight line passing through the center of the upper support 94 and the center of the ball joint 911. Assuming that the longitudinal direction of the vehicle is the X direction, the left and right direction of the vehicle is the Y direction, and the vertical direction of the vehicle is the Z direction, the king pin offset δ1 is the relationship between the king pin axis KP and the ground contact surface in the YZ plane, as shown in FIG. This is the distance between the intersection and the ground contact center SC. The contact surface is the contact surface of the tire with respect to the road surface. As shown in FIG. 6, the caster trail δ2 is the distance between the intersection of the kingpin axis KP and the ground (road surface) and the ground contact center SC in the XZ plane. Such a configuration is described in, for example, Japanese Patent Application Publication No. 2022-11895.

When the kingpin offset δ1 and the caster trail δ2 are 0 in a stopped state (a state in which the vehicle is not bouncing or rebounding), no moment is generated around the kingpin axis KP due to the vehicle weight. In this case, even if no control current is supplied to each steering motor 221, each steering angle will be in a state of 0 degrees (neutral position, straight-ahead position). That is, in this case, it is not necessary to supply power to each steering motor 221 when the vehicle moves straight. Such a configuration is preferable from the viewpoint of energy saving, and can be said to be a configuration that is easy to control because the abnormal wheel functions as a simple driven wheel even when cut-off control is executed.

When the caster trail δ2 is 0, the self-aligning torque is smaller than when the caster trail δ2 is not 0. However, since self-aligning torque is generated in the tire due to the pneumatic trail, the abnormal wheel that is in a free state can follow the traveling direction of the normal wheel. In this way, the steering system 1 is suitable for a vehicle configured such that the king pin offset δ1 and the caster trail δ2 are 0 when the vehicle is stopped, for example, a vehicle that does not need to supply control current to the left and right steering motors 221 when the vehicle is moving straight. It is preferable that it be installed.

On the other hand, when the kingpin offset δ1 and caster trail δ2 are not 0 when the vehicle is stopped, as in a general vehicle, in a configuration with single-wheel independent steering, each steering angle changes from 0 degrees to the inside of the vehicle due to the vehicle weight. (at an angle). According to this, in order to maintain each steering angle at 0 degrees when traveling straight, each steering controller 3A, 3B needs to continue supplying control current to the corresponding steering motor 221. With this configuration, when the cutoff control is executed, a force that tends to bring the wheel into toe-in is constantly applied to the abnormal wheel that is in the free state. Therefore, the normal controller needs to calculate a target steering angle that takes into account the force of the abnormal wheel in the toe-in direction with respect to the normal wheel.

For example, if the vertical position of the vehicle body relative to the wheels in a stationary state with no bounce or rebound is defined as the standard position, then from 1/2 of the position in the full bounce state to the position in the full rebound state across the standard position. The suspension device 9 may be configured so that the king pin offset δ1 and the caster trail δ2 become 0 within the range up to the 1/2 position.

Moreover, since the wheel drive device of this embodiment is the in-wheel motor unit 7, its driving force becomes the ground point input. Therefore, no moment is generated around the king pin axis KP due to the driving force, and variations in the traveling direction due to the application of the driving force to the wheels are prevented. Note that the steering system 1 of this embodiment can also be applied to a vehicle that employs an on-board drive system in which the drive source is located in the vehicle body rather than the wheels, and the drive force is transmitted to the wheels via a drive shaft or the like. . However, in the on-board type drive system, since the driving force is applied to the center of the wheel, a moment about the king pin axis KP is generated depending on the offset amount and speed. Therefore, this configuration requires steering control that takes this moment into consideration. When applying the steering system 1 to an on-board drive system, a configuration in which the wheel center king pin offset is small is preferable.

(others)
The present invention is not limited to the above embodiments. For example, monitoring and detection of abnormality in the controller may be performed between the two steering controllers 3A and 3B without the reaction force controller 5. In addition, when automatic driving is performed in the vehicle, each steering controller 3A, 3B uses a command value (for example, a target rotation amount) sent from the automatic driving ECU instead of the detection result of the steering wheel 41 (steering operation amount). (rudder angle and target yaw rate), the corresponding steering device is controlled. Further, in an automatic driving vehicle, the operating device 4 can be omitted. Furthermore, the in-wheel motor unit 7 may be provided on all the wheels 11 to 14 or on the rear wheels 13 and 14.

1...Steering system, 2A...Left steering device, 2B...Right steering device, 224...Rotation angle sensor (left steering angle sensor, right steering angle sensor), 3A...Left steering controller, 3B...Right steering Controller, 4... Operating device, 41... Steering wheel (operating member), 42... Steering sensor (operation amount sensor), 43... Reaction force applying device, 5... Reaction force controller, 7... In-wheel motor unit, 9... Suspension device .

Claims (5)

a left steering device that steers a left steering wheel;
a right steering device that steers a right steering wheel independently of the left steering device;
a left steering controller that controls the left steering device;
a right steering controller that controls the right steering device;
A single-wheel independent steering system comprising:
The left steering controller is configured to be able to detect an abnormality in the right steering controller, and when detecting an abnormality in the right steering controller, performs right cutoff control to cut off the supply of control current to the right steering device. Run
The right steering controller is configured to be able to detect an abnormality in the left steering controller, and when detecting an abnormality in the left steering controller, performs left cutoff control to cut off the supply of control current to the left steering device. execute,
steering system. an operating member operated by a driver for steering;
an operation amount sensor that detects an operation amount of the operation member;
a reaction force applying device that applies a reaction force to the operating member;
a reaction force controller that controls the reaction force applying device based on the detection result of the operation amount sensor;
Equipped with
The left steering controller controls the left steering device based on the detection result of the operation amount sensor,
The right steering controller controls the right steering device based on the detection result of the operation amount sensor,
The reaction force controller is configured to be able to detect an abnormality in the left steering controller and an abnormality in the right steering controller, and when detecting an abnormality in one of the left steering controller and the right steering controller, Executing target cutoff control to cut off the supply of control current to the steering device that is controlled by one of the controllers,
A steering system according to claim 1. a left steering angle sensor that detects a steering angle of the left steering wheel;
a right steering angle sensor that detects a steering angle of the right steering wheel;
Equipped with
The left steering controller detects a steering request value, which is an operation amount of an operating member in manual operation or a command value in automatic operation, and the left steering angle sensor in a state in which the right cutoff control is executed. controlling the left steering device based on the result and the detection result of the right steering angle sensor;
The right steering controller, in a state where the left cutoff control is executed, based on the steering request value, the detection result of the left steering angle sensor, and the detection result of the right steering angle sensor, controlling the right steering device;
A steering system according to claim 1. The right cutoff control is a control that prohibits operation of the right steering controller,
The left cutoff control is a control that prohibits operation of the left steering controller,
A steering system according to claim 1. Mounted on a vehicle configured so that the kingpin offset and caster trail are 0,
A steering system according to any one of claims 1 to 4.

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