JP2020114708A - Steering wheel neutral point detection device - Google Patents

Abstract

To automatically detect a neutral point of a steering wheel for a vehicle of steer-by-wire system.SOLUTION: The center of gravity of a steering wheel is out of the rotational center. A controller controls an actuator and rotates the steering wheel in the first direction and the second direction. Particularly, the controller executes the following processing with the steering wheel mechanically separated from wheels. The controller acquires, as a first and a second physical quantity, a physical quantity corresponding to a driving force of an actuator required to start the rotation from a stationary state to each of the first and the second directions. When an absolute value of a difference between the first physical quantity and the second physical quantity is larger than a threshold value and the first physical quantity is larger than the second physical quantity, the controller rotates the steering wheel in the first direction. The controller determines a position of the steering wheel obtained after repeating these processing until the absolute value of the difference is the threshold value or smaller as a neutral point.SELECTED DRAWING: Figure 3

Description

The present invention relates to a technique for detecting a neutral point of a steering wheel of a vehicle.

Patent Document 1 discloses a steer-by-wire type steering device. The steering device includes a steering wheel, a steering driving means for steering the wheels, a control means for controlling steering by the steering driving means based on a steering operation amount of the steering wheel, and a steering reaction force to the steering wheel. Steering reaction force applying means.

JP, 2006-137215, A

In a steer-by-wire system vehicle, when the steering wheel is upright, the wheels need to be oriented in the direction in which the vehicle travels straight (prevention of the steering wheel off center). Therefore, conventionally, a steering wheel neutral point correction work (center correction work) has been performed in an assembly plant or a repair plant. Specifically, it is necessary to make the wheels straight, measure the rotation angle of the steering wheel using the steering angle sensor, and write the value as a correction value with a service tool or the like. The accuracy and speed of this work depend on the skill level of the worker, and therefore the quality varies. Further, an increase in the number of work steps leads to an increase in cost.

An object of the present invention is to provide a technique capable of automatically detecting a neutral point of a steering wheel of a steer-by-wire type vehicle.

In one aspect of the present invention, there is provided a steering wheel neutral point detecting device for detecting a steering neutral point of a steer-by-wire type vehicle.
The center of gravity of the handle is displaced from the center of rotation of the handle.
The handle neutral point detection device,
An actuator for rotating the handle,
A controller that controls the actuator to rotate the handle in a first direction and a second direction opposite to the first direction.
With the steering wheel mechanically disconnected from the vehicle wheels, the controller
A first process for acquiring, as a first physical amount and a second physical amount, a physical quantity corresponding to a driving force of the actuator necessary for the handle to start rotating in each of the first direction and the second direction from a stationary state; ,
When the absolute value of the difference between the first physical quantity and the second physical quantity is larger than a threshold value and the first physical quantity is larger than the second physical quantity, a second process of rotating the handle in the second direction, ,
If the absolute value of the difference is larger than the threshold value and the second physical quantity is larger than the first physical quantity, a third process of rotating the handle in the first direction,
A fourth process of determining the position of the handle as the neutral point after repeating the first to third processes until the absolute value of the difference becomes equal to or less than the threshold value is performed.

According to the present invention, it becomes possible to automatically detect the neutral point of the steering wheel of a steer-by-wire system vehicle. As a result, the steering neutral point correction work in the assembly factory and the repair factory is significantly more efficient than in the past, and the cost is significantly reduced. Further, since the processing performed by the steering wheel neutral point detection device does not depend on the skill level of the operator, variation in quality is suppressed.

It is a block diagram which shows roughly the structure of the vehicle which concerns on the 1st Embodiment of this invention. It is a conceptual diagram which shows the shape example of the steering wheel of the vehicle which concerns on the 1st Embodiment of this invention. It is a conceptual diagram for demonstrating the influence of gravity with respect to the steering wheel of the vehicle which concerns on the 1st Embodiment of this invention. It is a block diagram which shows roughly the structure of the steering wheel neutral point detection apparatus which concerns on the 1st Embodiment of this invention. It is a flow chart which shows steering wheel neutral point detection processing concerning a 1st embodiment of the present invention. It is a conceptual diagram for demonstrating the steering wheel neutral point detection processing which concerns on the 2nd Embodiment of this invention. It is a conceptual diagram for demonstrating the steering wheel neutral point detection processing which concerns on the 3rd Embodiment of this invention. It is a conceptual diagram for demonstrating the steering wheel neutral point detection processing which concerns on the 4th Embodiment of this invention.

Embodiments of the present invention will be described with reference to the accompanying drawings.

1. 1. First embodiment 1-1. Steer-by-Wire System Vehicle FIG. 1 is a block diagram schematically showing a configuration of a vehicle 1 according to the present embodiment. The vehicle 1 is a steer-by-wire system vehicle (both mechanical linkless and mechanical clutch are acceptable). The vehicle 1 includes a steering wheel (steering wheel) 10, a steering shaft 20, a reaction force generation device 30, a steering device 40, wheels 50, a sensor group 60, and a control device 70.

The handle 10 is an operation member used by a driver for steering. The steering shaft 20 is connected to the steering wheel 10 and rotates together with the steering wheel 10.

The reaction force generation device 30 applies a reaction force torque to the handle 10 in a pseudo manner. Specifically, the reaction force generation device 30 includes a reaction force actuator connected to the steering shaft 20. Typically, the reaction force actuator is an electric motor. By operating the reaction force actuator, reaction force torque can be applied to the steering shaft 20 and thus the steering wheel 10. The operation of the reaction force actuator is controlled by the control device 70.

The steering device 40 steers the wheels 50. Specifically, the steered system 40 includes a steered actuator connected to the wheels 50 via a steered shaft. Typically, the steering actuator is an electric motor. The wheels 50 can be steered by operating the steering actuator. The operation of the steering actuator is controlled by the control device 70.

The wheel 50 and the steering wheel 10 (steering shaft 20) are mechanically disconnected or can be mechanically connected/disconnected. In the latter case, the connection/disconnection is controlled by the controller 70.

The sensor group 60 detects a steering state and a traveling state of the vehicle 1. For example, the sensor group 60 includes a steering angle sensor, a steering torque sensor, a vehicle speed sensor, an acceleration sensor, and the like. The steering angle sensor detects the steering angle of the steering wheel 10. The steering torque sensor detects the steering torque applied to the steering shaft 20. The vehicle speed sensor detects the vehicle speed that is the speed of the vehicle 1. The acceleration sensor detects lateral acceleration and vertical acceleration of the vehicle 1.

The control device 70 controls the vehicle 1. The control device 70 includes a microcomputer having a processor, a memory, and an input/output interface. The microcomputer is also called an ECU (Electronic Control Unit). Various processes by the control device 70 are realized by the processor executing the control program stored in the memory.

For example, the control device 70 controls the steering of the wheels 50 by controlling the steering device 40. Typically, the control device 70 controls the steering device 40 and steers the wheels 50 in accordance with the steering operation of the steering wheel 10 by the driver. For example, the control device 70 calculates the target turning angle based on the steering angle of the steering wheel 10 and the vehicle speed. Then, the control device 70 controls the steered device 40 so that the steered angle of the wheels 50 becomes the target steered angle.

Further, the control device 70 controls the reaction force generation device 30 to control the reaction force torque applied to the handle 10. Typically, the control device 70 controls the reaction force generation device 30 according to the steering operation of the steering wheel 10 by the driver to generate a reaction force torque. For example, the control device 70 calculates the target reaction torque based on the steering angle of the steering wheel 10 and the vehicle speed. Then, the control device 70 controls the reaction force generation device 30 so that the target reaction force torque is generated.

The control device 70 may separately include a first control device for controlling the steering device 40 and a second control device for controlling the reaction force generation device 30. In this case, the first control device and the second control device are communicably connected to each other and exchange necessary information with each other.

1-2. Effect of Gravity on Handle FIG. 2 is a conceptual diagram showing a shape example of the handle 10 according to the present embodiment. The rotation center (rotation axis) of the handle 10 is represented by reference symbol RC. The handle 10 rotates around the rotation center RC. The clockwise rotation direction (first direction) is hereinafter referred to as “A direction”. The counterclockwise rotation direction (second direction) is hereinafter referred to as “B direction”.

In the present embodiment, the center of gravity position GC of the handle 10 does not coincide with the rotation center RC and is displaced from the rotation center RC. For example, the handle 10 has a non-circular shape as shown in FIG. Since the gravity center position GC is deviated from the rotation center RC, the influence of gravity on the handle 10 varies depending on the rotation position of the handle 10.

FIG. 3 is a conceptual diagram for explaining the influence of gravity on the handle 10. In the present embodiment, the neutral point of the handle 10 means a gravitationally neutral position. <State A> in FIG. 3 is a state in which the handle 10 is rotated in the A direction from the neutral point. On the other hand, <state B> is a state in which the handle 10 is rotated in the B direction from the neutral point.

A load F in the direction of gravity acts on the gravity center position GC of the handle 10 due to the weight of the handle 10. The rotation component FR of the load F is a component of the load F in the rotation direction of the handle 10. That is, the rotation component FR generates torque that rotates the handle 10.

In the state A, the rotation component FR produces a torque in the B direction. The rotation component FR acts to counter the rotation of the handle 10 in the A direction and assist the rotation of the handle 10 in the B direction. Therefore, the driving force required for the handle 10 stopped in the state A to start rotating differs depending on the rotation direction, and becomes larger when the rotation direction is the A direction.

On the other hand, in the state B, the rotation component FR generates torque in the A direction. The rotation component FR acts to counter the rotation of the handle 10 in the B direction and to assist the rotation of the handle 10 in the A direction. Therefore, the driving force required for the handle 10 stopped in the state B to start rotating differs depending on the rotation direction, and becomes larger when the rotation direction is the B direction.

When the handle 10 is at the neutral point, the driving force required for the handle 10 to start rotating is the same regardless of the rotation direction.

In this way, the influence of gravity (load F) on the handle 10 varies depending on the rotational position of the handle 10 with respect to the neutral point. As a result, the driving force required for the handle 10 to start rotating from the stopped state also varies depending on the rotational position of the handle 10 with respect to the neutral point. According to the present embodiment, the neutral point of the handle 10 is automatically detected by utilizing such a property.

More specifically, a comparison is made of the driving force required for the handle 10 to start rotating in the A direction and the B direction from the stopped state. By this comparison, it is possible to determine whether the handle 10 is in the state A, the state B, or the neutral point. When the handle 10 is in the state A, it can be brought close to the neutral point by rotating the handle 10 in the B direction. On the other hand, when the handle 10 is in the state B, it can be brought close to the neutral point by rotating the handle 10 in the A direction. By repeating these processes, the neutral point of the steering wheel 10 can be automatically detected (searched).

1-3. Steering Wheel Neutral Point Detection Device FIG. 4 is a block diagram schematically showing the configuration of the steering wheel neutral point detection device 100 according to the present embodiment. The steering wheel neutral point detection device 100 automatically detects the neutral point of the steering wheel 10. The steering wheel neutral point detection device 100 includes an actuator 110 and a control device 120.

The actuator 110 rotates the handle 10. Specifically, the actuator 110 is connected to the steering wheel 10 via the steering shaft 20. When the actuator 110 operates, a driving force for rotating the steering shaft 20 and the steering wheel 10 is generated. For example, the actuator 110 includes an electric motor. The rotor of the electric motor is connected to the steering shaft 20 via a speed reducer. By rotating the electric motor, torque can be applied to the steering shaft 20 and thus the handle 10.

The control device 120 controls the rotation of the handle 10 by controlling the operation of the actuator 110. Specifically, the control device 120 generates a control signal for controlling the actuator 110 and outputs the control signal to the actuator 110. The actuator 110 operates according to the control signal and generates a driving force for rotating the handle 10. The control device 120 also receives an operating state signal indicating the operating state of the actuator 110. For example, the operating state signal indicates the rotation angle, rotation speed, motor current, motor voltage, torque, etc. of the electric motor.

Controller 120 typically includes a microcomputer with a processor, memory, and input/output interface. The processor executes the control program stored in the memory, whereby the processing by the control device 120 is realized.

Preferably, the reaction force generator 30 and the controller 70 shown in FIG. 1 are used as the actuator 110 and the controller 120, respectively. However, the steering wheel neutral point detection device 100 may be provided separately from the reaction force generation device 30 and the control device 70.

The control device 120 executes a steering wheel neutral point detection process for detecting the neutral point of the steering wheel 10. The steering wheel neutral point detection processing is executed in a state in which the steering wheel 10 is mechanically separated from the wheels 50.

FIG. 5 is a flowchart showing the steering wheel neutral point detection processing according to the present embodiment. Initially, the handle 10 is stationary in a rotational position.

In step S100, the control device 120 controls the actuator 110 to gradually increase the driving force for rotating the handle 10 in the A direction.

In step S110, the control device 120 determines whether or not the handle 10 has started to rotate in the A direction from the stationary state based on the operation state signal. When the handle 10 starts to rotate in the A direction from the stationary state (step S110; Yes), the control device 120 controls the actuator 110 so that the rotation of the handle 10 immediately stops. Then, the process proceeds to step S120. Otherwise (step S110; No), the process returns to step S100.

In step S120, the control device 120 acquires a physical quantity corresponding to the driving force of the actuator 110 required for the handle 10 to start rotating in step S110, based on the operation state signal. Examples of such physical quantity include driving force, driving torque, motor current, and electric energy of the electric motor. The physical quantity acquired in step S120 is hereinafter referred to as "first physical quantity P1". The control device 120 stores the first physical quantity P1 in the memory. Then, a process progresses to step S200.

In step S200, the control device 120 controls the actuator 110 to gradually increase the driving force for rotating the handle 10 in the B direction.

In step S210, the control device 120 determines, based on the operation state signal, whether or not the handle 10 has started to rotate in the B direction from the stationary state. When the handle 10 starts to rotate in the B direction from the stationary state (step S210; Yes), the control device 120 controls the actuator 110 so that the rotation of the handle 10 immediately stops. Then, the process proceeds to step S220. In other cases (step S210; No), the process returns to step S200.

In step S220, the control device 120 acquires a physical quantity corresponding to the driving force of the actuator 110 required for the handle 10 to start rotating in step S210, based on the operation state signal. The physical quantity acquired in step S220 is hereinafter referred to as "second physical quantity P2". The control device 120 stores the second physical quantity P2 in the memory. Then, a process progresses to step S300.

In step S300, the control device 120 compares the absolute value ΔP of the difference between the first physical quantity P1 and the second physical quantity P2 with a predetermined threshold value Pth. When the absolute value ΔP is larger than the threshold Pth (step S300; No), the process proceeds to step S400.

When the first physical quantity P1 is larger than the second physical quantity P2 (step S400; Yes), the handle 10 is in the state A (see FIG. 3) rotated in the A direction from the neutral point. In this case, the process proceeds to step S500. In step S500, the control device 120 controls the actuator 110 to rotate the handle 10 slightly in the B direction. Then, the process returns to step S100.

When the second physical quantity P2 is larger than the first physical quantity P1 (step S400; No), the handle 10 is in the state B (see FIG. 3) rotated in the B direction from the neutral point. In this case, the process proceeds to step S600. In step S600, the control device 120 controls the actuator 110 to slightly rotate the handle 10 in the A direction. Then, the process returns to step S100.

By repeatedly performing steps S100 to S600, the handle 10 approaches the neutral point. The control device 120 repeatedly executes steps S100 to S600 until the absolute value ΔP becomes equal to or less than the threshold value Pth. When the absolute value ΔP becomes equal to or less than the threshold value Pth (step S300; Yes), the process proceeds to step S700.

In step S700, control device 120 determines the current position of handle 10 as the neutral point.

1-4. Effects As described above, according to the present embodiment, it becomes possible to automatically detect the neutral point of the steering wheel 10 of the steer-by-wire type vehicle 1. As a result, the steering wheel neutral point correction work (center correction work) in an assembly plant or a repair plant is significantly more efficient than before, and the cost is also greatly reduced. Further, since the steering wheel neutral point detection processing by the steering wheel neutral point detection device 100 does not depend on the skill level of the operator, variation in quality is suppressed. If the neutral point of the steering wheel 10 is known, the absolute angle sensor can be omitted from the vehicle 1.

2. Second Embodiment FIG. 6 is a conceptual diagram for explaining the steering wheel neutral point detection processing according to the second embodiment. Descriptions that overlap with those of the first embodiment described above are omitted as appropriate.

The control device 120 controls the actuator 110 to sequentially rotate the handle 10 in both the A direction and the B direction. At this time, the magnitude of the driving force of the actuator 110 is set to be the same in the A direction and the B direction. The handle 10 rotates to a position where the driving force of the actuator 110 and the rotational component FR are balanced.

The control device 120 acquires a position where the driving force of the actuator 110 and the rotational component FR are balanced, that is, a position (angle) at which the rotation of the handle 10 has ended. As shown in FIG. 6, rotation of the handle 10 in the A direction ends at an angle θA, and rotation of the handle 10 in the B direction ends at an angle θB. The control device 120 acquires the angles θA and θB based on the operation state signal of the actuator 110 or the steering angle of the steering wheel 10 detected by the steering angle sensor. Then, the control device 120 determines the intermediate position between the angle θA and the angle θB as the neutral point of the handle 10.

According to the second embodiment, the same effect as that of the first embodiment can be obtained.

3. Third Embodiment FIG. 7 is a conceptual diagram for explaining the steering wheel neutral point detection processing according to the third embodiment. Descriptions that overlap with those of the first embodiment described above are omitted as appropriate.

In the third embodiment, a steering torque sensor is used. The steering torque sensor detects the steering torque applied to the steering shaft 20. When the steering wheel 10 is rotated, if the rotation component FR exists, the steering shaft 20 is twisted and a steering torque that is not zero is detected. When the steering wheel 10 is at the neutral point, the steering torque becomes zero. The control device 120 controls the actuator 110 to rotate the steering wheel 10 and determines the position where the steering torque becomes zero as the neutral point of the steering wheel 10.

According to the third embodiment, the same effect as that of the first embodiment can be obtained.

4. Fourth Embodiment FIG. 8 is a conceptual diagram for explaining the steering wheel neutral point detection processing according to the fourth embodiment. Descriptions that overlap with those of the first embodiment described above are omitted as appropriate.

The controller 120 controls the actuator 110 to gradually rotate the handle 10 in one direction. More specifically, the control device 120 repeats the process of rotating the handle 10 with a certain driving force and increasing the driving force when the rotation of the handle 10 is stopped.

As shown in FIG. 8, the driving force required to rotate the handle 10 is maximum when the handle 10 is rotated 90° from the neutral position. After the handle 10 reaches the position, the rotation of the handle 10 continues without increasing the driving force. The control device 120 detects the position where the increase of the driving force is completed, based on the operation state signal of the actuator 110. Then, the control device 120 determines, as the neutral point of the steering wheel 10, a position that is returned by 90° from the position where the increase of the driving force is completed.

The same effects as those of the first embodiment can be obtained by the fourth embodiment.

5. Fifth Embodiment When the vehicle 1 is not located on a flat road surface, the direction of gravity deviates from the vertical direction of the vehicle 1. This leads to a reduction in the accuracy of the steering wheel neutral point detection processing described above. In order to suppress such a decrease in accuracy, the control device 120 may perform the correction process based on the roll angle of the vehicle 1. The roll angle of the vehicle 1 can be calculated based on the detection result of the acceleration sensor, the roll sensor, etc. included in the sensor group 60. Alternatively, an acceleration sensor provided inside the handle 10 may be used.

The fifth embodiment can be combined with any of the above-described first to fourth embodiments.

1 vehicle 10 steering wheel (steering wheel)
20 Steering shaft 30 Reaction force generation device 40 Steering device 50 Wheels 60 Sensor group 70 Control device 100 Steering wheel neutral point detection device 110 Actuator 120 Control device GC Center of gravity position RC Rotation center

Claims (1)

A steering wheel neutral point detection device for detecting the neutral point of a steering wheel of a steer-by-wire system,
The center of gravity of the handle is displaced from the center of rotation of the handle,
The handle neutral point detection device,
An actuator for rotating the handle,
A control device that controls the actuator to rotate the handle in a first direction and a second direction opposite to the first direction,
With the steering wheel mechanically disconnected from the vehicle wheels, the controller
A first process for acquiring, as a first physical amount and a second physical amount, a physical quantity corresponding to a driving force of the actuator necessary for the handle to start rotating in each of the first direction and the second direction from a stationary state; ,
When the absolute value of the difference between the first physical quantity and the second physical quantity is larger than a threshold value and the first physical quantity is larger than the second physical quantity, a second process of rotating the handle in the second direction, ,
If the absolute value of the difference is larger than the threshold value and the second physical quantity is larger than the first physical quantity, a third process of rotating the handle in the first direction,
A steering wheel neutral point detection device that performs a fourth processing of determining the position of the steering wheel as the neutral point after repeating the first to third processing until the absolute value of the difference becomes equal to or less than the threshold value.

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