TWI852635B - Rear wheel steering system - Google Patents

Abstract

A rear wheel steering system includes a triaxial accelerometer and an electronic control circuit, wherein the triaxial accelerometer is connected to the electronic control circuit. The triaxial accelerometer is configured to detect the current acceleration of the car. The electronic control circuit is configured to send a steering command for controlling two rear wheels of the car according to at least the current acceleration when the current acceleration is greater than a preset acceleration.

Description

Rear wheel steering system

The present invention relates to a steering system, and more particularly to a rear wheel steering system.

Most of the vehicles currently on the market only have front wheel steering systems, and only a few models are equipped with rear wheel steering systems. The rear wheel steering system can reduce the inner wheel difference and turning radius when the vehicle turns. The electronic steering system can assist the driver to turn the steering wheel upward through electronic devices, especially providing greater assistance when driving at low speeds, allowing the driver to turn more easily. However, whether it is front and rear wheel steering or electronic steering systems, the driver still relies on the steering wheel to steer.

In view of the above, the present invention provides a rear wheel steering system with active steering function.

According to an embodiment of the present invention, a rear wheel steering system includes a three-axis accelerometer and an electronic control circuit, wherein the three-axis accelerometer is connected to the electronic control circuit. The three-axis accelerometer is used to detect the current acceleration of the vehicle. The electronic control circuit is used to generate and output a steering command for controlling two rear wheels of the vehicle at least according to the current acceleration when the current acceleration is greater than a preset acceleration.

With the above structure, the rear wheel steering system disclosed in the present invention can measure the acceleration of the vehicle when the vehicle is hit and issue a steering command to control the steering of the rear wheels according to the current acceleration of the vehicle, thereby providing an active steering function to stabilize the vehicle body.

The above description of the disclosed content and the following description of the implementation methods are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation of the scope of the patent application of the present invention.

The detailed features and advantages of the present invention are described in detail in the following embodiments, and the contents are sufficient to enable any person skilled in the relevant art to understand the technical contents of the present invention and implement them accordingly. Moreover, according to the contents disclosed in this specification, the scope of the patent application and the drawings, any person skilled in the relevant art can easily understand the relevant purposes and advantages of the present invention. The following embodiments are to further illustrate the viewpoints of the present invention, but are not to limit the scope of the present invention by any viewpoint.

Please refer to FIG. 1, which is a functional block diagram of a rear wheel steering system according to an embodiment of the present invention. As shown in FIG. 1, the rear wheel steering system 1 includes a three-axis accelerometer 11 and an electronic control circuit 12. The three-axis accelerometer 11 and the electronic control circuit 12 are connected to each other. The electronic control circuit 12 can be connected to a motor control circuit 2. The motor control circuit 2 can include a motor driver and a bridge circuit for controlling a rear wheel motor 3.

The three-axis accelerometer 11 is used to detect the current acceleration of the vehicle. The electronic control circuit 12 is used to generate and output a steering command for controlling two rear wheels of the vehicle to the motor control circuit 2 at least according to the current acceleration when the current acceleration measured by the three-axis accelerometer 11 is greater than the preset acceleration, wherein the preset acceleration may be, but is not limited to, 30 gravitational acceleration ( g ). Specifically, the electronic control circuit 12 may determine the direction of rotation indicated by the steering command to be left or right according to the direction of the current acceleration, or/and may determine the rotation angle indicated by the steering command according to the value of the current acceleration. The motor control circuit 2 may control the rear wheel motor 3 to rotate the rear wheels of the vehicle according to the steering command. In addition, the turning instruction may include a turning time in addition to the turning direction and/or turning angle mentioned above, wherein the turning time may be set to, but not limited to, 2 seconds.

In one embodiment, the electronic control circuit 12 can be implemented by a microcontroller, which has the function of electric power steering (EPS) for the rear wheels. When the electronic control circuit 12 determines that the current acceleration is greater than a preset acceleration, it can enter the EPS mode to control the rear wheels to actively rotate left or right through the motor control circuit 2, and after maintaining the rotation for a certain rotation time, the control of the motor control circuit 2 is returned to the vehicle stability unit, such as the vehicle control unit (VCU).

In another embodiment, the electronic control circuit 12 includes a microcontroller and a rear wheel EPS control unit, wherein the microcontroller is connected to the three-axis accelerometer 11, and the rear wheel EPS control unit is connected to the controller and the motor control circuit 2. The microcontroller is used to notify the rear wheel EPS control unit to intervene to control the rear wheel to actively rotate left or right through the motor control circuit 2 when it is determined that the current acceleration measured by the three-axis accelerometer 11 is greater than the preset acceleration, and return the control of the motor control circuit 2 to the vehicle stability unit, such as the VCU, after maintaining the rotation for a rotation time.

Please refer to Figure 2, which is a functional block diagram of a rear wheel steering system according to another embodiment of the present invention. As shown in Figure 2, the rear wheel steering system 1' includes a three-axis accelerometer 11, an electronic control circuit 12, an angle sensor 13 and a communication module 14. Among them, the functions and connection relationships of the three-axis accelerometer 11 and the electronic control circuit 12 are the same as those shown in Figure 1, so they are not elaborated on. The angle sensor 13 and the communication module 14 are connected to the electronic control circuit 12. Specifically, the connection between the three-axis accelerometer 11, the angle sensor 13 and the communication module 14 and the electronic control circuit 12 can be a wired connection or a wireless connection. Among them, the angle sensor 13 and the communication module 14 are selectively arranged devices.

The angle sensor 13, such as a rotary displacement sensor, is used to sense the angle of the rear wheel motor 3 of the two rear wheels. The electronic control circuit 12 can generate a steering command not only based on the current acceleration, but also based on the motor angle. In other words, the electronic control circuit 12 can generate and output a steering command based on the motor angle and the current acceleration measured by the angle sensor 13. The communication module 14, such as a network module or a Bluetooth communication module, is used to connect to the bus of the vehicle. Specifically, the communication module 14 can be a controller area network transceiver and is used to connect to the bus of the controller area network.

Please refer to FIG3, which is a flow chart of a method for generating a steering command according to an embodiment of the present invention. As shown in FIG3, the method for generating a steering command includes step S11: obtaining a current acceleration and a motor angle; step S12: determining whether the current acceleration is greater than a preset acceleration; if the current acceleration is not greater than the preset acceleration, then executing step S11 again; if the current acceleration is greater than the preset acceleration, then executing step S13: searching a preset motor angle corresponding to the current acceleration in a lookup table according to the current acceleration; step S14: obtaining a motor angle to be turned according to the motor angle and the preset motor angle; and step S15: generating and outputting a steering command indicating the motor angle to be turned. The method for generating a steering command may be applicable to the rear wheel steering system shown in FIG. 2 . The method shown in FIG. 3 is exemplarily described below using the rear wheel steering system shown in FIG. 2 .

In step S11, the electronic control circuit 12 obtains the current acceleration and the motor angle. Specifically, when the vehicle is hit sideways during driving, the three-axis accelerometer 11 can obtain the current acceleration of the vehicle and the angle sensor 13 can obtain the angle of the rear wheel motor 3, and can transmit the current acceleration and the motor angle to the electronic control circuit 12.

In step S12, the electronic control circuit 12 determines whether the current acceleration is greater than the preset acceleration. If the current acceleration is greater than the preset acceleration, the electronic control circuit 12 will then execute step S13, otherwise the electronic control circuit 12 will return to step S11 again to wait for the three-axis accelerometer 11 and the angle sensor 13 to measure and transmit the current acceleration and motor angle or control the three-axis accelerometer 11 and the angle sensor 13 to measure and return the current acceleration and motor angle.

In step S13, the electronic control circuit 12 searches the lookup table for the preset motor angle corresponding to the current acceleration according to the current acceleration. Specifically, a lookup table is stored in the electronic control circuit 12. The lookup table may include a plurality of motor angles corresponding to a plurality of preset accelerations, in other words, the angle to which the rear wheels should turn under each preset acceleration. For example, the lookup table may have the form of Table 1, in which the preset wheel angle corresponds to the preset motor angle. Specifically, the preset wheel angle may be directly used as the preset motor angle, or may be converted into the preset motor angle through a preset relationship.

Table 1 Default acceleration Default rotation angle 20 g ～40 g 1° 40 g ～60 g 2° ＞60 g 3°

In step S14, the electronic control circuit 12 obtains the motor angle to be rotated according to the motor angle measured by the angle sensor 13 and the preset motor angle. Specifically, after the electronic control circuit 12 obtains the preset motor angle, it can compare the preset motor angle with the measured motor angle to confirm how much the rear wheel motor needs to rotate to meet the preset motor angle, that is, the motor angle to be rotated. More specifically, the electronic control circuit 12 can use the difference between the preset motor angle and the measured motor angle as the motor angle to be rotated.

In step S15, the electronic control circuit 12 generates and outputs a steering command indicating the motor angle to be turned. Specifically, the electronic control circuit 12 generates a steering command indicating the motor angle to be turned according to the motor angle to be turned calculated in step S14 and sends a steering command to the motor control circuit 2, and the motor control circuit 2 can then rotate the rear wheel motor 3 by the motor angle to be turned to reach the preset motor angle according to the steering command. However, the steering command can not only indicate the motor angle to be turned of the rear wheel motor, but also indicate the steering duration of the rear wheel motor. The following will be explained with respect to controlling the steering duration of the rear wheels.

In another embodiment, the lookup table may include not only the correspondence between the preset acceleration and the preset motor angle, but also the correspondence between the preset acceleration and the preset turning time. The electronic control circuit 12 may obtain the preset turning time corresponding to the current acceleration from the lookup table and use it as part of the information of the turning instruction. In other words, the turning instruction indicates not only the motor angle to be turned but also the preset turning time.

In another embodiment, step S15 may include obtaining a target turning time according to the motor angle to be turned and the preset motor speed, and the turning instruction may include the target turning time.

Please refer to FIG. 4 , which is a functional block diagram of a rear wheel steering system according to another embodiment of the present invention. As shown in FIG. 4 , the rear wheel steering system 1″ includes a three-axis accelerometer 11, an electronic control circuit 12, an angle sensor 13, a communication module 14 and a power management chip 15, and line segments S1 to S3 represent signal connection relationships and line segments P1 to P5 represent power connection relationships. Among them, the implementation devices, functions and signal connection relationships of the three-axis accelerometer 11, the electronic control circuit 12, the angle sensor 13, and the communication module 14 (that is, line segments S1 to S3) are the same as those shown in FIG. 2 and are not described in detail here.

The power management chip 15 is electrically connected to the three-axis accelerometer 11, the electronic control circuit 12 and the power supply 4 and is used to receive power from the power supply 4 (line segment P5) and distribute it to the three-axis accelerometer 11 (line segment P1) and the electronic control circuit 12 (line segment P2). In addition, the power supply 4 can distribute power to the angle sensor 13 (line segment P3) and the power management chip 15 can distribute power to the communication module 14 (line segment P4)

In one or more embodiments of the present invention, the rear wheel steering system of the present invention can be applied to a vehicle-mounted device, such as a self-driving car, an electric car, or a semi-autonomous car, etc.

With the above structure, the rear wheel steering system disclosed in the present invention can measure the acceleration of the vehicle when the vehicle is hit and issue a steering command to control the steering of the rear wheels according to the current acceleration, thereby providing an active steering function to stabilize the vehicle body.

Although the present invention is disclosed as above with the aforementioned embodiments, it is not intended to limit the present invention. Any changes and modifications made within the spirit and scope of the present invention are within the scope of patent protection of the present invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

1,1’,1”: Rear wheel steering system 11: Three-axis accelerometer 12: Electronic control circuit 13: Angle sensor 14: Communication module 15: Power management chip 2: Motor control circuit 3: Rear wheel motor 4: Power supply S11-S15: Steps S1-S3: Line segment P1-P5: Line segment

FIG. 1 is a functional block diagram of a rear wheel steering system according to an embodiment of the present invention. FIG. 2 is a functional block diagram of a rear wheel steering system according to another embodiment of the present invention. FIG. 3 is a flow chart of a method for generating a steering command according to an embodiment of the present invention. FIG. 4 is a functional block diagram of a rear wheel steering system according to another embodiment of the present invention.

1:Rear wheel steering system

11: Three-axis accelerometer

12: Electronic control circuit

2: Motor control circuit

3: Rear wheel motor

Claims (8)

A rear wheel steering system includes: a three-axis accelerometer for detecting a current acceleration of a vehicle; an electronic control circuit connected to the three-axis accelerometer and used to generate and output a steering command for controlling two rear wheels of the vehicle at least according to the current acceleration when the current acceleration is greater than a preset acceleration; and an angle sensor connected to the electronic control circuit, the angle sensor being used to sense the motor angles of the two rear wheels; wherein the electronic control circuit The circuit is used to generate and output the steering command according to the motor angle and the current acceleration, and the electronic control circuit generates and outputs the steering command according to the motor angle and the current acceleration, and the steps executed by the electronic control circuit include: searching a preset motor angle corresponding to the current acceleration in a lookup table according to the current acceleration; obtaining a motor angle to be turned according to the motor angle of the two rear wheels and the preset motor angle; and generating and outputting the steering command indicating the motor angle to be turned. A rear wheel steering system as described in claim 1, wherein the lookup table further includes a preset steering duration corresponding to the current acceleration, and the steering instruction further indicates the preset steering duration. A rear wheel steering system as described in claim 1, wherein the steering instruction executed by the electronic control circuit to generate and output an indication of the motor angle to be turned includes obtaining a target steering duration based on the motor angle to be turned and a preset motor speed, and the steering instruction includes the target steering duration. A rear wheel steering system as described in claim 1, wherein the electronic control circuit is used to determine the direction of rotation indicated by the steering instruction according to the direction of the current acceleration. A rear wheel steering system as described in claim 1, wherein the default acceleration is 30 gravitational acceleration. The rear wheel steering system as described in claim 1 further comprises: a power management chip electrically connected to the three-axis accelerometer and the electronic control circuit, for receiving power from a power source and distributing it to the three-axis accelerometer and the electronic control circuit. The rear wheel steering system as described in claim 1 further comprises: a communication module connected to the electronic control circuit and used to connect to the bus of the vehicle. A rear wheel steering system as described in claim 7, wherein the communication module is a controller area network transceiver.

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