Steering control system and method

Abstract

The invention relates to a vehicle steering control method and system. The control method comprises the steps of monitoring a rotating speed indication signal of a steering wheel; determining a first torque for reversely rotating the steering wheel based on the rotating speed indication signal; based on comparison of the rotating speed indication signal and a rotating speed threshold value, the steering wheel reverse torque used for the power-assisted steering system is determined, and when the rotating speed indication signal is smaller than the threshold value, the first torque serves as the steering wheel reverse torque; otherwise, when the rotating speed indication signal is not smaller than the threshold value, a second torque smaller than the first torque is generated, and the second torque serves as the reversing torque of the steering wheel.

Description

Technical Field

[0001] The present invention relates to vehicle automatic driving, and in particular to a lane keeping function. Background Art

[0002] In the process of vehicle autonomous driving, the lane keeping assist (LKA) function is an important feature to achieve safe driving of the vehicle. Figure 1 As shown, when implementing the LKA function, the vehicle dynamic control (VMC) module usually determines the rotation torque T used to control the steering wheel to turn in the opposite direction, i.e., return to the normal direction, based on the detected rotation speed indication signal ω of the steering wheel, such as the angular velocity, which indicates the degree to which the vehicle deviates or is about to deviate from the center line of the lane, and provides the steering wheel control signal CtlSig to the power steering system (EPS). Therefore, the EPS system controls the steering motor to apply the rotation torque T to the steering column of the steering wheel based on the control signal CtlSig. Traditionally, in order to keep the deviation from the center of the lane as small as possible and achieve this goal as quickly as possible, when determining the rotation torque T, the VMC module will increase the feedback control parameter based on the rotation speed indication signal, i.e., control the EPS system to use a large rotation torque to act on the steering wheel; but this will lead to the following problems: when there are abnormal facilities such as manhole covers and road speed bumps on the road surface, the vehicle will generate an excessive angular velocity in a very short time, and the use of the existing LKA implementation method will cause vibration in the steering system, which is manifested as an oscillation phenomenon in which the steering wheel rotates back and forth quickly and is difficult to converge. Obviously, this will affect the comfort and bring certain safety hazards to autonomous driving.

[0003] Purpose of the Invention

[0004] The object of the present invention is to provide a solution for avoiding steering wheel oscillation by weakening the reverse rotation torque generated by the EPS system when a moving vehicle encounters an abnormal facility such as a road speed bump and the lane keeping assist (LKA) function is turned on.

[0005] According to one aspect of the present invention, a vehicle steering control method is provided, comprising: monitoring a speed indication signal of a steering wheel; determining a first torque for reversely rotating the steering wheel based on the speed indication signal; and determining a steering wheel reversal torque for a power steering system based on a comparison of the speed indication signal with a speed threshold, wherein when the speed indication signal is less than the threshold, the first torque is used as the steering wheel reversal torque; otherwise, when the speed indication signal is not less than the threshold, a second torque less than the first torque is generated, and the second torque is used as the steering wheel reversal torque.

[0006] According to another aspect of the present invention, a vehicle steering control system is provided, comprising: an angle monitoring unit for monitoring a speed indication signal of a steering wheel; a target determination unit for determining a target angular velocity or a target angle of the steering wheel required to keep the vehicle on the center line of a lane as a speed threshold; a torque determination unit, comprising: a torque calculation unit for determining a first torque for reversely rotating the steering wheel based on the speed indication signal; a torque adjustment unit for controlling a steering assist system to output a steering wheel reversal torque based on a comparison between the speed indication signal and the speed threshold, wherein when the speed indication signal is less than the threshold, the first torque is used as the steering wheel reversal torque; otherwise, when the speed indication signal is not less than the threshold, a second torque less than the first torque is generated as the steering wheel reversal torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram of a steering control system of the prior art is shown;

[0008] Figure 2 A partial schematic diagram of a steering control system according to an example of the present invention is shown;

[0009] Figure 3 A flow chart of a turning control method according to an example of the present invention is shown. DETAILED DESCRIPTION

[0010] An exemplary embodiment of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention. According to an embodiment of the present invention, a steering control system is composed of a VMC module and an EPS system, wherein the VMC module is improved according to the present invention in order to enable rapid convergence when an abnormal situation such as steering wheel oscillation occurs.

[0011] Figure 2 The VMC module according to one embodiment of the present invention is used to determine the steering wheel torque output by the EPS system according to the control mode of the present invention. As shown in the figure, the VMC module includes an angle monitoring unit 201, a target determination unit 202, and a torque calculation unit 203.

[0012] The angle monitoring unit 201 is used to monitor and obtain the speed indication signal ω of the steering wheel, which represents the measurement of the degree of deviation of the wheel from or about to deviate from the center line of the lane, so the speed indication signal ω can represent the deviation or steering angle of the steering wheel, and can also represent the steering angular velocity. Here, the angle monitoring unit 201 can directly obtain the real-time speed indication signal ω of the steering wheel from an on-board sensor such as a steering angle sensor.

[0013] When the vehicle is about to deviate from the center line of the lane, the target determination unit 202 may determine the target speed ω of the steering wheel or wheel required to keep the vehicle at the center line of the lane. T Here, the target determination unit 202 may adopt any known method in the existing LKA technology implementation to determine the target steering angle ω based on the real-time rotation speed or steering angle of the steering wheel. T .

[0014] The torque determination unit 203 is used to determine the steering wheel rotation torque T' output by the EPS system based on the real-time speed indication signal ω, so that the motor in the EPS system applies a force with a torque of T' to the steering wheel or steering column, thereby controlling the wheel rotation to avoid deviation from the lane centerline. As shown in the figure, according to this embodiment, the torque determination unit 203 includes a torque calculation unit 2031 and a torque adjustment unit 2032, wherein the torque calculation unit 2031 determines the initial torque T for reverse rotation of the steering wheel based on the steering wheel speed signal ω, such as Figure 1 As shown, the torque calculation unit 2031 can use any known technology in the prior art to determine the initial torque T for reverse steering. For example, when the LKA function is turned on, the torque calculation unit 2031 can be implemented by the LKA module to determine the required turning torque T when lane departure occurs. Generally, according to the prior art, for example, Figure 1 As shown, the initial torque T is directly provided to the EPS system; however, according to the present invention, the torque adjustment unit 2032 determines whether to adjust the initial torque.

[0015] According to one example, the torque adjustment unit 2032 compares the steering wheel speed ω with a critical threshold, where the threshold may be the target speed ω determined by the target determination unit 202. T The torque determination unit 203 generates a steering wheel control signal CtlSig according to the comparison result of the torque adjustment unit 2032 and provides it to the EPS system. Here, the torque adjustment unit 2032 can directly generate the steering wheel control signal CtlSig based on its comparison result, wherein the steering wheel control signal CtlSig indicates the steering wheel reverse torque T′ output by the steering motor in the EPS system and acting on the steering wheel steering column, wherein when the speed ω is less than the threshold ω T When the torque adjustment unit 2032 directly outputs the torque T as the steering wheel reverse torque T′, the EPS system controls the steering motor to generate the torque T; otherwise, if the speed indication signal is not less than the critical threshold value ω T, the torque adjustment unit 2032 determines a weakened torque T' which is less than the torque T as the steering wheel reversal torque T', and outputs a corresponding steering wheel control signal CtlSig; therefore, when an abnormal situation occurs and causes a sudden change in the steering wheel speed, the speed indication ω at this time is usually not less than the critical threshold ω T , the steering wheel reverse torque T′ actually applied by the EPS system to the steering wheel steering column is less than the initially determined torque T. According to the present invention, after the EPS system applies the steering wheel reverse torque T′ and the vehicle state changes, the target determination unit 202 further determines another target speed ω required to keep the vehicle at the center line of the lane T '; and the torque determination unit 203 further determines the target speed ω T ' is lower than the preset value corresponding to the current speed segment. For example, for a vehicle speed of 120 kph, the corresponding preset value can be set to 0.5 rad / s. T ′ is not lower than the preset value, T ' is updated to the critical threshold and the above process is repeated to update the steering wheel reversal torque T'. Therefore, according to the present invention, it can be ensured that the actual torque output acting on the steering wheel is in a convergent state when an abnormal situation occurs. Here, any method known in the prior art can be used to determine the weakening torque T', as long as it is ensured that the torque T' in each cycle is less than the torque T initially determined for the cycle. According to an example of the present invention, the torque adjustment unit 2032 determines the weakening torque T' using the torque attenuation coefficient. To this end, if Figure 2 As shown, the torque determination unit 203 may further include a coefficient determination unit 2033. When the torque adjustment unit 2032 determines that the speed ω is not less than the critical threshold ω T When the coefficient request signal Coff_Req is output to the coefficient determination unit 2033, the coefficient determination unit 2033 obtains the current speed V of the vehicle and the target speed ω provided by the target determination unit 202. T . Using speed V and target speed ω T As an index, the coefficient determination unit 2033 determines the attenuation coefficient table Coff_Table by querying the attenuation coefficient table Coff_Table. T According to an embodiment of the present invention, the attenuation coefficient Coff corresponding to various speed and rotation speed states stored in the attenuation coefficient table Coff_Table is a positive number less than 1 and can be obtained through experience or experimental testing. The following table shows an exemplary example of the attenuation coefficient Coff stored in the attenuation coefficient table Coff_Table:

[0016]

[0017] Typically, each empirical value in the attenuation coefficient table Coff_Table may correspond to a specific model of vehicle, such as an SUV, while a different attenuation coefficient table Coff_Table may be used for another model of vehicle, such as a sedan. Or for the same vehicle manufacturer, the same coefficient table may be used, while for another manufacturer, another attenuation coefficient table Coff_Table may be used. The coefficient determination unit 2033 returns the queried coefficient Coff to the torque adjustment unit 2032 as a response. The torque adjustment unit 2034 thus calculates the product of the torque T and the torque attenuation coefficient coff as the torque T′, that is, T′=T×Coff. For example, as shown in the table above, when the vehicle speed is 120kph and the steering wheel target speed ω T When the torque is 1 rad / s, the torque T can be multiplied by the weakening coefficient 0.4 to obtain the weakening torque T'. After the steering wheel torque is reduced, the steering wheel vibration can be suppressed in real time.

[0018] According to the present invention, when the vehicle encounters an abnormal situation such as a speed bump and the steering wheel oscillates, the target angular velocity ω can be updated by real-time monitoring of the steering wheel speed and continuously cyclically updating the target angular velocity ω. T , so that the vehicle can quickly stay on the center line and avoid constant oscillation. Figure 3 The flowchart of a vehicle steering control method according to an embodiment of the present invention is shown, which can quickly implement the LKA function.

[0019] As shown in the figure, in step 301, the steering wheel speed ω when the wheel deviates or is about to deviate from the center line of the lane is monitored, for example, the speed ω when the steering wheel oscillates when the vehicle encounters an abnormal situation such as a speed bump. Then, in step 303, when the vehicle deviates or is about to deviate from the center line of the lane, the target speed ω of the steering wheel or wheel required to keep the vehicle in the center line of the lane is determined. T .

[0020] In step 305 , based on the real-time speed signal ω, an initial torque T for reversely turning the steering wheel is determined. Here, the torque calculation unit 2031 may use any known technology in the prior art to determine the initial torque T for reversely turning the steering wheel. For example, the torque T may be determined by using an LKA module.

[0021] In step 307, the rotation speed ω is compared with a critical threshold, where the threshold may be the target steering angle ω determined in step 303. T However, in other examples of the present invention, the threshold value may also be implemented in other ways, such as being set to a predetermined value. TWhen the steering wheel is reversed, the process proceeds to step 309 to determine the initial torque T as the steering wheel reverse torque T′. The process then proceeds to step 311 to output a control signal CtlSig to the EPS system, whereby the EPS system controls the motor to generate a force with a torque T based on the control signal CtlSig and applies it to the steering wheel or steering column.

[0022] Otherwise, if it is determined in step 307 that the speed ω is not less than the threshold ω T , then in step 313, determine the torque attenuation coefficient Coff. Here, the coefficient Coff can be determined by querying a coefficient lookup table. For example, with the current speed V of the vehicle and the target speed ω T As an index, by querying a damping coefficient table Coff_Table, the corresponding speed ω T And the torque attenuation coefficient coff corresponding to the speed V. Therefore, in step 315, the product of the torque T and the torque attenuation coefficient coff is calculated as the torque T'. Then enter step 311, output the control signal CtlSig to the EPS system, whereby the EPS system controls the motor to generate a torque weakening force T' based on the control signal CtlSig and applies it to the steering wheel or steering column. According to an embodiment of the present invention, after the reverse torque T' is applied to the steering column, the process can return to step 301, cyclically monitor the updated speed of the steering wheel and continue to determine the updated target speed required to keep the vehicle on the center line of the lane. Thus, steps 301-315 are executed cyclically until the target speed ω T is zero or is lower than a predetermined value corresponding to the current vehicle speed, thereby achieving a fast LKA function without oscillation.

[0023] The above describes the general embodiment of the present invention in combination with specific examples, but it is obvious that the present invention is not limited thereto. For example, the steering control method according to the present invention can be implemented by a computing device, which can be implemented by a VMC module or by an on-board ECU (electronic control unit) executing the steering control method described in the present disclosure, and the computer program implementing the method can be stored in a machine-accessible storage medium. In addition, although Figure 2 The units shown appear in the form of separate modules or units, but one or more of these units can be implemented as separate modules and can be implemented in the form of circuits, software or firmware, etc. In short, those skilled in the art can know that more embodiments of the present invention can be obtained by combining the disclosed embodiments, and these embodiments are also within the protection scope of the present invention.

Claims

1. A vehicle steering control method, comprising: (A) Monitor the speed indication signal of the steering wheel; (B) determining a first torque for reversely rotating the steering wheel based on the speed indication signal; (C) determining a steering wheel reversal torque for a power steering system based on a comparison between the speed indication signal and a speed threshold, wherein when the speed indication signal is less than the speed threshold, the first torque is used as the steering wheel reversal torque; otherwise, when the speed indication signal is not less than the speed threshold, a second torque less than the first torque is generated, and the second torque is used as the steering wheel reversal torque.

2. The vehicle control method of claim 1 , wherein generating a second torque that is less than the first torque comprises: monitoring a current speed of the vehicle; Determine the torque attenuation coefficient corresponding to the steering wheel target speed and the current speed by querying the attenuation coefficient table; The second torque is the product of the first torque and the torque attenuation coefficient.

3. The method of claim 2, wherein the speed threshold refers to the steering wheel target speed or a predetermined value of the steering wheel required to keep the vehicle on the center line of the lane.

4. The method of claim 2 or 3, further comprising: The following steps are performed in a loop until the steering wheel target speed is zero or lower than a predetermined value: After the steering assist system applies the steering wheel reversal torque, further determining that a target speed required to keep the vehicle at the center line of the lane is updated to the speed threshold; Perform the steps (A) to (C). 5 . The method of claim 4 , wherein the rotation speed indication signal comprises a steering wheel angular velocity, and the steering wheel target rotation speed comprises a steering wheel target angular velocity.

6. A vehicle steering control system, comprising: Angle monitoring unit, used to monitor the speed indication signal of the steering wheel; a target determination unit, configured to determine a target rotation speed of the steering wheel required to keep the vehicle at the center line of the lane as a rotation speed threshold; Torque determination unit, comprising: a torque calculation unit, configured to determine a first torque for reversely rotating the steering wheel based on the rotation speed indication signal; The torque adjustment unit is used to control the steering power system to output a steering wheel reversal torque based on a comparison between the speed indication signal and the speed threshold, wherein when the speed indication signal is less than the speed threshold, the first torque is used as the steering wheel reversal torque; otherwise, when the speed indication signal is not less than the speed threshold, a second torque less than the first torque is generated as the steering wheel reversal torque.

7. The vehicle steering control system of claim 6, wherein the torque determination unit further comprises a coefficient determination unit configured to: Obtaining the current speed of the vehicle; Determine the torque attenuation coefficient corresponding to the target speed and the current speed by querying the attenuation coefficient table; The torque adjustment unit calculates a product of the first torque and the torque attenuation coefficient as the second torque.

8. The vehicle steering control system of claim 7, wherein the torque calculation unit is implemented by an LKA module.

9. The vehicle steering control system according to any one of claims 5 to 8, wherein after the steering assist system applies the steering wheel reverse torque, the target determination unit further determines another steering wheel target speed required to keep the vehicle on the center line of the lane; The torque determination unit is further configured as: determining whether the another steering wheel target speed is lower than a predetermined value; When the other steering wheel target speed is not lower than the predetermined value, the other steering wheel target speed is updated to the speed threshold and the steering wheel reverse torque is updated.

10. A vehicle control system comprising: Power steering system (EPC), used to provide steering wheel reverse torque according to the torque control signal; A vehicle dynamics system (VMC) for executing the method of any one of claims 1-5 to generate the torque control signal indicative of the steering wheel reversal torque.

11. A computing device comprising: a memory storing instructions; At least one processor, wherein the processor implements the method of one of claims 1-5 when executing the instructions.

12. A computer-readable storage medium having instructions stored thereon, wherein when the instructions are executed by at least one processor, the processor is caused to implement the method of any one of claims 1-5.

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