Intelligent angle fusion control method for electric power steering system

Abstract

The application discloses an intelligent angle fusion control method of an electric power steering system, and comprises the following steps: S1, calculating a required steering rack force; S2, calculating a current steering rack force; S3, calculating a difference value between the required steering rack force and the current steering rack force to obtain a steering rack force feedforward control; S4, calculating a difference value between an intelligent control angle request value and a current steering wheel angle value to obtain a steering wheel angle difference value; S5, performing closed-loop control on the steering wheel angle difference value to obtain a steering rack force feedback control; S6, summing the steering rack force feedforward control and the steering rack force feedback control to obtain a required steering rack force, and converting the required steering rack force into a preliminary steering motor request torque; S7, performing safety boundary limitation on the preliminary steering motor request torque to output an intelligent driving steering motor request torque; and S8, outputting a final steering motor request torque according to the intelligent driving steering motor request torque, a main steering motor request torque and a fusion control coefficient Z. The intelligent driving and driver steering coexistence man-machine co-driving comfort is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intelligent driving of vehicles, and in particular to an intelligent angle fusion control method of an electric power steering system. BACKGROUND

[0002] Most current electric power steering systems will provide additional steering assistance based on the current vehicle speed and the driver's steering torque to assist the driver in steering the vehicle after obtaining and determining the normal state of the vehicle.

[0003] The intelligent driving mode based on angle control is a high-precision control method for vehicle lateral control. The intelligent control system will send an intelligent control angle value to the electric power steering system, and the electric power steering system will drive the steering wheel to rotate to respond to the intelligent control angle value, thereby achieving intelligent lateral control of the vehicle.

[0004] Meanwhile, during the driving process when intelligent driving is activated, the electric power steering system needs to respond not only to intelligent angle control but also to the driver's active steering intention. When the intelligent angle control and the driver's active steering operation are different, it will cause resistance torque to the driver's active steering, resulting in uncomfortable or even limited active steering of the driver. SUMMARY

[0005] The present application is to solve the above technical problems by fusing intelligent driving angle control and driver steering control to avoid the conflict between intelligent driving angle control and driver steering control, thereby improving the comfort of human-machine co-driving when intelligent driving and driver steering coexist.

[0006] To solve the above technical problems, the present application provides an intelligent angle fusion control method of an electric power steering system, which comprises:

[0007] Step S1, calculating the required steering rack force according to the intelligent control angle request value and the vehicle speed lookup table;

[0008] Step S2, calculating the current steering rack force according to the current steering motor driving torque, the driver's steering torque, and the inertia force and friction force of the steering rack;

[0009] Step S3, calculating the steering rack force feedforward control by subtracting the current steering rack force from the required steering rack force;

[0010] Step S4, calculating the steering wheel angle difference by subtracting the current steering wheel angle value from the intelligent control angle request value;

[0011] Step S5, performing closed-loop control on the steering wheel angle difference to obtain steering rack force feedback control;

[0012] Step S6, sum the steering rack force feedforward control and the steering rack force feedback control to obtain the requested steering rack force, and convert the requested steering rack force into a preliminary steering motor requested torque;

[0013] Step S7, limit the preliminary steering motor requested torque within a safety boundary to output an intelligent driving steering motor requested torque, wherein the safety boundary limits the slope and amplitude of the preliminary motor execution torque, and the amplitude limit of the preliminary motor execution torque is subject to a fusion control coefficient Z, which is 0-1;

[0014] Step S8, output the final steering motor requested torque according to the intelligent driving steering motor requested torque, the active steering motor requested torque, and the fusion control coefficient Z.

[0015] Preferably, the closed-loop control in step S5 is a PID closed-loop control, which includes an integral anti-windup control method, and the integral anti-windup control method includes a fusion control coefficient Z, a stop integral control coefficient M, and a clear integral control coefficient N.

[0016] Preferably, when it is judged that the intelligent driving response angle control is dominant, the fusion control coefficient Z is set to 1, the stop integral control coefficient M is set to 1, and the clear integral control coefficient N is set to 1.

[0017] Preferably, when it is judged that the driver actively steers to intervene, the fusion control coefficient Z is adjusted based on the current driving condition, gradually reduced, and the stop integral control coefficient M is quickly faded to 0.

[0018] Preferably, when it is judged that the driver actively steers to intervene, the fusion control coefficient Z is adjusted based on the current driving condition, gradually reduced, and the stop integral control coefficient M is quickly faded to 0.

[0019] Preferably, when it is judged that the driver actively steers to intervene, the fusion control coefficient Z is adjusted based on the current driving condition, gradually reduced, and the stop integral control coefficient M is quickly faded to 0.

[0020] Preferably, when it is judged that the driver actively steers to intervene, the fusion control coefficient Z is adjusted based on the current driving condition, gradually reduced, and the stop integral control coefficient M is quickly faded to 0.

[0021] Preferably, the step S8, according to the intelligent driving steering motor requested torque, the active steering motor requested torque, and the fusion control coefficient Z, the calculation formula of the final steering motor requested torque is:

[0022] MotorTorquesum = MotorTorque Req * Z + MotorTorque Steering * (1-Z) ;

[0023] wherein MotorTorque sum represents the final steering motor request torque, MotorTorque Req represents the intelligent driving steering motor request torque, MotorTorque Steering represents the active steering motor request torque; the fusion control coefficient Z is 0-1

[0024] Preferably, when in the intelligent driving mode, the fusion control coefficient Z is 1; if the current driver steering torque is greater than the driver torque intervention judgment threshold, the fusion control coefficient Z will start to decrease from 1, and the decrease slope can be varied based on the current driver torque; the greater the driver torque, the faster the fusion control coefficient Z decreases; if the current driver steering torque is less than the driver torque intervention judgment threshold but greater than the driver torque fade-out judgment threshold, the fusion control coefficient Z will maintain the current value without change; if the current driver steering torque is less than the driver torque fade-out judgment threshold, the fusion control coefficient Z will gradually recover from the current value to 1, completing the intelligent driving control mode to dominate the control again.

[0025] Preferably, the driver torque intervention judgment threshold is greater than the driver torque fade-out judgment threshold; the driver torque intervention judgment threshold and the driver torque fade-out judgment threshold vary with the same direction change of the steering wheel angle difference.

[0026] Compared with the prior art, the electric power steering system applying the control method of the present application can respond to intelligent angle control while avoiding generating a large resistance torque to the driver's active steering, which leads to uncomfortable or even limited active steering of the driver, thereby improving the man-machine co-driving comfort of the coexistence of intelligent driving and driver steering. BRIEF DESCRIPTION OF DRAWINGS

[0027] The present application will be further described in detail below in combination with the accompanying drawings and specific embodiments:

[0028] Figure 1 A hardware module schematic diagram of the intelligent angle fusion control method of the electric power steering system of embodiment 1 is shown in the figure;

[0029] Figure 2 A control logic schematic diagram of steps S1 to S7 in the intelligent angle fusion control method of the electric power steering system of embodiment 1 is shown in the figure;

[0030] Figure 3A control logic diagram for step S8 in the intelligent angle fusion control method of the electric power steering system of embodiment 1 is shown in the figure;

[0031] Figure 4 A fusion control coefficient Z value change logic diagram for embodiment 1 is shown in the figure;

[0032] Figure 5 A diagram for determining the judgment threshold of the driver torque intervention and fade in embodiment 1 is shown in the figure. DETAILED DESCRIPTION

[0033] The advantages and technical effects of the present application can be fully understood by the skilled in the art from the disclosure of the present specification. The present application can also be implemented or applied in different specific embodiments, and the details in the present specification can be applied based on different viewpoints, with various modifications or changes made without departing from the general design idea of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. The exemplary embodiments of the present application can be implemented in various forms, and should not be interpreted as being limited to the specific embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application complete and complete, and to fully convey the technical solutions of these exemplary embodiments to the skilled in the art.

[0034] Embodiment 1

[0035] The present embodiment provides an intelligent angle fusion control method for an electric power steering system, comprising:

[0036] Step S1, calculating the required steering rack force according to the intelligent control angle request value and the vehicle speed lookup table;

[0037] Step S2, calculating the current steering rack force according to the current steering motor driving force, the driver steering torque, and the inertia force and friction force of the steering rack;

[0038] Step S3, calculating the steering rack force feedforward control by subtracting the current steering rack force from the required steering rack force;

[0039] Step S4, calculating the steering wheel angle difference by subtracting the current steering wheel angle value from the intelligent control angle request value;

[0040] Step S5, performing closed-loop control on the steering wheel angle difference to obtain the steering rack force feedback control;

[0041] Step S6, summing the steering rack force feedforward control and the steering rack force feedback control to obtain the request steering rack force, and converting the request steering rack force into a preliminary steering motor request torque;

[0042] Step S7, output the intelligent driving steering motor request torque after the preliminary steering motor request torque is limited by the safety boundary, the safety boundary limits the slope and amplitude of the preliminary motor execution torque; the amplitude limit of the preliminary motor execution torque is constrained by the fusion control coefficient Z, and the value of the fusion control coefficient Z is 0-1;

[0043] Step S8, output the final steering motor request torque according to the intelligent driving steering motor request torque, the active steering motor request torque and the fusion control coefficient Z.

[0044] Figure 1 An exemplary hardware module for implementing the intelligent angle fusion control method of the electric power steering system described in the embodiment is shown.

[0045] Through the sensor and communication input module, various signals such as the driver steering torque, the steering wheel steering angle, the steering motor rotor speed, the steering motor rotor acceleration, the vehicle speed signal, and the intelligent driving request signal can be obtained. How to obtain these signals is prior art, which will not be described in detail in the embodiment.

[0046] Through the active steering speed-assisted power module, the active steering motor request torque required in step S8 can be output. How to obtain the active steering motor request torque is also through prior art, so it will not be described in detail.

[0047] The intelligent driving angle control module is used to implement steps S1 to S7 in the intelligent angle fusion control method of the embodiment, the fusion control module is used to implement step S8 in the intelligent angle fusion control method of the embodiment, and the calculation of the fusion control coefficient Z in the previous steps.

[0048] The control logic of steps S1 to S7 is shown in Figure 2 , which will be described in detail below.

[0049] In step S1, when the intelligent driving mode request and the electric power steering system successfully handshake and interact, the required steering rack force is calculated according to the intelligent control angle request value and the vehicle speed lookup table. At the same time, this lookup table calculation can be associated with the current vehicle speed. Generally, the greater the vehicle speed, the smaller the steering rack force required at the same intelligent control angle request value.

[0050] In step S2, according to the current steering motor driving torque, the driver steering torque, and the inertia force and friction force of the steering rack, an exemplary calculation formula of the current steering rack force can be expressed as:

[0051] F Rack =i Mot2RackForce (M TBT *i TBT2Mot +MMot - M Inertia - M Fric )

[0052] wherein:

[0053] M Inertia = RotorAcc * J Inertia

[0054] M Fric = RotorSpeed * X Friction + (M TBT * i TBT2Mot + M Mot ) * X LoadFactor

[0055] In the above calculation:

[0056] F Rack represents the current steering rack force;

[0057] i Mot2RackForce represents the transmission ratio of the steering system drive motor to the rack motion;

[0058] M TBT represents the current driver steering torque, which is collected by the torque sensor;

[0059] i TBT2Mot represents the transmission ratio of the steering system steering wheel end to the motor end;

[0060] M Mot represents the current steering motor driving torque;

[0061] M Inertia represents the current rack inertia force;

[0062] RotorAcc represents the current steering system motor rotor acceleration, which is calculated from the motor rotor speed;

[0063] J Inertia represents the current steering system rotational inertia;

[0064] M Fric represents the current rack friction force

[0065] RotorSpeed represents the current steering system motor rotor speed;

[0066] X Friction represents the current steering system rack motion friction coefficient;

[0067] X LoadFactor represents the current steering system rack motion complex friction coefficient;

[0068] Step S3, the difference between the demand and the current steering rack force is calculated to obtain the steering rack force feedforward control;

[0069] Step S4, the difference between the intelligent control angle request value and the current steering wheel angle value is calculated to obtain the steering wheel angle difference value;

[0070] Step S5, the steering wheel angle difference value is closed-loop controlled to obtain the steering rack force feedback control; the closed-loop control in step S5 is PID closed-loop control. The embodiment increases the processing of the integral calculation item based on the traditional PID closed-loop control, and proposes an anti-integral saturation control method for clearing the integral operation, so as to reduce the phenomenon of the increase of the integral item cumulative error of the PID closed-loop control after the electric power steering system responds to the intelligent driving angle control in the subsequent calculation flow, and reduce the PID closed-loop output result.

[0071] The specific calculation formula is as follows:

[0072]

[0073] In the above calculation formula,

[0074] F RackFeedback (t) represents the steering rack force feedback control calculated in the current calculation period;

[0075] F RackFeedback (t-1) represents the steering rack force feedback control calculated in the previous calculation period;

[0076] e(t) represents the steering wheel angle difference value calculated in the current calculation period;

[0077] e(t-1) represents the steering wheel angle difference value used for calculation in the previous calculation period;

[0078] represents the transmission ratio from the steering angle end to the rack displacement end;

[0079] K p , K i , and K d are control parameters of the PID controller, and a calibratable mode of looking up a table according to the vehicle speed is adopted;

[0080] Z is a fusion control coefficient, and the value is 0-1;

[0081] M is a stop integral control coefficient of the anti-integral saturation control of the PID closed-loop controller, and the value is 0-1;

[0082] N is a clearing integral control coefficient of the anti-integral saturation control of the PID closed-loop controller, and the value is 0-1.

[0083] The main logic is as follows:

[0084] When it is judged that the intelligent driving response angle control is currently dominant control, the fusion control coefficient Z is set to 1, the stop integral control coefficient M is set to 1, and the clear integral control coefficient N is set to 1, at which time the intelligent driving angle closed-loop control full-output is output.

[0085] When it is judged that the driver actively steers to intervene, the fusion control coefficient Z is adjusted based on the current driving condition, gradually reduced, and at the same time the stop integral control coefficient M is quickly faded to 0, that is, at this time the intelligent driving angle closed-loop control stops the closed-loop control integral operation, and the active steering control is fused and compatible control.

[0086] When it is judged that the driver actively steers control is currently dominant control, the fusion control coefficient Z is quickly faded to 0, and at the same time the stop integral control coefficient M is quickly faded to 0, that is, at this time the intelligent driving angle closed-loop control stops the closed-loop control integral operation.

[0087] When it is judged that the driver actively steers control fades and returns to intelligent driving response angle control as dominant control, the clear integral control coefficient N is set to 0, that is, at this time the integral operation value of the intelligent driving angle closed-loop control is cleared. When it is completely returned to intelligent driving response angle control as dominant control, the fusion control coefficient Z is reset, the stop integral control coefficient M is set to 1, and the clear integral control coefficient N is set to 1.

[0088] Step S6, the steering rack force feedforward control and the steering rack force feedback control are summed to obtain the requested steering rack force, and the requested steering rack force is converted into a preliminary steering motor request torque.

[0089] The requested steering rack force can be converted into a preliminary steering motor request torque using the following calculation formula:

[0090]

[0091] Wherein, represents the transmission ratio from the rack end to the steering motor end;

[0092] F Req represents the requested steering rack force of the intelligent driving mode;

[0093] MotorTorque Req represents the preliminary steering motor request torque of the intelligent driving mode.

[0094] Step S7, the intelligent driving steering motor request torque is output after the preliminary steering motor request torque is limited by a safety boundary, the safety boundary limits the slope and amplitude of the preliminary motor execution torque; the amplitude limit of the preliminary motor execution torque is constrained by the fusion control coefficient Z; in this way, the resistance of the steering motor request torque generated by the intelligent driving mode to the active steering of the driver is taken into account, and the comfort during human-machine co-driving is improved.

[0095] The control logic of step S8 is shown in Figure 3 , Figure 3 The fusion controller in the fusion control module of step S8 outputs the final steering motor request torque according to the intelligent driving steering motor request torque, the active steering motor request torque, and the fusion control coefficient Z.

[0096] The fusion control module will adjust the active steering motor request torque and the intelligent driving steering motor request torque based on the fusion control coefficient Z, and the value change logic of the fusion control coefficient Z is shown in Figure 4 .

[0097] The calculation formula is:

[0098] MotorTorque sum =MotorTorque Req *Z+MotorTorque Steering *(1-Z);

[0099] MotorTorque sum represents the final steering motor request torque,

[0100] MotorTorque Req represents the intelligent driving steering motor request torque,

[0101] MotorTorque Steering represents the active steering motor request torque.

[0102] The value of the fusion control coefficient Z is 0-1

[0103] The fusion control module will also calculate the appropriate fusion control coefficient Z based on the current driving condition for subsequent fusion control and intelligent driving angle closed-loop control, intelligent driving request torque safety boundary limit calculation, which will mainly determine the judgment threshold of the driver torque intervention and fading based on the current steering wheel angle difference, as shown in Figure 5 .

[0104] With the increase of the steering wheel angle difference, the judgment threshold of the driver torque intervention is also increased, and the judgment threshold of the driver torque fade is also increased, but the judgment threshold of the driver torque intervention is greater than the judgment threshold of the driver torque fade.

[0105] When in the intelligent driving mode, the fusion control coefficient Z is 1, if the current driver steering torque is greater than the judgment threshold of the driver torque intervention, the fusion control coefficient Z will start to decline from 1, and the decline slope can be changed based on the current driver torque, the greater the driver torque, the faster the fusion control coefficient Z declines. If the current driver steering torque is less than the judgment threshold of the driver torque intervention but greater than the judgment threshold of the driver torque fade, the fusion control coefficient Z will maintain the current value without change. If the current driver steering torque is less than the judgment threshold of the driver torque fade, the fusion control coefficient Z will gradually recover from the current value to 1, and the intelligent driving control mode is completed to dominate the control again.

[0106] The application is described in detail above through specific embodiments and examples, but these do not constitute a limitation on the application. Those skilled in the art can also make many modifications and improvements without departing from the principles of the application, and these should also be considered as the protection scope of the application.

Claims

1. An intelligent angle fusion control method of an electric power steering system, characterized by, Comprise: Step S1, according to the intelligent control angle request value and vehicle speed table calculation obtained demand steering rack force; Step S2, according to the current steering motor driving torque, driver steering torque and steering rack inertia force and friction, calculate the current steering rack force; Step S3, the demand steering rack force and the current steering rack force difference value calculation, get steering rack force feedforward control; Step S4, the intelligent control angle request value and steering wheel current angle value difference operation, get steering wheel angle difference; Step S5, the steering wheel angle difference is closed loop control and obtains steering rack force feedback control; Step S6, the steering rack force feedforward control and steering rack force feedback control sum to obtain request steering rack force, request steering rack force is converted into preliminary steering motor request torque; Step S7, the preliminary steering motor request torque is limited after the safety boundary and the intelligent driving steering motor request torque is output, the safety boundary limit is limited to the slope and amplitude of the preliminary steering motor request torque; The amplitude limit of the preliminary steering motor request torque is constrained by the fusion control coefficient Z, the value of the fusion control coefficient Z is 0~1; Step S8, according to the intelligent driving steering motor request torque, active steering motor request torque and fusion control coefficient Z output final steering motor request torque.

2. The intelligent angle fusion control method of the electric power steering system according to claim 1, characterized by, The closed loop control in step S5 is PID closed loop control, which contains integral anti saturation control method, and the integral anti saturation control method contains fusion control coefficient Z, stop integral control coefficient M and clear integral control coefficient N. 3.The intelligent angle fusion control method of an electric power steering system according to claim 2, characterized in that, When it is judged that the current is intelligent driving response angle control dominant control, the fusion control coefficient Z is set to 1, the stop integral control coefficient M is set to 1, and the clear integral control coefficient N is set to 1.

4. The intelligent angle fusion control method of the electric power steering system according to claim 2, characterized by, When it is judged that the current is driver active steering intervention, the fusion control coefficient Z is adjusted based on the current driving condition, which is gradually reduced, and the stop integral control coefficient M is quickly faded to 0.

5. The intelligent angle fusion control method of the electric power steering system according to claim 2, characterized by, When it is judged that the current is driver active steering control dominant control, the fusion control coefficient Z is quickly faded to 0, and the stop integral control coefficient M is quickly faded to 0.

6. The intelligent angle fusion control method of the electric power steering system according to claim 2, characterized by, When it is judged that the current is driver active steering control fade, and the intelligent driving response angle control is dominant control again, the clear integral control coefficient N is set to 0. 7.The intelligent angle fusion control method of an electric power steering system according to claim 2, characterized in that, When it is judged that the current is intelligent driving response angle control dominant control again, the fusion control coefficient Z is reset, the stop integral control coefficient M is set to 1, and the clear integral control coefficient N is set to 1. 8.The intelligent angle fusion control method of an electric power steering system according to claim 1, wherein, The calculation formula of step S8 is as follows: ； wherein represents the final steering motor request torque, represents the intelligent driving steering motor request torque, represents the active steering motor request torque; the value of fusion control coefficient Z is 0-1. 9.The intelligent angle fusion control method of an electric power steering system according to claim 1, characterized in that, When in intelligent driving mode, the fusion control coefficient Z is 1;If the current driver steering torque is greater than the judgment threshold of driver torque intervention, the fusion control coefficient Z will start to decline, and the decline slope can be changed based on the current driver torque. When the driver torque is greater, the fusion control coefficient Z declines faster. If the current driver steering torque is less than the driver torque intervention judgment threshold, but greater than the driver torque fade judgment threshold, the fusion control coefficient Z will maintain the current value unchanged; if the current driver steering torque is less than the driver torque fade judgment threshold, the fusion control coefficient Z will gradually recover from the current value to 1, completing the intelligent driving control mode to dominate the control. 10.The intelligent angle fusion control method of an electric power steering system according to claim 9, wherein, The driver torque intervention judgment threshold is greater than the driver torque fade judgment threshold; the driver torque intervention judgment threshold and the driver torque fade judgment threshold change with the same direction of the steering wheel angle difference.

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