Intelligent angle fusion control method of electric power steering system

Abstract

The invention discloses an intelligent angle fusion control method for an electric power steering system. The intelligent angle fusion control method comprises the steps that S1, needed steering rack force is obtained through calculation; s2, calculating a current steering rack force; s3, performing difference calculation on the required steering rack force and the current steering rack force to obtain steering rack force feed-forward control; s4, performing difference operation on the intelligent control angle request value and the current angle value of the steering wheel to obtain an angle difference value of the steering wheel; s5, performing closed-loop control on the steering wheel angle difference value to obtain steering rack force feedback control; s6, summing the steering rack force feedforward control and the steering rack force feedback control to obtain a request steering rack force, and converting the request steering rack force into an initial steering motor request torque; s7, performing safety boundary limitation on the initial steering motor request torque, and then outputting 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, the active steering motor request torque and the fusion control coefficient Z. And the man-machine co-driving comfort of coexistence of intelligent driving and driver steering is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle intelligent driving, and in particular to an intelligent angle fusion control method for an electric power steering system. Background Art

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

[0003] The intelligent driving mode based on angle control is the current 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. The electric power steering system will drive the steering wheel to rotate in response to the intelligent control angle value, thereby realizing intelligent lateral control at the vehicle level.

[0004] At the same time, during driving with intelligent driving activated, the electric power steering system not only needs to respond to the intelligent angle control, but also needs to respond to the driver's active steering intention. When the intelligent angle control is different from the driver's active steering operation, it will cause resistance torque to the driver's active steering, causing the driver's active steering to be uncomfortable or even limited. Summary of the invention

[0005] The present invention is precisely to solve the above-mentioned technical problems and to integrate the intelligent driving angle control and the driver steering control to avoid the confrontation between the intelligent driving angle control and the driver steering control, which may cause the driver to turn uncomfortable or even limit the driver's active steering, thereby improving the human-machine co-driving comfort of the coexistence of intelligent driving and driver steering.

[0006] In order to solve the above technical problems, the present invention provides an intelligent angle fusion control method for an electric power steering system, comprising:

[0007] Step S1, obtaining the required steering rack force by looking up the table according to the intelligent control angle request value and the vehicle speed;

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

[0009] Step S3, calculating the difference between the required steering rack force and the current steering rack force to obtain steering rack force feedforward control;

[0010] Step S4, performing a difference operation on the intelligent control angle request value and the current steering wheel angle value to obtain a steering wheel angle difference value;

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

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

[0013] Step S7, outputting the intelligent driving steering motor request torque after performing safety boundary limitation on the preliminary steering motor request torque, wherein the safety boundary limitation limits the slope and amplitude of the preliminary motor execution torque; the amplitude limitation 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 to 1;

[0014] 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.

[0015] Preferably, the closed-loop control in step S5 is a PID closed-loop control, in which an integral anti-saturation control method is included, and the integral anti-saturation 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 determined that the intelligent driving response angle control is currently the 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.

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

[0018] Preferably, when it is determined that the driver's active steering control is currently the dominant control, the fusion control coefficient Z is quickly faded to 0, and the stop integral control coefficient M is quickly faded to 0.

[0019] Preferably, when it is determined that the driver's active steering control is currently fading out and the intelligent driving response angle control is returned to being the dominant control, the clear integral control coefficient N is set to 0.

[0020] Preferably, when the intelligent driving response angle control is completely returned to the 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.

[0021] Preferably, in step S8, the calculation formula for outputting 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 is:

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

[0023] 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 to 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 judgment threshold of the driver torque intervention, the fusion control coefficient Z will start to decrease from 1, and the descending slope can vary based on the current driver torque size. When the driver torque is larger, the fusion control coefficient Z decreases faster; 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 and will not 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 re-dominant control of the intelligent driving control mode.

[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 change in the same direction with the steering wheel angle difference.

[0026] Compared with the prior art, the electric power steering system using the control method of the present invention responds to intelligent angle control while avoiding generating a large resistance torque to the driver's active steering, which would cause discomfort or even limited active steering for the driver, thereby improving the human-machine co-driving comfort of coexisting intelligent driving and driver steering. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0028] Figure 1 A schematic diagram of hardware modules for implementing the intelligent angle fusion control method for an electric power steering system according to Embodiment 1;

[0029] Figure 2 This is a control logic diagram of steps S1 to S7 in the intelligent angle fusion control method for an electric power steering system of Example 1;

[0030] Figure 3This is a control logic diagram of step S8 in the intelligent angle fusion control method for an electric power steering system of Example 1;

[0031] Figure 4 This is a logic diagram of the change of the value of the fusion control coefficient Z in Example 1;

[0032] Figure 5 This is a schematic diagram of determining the judgment threshold for driver torque intervention and fading in Example 1. DETAILED DESCRIPTION

[0033] The following describes the implementation methods of the present invention through specific specific embodiments, and those skilled in the art can fully understand other advantages and technical effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through different specific implementation methods, and the details in this specification can also be applied based on different viewpoints, and various modifications or changes can be made without deviating from the overall design concept of the invention. It should be noted that the following embodiments and the features in the embodiments can be combined with each other in the absence of conflict. The following exemplary embodiments of the present invention can be implemented in a variety of different 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 invention thorough and complete, and to fully convey the technical solutions of these exemplary specific embodiments to those skilled in the art.

[0034] Example 1

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

[0036] Step S1, obtaining the required steering rack force by looking up the table according to the intelligent control angle request value and the vehicle speed;

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

[0038] Step S3, calculating the difference between the required steering rack force and the current steering rack force to obtain steering rack force feedforward control;

[0039] Step S4, performing a difference operation on the intelligent control angle request value and the current steering wheel angle value to obtain a steering wheel angle difference value;

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

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

[0042] Step S7, outputting the intelligent driving steering motor request torque after performing safety boundary limitation on the preliminary steering motor request torque, wherein the safety boundary limitation limits the slope and amplitude of the preliminary motor execution torque; the amplitude limitation 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 to 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 is shown for implementing the intelligent angle fusion control method of the electric power steering system described in this embodiment.

[0045] Various signals such as driver steering torque, steering wheel steering angle, steering motor rotor speed, steering motor rotor acceleration, vehicle speed signal, intelligent driving request signal, etc. can be obtained through sensors and communication input modules. How to obtain these signals is a prior art and will not be described in detail in this embodiment.

[0046] The active steering speed-dependent power assist module can output the active steering motor request torque required in step S8. How to obtain the active steering motor request torque is also known from the 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 this embodiment, and the fusion control module is used to implement step S8 in the intelligent angle fusion control method of this embodiment, as well as the calculation of the fusion control coefficient Z in the previous steps.

[0048] The control logic of step S1 to step S7 is as follows: Figure 2 As shown, the following is described in detail.

[0049] In step S1, when the intelligent driving mode request successfully interacts with the electric power steering system, the required steering rack force is obtained by table lookup calculation based on the intelligent control angle request value and vehicle speed. At the same time, this table lookup calculation can be associated with the current vehicle speed. Generally, the higher 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 for calculating the current steering rack force can be expressed as:

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

[0052] in:

[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 formula:

[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 movement;

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

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

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

[0061] M Inertia Represents the inertia force of the current rack;

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

[0063] J Inertia Represents the current moment of inertia of the steering system;

[0064] M Fric Represents the friction of the current rack

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

[0066] X Friction Represents the friction coefficient of the current steering system rack movement;

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

[0068] Step S3, calculating the difference between the required steering rack force and the current steering rack force to obtain steering rack force feedforward control;

[0069] Step S4, performing a difference operation on the intelligent control angle request value and the current steering wheel angle value to obtain a steering wheel angle difference value;

[0070] Step S5, performing closed-loop control on the steering wheel angle difference to obtain steering rack force feedback control; the closed-loop control in step S5 is PID closed-loop control. This embodiment adds processing of integral calculation items based on traditional PID closed-loop control, and proposes an anti-integral saturation control method for clearing integral calculations, so as to reduce the phenomenon of increased cumulative error of PID closed-loop control integral items after the electric power steering system responds to intelligent driving angle control in subsequent calculation flows, and reduce the PID closed-loop output results.

[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 cycle;

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

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

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

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

[0079] K p , K i , K d The control parameters of the PID controller are calibrated by looking up the table with the vehicle speed;

[0080] Z is the fusion control coefficient, ranging from 0 to 1;

[0081] M is the stop integral control coefficient of the PID closed-loop controller's anti-integral saturation control, and its value ranges from 0 to 1;

[0082] N is the clearing integral control coefficient of the PID closed-loop controller's anti-integral saturation control, and its value ranges from 0 to 1.

[0083] Its main logic is:

[0084] When it is determined that the intelligent driving response angle control is the 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 this time, the intelligent driving angle closed-loop control is fully output.

[0085] When it is determined that the driver is actively steering the vehicle, the fusion control coefficient Z is adjusted based on the current driving conditions and gradually reduced. At the same time, the stop integral control coefficient M is quickly faded to 0. That is, the intelligent driving angle closed-loop control stops the closed-loop control integral operation and is integrated and compatible with the active steering control.

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

[0087] When it is determined that the driver's active steering control is fading out and the intelligent driving response angle control is returned to the dominant control, the clear integral control coefficient N is set to 0, that is, the integral operation value of the intelligent driving angle closed-loop control is cleared at this time. When the intelligent driving response angle control is completely returned to the 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, summing the steering rack force feedforward control and the steering rack force feedback control to obtain the requested steering rack force, and converting the requested steering rack force into a preliminary steering motor requested torque.

[0089] The required steering rack force can be converted into the initial steering motor required torque using the following calculation formula:

[0090]

[0091] in, Represents the transmission ratio from the rack end to the steering motor end;

[0092] F Req Represents the requested steering rack force for the intelligent driving mode;

[0093] MotorTorque Req Represents the initial steering motor request torque for intelligent driving mode.

[0094] Step S7, after the preliminary steering motor request torque is subject to safety boundary limits, the intelligent driving steering motor request torque is output, wherein the safety boundary limits the slope and amplitude of the preliminary motor execution torque; the amplitude limit of the preliminary motor execution torque is subject to the constraints of the fusion control coefficient Z; thereby taking into account the resistance of the steering motor request torque generated by the intelligent driving mode to the driver's active steering, and improving the comfort of human-machine co-driving.

[0095] The control logic of step S8 is as follows: Figure 3 As shown, Figure 3 The fusion controller is the fusion control module. 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.

[0096] The fusion control module will make a fusion adjustment on the active steering motor request torque and the intelligent driving steering motor request torque based on the fusion control coefficient Z. The value change logic of the fusion control coefficient Z is as follows: Figure 4 shown.

[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 to 1

[0103] The fusion control module will also calculate the appropriate fusion control coefficient Z based on the current driving conditions for subsequent fusion control and intelligent driving angle closed-loop control, intelligent driving request torque safety boundary limit calculation. The main calculation method will be based on the current steering wheel angle difference to determine the judgment threshold of driver torque intervention and fade-out, such as Figure 5 shown.

[0104] As the steering wheel angle difference increases, the judgment threshold for judging the driver's torque intervention also increases, and at the same time, the judgment threshold for judging the driver's torque fading also increases, but the judgment threshold for judging the driver's torque intervention will be greater than the judgment threshold for judging the driver's torque fading.

[0105] When in the intelligent driving mode, the fusion control coefficient Z is 1. If the current driver's steering torque is greater than the judgment threshold of the driver's torque intervention, the fusion control coefficient Z will start to decrease from 1. The slope of the decrease can be changed based on the current driver's torque. The larger the driver's torque, the faster the fusion control coefficient Z decreases. If the current driver's steering torque is less than the driver's torque intervention judgment threshold, but greater than the driver's torque fade-out judgment threshold, the fusion control coefficient Z will maintain the current value and will not change. If the current driver's steering torque is less than the driver's torque fade-out judgment threshold, the fusion control coefficient Z will gradually return from the current value to 1, completing the re-dominant control of the intelligent driving control mode.

[0106] The present invention has been described in detail above through specific implementation modes and embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may also make many variations and improvements, which should also be regarded as the protection scope of the present invention.

Claims

1. An intelligent angle fusion control method for an electric power steering system, characterized in that: include: Step S1, obtaining the required steering rack force by looking up the table according to the intelligent control angle request value and the vehicle speed; Step S2, calculating the current steering rack force according to the current steering motor driving torque, the driver steering torque, and the inertia force and friction force of the steering rack; Step S3, calculating the difference between the required steering rack force and the current steering rack force to obtain steering rack force feedforward control; Step S4, performing a difference operation on the intelligent control angle request value and the current steering wheel angle value to obtain a steering wheel angle difference value; Step S5, performing closed-loop control on the steering wheel angle difference to obtain steering rack force feedback control; Step S6, summing the steering rack force feedforward control and the steering rack force feedback control to obtain a requested steering rack force, and converting the requested steering rack force into a preliminary steering motor requested torque; Step S7, outputting the intelligent driving steering motor request torque after performing safety boundary limitation on the preliminary steering motor request torque, wherein the safety boundary limitation 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 to 1; 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.

2. The intelligent angle fusion control method of the electric power steering system according to claim 1, characterized in that: The closed-loop control in step S5 is a PID closed-loop control, in which an integral anti-saturation control method is included. The integral anti-saturation control method includes a fusion control coefficient Z, a stop integral control coefficient M and a clear integral control coefficient N.

3. The intelligent angle fusion control method of the electric power steering system according to claim 2, characterized in that: When it is determined that the intelligent driving response angle control is currently the 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 in that: When it is determined that the driver is actively steering and intervening, the fusion control coefficient Z is adjusted based on the current driving conditions and 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 in that: When it is determined that the driver's active steering control is currently the 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 in that: When it is determined that the driver's active steering control is fading out and the intelligent driving response angle control is returned to be the dominant control, the clear integral control coefficient N is set to 0.

7. The intelligent angle fusion control method of the electric power steering system according to claim 2, characterized in that: When the intelligent driving response angle control is completely returned to the 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.

8. The intelligent angle fusion control method of the electric power steering system according to claim 1, characterized in that: In step S8, the calculation formula for outputting 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 is: MotorTorque sum =MotorTorque Req *Z+MotorTorque Steering *(1-Z); 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 between 0 and 1.

9. The intelligent angle fusion control method of the electric power steering system according to claim 1, characterized in that: When in the intelligent driving mode, the fusion control coefficient Z is 1; if the current driver's steering torque is greater than the judgment threshold of the driver's torque intervention, the fusion control coefficient Z will start to decrease from 1, and the decreasing slope can be changed based on the current driver's torque. When the driver's torque is larger, the fusion control coefficient Z decreases faster; 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 and will not 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 and re-dominating the control.

10. The intelligent angle fusion control method of the electric power steering system according to claim 9, characterized in that: 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 change in the same direction with the steering wheel angle difference.

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