Method and system for establishing steering torque simulation model of steering wheel

Abstract

The invention discloses a method and a system for establishing a steering torque simulation model of a steering wheel. The method comprises the steps that transfer functions of all key parameters are obtained, and the key parameters comprise power-assisted steering, suspension system friction force, suspension system damping force, steering system friction force and steering system damping force; a whole vehicle model and simulation working conditions are established in Carsim, and all key parameters are set as external input in the whole vehicle model; based on the transfer function of each key parameter and the whole vehicle model, establishing an initial joint simulation model in Simlink; and optimizing the initial joint simulation model, and determining a final optimization result of the initial joint simulation model as a steering wheel steering torque simulation model until a steering wheel steering torque result in simulation operation under a simulation working condition meets a set requirement. Through Carsim and Simulink joint simulation, the problem of frictional force and damping force modeling of a suspension system and a steering system is solved, and the steering torque simulation confidence is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle simulation analysis, and in particular to a method and system for establishing a steering wheel steering torque simulation model. Background Art

[0002] At present, multi-body dynamics simulation models are generally built based on MSC Adams (Automatic Dynamic Analysis of Mechanical Systems, Adams for short). Taking the McPherson suspension as an example, the triangle arm and the subframe of the front suspension system are connected by bushings, the triangle arm and the steering gear are rigidly constrained by ball joints, the steering column of the steering system is rigidly connected, etc. The various components are connected by bushings or rigid constraint pairs, and a simple nonlinear power-assist curve is added to the steering system. The tire model uses PAC2002 tires. When simulating the whole vehicle, the road model provided by the system or the road model obtained by scanning the actual road surface can be used. According to the test conditions, the vehicle speed angle control signal is input to obtain the steering wheel torque curve of the center steering with the angle change.

[0003] However, this multi-body dynamics simulation model cannot add the motion friction and damping of the connection positions between components into the model. For example, the triangle arm and the steering knuckle are actually connected by a ball joint rigid connection. The ball joint has friction and small damping during the movement. This only has a constraint relationship in the model, but lacks force input. The steering system also lacks friction and damping between components. At the same time, the steering column in the Adams model uses rigid constraints, ignoring the stiffness of the column itself. Therefore, due to the limitations of the model, the simulation results of the steering torque have a low confidence level. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method and system for establishing a steering wheel steering torque simulation model. The method solves the problem of friction and damping force modeling of the suspension system and the steering system through joint simulation of Carsim and Simulink, improves the confidence of steering torque simulation, and provides guidance for the hardware design of the suspension and steering systems in the early stage of design.

[0005] In order to solve the above technical problems, the present invention provides a method for establishing a steering wheel steering torque simulation model, comprising:

[0006] Obtaining transfer functions of various key parameters, wherein the key parameters include: steering assist, suspension system friction, suspension system damping, steering system friction, and steering system damping;

[0007] Establishing a vehicle model and simulation conditions in Carsim, wherein each of the key parameters is set as an external input in the vehicle model;

[0008] Based on the transfer functions of the key parameters and the vehicle model, an initial joint simulation model is established in Simlink;

[0009] The initial joint simulation model is optimized until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then the final optimization result of the initial joint simulation model is determined as the steering wheel steering torque simulation model.

[0010] In the above-mentioned method for establishing the steering wheel steering torque simulation model, the joint simulation of Carsim and Simulink is used to solve the problem of modeling the friction and damping force of the suspension system and the steering system, improve the confidence of the steering torque simulation, and provide guidance for the hardware design of the suspension and steering systems in the early stage of design.

[0011] Furthermore, the transfer function for obtaining the friction force of the suspension system includes:

[0012] Through real vehicle tests, collect data tables showing the change of friction force of the suspension system with steering wheel angle;

[0013] Based on the data table of the change of suspension system friction force with steering wheel angle, the transfer function of suspension system friction force is determined.

[0014] Furthermore, based on the transfer functions of the key parameters and the vehicle model, establishing an initial joint simulation model in Simlink includes:

[0015] Importing the vehicle model into Simlink;

[0016] Based on the transfer functions of various key parameters, establish the transfer function modules of various key parameters in Simlink;

[0017] In Simlink, establish a gain module for each transfer function module;

[0018] The whole vehicle model, each transfer function module and each gain module are connected for signal interaction.

[0019] Furthermore, the transfer functions of various key parameters include:

[0020] The transfer function of the steering power f0(M,v) and the transfer function of the friction force of the suspension system Transfer function of damping force of suspension system Transfer function of friction force in steering system and the transfer function of the steering system damping force

[0021] Where M is the steering wheel torque, v is the vehicle speed, θ is the steering wheel angle, is the angular velocity of the steering wheel.

[0022] Furthermore, the signal interactive connection between the vehicle model, each transfer function module and each gain module includes:

[0023] The output signal of the transfer function module of the power steering is used as the input signal of the corresponding gain module;

[0024] Using the output signal of the steering assist gain module as the input signal of the steering assist parameter of the whole vehicle model;

[0025] The steering wheel steering torque signal and the vehicle speed signal of the whole vehicle model are used as input signals of the transfer function module of the steering assist.

[0026] Furthermore, based on the transfer functions of the key parameters and the vehicle model, establishing an initial joint simulation model in Simlink includes:

[0027] In Simlink, an oscilloscope module is established for the output of each gain module.

[0028] Furthermore, based on the transfer functions of the key parameters and the vehicle model, establishing the initial joint simulation model in Simlink also includes:

[0029] A steering wheel steering torque fluctuation module is established in Simlink, and the steering wheel steering torque fluctuation module is used to calculate the fluctuation value of the steering wheel steering torque.

[0030] Furthermore, based on the transfer functions of the key parameters and the whole vehicle model, establishing the initial joint simulation model in Simlink also includes: establishing an oscilloscope module in Simlink for displaying the output signal of the whole vehicle model.

[0031] Furthermore, the setting requirements include:

[0032] The deviation between the simulation result of the steering wheel steering torque and the test result does not exceed the first set value; and the fluctuation of the steering wheel steering torque during the simulation process does not exceed the second set value.

[0033] In order to solve the above technical problems, the present invention also provides a steering wheel steering torque simulation model establishment system based on the above steering wheel steering torque simulation model establishment method, comprising:

[0034] An acquisition module, used for acquiring transfer functions of various key parameters, wherein the key parameters include: steering assist, suspension system friction, suspension system damping, steering system friction and steering system damping;

[0035] A first establishment module is used to establish a vehicle model and a simulation condition in Carsim, wherein each of the key parameters is set as an external input in the vehicle model;

[0036] A second establishment module is used to establish an initial joint simulation model in Simlink based on the transfer functions of each of the key parameters and the vehicle model;

[0037] The optimization module is used to optimize the initial joint simulation model until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then determine that the final optimization result of the initial joint simulation model is the steering wheel steering torque simulation model.

[0038] Similar to the beneficial effects of the above method, by solving the problem of modeling the friction and damping force of the suspension system and steering system, and by refining the parameter input in the simulink module and improving the simulation accuracy, it is possible to achieve refined simulation optimization of the steering torque and provide simulation support for the development of the suspension steering system.

[0039] In summary, the above-mentioned steering wheel steering torque simulation model establishment method and system are adopted, and the problem of friction and damping force modeling of the suspension system and steering system is solved through joint simulation of Carsim and Simulink, the confidence of steering torque simulation is improved, and guidance is provided for the hardware design of the suspension and steering system in the early stage of design. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the attached picture:

[0041] Figure 1 The present invention is a flow chart of a method for establishing a steering wheel steering torque simulation model.

[0042] Figure 2 It is the initial joint simulation model in the method for establishing the steering wheel steering torque simulation model of the present invention.

[0043] Figure 3 The schematic diagram of the structure of the system for establishing the steering wheel steering torque simulation model of the present invention.

[0044] In the figure, 11, the first transfer function module; 12, the second transfer function module; 13, the third transfer function module; 14, the fourth transfer function module; 15, the fifth transfer function module; 21, the first gain module; 22, the second gain module; 23, the third gain module; 24, the fourth gain module; 25, the fifth gain module; 31, the first oscilloscope module; 32, the second oscilloscope module; 33, the third oscilloscope module; 34, the fourth oscilloscope module; 35, the fifth oscilloscope module; 41, the steering wheel steering torque fluctuation function module; 42, the switch module; 43, the constant module; 5, the fifth oscilloscope module. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0046] Simlink is a visual simulation tool in MATLAB launched by MathWorks, USA. It is a software package used to model, simulate and analyze dynamic systems. It supports continuous, discrete or mixed linear and nonlinear systems, as well as multi-rate systems with multiple sampling rates. Users can use the module library provided by Simulink to build system models, simulate and analyze in a graphical way.

[0047] Carsim is a vehicle dynamics simulation software developed by Mechanical Simulation Corporation (MSC). It is mainly used to simulate and analyze vehicle motion and control. It can simulate the vehicle's response to the driver, road surface and aerodynamic input, and predict and simulate the vehicle's handling stability, braking, ride comfort, power and economy. It is suitable for modeling and simulation of cars, light trucks, light multi-purpose transport vehicles and SUVs, and can analyze the vehicle's power, fuel economy, handling stability, braking and ride comfort.

[0048] KC test platform usually refers to the test equipment used to test the K&C (Kinematics & Compliance) characteristics of the automobile suspension system. This platform plays a vital role in the development and adjustment of automobile chassis performance.

[0049] Example 1

[0050] Figure 1 The present invention shows a method for establishing a steering wheel steering torque simulation model. Figure 1 As shown, the method for establishing the steering wheel steering torque simulation model includes the following steps S10-S40.

[0051] Step S10: obtaining the transfer function of each key parameter, wherein the key parameters include: steering assist, suspension system friction, suspension system damping force, steering system friction and steering system damping force.

[0052] When the vehicle is driving, some direct factors that affect the steering torque of the steering wheel are key parameters, including: steering assistance, suspension system friction, suspension system damping, steering system friction and steering system damping. Each key parameter changes with certain state quantities of the vehicle. This change relationship is usually not linear, and it is necessary to use a mathematical function to approximate this nonlinear relationship. This mathematical function used to approximate the change relationship is the transfer function.

[0053] First, the transfer function acquisition of the steering assist is described. In the usual sense, steering assist refers to a steering assist system, which reduces the force required by the driver when steering by increasing external force, thereby making it easier to complete the steering operation. It is mainly divided into three types: mechanical hydraulic power steering system, electronic hydraulic power steering system and electric power steering system (EPS, Electronic Power Steering). The steering assist in this method refers to a vehicle state parameter, specifically the steering assist value provided by the steering assist system during vehicle driving.

[0054] Since the vehicle's power steering system needs to be strictly calibrated, that is, it has its own calibration curve, which is usually the relationship between the steering power value and the steering torque M of the steering wheel and the vehicle speed v. Therefore, the transfer function f0(M,v) of the steering power can be obtained according to the calibration curve of the vehicle's power steering system. Specifically, one or more suitable function models can be selected to fit the calibration curve. Common models include polynomial functions, exponential functions, logarithmic functions, power functions, piecewise linear functions, and more complex nonlinear models (such as neural networks, support vector machines, etc.).

[0055] Secondly, the transfer function acquisition process of the suspension system friction force, suspension system damping force, steering system friction force and steering system damping force is described. The process is similar and includes the following steps: first, through the actual vehicle test, collect the data table of the key parameters changing with the corresponding state variables; then, according to the data table of the key parameters changing with the corresponding state variables, determine the transfer function of the key parameters, usually using the approximate fitting method. The following is a detailed description of the process of obtaining the transfer function of the suspension system friction force as an example, specifically including the following steps a1 and a2.

[0056] Step a1: Through actual vehicle testing, collect a data table showing the change in friction of the suspension system with steering wheel angle.

[0057] There are many specific test operation methods. The following describes a feasible test method: Place the vehicle on the KC test platform to ensure that the vehicle tires can rotate freely without ground resistance. Use a quasi-static rotation angular velocity (the angular velocity needs to be maintained steadily when turning the steering wheel) to turn the steering wheel to different angles. The data tested by the steering wheel torque robot is the sum of the friction of the steering system and the friction of the suspension system. Then, disconnect the steering rod and use a quasi-static angular velocity to turn the steering wheel to different angles. The data tested by the steering wheel torque robot is the friction of the steering system. The above data minus the below data is the friction of the suspension system. In addition, in actual tests, some points are usually determined within the range of the steering wheel angle and the steering wheel rotation angular velocity for testing, that is, a series of discrete data are collected.

[0058] The reason for separating the steering system and the suspension system is explained here. It is to facilitate the subsequent optimization in step S40. Separating the steering system and the suspension system will make the optimization more detailed and can propose actual vehicle optimization needs to steering professionals and suspension professionals respectively, making it convenient for the actual vehicle to be optimized according to the simulation results.

[0059] In addition, a feasible method to obtain the damping force of the suspension system and the steering system is as follows: first test a damping coefficient on the KC test platform. This coefficient reflects the energy dissipation characteristics of the steering system during rotation and is determined by the steering wheel angle and the steering wheel angular velocity; then the damping size is the product of the damping coefficient and the steering wheel angular velocity.

[0060] Step a2: Determine the transfer function of the friction force of the suspension system according to the data table of the change of the friction force of the suspension system with the steering wheel angle. There are many specific methods, such as function fitting and interpolation.

[0061] Finally, the transfer functions of the key parameters include: the transfer function of the steering power f0(M,v), the transfer function of the friction force of the suspension system Transfer function of damping force of suspension system Transfer function of friction force in steering system and the transfer function of the steering system damping force Where M is the steering wheel torque, v is the vehicle speed, θ is the steering wheel angle, is the angular velocity of the steering wheel.

[0062] Step S20: Establish a whole vehicle model and simulation conditions in Carsim, wherein each key parameter in the whole vehicle model is set as an external input.

[0063] There is a special vehicle model setting module in Carsim. For example: first enter the vehicle model setting interface to set the basic parameters of the vehicle, such as mass, inertia matrix, and size; then define the suspension system and make customized settings according to the actual suspension system parameters of the vehicle; then select the appropriate tire model and set the tire size, load, cornering stiffness and other parameters; then configure the transmission system and set the transmission, differential, drive shaft and other parameters according to the actual transmission system configuration of the vehicle; finally define other systems, such as braking system, steering system, etc., and make corresponding settings as needed.

[0064] Specifically, the main parameter input sources of the vehicle model of the present invention are: the design values ​​of the early prototype design, which can be directly brought into the model; the above-mentioned key parameters are the parameters for interaction with Simulink later. The main parameter input sources of the steering system are shown in Table 1 below. Table 1 Main parameter input sources of the steering system

[0065]

[0066]

[0067] The simulation condition is used to evaluate the performance of the vehicle steering system. Through simulation analysis, the changes in steering wheel torque under different conditions can be simulated, providing an important basis for vehicle design and optimization. This method uses the center area steering test condition.

[0068] Step S30: Based on the transfer functions of various key parameters and the vehicle model, an initial joint simulation model is established in Simlink.

[0069] The vehicle model in Carsim and some modules in Simlink are interactively connected to form the required simulation model. Through simulation analysis, the changes in steering wheel torque under different working conditions can be simulated. Specifically, the following steps b1-b5 are included.

[0070] Step b1: Import the vehicle model into Simlink. You can select the "Send to Simulink" option in CarSim and specify the path and name of the Simulink model. CarSim will automatically generate a Simulink model file (such as .slx or .mdl file) containing the vehicle model. You can open the model file in Simulink. Alternatively, you can save the vehicle model in CarSim first and then import it directly in Simulink.

[0071] Step b2: Based on the transfer functions of the key parameters, the transfer function modules of the key parameters are established in Simlink. This mainly involves using the Transfer Fcn (transfer function) module in the built-in library of Simulink. The transfer function module allows the dynamic characteristics of a linear time-invariant system to be specified, which is usually defined by the numerator and denominator polynomial coefficients, that is, the transfer function obtained in step S10 is configured into each corresponding Transfer Fcn (transfer function) module.

[0072] Step b3: Establish a gain module for each transfer function module in Simulink. In Simulink, establishing a gain module can be achieved by adding a "Gain" module, which allows setting a single gain value, which will multiply the signal passing through it. Specifically, the initial gain value of each gain module is set to 1. When the model is optimized in step S40, the optimization can be achieved by adjusting the gain value of each gain module.

[0073] Step b4: connect the whole vehicle model, each transfer function module and each gain module through signal interaction.

[0074] The specific method of connecting the transfer function module and gain module of each key parameter with the whole vehicle model for signal interaction is similar. The following description takes the power steering as an example. The signal interaction connection of the transfer function module, gain module and whole vehicle model of the power steering includes: using the output signal of the transfer function module of the power steering as the input signal of the corresponding gain module; using the output signal of the gain module of the power steering as the input signal of the steering power assistance parameter of the whole vehicle model; using the steering wheel steering torque signal and the vehicle speed signal output by the whole vehicle model as the input signal of the transfer function module of the power steering.

[0075] In Simulink, you can connect modules by dragging the mouse from the output port of one module to the input port of another module. Figure 2 As shown in FIG. 1 , the transfer function modules of the steering assist, the suspension system friction, the suspension system damping, the steering system friction and the steering system damping are named in sequence: a first transfer function module 11, a second transfer function module 12, a third transfer function module 13, a fourth transfer function module 14 and a fifth transfer function module 15; the corresponding gain modules are named in sequence: a first gain module 21, a second gain module 22, a third gain module 23, a fourth gain module 24 and a fifth gain module 25, which are connected as shown in FIG. Figure 2 shown.

[0076] Step b5: Create an oscilloscope module for the output of each gain module in Simlink.

[0077] Creating an oscilloscope module in Simulink is a straightforward and simple process. An oscilloscope module (often called a "scope") is a "sink" module in Simulink that is used to display the changes of a signal over time. Figure 2 As shown, the oscilloscope modules corresponding to the gain modules are named as: a first oscilloscope module 31 , a second oscilloscope module 32 , a third oscilloscope module 33 , a fourth oscilloscope module 34 and a fifth oscilloscope module 35 .

[0078] Step b6: Create a steering wheel steering torque fluctuation module in Simlink. The steering wheel steering torque fluctuation module is used to calculate the fluctuation value of the steering wheel steering torque.

[0079] like Figure 2 As shown, the steering wheel steering torque fluctuation module may include a steering wheel steering torque fluctuation function module 41, a switch module 42 and a constant module 43. The steering wheel steering torque fluctuation function module 41 is similar to the transfer function module, and is configured with a calculation function of the steering wheel steering torque fluctuation, which is usually the difference between the current steering wheel steering torque and the steering wheel steering torque at the previous moment, that is, the current steering wheel steering torque fluctuation value. In Simulink, the switch module 42 (Switch module) is a commonly used control module, which determines from which data input port to transfer the signal to the output port according to the value of one or more control inputs. The constant module 43 is used to generate a constant signal.

[0080] Specifically, the output end of the steering wheel steering torque fluctuation function module 41 and the output end of the constant module 43 are respectively connected to the input end of the switch module 42. In the switch module 42, the threshold of the input condition can be controlled to be 0.2. If the current steering wheel steering torque fluctuation value is greater than 0.2, that is, when the fluctuation value is large, the current steering wheel steering torque fluctuation value is output for post-processing; if the current steering wheel steering torque fluctuation value is ≤0.2, the set value 0 of the constant module 43 is directly output.

[0081] In addition, the steering wheel steering torque signal of the whole vehicle model is used as the input signal of the steering wheel steering torque fluctuation function module 41 .

[0082] Step b7: Create an oscilloscope module in Simlink to display the output signal of the vehicle model. The oscilloscope module is used to display the waveforms of the steering wheel torque, vehicle speed, steering wheel angle, and steering wheel angular velocity; it can also display the waveform of the fluctuation value of the steering wheel torque for simulation post-processing to facilitate optimization.

[0083] like Figure 2As shown, the oscilloscope module for displaying the output signal of the whole vehicle model is marked as the fifth oscilloscope module 5 to distinguish the oscilloscope module of the gain module. The steering wheel steering torque signal, vehicle speed signal, steering wheel angle signal and steering wheel rotation angular velocity signal of the whole vehicle model, and the output signal of the steering wheel steering torque fluctuation function module 41 are used as input signals of the oscilloscope module 5, and waveforms are displayed respectively.

[0084] Step S40: Optimize the initial joint simulation model until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then determine the final optimization result of the initial joint simulation model as the steering wheel steering torque simulation model.

[0085] The initial joint simulation model established in step S30 needs to be optimized multiple times to meet the set requirements. The final optimization result is taken as the output, which is the steering wheel steering torque simulation model we ultimately need.

[0086] Step S40 mainly involves result post-processing and test result benchmarking. Post-processing involves analysis and visualization of simulation data to better understand the performance of the vehicle under different working conditions. The accuracy and reliability of the simulation results are verified by benchmarking the test results, that is, comparing with the actual vehicle test data or theoretical calculation results. If it is found that there is a large deviation between the simulation results and the actual situation, it is necessary to return to the simulation model for parameter adjustment or model optimization.

[0087] The simulation result of the steering wheel steering torque is the corresponding relationship between the steering wheel steering torque and the steering wheel angle under the set working condition. The specific setting requirements are: the deviation between the steering wheel steering torque simulation result and the test result does not exceed the first set value; and the steering wheel steering torque fluctuation during the simulation process does not exceed the second set value. That is, under the simulation working condition, the steering wheel steering torque-steering wheel angle relationship can be obtained by experiment according to the relevant test standards, and then compared with the results obtained by simulation. The setting requirements are: the difference between the test steering wheel steering torque corresponding to each steering wheel angle and the simulated steering wheel steering torque does not exceed the first set value, and the first set value is usually 0.2N*m. Moreover, it is required that the steering wheel steering torque fluctuation (the output of the steering wheel steering torque fluctuation function module 41) during the simulation process does not exceed the second set value, and the second set value is usually 0.2N*m. By adjusting the gain values ​​of each gain module, the simulation results meet the above two conditions to obtain the optimal simulation model.

[0088] Example 2

[0089] Figure 3 The present invention shows a steering wheel steering torque simulation model establishment system based on the above-mentioned steering wheel steering torque simulation model establishment method. Figure 3As shown, the steering wheel steering torque simulation model establishment system includes: an acquisition module, which is used to obtain the transfer function of each key parameter, wherein the key parameters include: steering assist, suspension system friction, suspension system damping force, steering system friction and steering system damping force; a first establishment module, which is used to establish a whole vehicle model and simulation conditions in Carsim, wherein each key parameter is set as an external input in the whole vehicle model; a second establishment module, which is used to establish an initial joint simulation model in Simlink based on the transfer function of each key parameter and the whole vehicle model; an optimization module, which is used to optimize the initial joint simulation model until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then determine that the final optimization result of the initial joint simulation model is the steering wheel steering torque simulation model.

[0090] When working, the acquisition module, the first establishment module, the second establishment module and the optimization module work together to complete the steering wheel steering torque simulation model establishment method in implementation 1, which has the beneficial effects of the above-mentioned steering wheel steering torque simulation model establishment method.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A method for establishing a steering wheel steering torque simulation model, characterized in that: include: Obtaining transfer functions of various key parameters, wherein the key parameters include: steering assist, suspension system friction, suspension system damping, steering system friction, and steering system damping; Establishing a vehicle model and simulation conditions in Carsim, wherein each of the key parameters is set as an external input in the vehicle model; Based on the transfer functions of the key parameters and the vehicle model, an initial joint simulation model is established in Simlink; The initial joint simulation model is optimized until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then the final optimization result of the initial joint simulation model is determined as the steering wheel steering torque simulation model.

2. The method for establishing a steering wheel steering torque simulation model according to claim 1, characterized in that: The transfer function for obtaining the friction force of the suspension system includes: Through real vehicle tests, data tables showing the change of friction force of the suspension system with steering wheel angle are collected; Based on the data table of the friction force of the suspension system changing with the steering wheel angle, the transfer function of the friction force of the suspension system is determined.

3. The method for establishing a steering wheel steering torque simulation model according to claim 1, characterized in that: Based on the transfer functions of various key parameters and the vehicle model, the initial joint simulation model is established in Simlink including: Importing the vehicle model into Simlink; Based on the transfer functions of various key parameters, establish the transfer function modules of various key parameters in Simlink; In Simlink, establish a gain module for each transfer function module; The whole vehicle model, each transfer function module and each gain module are connected for signal interaction.

4. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: The transfer functions of various key parameters include: The transfer function of the steering assist f0(M,v), the transfer function of the suspension friction f1(θ, ), the transfer function f2(θ, ), the transfer function of the steering system friction force f3(θ, ) and the steering system damping force transfer function f4(θ, ); Where M is the steering wheel torque, v is the vehicle speed, θ is the steering wheel angle, is the angular velocity of the steering wheel.

5. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: The signal interactive connection of the vehicle model, each transfer function module and each gain module includes: The output signal of the transfer function module of the power steering is used as the input signal of the corresponding gain module; Using the output signal of the steering assist gain module as the input signal of the steering assist parameter of the whole vehicle model; The steering wheel steering torque signal and the vehicle speed signal of the whole vehicle model are used as input signals of the transfer function module of the steering assist.

6. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: Based on the transfer functions of various key parameters and the vehicle model, the initial joint simulation model is established in Simlink including: In Simlink, an oscilloscope module is established for the output of each gain module.

7. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: Based on the transfer functions of various key parameters and the vehicle model, establishing an initial joint simulation model in Simlink also includes: A steering wheel steering torque fluctuation module is established in Simlink, and the steering wheel steering torque fluctuation module is used to calculate the fluctuation value of the steering wheel steering torque.

8. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: Based on the transfer functions of various key parameters and the whole vehicle model, establishing an initial joint simulation model in Simlink also includes: establishing an oscilloscope module in Simlink for displaying the output signal of the whole vehicle model.

9. The method for establishing a steering wheel steering torque simulation model according to claim 3, characterized in that: The setting requirements include: The deviation between the simulation result of the steering wheel steering torque and the test result does not exceed the first set value; and the fluctuation of the steering wheel steering torque during the simulation process does not exceed the second set value.

10. A steering wheel steering torque simulation model establishment system based on the steering wheel steering torque simulation model establishment method according to any one of claims 1 to 9, characterized in that: include: An acquisition module, used for acquiring transfer functions of various key parameters, wherein the key parameters include: steering assist, suspension system friction, suspension system damping, steering system friction and steering system damping; The first building module is used to build the vehicle model and simulation conditions in Carsim, where: Setting each of the key parameters as external input in the vehicle model; A second establishment module is used to establish an initial joint simulation model in Simlink based on the transfer functions of each of the key parameters and the vehicle model; The optimization module is used to optimize the initial joint simulation model until the steering wheel steering torque result of the simulation operation under the simulation condition meets the set requirements, and then determine that the final optimization result of the initial joint simulation model is the steering wheel steering torque simulation model.

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