Mechanical Characteristic Analysis And Control Simulation Research Of Electric Power Steering System

Electric Power Steering(EPS)is a steering system that can provide assist torque on demand according to vehicle speed and steering wheel torque.It has the advantages of high safety,light weight and energy saving.With the rapid development of the new energy vehicle industry,the research and application of key technologies for electric power steering systems has become a hot spot.High-quality EPS is of great significance to improving vehicle handling and comfort.This paper aims to improve the performance of EPS,analyzes the mechanical characteristics of the key parts of the EPS,designs corresponding control strategies,conducts simulation research,tests the relevant performance of the EPS in combination with the bench experiment,and finally verifies the power-assisting characteristics and portability of EPS.The main contents of this article are as follows:(1)EPS mechanical characteristics analysis:Firstly,analyze the steering resistance torque,steering wheel torque and assist torque based on the tire and suspension model,discuss the relationship between the three under steady-state circular driving,and design the assist characteristic curve according to the vehicle structure parameters.Secondly,establish the friction model of the rack and briquette based on the Lugre model,describe the Dahl effect and the Stribeck effect between the friction pairs through simulation.Finally,calculate the equivalent mass of the rack through the energy method,and establish the transfer function of the rack lateral motion.(2)EPS control strategy design:Based on the driver’s steering intention and execution action,the logic sequence of the function release of different steering control modules is analyzed and formulated.Combining traditional PID control and advanced fuzzy control,design a two-input and three-output fuzzy PID controller to control the target current of the steering motor,and use MATLAB software to establish the control strategy.Based on the analysis of the mechanical characteristics of EPS,friction compensation and inertia compensation control strategy are established to improve control effects.(3)EPS modeling and simulation:Take dual pinion EPS as the research object,establish dynamic models of steering wheel and steering shaft,torque sensor,power-assisted motor,rack and pinion,establish a two-degree-of-freedom dynamic model of the whole vehicle,and use MATLAB/Simulink to build the overall model of the system.Simulation is used to verify the accuracy of the modeling of the booster module,analyze the influence of different controllers on vehicle handling stability,and verify control effects of the compensation controller.(4)EPS bench experiment:In order to further verify the actual performance of the EPS using the above control strategy,a variable load steering experiment platform was built,and analyze the composition of the experiment platform and the principle of data measurement.Relying on the bench test,the assist current following experiment,the no-load steering experiment and the steering portability experiment were carried out.The experimental results verified the power-assisted characteristics,ride comfort and portability of the EPS.