Research On Road Feeling Simulation Control Strategy Based On Distributed Steering System

The distributed steering system is a new steering form,which cancels the mechanical connection between steering wheel and the steering wheel.The driver's operation intention is transmitted to the steering execution system through bus,so the design of the steering system is more transparent and free.Distributed road feeling simulation system is an important way for drivers to feel and detect road information and vehicle state,and so on,which is particularly important for safe driving and comfortable driving.The purpose of this paper is to solve the problem of distributed steering sense simulation."Road feeling" refers to the feedback of the road condition and vehicle state for the driver through the steering wheel."Road feeling" can be defined as the steering resistance torque on the steering wheel which is fed back to the steering wheel by the mechanical transmission device.In this paper,the main problem is to plan the target road feeling,accurately load the road feeling torque and carry out simulation and experiment to validate the road feeling control strategy can performance well.The main contents of this paper are as follows:1)Puts forward the significance of road feeling research and torque loading control strategy,introduces the working principle of distributed road feeling simulation system and the key issues involved,investigates the research status of road feeling simulation system and torque loading control,analysis of the advantages and disadvantages of the domestic and foreign research methods.2)The road feeling torque planning is carried out for the distributed steering vehicle.The target road feeling torque is superimposed on two parts of the steering resistance torque and the assistance characteristic.First,a dynamic model of distributed steering vehicle is established,including the distributed steering system angle allocation model,three degree of freedom vehicle body model and Magic Formula tire model,and the steering resistance torque of vehicles is estimated.Then,the characteristics of three kinds of assistance characteristic curves are analyzed.Considering the need of steering system's low speed portability and high speed road feeling,a new assistance characteristic curve is designed,which increases gradually from the convex curve to the concave curve with the increase of vehicle speed.CarSim-Simulink joint simulation is carried out for the road feel torque obtained from the assistance characteristic and resistance moment.The results show that the planned road feeling torque has good low-speed steering portability and high speed road feeling.3)The model of road feeling torque loading system is set up and key parameter identification is carried out.A model of road loading motor,reducer,torque sensor and steering wheel assembly is established,and the transfer function of each component is knocked down,then a complete road feeling torque loading system model is established.The key parameters of the system,such as the road feeling motor friction torque,torque coefficient,torque sensor stiffness and road feeling motor reducer damping coefficient and inertia,are identified through bench test.Combined with known parameters,all parameters of road feeling simulation loading system are obtained.4)Analyze the stability of road feeling torque loading system.Analyze the frequency characteristics of the forward channel and the system is in the unstable state.The influence of inertia,damping coefficient and sensor stiffness on the stability of the system is analyzed by plotting Bode diagram of different inertia,damping coefficient and sensor stiffness.A stability controller is designed to improve the stability of the system,including pole reconfiguration,torque closed-loop control and pre-filter design.The stability of the system is verified by simulation and bench test.5)Suppress the surplus force of the road feeling torque loading system.Analyze the mechanism of surplus force through the mechanical characteristic curve of the road feeling motor.By plotting the Bode diagram of the disturbance channel of the system,the influence of inertia,damping coefficient and sensor stiffness on the surplus force is analyzed Based on the principle of structure invariance,the angular velocity feed forward compensation is designed to suppress the surplus force of the system,and a real-time angular velocity estimation method is proposed.The suppression effect of the surplus force on the steering wheel displacement disturbance is verified by simulation and bench test.