Research On Automobile Steering System By Wire Based On Fuzzy PID Control

Cars with wire-controlled steering systems are easier and more stable to drive than conventional mechanical steering structures.It changes the fixed drive ratio of the traditional mechanical steering structure into a designable variable transmission ratio,and under the fixed cross-swing angle speed gain,the size of the transmission ratio is only affected by the speed size,which reduces the driver’s operating burden at low speed segments and reduces the probability of roll-over risk due to the large steering wheel at high speed segments.In this paper,the design method of building the vehicle model,the design method of the transmission ratio,the line control method based on fuzzy PID and the experimental analysis of hardware and software are studied,mainly on the design method of the transmission ratio and the influence of the line control method based on fuzzy PID on the stability of the car.First of all,the line control steering technology at home and abroad is analyzed and summarized,clearly from the ideal transmission ratio and the front wheel corner control strategy of the two directions.This paper studies the mathematical model of steering input system and steering execution system,which mainly carries on the mathematical analysis to steering wheel module,steering motor module and steering execution module,and establishes the mathematical model,and establishes the whole vehicle steering control model with the simulated mathematical model and the simulation software CARSIM.The simulation results show that the effect of mechanical steering system and line-controlled steering system on the target angle response is basically the same,the peak error is less than 3%,the error is in a reasonable range,so the line-controlled steering system simulation model and CARSIM joint simulation can meet the requirements of the target operating conditions.The two degrees of freedom model basically re-fits the cross-swing angle response curve under mechanical control and line control to meet the requirements of follow-up research.Secondly,the design of the transmission ratio can be divided into two directions depending on the control variable,one is to control the cross-swing angle speed gain value of the steering wheel corner,so that it is at a constant value,or the steering sensitivity is unchanged design method,and the other is to control the lateral acceleration gain value of the steering wheel corner,so that it is at a constant value design method.Verification analysis shows that,with fixed steering sensitivity,it can improve the operator’s operational complexity under a variety of operating conditions,and prevent the car from being caused by high sensitivity at high speeds and other hazards such as driving rollover.In order to determine the use of steering sensitivity unchanged design method.Genetic algorithms are used for the determination and optimization of steering sensitivity.The data obtained by optimization analyze the change of the value of the manipulation stability index at different speeds and sensitivity,and determine that the final optimized steering sensitivity value is 0.31.Finally,the fuzzy PID algorithm is used to give feedback compensation control to the input corner of the line-controlled steering system and analyze the control effect.In the course of stable driving of the vehicle,the steering characteristics of the vehicle can be reflected mainly from the swing angle speed.Through the comparative analysis of the joint simulation,compared with the index of mechanical steering,the response peak of the compensation angle control method with only PID control and the compensation angle control method with fuzzy PID was reduced by about 21.7%,the steady-state response time was reduced by nearly 10.7%and 26.1%,respectively,and the line-controlled steering system had better control effect on system stability.And the compensation angle control method of adding fuzzy PID is nearly16% shorter than the steady-state response time of the compensation angle control method of adding PID,and the Fuzzy PID response result under the condition of peak controllable is more satisfied with the expected value,which proves that fuzzy PID can effectively improve the steering performance of the car during the steering process.Because of the advantages of simple,convenient operation and high control sensitivity,the fuzzy PID membership function is a triangular membership function.And analyzes the influence of the distribution state of the triangular membership function on the control effect,and the distribution state of the best triangular affiliation function is the overlapping rate distribution state with width of 4.The hardware system and software system of the main controller are analyzed simply.