Study On The Stability Analyse And Fuzzy-PID Control For The Integrated System Of Vehicle's SAS And EPS

Vehicle chassis integrated control has been a new research focus in the technology field of vehicle engineering.Its content is being continuously enriched with the development of advanced technologies,such as modern control theories,the microcomputer and computer simulation technology,the modern electronic technology,the vehicle X-by-wire technology,new sensors and information fusion and so on.It will be an inevitable trend of vehicle chassis control.The suspension and the steering system are two important sub-systems of the vehicle chassis.They affect the vehicle dynamics performance,such as the ride comfort,safety,handling stability and so on. There is some coupling effect between suspension and steering system.They act and affect each other.But it does not eliminate the influence of the coupling effect and is hardly to improve the whole vehicle synthesis performance that the semi-active suspension(SAS) and electric power system (EPS) control vehicle separately as they are combined simply.The integrated control of SAS and EPS is very necessary.The coupled relations between the suspension and steering system is analysed,the mathematical model of the integrated control system about SAS and EPS is established and its stability is analysed.The research about the integrated control system of SAS and EPS in its theory and experiment is done exploringly in this paper with PID and fuzzy contol.Firstly,vehicle force and kinematic status are analysed in the condition when the vehicle is turning,based on the vehicle dynamic system.The influence of SAS and EPS to the vehicle body attitude is analysed,and the integrated control model of whole vehicle is established,which includes the suspension,the steering system,tyres and the road input.The model can show the vehicle roll,pitch,yaw and vertical motion well.The system's state equation is derived from these,and its stability analysis is done with the Lyapunov stability principle,and the effect of the change of the vhicle total mass,the suspension stiffness,the stabilizer bar stiffness,the tire stiffness and the tire cornering stiffness on its stability is done.Secondly,a new fuzzy-PID integrated control strategy is put forward. The fuzzy-PID integrated control system of SAS and EPS is constructed and the work conditions of the integrated control system,the steering wheel's step and impulse input,are simulated in Matlab7.0/Simulink6.0.The simulation result show that the integrated control system,compared with the separate control system,optimizes the whole dynamics performance in its running condition and improve the handle stability,ride comfort and safety furtherly.At last,the sofeware and hardware are designed on the development board platform of EasyARM2131,and developed the electronic control unit of SAS and EPS integrated system which takes LPC2131 as its microprocessor. In order to validate the correctness of the theory and simulation analysis in this paper by the experiment,the test system is designed on a minisize car.Vehicle road tests are done,such as the random input running test,and impulse input running test,the steering wheel step input test,the steering wheel impulse input test and the steering portability test.It is shown that the simulation and calculation result is bascically in accordance with the test data.It validated the correctness and validity of the model and control strategy.So the integrated control system of SAS and EPS overcome the separate control shortage,make they work harmonize,and improve better the vehicle synthesis dynamics performance in the running condition.The research provides some references in theory and engineering experience.