Research On Control Method And Simulation Of Active Suspension

Suspension is one of the most important components of the vehicle, which connects the wheel and vehicle body flexibly,plays an important role in effecting the multiple perfomance of vehicle. Meanwhile, suspension is a very complex assembly, which is very diffcult to reach perfection, because it should satisfy the requirement for the ride performance and automotive controllability and stability. Suspension can be divided into passive suspension, semi-active suspension and active suspension according to the control force.Now the researches into active suspension focus on two fields, one is the control theory and the other is the actuator. In the the research into the suspension control theory, LQG theory is in the dominant position. First the road signal is random, so the acceleration of the road can be taken as white gaussian noise, and theperformance of the suspension can be expressed with quadratic functional differential equation. On the other hand LQG theory provide perfect tool for the state feedback and output feedback.Intelligent control including Fuzzy control is the focus of the active suspension control theory. Adaptive Fuzzy-PID combines the Fuzzy controller and normal PID controller, and possess the both advantages of the two controllers. First it possesses the adaptive ability , recognise and set the parameters automatically, so it can adjust the parameters in the control process. Second it has simple structure, robust ability and high reliability.This dissertation mainly combined the Jilin University 985 autombile innovation project"The research on large working space of active ans semi-active suspension", It mainly made research into the active suspension control theory. For some vehicle, it took the acceleration as the road input signals and built 2-DOF dynamics model of 1/4 vehicle based on active and passive suspenion and 7-DOF dynamics model of the whole vehicle based on active suspension. It made research on LQG control theory, PID control theory, Fuzzy control theory and adaptive Fuzzy-PID control theory. It took use of MATLAB-SIMULINK and analysed the active suspension and passive suspension with different input signals. The experiment rusults validated the advantage of the active suspension and it made comparewith each other.Below are the main job of this dissertation:1.The meaning, mission and origin of this dissertation is introduced. First introduced the suspension including its function,makeup and several sorts, compared the peformance between active suspension and passive suspension. It made research into the control theory ,application and development trend and analysed the the international and native research situation. Fianally ,It listed the goal and mission of this dissertation.2.The dissertation introduced the the suspension'effect on ride performance and controllability and stability as well as the suspension performance estimate manners. It established the 1/4 vehicle 2-DOF dynamic model based on passive and active suspension and 7-DOF dynamic model respectively. With the modern control theroy, it took the acceleration of the road as input signal and analysised the system. At last, the dissertation introduced the road model and the power spectrum of the road.3.The dissertation made research into LQG(Linear quadratic gaussian) ,figured out the suspension model based on full states feedback, build the performance funtion under the primary abilities, and get the control function U = K×x. For the none-full state system, we usually replace the state with best estimate using Kalman filter.4.The dissertation analysd the PID control theory and Fuzzy control theory, then took use of the two control theory on active suspension. It also combined the two theories, researching into adaptive Fuzzy-PID control theory, which was the focus of the control theory on active suspension. Also, this dissertation designed PID controller and Fuzzy controller of active suspension, and makes reseach into the design of Adaptive Fuzzy-PID controller.5.The dissertation analysed the 2-DOF passive suspension model with amplitude frequency picture with the different parameters. It analysed the vehicle model based on active suspension and passive suspension 2-DOF model with MATLAB-SIMULIN software. And it analysed the response of body acceleration, suspension working space and dynamic tyre load to different signals(sine signals, step signals and white gaussian noise ) with different control theorys. Finally, it analysed the experiment datas and validated the advantage of the active suspension. 6.After analysing the experiment datas, it got the conclusions as follows: In improving body acceleration, LQG control, PID control, Fuzzy Control and Fuzzy-PID control reduce the body acceleration respectively 35%,13%,24%和36%; In improving suspension working space, LQG control, PID control, Fuzzy Control and Fuzzy-PID control reduce the body acceleration respectively 20%,4%,8%和5%; In improving dynamic tyre load, LQG control, PID control, Fuzzy Control and Fuzzy-PID control reduce the body acceleration respectively 21%,5%,2%和15%. After analysing the control theories and experiment datas, so adaptive Fuzzy-PID control will be the focus of the suspension control.