Simulation Study On Technology Of Specialty Vehicle Active Suspension

The suspension system is one of the most important devices of the vehicle. It links the vehicle body and wheel flexibly, in order to achieve the goal that make the vehicle running normally, the suspension transfers the force and the moment between vehicle body and wheel,and mitigate the body vibrancy that is brought by impact force.With the increasing of the people's living standards and the rapid developing of automobile industry, people have a higher demand to the vehicle's comfort and manipulation. Similarly, if the vehicles used in the war have better tactical mobility and better stability, weapons systems on the vehicle can aimed at the target easily, we are more in urgent need of running smoothly and operation stability. Therefore the requirements to the suspension in the future has become increasingly high, passive suspension has been far from demand. However, because the cost is great and energy is also big, active suspension are limited to install in the racing cars and some senior cars. We still have a lot of work to do in the active suspension, do some work in control algorithm, improving system stability, reducing the energy consumption and so on.This dissertation mainly combined the Jilin University 985 autombile innovation project"The research on large working space of active ans semi-active suspension"and ministry of the new century talents funded projects"The research on the technology of the inertia control active/semi-active suspension". In orde to improve running smoothly and operation stability, through anaylyzing the devlop status and crrent of the active suspension, using a certain vehicle, we built the 7-DOF dynamics model of the whole vehicle based on the passive suspension and the active suspension. Then we designed the actuators of the the active suspension which were controlled by servo value, the actuators actually were some cylinders. At last, we had some research on the control methods of the active suspension,and did some simulation works to the control system.The main jobs of this dissertation are as following:1. The meaning, mission and origin of this dissertation are introduced. Firstly, we introduced the suspension including its function, makeup and sorts, compared the peformance between active suspension and passive suspension. It made research into the control theory, application and development trend and analyzed the international and native research situation. Fianally, it listed the goal and mission of this dissertation.2. The dissertation introduced the suspension performance estimate manners, built the road input model, and expounded the road surface roughness as well as the power spectrum of it. It analyzed the frequency range of the vehicle vibrant, simplified the vehicle dynamic model. It took the acceleration of the road as input signal, established the 7-DOF dynamic model based on passive and active suspension respectively. With the analytical method of the state space, it established the state equation of the system.3. The dissertation analyzed the work principle of suspension system, brought forward the whole project of the suspension's hydro-electric servo control system and expounded the style and the function of the component in the servo system. It established the mathematics model that the servo value controlled the non-symmetry cylinder which was used as the executive component, find out the transfer function of the hydro-electric servo value, so it can obtained the maths expression of the transfer function which took the displacement of the servo value core as the input and took the exported force of the cylinder as the output.4. The dissertation had a research on LQG (Linear quadratic gaussian), figured out the suspension model based on full states feedback, build the performance function under the primary abilities, and get the control functionU = K×x. For the none-full state system, we usually replace the state with best estimate using Kalman filter. It analyzed the principle and the characteristic the Fuzzy control, through summarize the manipulate rule of the representative control system, obtained the rule of the suspension system, and designed the Fuzzy controller which was taken the body acceleration, pitch acceleration, roll acceleration and dynamic deflection as the control goal.5. The dissertation established the simulation module of the 7-DOF dynamic model based on the passive suspension, obtained the frequency-domain simulation curve with MATLAB–SIMULINK. It established the simulation module of the 7-DOF dynamic model based on the LQG control and Fuzzy control suspension, contrastingly analyzed the amplitude frequency and phase frequency response curve based on passive and active suspension. It made use of the established road model and different control theory, analyzed the simulation data and validated the advantage of the active suspension.6.After analysing the simulation data, it got the conclusions as follows: In the aspect of improving body acceleration, LQG control, Fuzzy control reduce the body acceleration respectively 21.9% and 32%; In the aspect of improving Pitching acceleration, LQG control, Fuzzy control reduce Pitching acceleration respectively 18.3% and 15.1% ; In the aspect of improving rolling acceleration, LQG control, Fuzzy control reduce the rolling acceleration respectively 19.6% and 18.7%; In the aspect of improving suspension working space, LQG control, Fuzzy control reduce the suspension working space respectively 32.2% and 25.4%; In improving dynamic tyre load, LQG control, Fuzzy control reduce the dynamic tyre load 12.5% and -4.9%.