Research On Nonlinear Control Of Automotive Semi-active Suspension

The suspension is one of important automotive assembly, which has prodigious influence on performance of ride quality and handing stability. So it is crucial to design excellent suspension system for automotive quality. Passive suspension is difficult to met requirements for a car which pursuit under levity perplexing environments. The complex active suspension is development direction but still rest on phases of theoretic researches and experiments because of being costly and lacking in reliability. Recently semi-active suspension composed of springiness element and controllable damper engender fine power of weaken vibration according to control law and feedback signal, sequentially, which can improve ride quality. For the low cost and brief configuration semi-active suspension has become a kinetic research topic of automotive field in the world.Automotive suspension is a nonlinear system, but groovy control methods take on stated limits when applied to the system. So more efficient control polices are required for better approaching practical system and control effect, In this dissertation nonlinear control methods in allusion to semi-active suspension are investigated based on its nonlinear characteristics to design different nonlinear controller and carry on research simulation.Firstly, considering nonlinear rigidity of springiness element, the nonlinear dynamic mode of a quarter-car semi-active suspension is built with MR fluid damper that possesses some performance of continuous control and rapid response through the analysis of nonlinear characteristics of automotive suspension system. Differential geometry theory non-linear control strategy is firstly applied to execute feedback control on semi-active suspension. The nonlinear model of the semi-active suspension is transferred to a simple linear system through a nonlinear state feedback. Synchronously according to road excitation, fuzzy logic and neural network controllers are designed to improve automotive ride comfort.Then the simulation results of three non-linear control methods on semi-active suspension compared with each other showed that low impact response and vibration intensity is attained after fuzzy logic and neural network control policy applied and they possess more superior performance than differential geometry theory control strategy.Besides considering nonlinear rigidity springiness element, 6-DOF car dynamic model of semi-active suspension is presented by combining transfer characteristics of vibration energy in human-machine-car system and excellent performance of MR damper. The dynamic models are the basis of the non-linear control researches.Especially, Integrating mutual superiorities of fuzzy logic and neural network developed MRAC controller of fuzzy neural network configuration by controlling automotive vertical acceleration in allusion to 6-DOF dynamic model of semi-active suspension. The result of simulation showed: analysis demonstrates the nonlinear-control strategies of fuzzy neural network can attain excellent performances, these suspensions model exactly coincide with the practical condition and the MR fluid damper offered considerable potential to achieve a better compromise between the shock and vibration attenuation performance of suspension. The results showed the semi-active control not only consume few energy sources, but also can attain an excellent effect on weakening vehicle vibration and disturbance.Eventually, considering practice, a HILS system of control experiment is designed at ride comfort level of unspring mass vertical acceleration, furthermore, the advice is put forward how to mount hardware and execute in semi-active control on a car.