Design Methods Of Holographic Optimal Sliding Mode Controllers For Vehicle Active Suspensions

With increasing demands for vehicle ride comfort and handling stability, active suspension systems were put forward and had attracted high interests for many years in vehicle engineering. Control method meets the requirements of suspension comprehensive performance is one of key technologies in current active suspension. The optimal performance and robust stability are two key elements for all control systems. To obtain both better suspension comprehensive performance under the nominal running condition and enhanced robustness under parameters and running condition variations, design methods of holographic optimal sliding mode(HOSM) controllers for vehicle active suspensions is developed. For this reason, there are mainly several following aspects in this paper:Firstly, a current optimal sliding mode(COSM) controller for the active suspension system based on a quarter car model with 2-degrees of freedom is designed and the reason that the COSM controller cannot obtain the optimal performance and robustness is analyzed through theoretical derivations.Secondly, based on the invention patent application titled “A holographic optimal sliding mode(HOSM) controller for active suspension system”, a novel HOSM controller for the active suspension is designed based on the newly established augmented optimal SM manifold function consider ing all of the suspension structural and expected performance information.Thirdly, considering the nonlinear characteristics of suspension system, nonlinear suspension dynamics equation of a quarter vehicle model is established, and then its nonlinear control scheme using the HOSM control is applied, including linearizing the nonlinear active suspension system based on the feedforward and feedback linearization method, controller design for the linearized control system, and de- linearizing.Finally, advantages of the proposed HOSM controller are illustrated in the present study through simulations. The performances of the holographic optimal SM control, the fuzzy logical SM(FLSM) control(the FLSM controller instead of the general optimal SM controller because of the general optimal SM control cannot work in the linearized control system) and the passive suspension are compared.The study results of this paper about design methods of holographic optimal sliding mode controllers for vehicle active suspensions will provide important reference for future theory and test study of active suspension which is of certain theory and practical engineering significance.