Simultaneous system identification and disturbance estimation for linear time varying system with application to active suspension system

"Various control techniques have been developed in order to improve the suspension performance since late 20th century. Controllers have been developed to reject the road disturbance in case of time invariant suspension systems. Although some of these researches give good results for non-linear suspension systems with parameter uncertainties, there is not much research done which treats a time varying system. I propose here an approach based on output tracking state feedback controller with disturbance rejection for linear time varying system to tackle this problem in case of a quarter car suspension model. The proposed controller works even in case of completely unknown plants. This algorithm, combined with a pole placement controller, can be used to ensure ride comfort and to avoid damage to vehicle components. If a nominal model is known, it can also estimate time varying road disturbances which can be written as a summation of sinusoids and this estimate can be used as a preview to enhance the control performance of other vehicles. We compare the proposed algorithm with LQR tracking algorithm in simulation and superior performance is demonstrated. Bounds on the time varying parameters are derived in terms of norm of the states, within which the proposed algorithm is guaranteed to work."--Page ii.