Robust L2 gain controller design for landing gear system having polytopic uncertainty and input delay

Vibration control of landing gear systems is one of the attractive topic in the last years. Traditional passive damping system cannot work effectively against different and changing operational conditions. Due to insufficient performance of passive systems semi-active and active control have been applied for vibration control of landing gear system. However, one of the important issue of active control is the existence of input delay. Input delay may occur result of online date acquisition from long distance sensors at different locations, computing the control force, transmitting data and signals to actuator and applying control force to system. Due to time delay in control input, unsynchonized control force is applied to the system and this may cause loss of control performance or even instable behavior. The other instability and performance deterioration source is parameter uncertainty. Due to modelling errors, variation in material properties and changing environment conditions, systems contain uncertainty. Robust control methods are offered for the active control applications to eliminate effect of uncertainty. Input delay and parameter uncertainty problems are the most critical issues of active control systems. In order to overcome these problems robust delay dependent controller design may be preferred. In this M.Sc. thesis a state feedback robust delay dependent L2 controller is designed in order to control of landing gear vibration. Based on the selection of suitable Lyapunov-Krasovskii functional, first a Bounded Real Lemma (BRL) is obtained which enables defining stability criteria of the system having polytopic uncertainty and time varying input delay, in terms of Linear Matrix Inequality (LMI). Then L2 controller is designed for a system having, politopic uncertainties and actuator delay by the use of extended BRL and stabilization criteria. This sufficient condition for designing such controller is given by delay-dependent bilinear matrix inequalities and a cone complementary algorithm is also utilized to solve the non-convex optimization problem. To show the effectiveness of proposed controller on landing gear vibration, simulation studies are given. Time responses of system show that the controller guarantee stability of system with time delay and parametric uncertainty and has sufficient disturbance attenuation performance.