Nonlinear feedback control of a stroke limited inertial actuator using a state estimation approach

Inertial actuators can be used with velocity feedback controllers to reduce structural vibration, but the finite stroke length can affect the behaviour and the stability of the control system. Stroke saturation results in impulse-like excitation, which is transmitted to the structure and may result in damage. Moreover, the shocks produced by the impacts reduce the overall damping and eventually leads to instability and limit cycle oscillations. This paper examines the implementation of a nonlinear feedback controller in order to avoid collisions of the proof mass with the actuator's end stops, thus preventing this instability. Firstly, the nonlinear model of a stroke limited inertial actuator is identified experimentally. Secondly, a nonlinear control strategy is presented, which actively increases the internal damping of the actuator, and its experimental implementation is discussed. Finally, the estimation of the relative proof mass velocity is presented using the nonlinear model of the actuator and an extended Kalman filter algorithm.