Non-linear control strategy for handling stroke limits of an active mass driver system

In this paper, a non-linear control strategy is proposed for handling stroke limits of an active mass driver system. The control force is given by the sum of a linear function of the state of the system and a non-linear dissipative force that becomes effective in the proximity of the physical limit of the actuator. The proposed approach is a generalization of the classic skyhook strategy, where the gain coefficient is modulated by a smooth non-linear function of the displacement of the movable mass relative to structure. The effectiveness of the control law is demonstrated by both experimental tests and numerical simulations, considering a scaled-down five-story frame structure equipped with an active mass driver. The proposed non linear control law proved to be effective in reducing the structural response and avoiding the stroke limit crossing, at the expense of a small increase of structural displacements and a slight increase of structural accelerations.