Semiactive Controllers for Magnetorheological Fluid Dampers

It is challenging to control the damping forces of magnetorheological (MR) fluid dampers because of the strong nonlinearity between the damping force of an MR fluid damper and the velocity across the damper, and the semiactive relationship between the damping force and the applied voltage/current. Hence, the desired damping force ought to be generated by an MR fluid damper cannot be commanded directly, only the command voltage applied to the current driver for the MR damper can be directly controlled. In this article, the configuration of a semiactive control system with MR fluid dampers is discussed and a damper controller based on signum function for MR fluid dampers is proposed. The damper controller is used to generate and adjust the command voltage to track the desired damping force determined by the system controller based on the desired and the actual damping forces. Two key factors for controlling the damping force of an MR fluid damper through a damper controller are considered in this article: (1) tracking ability of the controlled damping force to the desired damping force, and (2) energy requirement for the MR fluid damper. The characteristics of the controlled damping force and its corresponding command voltage are analyzed and compared with the Heaviside function damper controller. The simulation results show that the signum function controller outperforms the Heaviside function controller for better damping tracking ability while requiring less energy for the MR damper.