An Energy-efficient Current Controller for Linearizing Electromagnetic Negative-Stiffness Spring

Abstract:
The electromagnetic negative stiffness technique has attracted much attention in developing low-frequency isolators. But its application is limited by nonlinear stiffness and energy consumption. In this paper, an energy-efficient current controller for linearizing a 2-layer electromagnetic negative-stiffness spring (ENSS) is proposed. The quadratic programming method is employed to minimize the energy of currents when linearizing the ENSS, which solves a weighted objective function which takes the constraints of the rated coil-current into account. Therefore, a parameterized control law is obtained. The optimal parameter is determined by weighting the impacts of nonlinearity and energy efficiency of the ENSS. To verify the feasibility, a prototype is constructed and the experiments are performed. When the required stiffness is -500N/m, the experimental and simulated results show that the controlled ENSS’s maximal linear stroke has an increase of 47%, and the energy efficiency has an improvement of 42% compared with the constant-current driven one.