Study on the impedance dynamics and control of the active suspensions based on the equilibrium trajectory error

A novel approach to design the controller of the active suspension is presented in light of the suspensions’ mechanical impedance dynamics, where the sprung-mass kinematic states, including acceleration, velocity, and displacement are comprehensively modeled considering the concept of suspension mechanical impedance. The proposed impedance controller is designed by tracking the equilibrium trajectory error of the sprung-mass states. The approximate transfer function of the active suspension is derived for choosing the parameters of the virtual mechanical impedance system. The numerical simulation of the suspension amplitude–frequency response is carried out, which demonstrates that the virtual mass and damping parameters have greater influence than the virtual spring parameter. The ride comfort of the suspension controlled by the designed impedance control behaves well in a wide range of road conditions, and the road holding with it is even better than that with the Linear Quadratic Regulator (LQR) control especially around the second-order resonance frequency. The numerical simulation and experimental comparison all demonstrate that the proposed impedance control law, which does not strictly rely on the suspension parameters, could achieve a better power economy and road holding than that of the LQR control.