Simulation analysis on hydraulic-electrical energy regenerative semi-active suspension control characteristic and energy recovery validation test

Abstract: To recycle the vibration energy of vehicles over rough roads, a vehicular hydraulic-electrical energy regenerative semi-active suspension (HERSS) was designed in this work. Simulations and bench tests were performed with focus on its suspension performance and energy harvesting characteristic, respectively. The key component in the HERSS was the hydraulic-electrical energy regenerative absorber (HERA), and the HERA was composed of a hydraulic cylinder, three check valves, two accumulators, a hydraulic motor, a generator, and hydraulic lines. Firstly, on the basis of the HERSS principle, the system configuration and working principle were described. The test bench was constructed according to the HERA theory, and the speed characteristic curve of HERA was obtained through bench test. Secondly, the two degrees of freedom HERSS dynamic model was constructed. From the model equation, damping force of HERSS contained viscous damping force and motor control force. The viscous force was the inherent damping characteristic of HERSS caused by throttle resistance of check valves, frictional resistance of pipe lines, throttle resistance of hydraulic motor. The motor control force can be adjusted according to the control strategy. According to the HERSS principle, the motor control force can be adjusted in the extension stroke only and as such, the control strategy can be used to identify suspension motion state. When the suspension in the compression stroke, the motor control force could not affect the HERSS, but in the extension stroke, the motor control force was variable according to the control strategy. In order to evaluate the HERSS performance, sprung mass acceleration, suspension deflection and tire dynamical displacement were chosen as assessing index. Then, the Linear Quadratic Gaussian (LQG) controller was designed for HERSS. In the processing of LQG design, the weighting coefficient of HERSS performance index was determined by Analytic Hierarchy Process (AHP). Thirdly, the performance of HERSS with LQG control was compared with passive suspension (PS), traditional semi-active suspension (TSS) with LQG control through simulation tests. The frequency results indicated that: (i) in the resonance frequency of sprung mass, the amplitude of suspension index parameters ranked in a descend order, PS, HERSS and TSS. The results reflected that LQG strategy could reduce the sprung mass vibration effectively. And because HERSS could not change its damping force during compression stroke, its effect of vibration elimination was better than the PS, but worse than the TSS; (ii) in the resonance frequency of unsprung mass, the amplitudes of sprung mass acceleration calculated by three models were similar. The amplitudes of suspension deflection were too small to display as frequency of peak. And the amplitudes of tire dynamical displacement ranked in a descend order, PS, HERSS, TSS. In general, in the resonance frequency of unsprung mass, the differences of amplitude of suspension index parameters were very small; (iii) in the transition frequency band, which was between the resonance frequency of sprung mass and the resonance frequency of unsprung mass, the amplitudes of sprung mass acceleration and tire dynamical displacement ranked in a descend order, TSS, HERSS, PS. The differences of amplitudes of suspension deflection were small. Lastly, the absorber dynamical displacement data was collected through road test. The acquisition data used in energy harvesting bench test as input signal. The bench test results showed that the HERSS was feasible, and the harvested energy power and energy harvesting efficiency of HERA were increasing with the rise of the control current.