Simulation and test for hydraulic electromagnetic energy-regenerative shock absorber

Abstract: With the rising concerns of global environmental issues, energy saving in automobiles becomes an important subject. In order to achieve the purpose of vibration reduction, the traditional passive shock absorber converts the vehicle vibration energy to thermal energy, and then the thermal energy is released into the air. However, the energy-regenerative shock absorber could harvest this part of the energy. This paper presents a vehicular hydraulic electromagnetic energy-regenerative shock absorber (HESA) which is designed for acquiring the vibration energy caused by road irregularity. It is composed of a hydraulic cylinder, two check valves, two accumulators, a hydraulic motor, a generator, and hydraulic lines. When the vehicle is subjected to vertical vibration, the oil in the HESA flows to the hydraulic motor through a hydraulic line, then the rotating hydraulic motor drives a generator to produce electricity. In order to consider the vibration reduction performance of the HESA, the damping characteristic was analyzed in detail. Through theoretical analysis, the damping force mathematical model of the HESA was deduced, and the calculation program was written in MATLAB, based on the HESA damping force mathematical model. The indicator diagram characteristic and speed characteristic of the HESA under the working condition of a sinusoidal displacement input of 1.67Hz was obtained from simulation tests, which was designed according to a national absorber test procedure. A test bench was constructed to verify the results of a simulation. The comparison between the bench test data and simulation data showed that the value of a compression travel damping force was smaller than the rebound travel's, and the peak value of the simulation data was identical with the value in test data. The simulation speed characteristic curve of the HESA was compared with the bench test data. However, there were some distortions in the test indicator diagram characteristic curve because of the inappropriate accumulator parameters. The influences on the HESA caused by the accumulator parameters, such as changes of accumulator pressure, accumulator volume, hydraulic motor displacement, check valve orifice area, and hydraulic pipeline inner diameter were investigated. The results of simulation analysis shows that the damping force was increased with the rising of the accumulator pressure, and decreased with the rising of accumulator volume, check valve orifice area, and hydraulic pipeline inner diameter. Besides, the rebound travel damping force was only influenced by hydraulic motor displacement, that is, the damping force was decreased with the rising of hydraulic motor displacement. The key point is that the value of a compression travel damping force was smaller than the rebound travel's, which was consistent with the traditional absorber. So we can conclude that the HESA has the damping characteristic matching with the traditional vehicle suspension system, and therefore it has some certain potential applications.