The Structure Selection And Performance Simulation Of Automobile Energy Regenerative Suspension

Automobile suspension is a nonlinear vibration system which contains spring and damping components. Suspension system will lead to a random vibration because of roughness of road surface and force of vibration source such as the engine. Usually this part of vibrating mechanical energy is converted into heat energy by the automobile suspension damper and is finally dissipated to the external environment. However, with the increasing shortage of global energy sources, the development of energy-saving technology has become one of the most important trends in automobile industry. If the suspension vibration energy can be recovered and utilized, the automobile energy consumption will be decreased with the energy-saving purpose fulfilled. Based on such an idea, energy regenerative suspension(ERS) studied in this paper recovers suspension vibration energy which is originally consumed by the damper.At present, domestic and foreign scholars have proposed two methods of energy recovering: hydraulic energy-storing and electromagnetic-storing. The recovery efficiency of electromagnetic-storing suspension(ESS) is higher than hydraulic energy-storing suspension(HSS). The ESS can reduce energy demand by active suspension. And compared to HSS, ESS excels in its light additional weight, response speed and execution precision as well. Besides, ESS contributes to managing electric power supply of automobile because it converts vibration energy into electric energy. What is more, the electric trend of vehicle components'control is more suitable to develop ESS. According to the literature retrieved, there are mainly six structural styles of regenerative suspension: hydraulic, electromagnetic coil, gear-rack, ballscrew, crank-connecting rod and linear motor regenerative suspension.A detailed study on the feasibility analysis of regenerative suspension is given in the preparatory work of this subject. We choose gear-rack regenerative suspension to do the simulation test. The result shows that energy regenerative suspension can recover vibration energy and its damping characteristic is practical in meeting requirements of ordinary cars. The research of ERS focuses on maximizing fuel saving and reducing fuel consumption. However, performance of ERS and vehicle characteristics affected by it are not studied thoroughly. And the structure of energy regenerative damper(ERD) need to be improved. As a supplement and perfection to this subject, this paper intends to design a more reasonable project of energy regenerative suspension and make a further study on performance of ERS and its effects on vehicle characteristics through simulation testing. This paper mainly covers the following contents:First of all, a structure selection of energy regenerative suspension is processed.According to operation requirements of the suspension system, the author proposes six evaluation indexes of ERS, which are availability of regenerative energy, adaption relationship between damping force and device's geometry size, device's installability, structural reliability, regenerative efficiency and manufacturing cost. Then a best program is selected through an overall evaluation on six styles of energy regenerative suspension based on fuzzy entropy.Second, the regenerative damper is designed.The evaluation of structure selection turns out that the best style is ballscrew regenerative suspension. Referring to relevant information and patents, the author designs a more reasonable ballscrew regenerative suspension and illustrates its principles and structure layout. And the author also selects and designs main spare parts of ballscrew regenerative suspension, and draws the assembly diagram to make sure that the suspension resembles real prototype. Thus, the preparation is done for designing real prototypes and conducting bench tests and car tests.Finally, the simulation of ERS is conducted.Using simulation softwares like MATLAB/SIMULINK, SIMPOWER and ADAMS/CAR, the author builds a ballscrew regenerative suspension model and a vehicle model. Then the paper analyzes performance of ERS and its differences from conventional ERS. Furthermore, an analysis of characteristics of vehicles in which ERS is installed is conducted.Through the analysis of ERS, we can arrive at three conclusions: (1) From the analysis of performance of regenerative damper, we can observe that damping characteristic of ERS is similar to that of conventional viscous damper and ERS can recover energy. The indicator diagram of regenerative damper witnesses that when excitation of road displacement has the same amplitude but different frequencies, the higher the frequency is, the longer the relative displacement of regenerative damper will be and the greater the potential of recovering energy will be.However, there are some problems of ERS, such as how to overcome dead zone.(2)In the simulation of random road, performance indexes of ERS are higher than those of conventional suspension, which shows performances of the latter in dynamic state are worse than the former. But ERS meets various requirements of automobile can be employed in cars. At the same time, motor of ERS always work in transient state, and its transient damping coefficient is lower than the steady one. Deviation between the two coefficients is obvious when frequency is high.We also draw a conclusion that damping performance of ERS is more excellent in simulations of plank road and sine road. With the increasing speed and road roughness, performance of ERS in dynamic state becomes worse. This fact is contradictory to requests of recovering energy, because when vehicle speed is higher and the road is rougher, energy recovered should be more accordingly.(3) The car installed the energy regenerative suspension which is passive rides at lower speed and on flat road, the car riding comfort is well, dut the regenerating energy by regenerative suspension is few. The car installed the energy regenerative suspension which is passive rides at higher speed and on rough road, the regenerating energy by regenerative suspension is plenty, but the car riding comfort is poor. Since it is very hard to coordinate these factors, our next research concern should be focused on how to improve performance of suspension system by adding control logics of active suspension to energy regenerative suspension.