Research On Modeling And Control For EHA Active Suspension Based On AMESim

There are three evaluation indexes of the vehicle suspension system: the vertical acceleration of vehicle body, the suspension dynamic deflection and the dynamic load of tire, which respectively reflect the riding comfort, the spring life of suspension and the tire traction. The design of suspension system should be usually considered to improve all indexes. Due to the parameters are fixed for the passive suspension once design finalizes, it is difficult to completely take into account a variety of pavement types and driving modes. Essentially it has caused the contradiction among different evaluation indexes of the passive suspension. As a kind of advanced suspension system, the active suspension technology is rising gradually, which could according to real-time pavement conditions control the output force of the actuator to ensure the best condition of the vehicle.Firstly, it needs to research the pavement models as the impact of external incentives for the vehicle suspension system. Thus it has established different pavement models, including the grade pavement model of random signal and the special road models of definite signals of step, sine and square through the system modeling and simulation software AMESim. And a simulation is carried out in time domain. Then it has studied the general composition and working principle of the passive suspension, the active suspension and the semi-active suspension as subordinate. It has established the dynamic model of 1/4 vehicle active/passive suspension. And a study on the EHA system of the active suspension is carried out. Next, it has established the simplified equivalent model according to the principle of Brushless DC Motor and the pump-hydraulic cylinder system. The following step is the combination of the models above, which would obtain the complete model of the EHA system. Then it has studied the response and error of the EHA system through simulation. And then it gets the general model of the EHA active suspension by combining the EHA model and the general model of active suspension.The control algorithm of active suspension determines the ultimate performance. The study has focused on the algorithms models of the sky-hook, the ground-hook and the PID control. Next, it has carried on the joint simulation analysis of each control algorithm through AMESim and Simulink under the excitation of different pavement models. The simulation results show that all kinds of control algorithms of active suspension compared with the passive suspension could improve one or several indexes of suspension performance generally. Due to the characteristics of different algorithms, entirely the performance of active suspension is not ideal. And sometimes even makes it inferior to the passive suspension. Generally sky damping control and PID control are much ideal control algorithms when takes account of the complexity of the algorithms and the feasibility of vehicle. It is mainly because they could effectively improve 45.6% and 41% respectively compared with the passive suspension for the most important index of the suspension system which means riding comfort. On the contrary, the ground damping control of active suspension model is better at the index of the dynamic load of tire, improving about 33.8% compared with the passive suspension. Meanwhile the index of the vertical acceleration of vehicle body just improves about 11.3%.Finally the dissertation designs a test bench of 1/4 vehicle suspension, using a set of independent electro-hydraulic actuator system to generate oscillation to simulate the pavement fluctuating. Different from other literatures of common mechanical CAM vibration table, the design of suspension test bench could generate any form of external incentives in theory. Besides, it would be more helpful for the study of suspension system, meanwhile making the structure of the test bench more compactly. Then different design schemes of test bench are simulated to build in the 3d design software CATIA to optimize and determine the final design scheme. And it selects the main experiment equipment based on the calculation and analysis, actuator and hydraulic package for example. In addition, it also plans the detail steps of the test bench construction to make full preparations for the future research.