The Research Of Integrated Control Strategy Of The Vehicle Active Suspension

Vehicle suspension system is an important part of the ride system due to its important role in travelling smoothness, ride comfort and operation stability. For now, passive suspension is the most widely used vehicle suspension system, because it improves vehicle ride comfort and operation stability in a certain extent, however, its structure parameters can not automatically change with external ride conditions and different vehicle states, which greatly restrictes its application. With the rapid development of micro-computer technology, mechanical and electronic technology and the improvement of human life, active suspension system will become the best solution for the higher requeston for the vehicle ride comfort and operation stability, so research on the active suspension system will be in the sense of profound realistic meaning and great foreground of application.1,the establishment of the road model and the vehicle suspension modelIt has been well recognized that the mathematical model of the controlled objects is the basis of designing control algorithm. So the control algorithm of vehicle active suspension is not exceptional. It is necessary to establish the mathematical model of road and suspension system before the design of the control algorithm, then the effectiveness of the control algorithm could be verified by the numerical simulation, meanwhile the foundation is built for the hardware in loop test platform based on dSPACE system. Firstly, the relationship of the road input between the space model and time model was introduced; secondly, the half-car four-degree-of-freedom active suspension linear mathematical model was elaborated in this paper; Actually the suspension system is a very complicated nonlinear system, finally, a kind of nonlinear passive suspension model was given .2,the design of strictly dissipative controller for active suspension based on the dissipative control theoryThe key of designing an active suspension is designing the control algorithm, which uses the external input signals to get output to drive the actuator in order to achieve the control targets of suspension system. Using different control algorithms for the active suspension would get different performances of vehicle suspension .In view of analyzing the influence of a new control algorithm for the active suspension, this paper applied the dissipative control theory to design the active suspension controller, applied supply rate function to optimize the suspension performance indexes, and finally gave the design methods of state feedback controller and static output feedback controller, which confirm that the suspension system was strictly dissipative. A strictly dissipative state feedback controller for the half car 4-degree-of-freedom active suspension was designed, and the numerical solution was achieved by using Matlab LMI toolbox. The simulations based on Matlab/Simulink environment were performed, compared with passive suspension, the ride comfort and traveling smoothness of the vehicle were improved enormously, meanwhile the active suspension was stable and dissipative. A strictly dissipative static output feedback controller for the 2-degree-of-freedom active suspension was designed, compared with the full states feedback, it only used two states of vehicle suspension to improve the performances. The results of simulation by Simulink proved the validity of the control algorithm.3,proposing a kind of active suspension integrated control strategyIt is not common that the good suspension performance were achieved by using single control algorithm in the domain of active suspension system. The main reason is that performance indexes of active suspension are in conflict by using one kind of control algorithm. Therefore, the compromise was achieved in order to enhance the overall performance. Motivated by the above discussion, this paper put forward a new kind of active suspension master-slave integrated control strategy. The core idea of it is to build two controllers, the main controller and the slave controller, which work in parallel. The main controller and the slave controller adopt different control algorithm and they are matched based on the specific circumstances of the control object. The control effect of active suspension with the integrated control strategy would be better than the one with the single control algorithm. The main controller is used to realize the whole control target, the slave controller is used to optimize certain performance parameter, therefore the overall performances of the suspension system should be improved. It is noted that the slave controller should have a small influence on the main controller.4,the research of active suspension integrated control strategy based on pitch angle optimizationThe rough vehicle body pitch motion would happen when the vehicle is running on the rough road, the vehicle is accelerating or decelerating. For some special vehicles with strict demand for pitch angle, wide fluctuations of pitch angle is unacceptable. Motivated by the above discussion, this paper put forward an active suspension integrated control strategy based on pitch angle optimization, which can greatly reduce the body pitch angle. The main controller adopted the LQG control algorithm to get the whole performances and the slave controller adopted the phase plane division control algorithm to optimize the pitch angle. The phase plane division control algorithm has the advantage of simple structure, simple control rules, easily parameter setting. So it is very suitable for single goal optimization of the system. The numerical simulation results indicated that the vehicle body pitch angle was reduced evidently by using the integrated control, which had a small influence on the LQG control effect.5,the research of active suspension integrated control strategy based on pitch angle and dynamic tire displacement optimizationVehicle ride comfort is often in conflict with operation stability. When the ride comfort is improved, the operation stability will decline correspondingly. The integrated control based on the pitch angle optimization can improve the ride comfort obviously, however the operation stability would decline in a certain extent. Motivated by the above discussion, this paper put forward an active suspension integrated control strategy based on pitch angle optimization and dynamic tire displacement optimization. The main change from the control strategy was the slave controller with an improved control algorithm, which adopted skyhook pitch angle damping control algorithm and the groundhook spring control algorithm which optimized the dynamic tire displacement of the wheel based on groundhook control theory. The situation results showed that the body pitch angle was controlled into a smaller range and the dynamic tyre displacement was optimized by choosing appropriate control parameters. Meanwhile, the slave controller had a small influence on the LQG control effect. 6,the hardware in the loop simulation test platform and experimental researchIn order to verify the control effect of the control strategy proposed in this paper, the hardware in the loop simulation test platform based on the dSPACE real time system was built when the suspension system model and controller model were ready. The road input and states of the suspension system would be simulated in high precision by using the HIL test platform, which had advantages of simple structure, short time for ready and low test cost. The hardware in the loop test platform in this paper mainly included: dSPACE real time system, automotive ECU, and Matlab/Simulink software. Firstly, the active suspension controller model was established by Simulink, then the model would be compiled into corresponding instruction code which would be downloaded to the ECU; secondly, the road model and suspension system model would be downloaded to the dSPACE system; finally, the test loop would be enclosed by the CAN bus. The effects of the integrated control strategy and dissipative control algorithm were verified by the hardware in the loop test platform, the performances of suspension system were improved evidently .The HIL test also provided important reference for the further research of active suspension control system.