Research On Control Strategy Of SUV Hydraulic Active Suspension System

This paper combines the"985 project"of JLU, the second stage of science and technology innovation platform about automotive engineering, studying on the SUV active suspension system and its control strategy, mainly on the autobody stability of SUV in high speed.At present, the demanding on the performance of vehicles is increasing. Traditional passive suspension has been unable to fulfill the requirements of vehicles performance. With its own energy devices, active suspension that can adapt to the different traffic status came into being. Active suspension is a modern suspension system, it can produce the control force actively and timely to restrain external environment disturbance. It can improve riding comfort and handling stability.Back in the 1980s in Japan, Toyota and Nissan was used hydraulic active suspension in the car, creating a certain market share. Because of its cost far more than ordinary vehicles, as well as a number of other shortcomings, it didn't meet a wide range of applications. So this paper puts forward the electronic controlling hydraulic active suspension system of a simple, low cost, anti-pollution power HSV as controlling. Based on the research needs, the paper select the 2 freedom quarter body as analysis model.Designed the structure of active suspension according to the basic composition of suspension. The suspension include the controller(ECU), the HSV, the hydraulic jar. According to the structure parameter of the suspension and basic principle of design hydraulic system, have confirmed the oil source pressure and initial pressure of hydraulic jar. The HSV has been chosen using for research, its operation principle and performance parameter and PWM are introduced. PWM can be made by analog circuit, software or software and hardware combined. This chapter mainly introduces analog circuit generating PWM signal.At present, domestic and foreign scholars largely ignored the initiative to control the implementation of the components on active suspension system, and only study on the controller to directly control initiative, it is not practical application of cars. Therefore, this paper under the assumption consider control valve and actuator constitute suspension system mechanical system dynamics model and the hydraulic system dynamics model, the state-space analysis method of the average import volume of input control variable, speed for the road of jamming variables, (body vertical speed, tire relative displacement of the road) of system output variables, (body vertical speed, the vehicle deflection relative to the tire surface displacement) system state variables to the system equations of state and system output equation. As the topic of digital computer control, need to suspension systems for the state equation of discrete systems into discrete state formula. The controllability and observability of system was certificated in MATALB.Active suspension control system and reliability of program design and reasonable choice of components, controller design also play a crucial role. Sky-hook damping is a simple and feasible classic active suspension control method. In fact the vehicle widely used it. Under the sky-hook damping control theory, identified by the controller control signal d = ?Cs' kyx2, 'C sky is Equivalent to the sky-hook damping feedback gain. Through repeated simulation results more control to finalize than sky-hook feedback gain. The typical road signal input awning active suspension damping control system is effective isolation properties effectively improve vehicle ride; it analyzes the high-speed switching valve block zero-choice and hydraulic piping system vibration isolation performance of the impact analysis shows : When the valve block zero d=0.5, the suspension system of evaluation criteria were improved, hydraulic piping systems of a very small role in the delay. Evaluation of a suspension system performance is good or bad, evaluation of three indirect indicators are : suspension vertical velocity (or acceleration), the suspension of dynamic deflection and dynamic load tires. Therefore, application of discrete linear quadratic optimal control technology and pole configuration for the active suspension system with a design observer status is the optimal regulator controller spplication output feedback considering the three indicators to improve the performance of the suspension system. Application AMESIM multidisciplinary simulation software for the entire suspension system simulation. Simulation results show : state observer in a timely tracking system state variables, optimal control active suspension system than sky-hook damping active suspension system to achieve overall performance improved.Digital controller is the core of the active suspension system. This paper describes how to apply the SCM on designing sky-hook damping digital controller and optimal digital controller. This paper gives the software program diagram. And the paper introduce how to generate PWM signal by SCM timers through software program. The computer can't drive the HSV because fo the small output power. So design the driving circuit consists of VMOS, voltage synchronous devices, optoelectronic coupler. Finally, the HSV unload flow test carried on by utilizing the multi-purpose hydraulic test-bed. Its unload flow-duty curve was fitted by polynomial-fit method in MATLAB.