Research Of Active Control And State Estimation For Hydro-pneumatic Suspension

Acitve hydro-pneumatic suspension（AHP） is considered to be an suitable suspensionstructure and gets the actual vehicle application,but high energy consumption,highmanufacturing costs and high system complexity seriously restrict its further developmentand its scope of application. AHP is the interconnected system which consists of suspensionsubsysyem and actuator subsystem,and theory of AHP effectively guids engineeringpractice and reduces development costs.Paper systematically discusses research of systemdynamics, control strategy and observer algorithm for AHP,combined with project practice.1.Based on bond graph theory, AHP driven by pump is taken for example to analyze itsmain parts and build its element models specifically on the capacitive field of hydraulicpump and the coupling field that oil flow through the liquid resistance, and in the endelememt models are integrated through bond graph model of AHP to obtain nolinear stateequation.At the same time,bond graph model and nonlinear equation of AHP driven byelectrohydraulic proportional servo valve are listed.2.The mechanism of force generation in hydraulic actuator coupled withhydro-pneumatic spring is analyzed,and Sliding mode force and velocity tracking controland disturbance rejection algorithm are put forward.Due to use of integral sliding modecontrol,body height adjustment for vehicle becomes possible.3.Spring compensator in parallel with suspension position sensor is designed forachieveable suspension subsystem.Design thought of state observer for suspensionsubsystem is proposed,which uses suspension working space as measured variable and usesactuator cylinder pressure as input signal.After effective combinations of state variables forsuspension subsystem are analyzed, suspension models for road displacement input androad velocity input are presented. Ignoring nolinear factor of friction, kalman observer isdesigned by means of suspension models for road velocity input,and based upon unknowinput observer theory, UIO is designed through suspension model for road displacementinput.4.On the foundation of analyzing Observability of system and subsystems for AHP,theconception of morbid observability and design thought of interconnected state observer forAHP are put forword.Nolinear factors of hydro-pneumatic spring and friction are linearizedby means of differential mean value theorem, and feedback gain of state observer for actuator subsystem is configured based on stability theory of interconnected system.Nolinear UIO for suspension subsystem is designed by method of UIO and LMI. Finallybased on stability theory of interconnected system,interconnected stability design is madefor state observer for actuator subsystem and nolinear UIO for suspension subsystem.