Vehicle Attitude Control Based On Hydro-Pneumatic Suspension

Because the road automobile running on is complexity and often changed, the automobile will often meet the condition of velocity changing or steering suddenly, these will cause the attitude of automobile changing greatly, which can make harm for riding comfort and handling and stability. Because the hydro-pneumatic suspension(HPS) has good non-linear rigidity characteristic and non-linear damping characteristic, get favor from widespread, but the attitude of automobile changing suddenly while running can not satisfy the requirement people desired.The thesis mainly research contents: (1) A physical model and a non-linear mathematical of HPS dual gas-accumulators are built up; (2) The automobile model of 18 degrees of freedom is built up; (3) Study the tactic of attitude control. The thesis can be divided into five parts as follows:(1) Expatiating the need of controlling the attitude of automobile, particularly introducing the working principles of passive suspension,semi-active suspension and active suspension.(2) Introducing HPS's development history, application status and the installation of HPS on the automobile.(3) The automobile model use HPS dual gas-accumulators, andparticularly introduce its working principles. A physical model and a non-linear mathematical of HPS dual gas-accumulators are built up, particularly calculate the HPS dual gas-accumulators's condensation and rebound journal spring force and damping force, and analysis their characteristics.(4) In allusion to the automobiles's mainly running status, on based of research precision, make the TJ7100 automobile model predigest necessarily, A automobile model of 18 degrees of freedom is built up(including the six freedoms of vehicle body and twelve freedoms of four wheels with steering, rotation and vertical motion). Particularly list the entire model's longitudinal and lateral differential eguation, the sprung mass's pitching,list and vertical movement differential eguation, the unsprung mass's vertical and rotation movement differential eguation. The automobile's imitatation model is built up utilized Matlab/Simulink software.(5) Researching the attitude control of bodywork and simulation, avtive suspension is a system has many improt and many outport. the mainly movement of the body is vertical,pitching and list movement.In design of active suspension with attitude control,the control strategy includes two control loops:inner loop and outer loop.inner loop control ride and outer loop control attitude. a separate and switch loop built up relation between inner and outer loop. Many former control strategies for active suspension can be regarded as the ride control loop operating only.the libration transfer from wheels to the body that caused by inequality unevenness road is seperated by ride control loop;the attitude loop is used to maintain the load and distribute while steering. Activesuspension controled by two loops has many strongpoints:these two control loops can be used together or operate respectively. Briefly introduce some correlate contrling theoretics,in thesis skyhook is uesed as inner loop,skyhook damp control can be regarded as a sort of optimization control,and can be used more agility than optimization control. Through choosing some reasonable correlate parameters, sympathetic vibration phenomena can be eliminate quitely, its capability better than passive suspension.Skyhook control is as good as entirely estate feedback control method, as long as a sensor installed on theautomobile body,outer attitude control force realized by forse arise implement. and then form four category suspensions: passive HPS,passive HPS with attitude controled,active suspension with skyhook control, skyhook active suspension with attitude controled. Imitatate automobile with these four category suspensions, using two category roads as import: ideal road with no powerr and sine ware road.Through imitatating, Skyhook active suspension with attitude controled which belong to two control loops strategy has good capabilites than one loop controled only, thereby validate control theory and attitude control strategy in my thesis are axactly. And that Nomatter which road model as input, passive HPS with attitude controled and active suspension with skyhook control have good capabilites than passive HPS, skyhook active suspension with attitude controled has good capabilites than anyone, suspension with two loops have good capabilites than suspension with one loop.