Development Of LQG Controller Of Active Suspension System For Vehicle Roll Safety

With the intensity of expressway network and the continuous new records of the car ownership,the requirement of vehicle roll safety performance is higher and higher.In order for vehicles to improve roll safety performance,this paper develops a linear quadratic gaussian(LQG)controller design method of active suspension system to directly control lateral-load transfer ratio(LTR).The main research contents are as follows:(1)Based on the vehicles steering-rolling three degree-of-freedom(DOF)dynamics models,LTR,roll angle and its acceleration are chosen to establish the comprehensive vehicle roll safety performance evaluation index.Through theoretical derivation and analyze,the conventional LQG controller design method for active suspension system cannot track the front axle steering angle to control active suspension system and control the comprehensive vehicle roll safety performance evaluation index.(2)A novel design approach for LQG controller of active suspension system is proposed based on the interference differential deformation and infinitesimal control variables increases.The LQG design approach combines the differential deformation of the front axle steering angle that satisfies the minimum phase system and the state equations of the original active suspension system into new augmented system equations.Two infinitesimals that contain control variables join in the comprehensive performance evaluation index to meet the LQG controller design conditions.(3)For a better roll safety performance control effect,subjective weights of LTR,roll angle and its acceleration are determined by analytic hierarchy process.Objective weights are determined by normalization method based on performance simulation data of the passive suspension under fish-hook maneuver which is regarded as a typical running condition.Control weights of LQG controller are calculated by combination of subjective and objective weights.(4)For coordination vehicle roll safety and ride comfort,a coordinated control strategy between vehicle roll safety and ride comfort is developed based on the vehicles steering-rolling six-DOF dynamics models.Lateral acceleration is selected as judgmentstandard to determine modes switches among active suspension system ride comfort mode,roll safety mode and rollover warning mode for reminding the driver to decrease vehicle speed.The research results show that(1)compared with passive suspension system,the developed LQG controller based on the three-DOF vehicle steering-rolling dynamics model decrease the comprehensive vehicle roll safety performance evaluation index value to 38.00%,34.31% and 40.66% and decrease the root-mean-square(RMS)values of LTR to 17.66%,18.04% and 15.89%,respectively,on the fish-hook maneuver,the slalom maneuver and the double lane change maneuver.The LQG controller only controlling LTR will increase roll angle,roll angle acceleration and the comprehensive vehicle roll safety performance evaluation index abnormally.(2)Compared with passive suspension system,the active suspension system adopting the vehicle roll safety and ride comfort coordinated control strategy decrease to 20%,20%,22.71%,44.35%,94.98%,62.46%,56.73% and 16.07% of the RMS among the dynamic deformation of left and right tires,the dynamic deflection of the left and right suspension,the vertical acceleration of the body,the roll angle acceleration,the roll angel and LTR on the right-angled bend maneuver,respectively.The coordinated control strategy has a good control effect of roll safety and ride comfort by restraining dynamic deformation of tires and suspension systems.Due to ignore road inputs,the LQG controller based on three-DOF dynamic model overestimate roll state of vehicles.The LQG controller for roll safety and driver warning device will not work timely.The research findings on the development of LQG controller of active suspension system for vehicle roll safety in this paper can offer a reference of active suspension system controller design method and roll safety control techniques researches.