Research And Simulation On The Active Roll Control System Based On A Slow-active Suspension

The performance of the suspension system directly influences handling stability,ride comfort and active safety of the vehicle.But the performance of traditional passive suspension is not able to match the requirement of the modern high mobility multipurpose wheeled vehicle.Based on analyzing the body roll angle's influence on handling stability performance during high speed turning,this paper presents the idea of "body reverse roll control" via a type of slow-active suspension using hydraulic cylinders in a serial configuration with the spring and damper elements of a typical passive suspension system for sport utility vehicles(SUV),so as to improve handling stability and active safety fundamentally without deteriorating ride comfort.The main research work are as follows:(1)A linear model with three degrees of freedom(DOF)is established in a frame of coordinates fixed on the vehicle body,including lateral motion,yaw motion and body roll motion.Then,body roll angle's influence on the handling stability during high speed turning has been analyzed based on the three DOF model.This document presents the idea of "body reverse roll control”,which means actively tilting the body toward the inside of the curve via a slow-active suspension system,so as to reduce the roll moment acting on the body,thus reducing the lateral load transfer,improving the cohesive conditions between tires and road.Therefore,the handling stability has been improved fundamentally.(2)In order to study the body roll angle's influence on the handling stability during high speed turning more accurately and comprehensively,this paper will simplify the vehicle into a multi-body system and then establish a fourteen DOF dynamic model including coordinate system transformation,body module,unsprung mass module and nonlinear tire dynamic model.And the derived model is verified by comparing with a Carsim multi-body dynamic model.(3)Simulations under the condition of J-turn maneuver based on the dynamic model of 14 DOF with different initial roll angles are carried out.The dynamic responses are compared and analyzed.And then this paper comes up with a new algorithm for calculating the target roll angle,combining with previous research findings on tilt suspension system for narrow commuter vehicles and the structural characteristics of the ordinary four-wheeled vehicle.(4)The active roll control strategy is developed based on fuzzy self-adjusting PID control method,so as to adjust to the nonlinear characteristics of the slow-active suspension system and the loading changing and the various interference factors during the roll attitude adjustment process.Under the control of this active roll controller,the function of adjusting roll angle has been achieved steadily and accurately.Besides,the problem of height and pitching disturbance is effectively controlled in the process of adjusting the body roll attitude.Finally,this paper simulates the conditions of J-turn,double line change and fishhook using the Carsim,AMESim and Matlab/Simulink joint simulation platform.The results prove that the designed active roll control strategy based on fuzzy self-adjusting PID control improves the handling stability and driving safety effectively.