Research On Control Method Of Air Spring Suspension System In Commercial Vehicle Ca

Commercial vehicle drivers work intensely for long periods of time.How to improve riding comfort and reduce driving fatigue is an important issue concerning drivers’ health and driving safety.In view of the lack of research on cab suspension system at home and abroad,taking a domestic heavy commercial vehicle as a reference model,the four-point suspension cab air spring suspension system was studied,and damping adaptive control based on CDC damper and posture control based on air spring were realized.Firstly,the working characteristics of the air spring in the suspension system are described in detail from the stiffness characteristics and frequency characteristics,and the charging and discharging system model of the air spring is constructed.Based on the working principle and experimental data of CDC shock absorber,the relationship of "excitation velocity-input current-damping force" was obtained,and the model of shock absorber was completed.According to different simulation requirements,taking Class C and Class A pavement as examples,the simulation model of single wheel pavement and vehicle pavement were established respectively,which provided the basis for ride comfort and posture control of cab suspension system.Secondly,in order to obtain the basic parameter of cab mass,a Recursive Least Squares(RLS)method of cab mass acquisition for commercial vehicles was proposed.The feasibility of the estimation method was verified in MATLAB simulation environment and real vehicle testing environment respectively.Finally,this parameter is used in the research of ride comfort and posture control of cab mounting system.Thirdly,aiming at the cab ride comfort problem,the CDC damper adaptive adjustment is realized based on the fuzzy adaptive PID algorithm.Using the 1/4 suspension model,the air spring is simplified into a spring model with fixed stiffness,and the feasibility of the simplified model is verified.Based on fuzzy adaptive PID algorithm,the cab semi-active 1/4suspension system model is established in MATLAB/Simulink environment to realize adaptive adjustment of damping.The simulation results show that the root-mean-square value of cab vertical acceleration decreases by 26.6% under class C road surface,which improves ride comfort.Finally,aiming at the problem of excessive cab inclination under braking and steering conditions,a cab posture Control method based on Model Predictive Control(MPC)was proposed.The dynamics model of 7 degrees of freedom cab air spring suspension system is established.On the basis of the original MPC,the first difference and second difference of the output are introduced into the cost function to realize the limitation of the acceleration and impact of the output(vertical displacement of cab,side Angle and pitch Angle).The simulation of cab posture control under braking and steering conditions is completed.The results show that the root-mean square of cab pitch acceleration decreases by 58.0% under emergency braking conditions(the deceleration is 0.5g).Under steering conditions(lateral acceleration is 0.1g),the root-mean-square value of cab side Angle acceleration decreases by89.3%,which greatly improves occupant comfort during braking and steering.