Research On The Control Strategy Of Semi-active Suspension System Based On Continuous Damping Control Shock Absorber

The intelligent control technology for vehicle is blooming nowadays,advanced suspension system with effective control strategy can obviously improve the safety and comfort of driving.The application of suspension control strategy requires that the core damping adjustable unit of vehicle suspension system should be highly controllable,and its damping can be continuously adjustable.Therefore,the semi-active suspension system based on CDC shock absorber was established in this paper.The effectiveness of vibration suppression and the improvement rate of comprehensive performance under multiple control strategies were also studied.The main research points are outlined as follows:（1）Based on the analysis of the structural composition,working principle and internal oil flow direction of CDC shock absorber,the hydraulic circuit models of rebound and compress stroke were derived,the dynamic model of CDC shock absorber was established,and the mathematical relationship concerning“damping force-working current-excitation velocity”of CDC shock absorber was obtained through theoretical derivation;the variation law of external characteristics of CDC shock absorber was analyzed,and the results show that when the excitation velocity v=0-0.524 m/s and working current I=0-1.5A,the variation range of the damping coefficient of CDC shock absorber is 700-2677 N·s·m^-1.（2）The electro-hydraulic servo test bench for shock absorber and the external characteristic experiment of CDC shock absorber were established and completed respectively.Compared with the simulation results,the experimental results show that:When the excitation velocity v=0-0.524m/s and working current I=0-1.5A,the peak error between simulation and experiment can be limited between 7.6%and 23.2%,which verifies the validity of dynamics model derivation and the rationality of simulation modeling in previous part;The reason for the appearance of“inflection point”（v=0.256m/s,I=0A）in the force-velocity characteristic experimental curve of rebound stroke is that the oil pressure in the cavity of CDC shock absorber is approaching its limit,and the relief valve in CDC control valve is gradually opening for unloading.（3）The typical road excitation model and vibration model of 2 DOF semi-active suspension system of 1/4 vehicle was established,and its time domain and frequency domain characteristics of simulation analysis were simulated and analyzed,the results show that:the damping coefficient of suspension c_s is the most significant factor affecting the suspension system vibration characteristics,the most effective way to improve the comprehensive performance of suspension is to adjust the suspension damping coefficient c_s,by which the optimal driving experience can be obtained;The comprehensive performance evaluation function of vehicle suspension system H_cp（ξ,ζ）was established.Besides,the comprehensive performance evaluation standard of vehicle suspension system based on ride comfort was formulated,its content is emphasizing on improving ride comfort of vehicle and taking its handling stability into consideration,which makes the comprehensive performance of vehicle suspension system optimal.（4）Three control strategies,including PID control,self-adaptive fuzzy PID control and parallel-compound fuzzy and PID control,were introduced in the Simulink simulation model of the semi-active suspension system based on CDC shock absorber.The step excitation signal and the established typical road excitation model were used as the road input to complete the simulation analysis of time domain and frequency domain characteristics,and the evaluation function H_cp0and H_cp were used as evaluation methods.The results show that:Compared with the passive suspension system under the same conditions,the comprehensive performance of the semi-active suspension system based on CDC shock absorber is obviously improved after the introduction of three control strategies.The effectiveness of three control strategies was further compared,the results reveal that:The semi-active suspension system based on CDC shock absorber not only realizes self-tuning and self-adaptive control of its vibration under multiple different road excitation,but also emphasizes on improving ride comfort of vehicle and takes its handling stability into consideration,which makes the comprehensive performance of vehicle suspension system optimal.