Study On The Characteristics Of An Adjustable Damper With Temperature Compensation

Vehicle ride comfort will have a direct impact on passengers’ comfort and vehicles life.Vehicle suspension system is the key to improve ride comfort. An adjustable damper hasbecome the main researching direction in the semi-active suspension. The most part of heatthat shock absorber produces is absorbed by damper element and internal oil. It leads toincrease oil temperature of the shock absorber. Due to the dissipation of energy, thetemperature of the damper increases and influences its damping behavior. Especially, when avehicle runs over a long rugged track, these effects are much more strongly. However, mostscholars tend to ignore that the changes of shock absorber oil temperature may influencedamping characteristics. Therefore, this paper focuses on that the shock absorber oiltemperature affects the damping characteristics and proposes the solution of temperaturecompensation.By analyzing working principle and heat Principle of adjustable damper, this paperestablishes mathematical model and thermodynamic model. By Combining with shockabsorber temperature characteristic test, the paper constructs the relationships betweendamping force, speed, current and temperature. Based on the optimal control theory, thepaper designs the semi-active suspension control system. In this paper, researches ofadjustable damper characteristics and the conclusions are as follows:1) Establish the mathematical model of adjustable damper. Firstly, analyze theadjustable damper structure and working principle. Secondly, according to the knowledge offluid mechanics, build the simplified damper system model. Thirdly, validate the adjustabledamper modelis by Matlab/Simulink procedure.2) Establish the thermodynamics model of shock absorber. According to the First Lawof Thermodynamics, the equations on heat conduction, heat convection, as well as radiationheat transfer are analyzed, and equilibrium temperature of shock absorber is calculated.According to the relevant temperature test, the shock absorber force is influenced on the viscosity temperature characteristic. It is concluded that damping force decreased slowly inthe condition of low temperature. Damping force decreased rapidly in the condition of hightemperature. Temperature characteristics also impact on the current.3) Design control strategies to realize semi-active suspension with temperaturecompensation function. Establish a quarter vehicle model and deduce the state equation ofvehicle system. Based on optimal control theory, the optimal damping force is obtained.Compare the state response of three kinds of suspension (passive suspension, semi-activesuspension without temperature compensation, semi-active suspension with temperaturecompensation). When the temperature is100℃, compared to the passive suspension, thebody vertical acceleration values semi-active suspension without temperature compensationdecrease14.45%, the body vertical acceleration values of semi-active suspension withtemperature compensation decrease25.43%. When the temperature is20℃, the bodyacceleration values of the passive suspension are the same as semi-active suspension withouttemperature compensation and semi-active suspension with temperature compensation. Sothe paper concludes that the semi-active suspension with temperature compensation greatlyimprove vehicle ride comfort.