Dynamic Analysis And Control Research Of Vehicle With Hydraulic Interconnected Suspension Based On The Hydraulic Energy-Regenerative Shock Absorber

In the traditional vehicle suspension,the vibration energy is usually converted into the heat loss energy by the orifices and damping valves in piston,while in the energy regenerative suspension,the vibration energy is converted into electric energy through different energy conversion mechanisms.On the basis of the hydraulic energy-regenerative shock absorber(HESA)and interconnectd suspension,this paper proposed a novel hydraulic interconnected suspension based on the hydraulic energy-regenerative shock absorber(HIS-HESA).The HIS-HESA can not only harvest power,but also provide the ability of anti-roll and anti-pitch.Aimming at the HIS-HESA and the vehicle dynamic performance,the research of this paper focuses on the structure design,suspension characteristics,ride comfort,handling stability and control problem.Some simulation and experiments are taken,and the specific contens are as follows.(1)Based on the full bridge type hydraulic energy regenerative shock absorber and the interconnection structure,a hydraulic regenerative interconnected suspension system for the vehicle is designed and put forward.In HIS-HESA,the four shock absorbers only need one set of hydraulic motor and generater.At the same time,four sets of rectifier bridge can keep the flow direction is high pressure accumulator→hydraulic motor→low pressure accumulator.Compared with the single HESA,the energy effiency is improved very much,and the cost is greatly reduced.According to theoretical calculation and analysis,when the suspension excitation is 1.67hz-50 mm,the HIS-HESA is 49%,which is about 2 times(23%)of the sum of the four single HESA.(2)In HIS-HESA,the accumulator can be treated as gas spring,and the oil always flows into or out from the accumulator,so the accumulator mainly plays a role of attenuating hydraulic fluctuation and eliminating volume difference.At the same time,under the special form of interconnection structure,the oil flow of accumulator is greater than the single HESA,so it can provide stiffness,which affects the vehicle ride comfort and handling stability,therefore,the accumulator stiffness characteristic should be considered in the analysis;Since the state equation of the accumulator is a transcendental equation,the analytical expressions of the instantaneous pressure,volume and flow of the accumulator cannot be directly obtained,and only the numerical solutions can be obtained.So a local linearization method is proposed in this paper to reduce the order of the accumulator’s state equation,so that the analytical solutions of all instantaneous states of the accumulator can be obtained.Becasue the accumulator stiffness and the generator impedance are coupled,it is impossible to simply decouple the suspension stiffness,so based on the "Pressure –Volume(P-V)" curve of the accumulator state change,the stiffness of accumulator is proposed,which reflects the working state of the accumulator under different suspension velocity input,and also qualitatively reflects the suspension stiffness change.(3)Based on the “flow rate-pressure loss(Q-ΔP)” characterisitcs of the hydraulic components,the model of checke valve,pipe line,haydraulic motor and generator model are established respectively.Considering the mechanical-hydraulic coupling boundary conditions,the hydraulic cylinder force expression is derivated.According to the newton’s law of motion,a 14 degrees of freedom vehicle considering the vertical,lateral and longitudinal dynamics is modeled.A simulation model of HIS-HESA is established on AMESim platform,and the parameter analysis of excitation input,load resistance,hydraulic motor and accumulator on system characteristics is conducted.The vehicle dynamics model was built on Matlab/Simulink platform,and the co-simulation model of HIS-HESA was obtained.Lastly,the influences of HIS-HESA on the ride comfort and handling stability of the vehicle was analyzed on the driving conditions of DLC(double lane change)and straight braking.(4)Considering the linear relationship between the generator’s electromagnetic torque and the circuit current,two types of current tracking circuits are proposed firstly.One is a feedback control circuit based on the load resistance regulation,and anther one is feedback control circuit based on DC/DC boost module.And through some simulations,the comparison of the effects of the two current tracking circuits can be obtained.Finally,from the perspective of structure improvement and handling stability,a HIS-HESA with solenoid valve is proposed.Through the reasonable solenoid valve control switch,it can realize two modes of ride mode and handling stability mode.The influences of HIS-HESA with solenoid valve on the ride comfort and handling stability of the vehicle was analyzed on the driving conditions of DLC(double lane change)and straight braking.(5)The relevant experimental research is taken for HIS-HESA.Firstly,the bench tests of HESA are conducted based on structure similarity,to verify the mathematical model of the hydraulic element through the force-displacement chracteristic.And the damping characteristic of HESA is obtained through some differnet simulations.In which the load current is changed to verify the motor adjustable damping characteristic.Lastly,the vehicle tests of HIS-HESA on different raods are done to analyze the influences of HIS-HESA on the performance of the vehicle.In which the suspension displacement,body vertical acceleration,power harvested,roll angle and pitch angle are measured as the evaluation indices.