Research On Working Stability Of Electro-mechanical-hydraulic Coupler

The electromechanical-hydraulic coupler overcomes the shortcomings of the traditional electromechanical-hydraulic system such as loose structure,low efficiency,and single working model,and realizes the arbitrary conversion of mechanical energy,electrical energy,and hydraulic energy.As a new type of power device,multiple modes of electromechanical-hydraulic coupler work together need external control,and the working stability of different working modes determines the regulation and control mode,which is an important basis for building the coupler cooperative control strategy.In this paper,the working characteristics of the coupler are explored in detail,and the working stability of each mode is studied by theoretical and simulation methods,which provides a theoretical basis for the study of the electro-mechanical-hydraulic coupler and the control strategy of the whole vehicle.Based on the working principle of the electro-mechanical-hydraulic coupler for its structural design,the relevant dimensional parameters are determined,while the mathematical model is established from the perspective of coupling the two modules of hydraulic and electric motor,and the main physical parameters are obtained by using finite element analysis,which completes the determination of the whole coupler model.The electromechanical-hydraulic coupler is applied to the pure electric vehicle,and the electromechanical-hydraulic power coupled electric vehicle is proposed,and it is divided into four working modes according to the working characteristics: hydraulic mode,pure electric mode,electro-hydraulic hybrid mode and regenerative braking mode,which lays the foundation for further research on the response characteristics and working stability.The response characteristics are analyzed by establishing the equations of motion through the hydraulic mode start-up motion state,while the system state variables of the purely electric mode and electro-hydraulic hybrid mode are determined,and the state equations of the two modes are established respectively to study the response characteristics of the corresponding mode start-up,and the response times of the variables are analyzed by using the obtained coupler variable system transfer functions.Based on the differential method,the operating stability of the hydraulic model and the purely electric mode,as well as the stability of several typical operating modes of the electro-hydraulic hybrid mode is determined;again,the Liapunov second method is used to study the operating stability of the hydraulic model,the purely electric mode and the electro-hydraulic hybrid mode,and the derivative of the Liapunov function V(x)is determined to be negative definite and V(x)is positive definite using the variable gradient method,and it is determined that the three The two methods corroborate each other to form a reliable stability criterion.Based on AMEsim software,the hydraulic power model was built,and the reliability of the model was verified by simulating the pump and motor modes of the hydraulic module,and the coupler was judged to have working stability when driven in hydraulic mode;the variable system model was built according to the variable mechanism structure principle,and the coupler variable simulation was carried out;the motor power simulation model was jointly built by AMEsim and Simulink,and the coupler was judged to have working stability when driven in pure electric mode through The coupler was determined to be stable when driven in pure electric mode through simulation;the electro-hydraulic hybrid model was built by combining the hydraulic and motor power models to verify that the coupler has working stability when driven in electro-hydraulic hybrid mode.