Nonlinear dynamic model for the free rotor of the swash plate-rotating hydraulic transformer

Hydraulic transformer (HT) is an energy conservation component used in the common pressure rail system and achieves an excellent energy-saving effect in construction machinery and vehicle transmission. This paper reports a complete nonlinear dynamic model and validation for the free rotor in a swash plate-rotating hydraulic transformer (SPRHT), accounting for various time-varying effects. A parameter characterization model for the oil properties considering gas-liquid phase and pressure is described. Based on the lumped element method, the fluid dynamic model for the working chambers is established, taking account of the variation of the control volume/flow area in the working chambers and leakage. The dynamic model for the free rotor is constructed, accounting for the piston distribution and nonlinear friction. Combining the above models, the speed of the free rotor is solved by the Runge-Kutta method. The SPRHT is simulated in the AMESim. Particularly, a prototype is developed, and the dynamic test is carried out. Then the potential of the nonlinear model for the free rotor is verified. The proposed nonlinear dynamic model of the free rotor can be used for the dynamic behavior analysis and energy efficiency optimization of the HT.