Stability analysis for mode switch of multi-mode electro-mechanical transmission (EMT)

Dynamics and stability control are the key factors to determine mode switch characteristics of multi-mode electro-mechanical transmission (EMT) which has been extensively applied in heavy-load vehicles as an innovative power-split transmission technology of hybrid electric vehicle. Based on cooperative work between the diesel engine with variable-speed governor and the generator with torque control, a dynamic model of time-varying nonlinear system is developed and stability criteria for mode switch of the powertrain system can be derived using center manifold theorem. The simulation results illustrate that both the load torque and torque response time of the generator are the critical factors affecting the stability properties of the mode switch. In addition, the mode switch quality determined by the hydraulic pressure characteristics of brake is also validated.