A compact hydro-mechanical transmission solution to wheel loader propulsion system and its control strategy

Abstract

Given the need for high efficiency to wheel loader powertrain, hydro-mechanical transmission is a promising solution to wheel loader propulsion system since it enables efficient engine operations owing to its continuously variable transmission function. The current hydro-mechanical transmission consists of planetary gear set and two hydrostatic units, making it bulky and complex in controls. This study proposes a simple and compact hydro-mechanical transmission solution to wheel loader powertrain. It improves vehicle acceleration performance by providing hydraulic torque assistance at low vehicle speed. The steady-state characteristics of the proposed hydro-mechanical transmission are analyzed, and the mathematical models of proposed wheel loader powertrain are constructed. An optimization strategy is developed as a reference for the design of an engine-speed based control strategy. The simulation results of the key components of proposed powertrain are analyzed. Furthermore, the engine-speed based control strategy is evaluated by the optimization strategy in different forms of the loading cycles. The results demonstrate the effectiveness of proposed wheel loader powertrain and its control strategy.