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A Torque Conversion Solution to the Powertrain of Mobile Machine and Its Control Strategy

The demand for reducing fuel consumption and emission of mobile machines is increasing since they consume large amount of energy and generate huge exhaust each year. The wheel loader is a representative mobile machine and large wheel loader typically employs a hydrodynamic torque converter and an automatic transmission in the powertrain. The torque converter provides large torque amplification at low vehicle speed, however generates large amount of heat inside. This brings a challenge during frequent vehicle start and stop. In this study, an alternative torque conversion solution to the powertrain of mobile machine with a power split hydraulic transmission is proposed, where the hydraulic transmission is a substitute for the torque converter. It eliminates overheating problem by dissipating the heat inside through its outlet. The mathematical models of the proposed powertrain including the wheel drive and working function are developed. An engine-speed-based system optimization is conducted and a rule-based control strategy based on optimization results is developed. The engine operations and engine fuel consumptions with optimization-based and rule-based control strategies are compared using three different loading cycles (57 s, 30 s, 90 s). The results show the effectiveness of proposed powertrain solution and its control strategy.