Energy management strategy for a power-split hydraulic hybrid wheel loader

Abstract

Energy management strategies for a power-split hydraulic hybrid wheel loader are studied in this paper. The differences between the powertrain and the energy management system for on-road vehicles and the powertrain and the energy management system for off-road vehicles are first identified. Unlike on-road vehicles where the engine powers only the drivetrain, the engine in a wheel loader powers both the drivetrain and the working hydraulic system. In a non-hybrid wheel loader, the two subsystems interfere with each other since they share the same engine shaft. By using a power-split powertrain, this not only allows for optimal engine operation and regenerative braking but also greatly reduces the interference between the drivetrain and the working functions. An energy management strategy based on dynamic programming is developed to give full system optimization including both the drivetrain and the working functions. Both a long loading cycle and a short loading cycle are studied in this paper. The dynamic-programming-based strategy is compared with a rule-based strategy using simulation studies.