The control strategy for improving the stability of a powertrain for a compound hybrid power excavator

Abstract

Nowadays, hybrid power excavators are an active research subject in the construction machinery area. The primary focus of this study is to investigate the control strategy for improving the stability of a powertrain for compound hybrid power excavators. First, the power flow and the dynamics of the powertrain of compound hybrid power excavators are analysed. It is concluded that the control strategy for compound hybrid power excavators has to guarantee the charge and discharge priority for operation of the swing and the boom lowering. Otherwise, large-scale switches of the operation point of the engine have to be performed in order to keep the state of charge in the appropriate range, which results in worse stability of the powertrain. Then, an improved rule-based control strategy is presented, which incorporates a load torque distributor, a charge-sustaining strategy and a dynamic torque compensator. The simulation model of a 20 ton compound hybrid power excavator, namely the ZE205E hybrid, is established. The improved rule-based control strategy, the thermostat control strategy and the control strategy presented by Yoo in 2009 are compared with respect to the stability of the powertrain and the fuel consumption through simulations. The simulation results show that the improved rule-based control strategy is best for the stability; however, for the fuel consumption, the improved rule-based control strategy is better than the thermostat control strategy but poorer than the control strategy described by Yoo. Taking into overall consideration the stability of the powertrain and the fuel consumption, the improved rule-based control strategy presented in this paper is more applicable for compound hybrid power excavators.