Abstract
Hybrid power technology is a practicable method for construction machinery to improve fuel utilization and reduce emissions. In this article, in order to achieve the maximum degree of energy conservation for hybrid hydraulic excavator, a study on a control strategy of the hybrid power train system for a 20-t hybrid hydraulic excavator is conducted. A rule-based method which stabilizes the engine operating points in high-efficiency area and maintains the state of charge of the ultra-capacitor in a feasible operating range is presented. Meanwhile, to improve the reliability of the ultra-capacitor, a two-stage state of charge constraint is applied. To validate the effectiveness of the control strategy, a hybrid power train system simulation loading experiment platform is built. The working characteristics and the energy conservation characteristics of the hybrid power train system are explored. Actual load profiles measured from a 20-t traditional excavator are measured and applied in the system. The experimental results show that the proposed control strategy for the hybrid power train system can improve the fuel economy of the hybrid hydraulic excavator. Meanwhile, dynamic performance of the hybrid power train system is better than that of the traditional excavator.
Highlights
With the development of society, the demand for construction machinery is increasing day by day
The state of charge (SOC) of ultra-capacitor can be expressed as where Tem + is the maximum target control torque of the electric machine works in motor mode
The same load to the two power train systems in the same period of time, the energy-saving rate of the hybrid power train systems (HPTSs) can be improved by about 6.98% compared with that of the traditional engine direct-drive system
Summary
With the development of society, the demand for construction machinery is increasing day by day. This control strategy stabilizes the engine operating points in highefficiency area and maintains the ultra-capacitor SOC in a feasible operating range as well. In the parallel type HPTS, an electric machine is employed to balance the fluctuation of the load and to maintain the operating points of the engine in high-efficiency area.
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