Development of supervisory control algorithm for compound hybrid excavator

This paper presents a supervisory control strategy for a compound type hybrid excavator. The compound type hybrid drive train means that the parts of the hydraulic actuators are replaced by electric motors. Therefore, the required power of the replaced actuator should be provided by the electric energy storage device. This structure makes it difficult to design the supervisory control strategy, since the consumed energy by the electric motor causes the charge sustaining problem. To that end, hybrid supervisory control algorithm has been proposed in this paper. The algorithm composed of two parts: the optimal power distribution controller and engine set speed controller. The optimal power distribution controller determines engine assist motor power by considering the charge sustaining and fuel economy. The engine set speed control strategy determines engine set speed based on the pump load to shift engine operating points to the optimal operating line. The performance of the proposed supervisory controller has been compared with the thermostat controller using simulation. The simulation results indicate that the proposed controller improves 2–3% of fuel efficiency compared the thermostat controller and show excellent charge sustaining performance.