Abstract: Increasing the power density and overload capability of the energy-supply units (ESUs) is always one of the most challenging tasks in developing and deploying legged vehicles, especially for heavy-duty legged vehicles, in which significant power fluctuations in energy supply exist with peak power several times surpassing the average value. Applying ESUs with high power density and high overload can compactly ensure fluctuating power source supply on demand. It can avoid the ultra-high configuration issue, which usually exists in the conventional lithium-ion battery-based or engine-generator-based ESUs. Moreover, it dramatically reduces weight and significantly increases the loading and endurance capabilities of the legged vehicles. In this paper, we present a hybrid energy-supply unit for a heavy-duty legged vehicle combining the discharge characteristics of lithium-ion batteries and peak energy release/absorption characteristics of supercapacitors to adapt the ESU to high overload power fluctuations. The parameters of the lithium-ion battery pack and supercapacitor pack inside the ESU are optimally matched using the genetic algorithm based on the energy consumption model of the heavy-duty legged vehicle. The experiment results exhibit that the legged vehicle with a weight of 4.2 tons can walk at the speed of 5 km/h in a tripod gait under a reduction of 35.39% in weight of the ESU compared to the conventional lithium-ion battery-based solution.

Key words: Heavy-duty legged vehicles , · Hybrid energy-supply unit , · Power fluctuation , · Optimal matching of lithium-ion battery pack and supercapacitor pack