Walking Trajectory Design of Hydraulic Legged Robot with Limited Powered Pump

A hydraulic drive system can generate a large force and is impact resistant. Thus, robots that utilize hydraulic drive systems have been developed for use in disaster areas. In a hydraulic drive system, it is necessary to design the motion of the robot within the capacity of the pump unit, but it is generally difficult to predict the required flow rate and pressure. Especially for hydraulically driven legged robots, the periodic significant changes in the required flow rate and pressure can make it difficult to select a pump and design the leg operation within pump capacity. Therefore, most operations are not designed in full consideration of the characteristics of the pump. By designing the operation of the robot considering the characteristics of the pump, improvements in energy efficiency and working speed can be expected. In this study, we theoretically derive the relationship between the leg motion of the hydraulic leg robot and the required pressure and flow rate. Based on the results, a method for designing the operation considering the characteristics of the pump is proposed, and its validity is experimentally confirmed.