Compliant Walking Control for Hydraulic Driven Hexapod Robot on Rough Terrain

This article describes the proposed force-based walking method for hydraulically driven hexapod robot named COMET-IV, to walk on the large scale rough terrain. The trajectory is designed where foot step motion for each leg is decided by vertical force on the foot that is calculated from cylinder torque of thigh and shank. This proposed walking trajectory is established with compliant control strategy, which consists of force control based on position range from the trajectory motion signal. This force controller is dynamically control ON/OFF by proposed decision algorithms that derived from the changes of kinematic motion of the trajectory itself. In addition logical attitude (body) control is designed as a part of the decision control module that makes a pre-calculation of decision making based on leg sequence changes. For more stability dynamic swings raising control is derived from trajectory equations to perform a different degree of swing rising for each leg when the robot stepping on the different level of terrain. All proposed controllers are verified in the COMET-IV actual system with walking on the designed rough terrain platform consists of random levels of hard bricks and rubber pads.