Softly Stable Walk Using Phased Compliance Control with Virtual Force for Multi-Legged Walking Robot

Abstract

For the multi-legged walking robot, in order to decrease impact force between the foot and the terrain when the foot lifting and landing to realize its better stability, we did the following studies. We introduced a phased compliance control using virtual compliance force for multi-legged walking robot, which can effectively reduce the impact force when the robot walks. Concretely, we add a virtual compliance force to change the trajectory of the foot before the foot contacts the ground based on the conventional compliance control. And then, we divide the walking movement into six phases to adjust the compliance gain to realize reducing the impact force when robot lifting and landing leg in the same walking speed as the conventional compliance control. We designed a hierarchical control system for multi-legged walking robot, which is combined the proposed phased compliance control with a posture and vibration control based on virtual suspension model, to realize the stable walking on unknown rough terrain. According of the walking experimental results of pentapod gait and tripod gait using a sixlegged robot, the impact force between the foot and the terrain is reduced about 70%, the changes of pitch angle and roll angle of the robot body are decreased about 50% using our introduced method comparing with the results using the conventional compliance control, so the effectiveness of the proposed method for multi-legged walking robot was verified.