Tension Feedback Control for Musculoskeletal Quadrupedal Locomotion over Uneven Terrain

Musculoskeletal quadruped robots driven by pneumatic artificial muscles (PAMs) have great softness. Due to the softness, the proprioceptive information of PAMs (e.g. tension) reflects the environmental information. However, how to utilize this information for stable quadrupedal gait has been rarely explored. In this work, we utilized PAM tension for stable locomotion control over uneven terrain. We newly developed a durable tension sensor and proposed tension feedback control for quadruped locomotion over uneven terrain. Our proposed controller stabilizes the trunk posture by modulating the phase of the leg. To verify the effectiveness of the proposed controller, we implement it in a simple quadrupedal model and a musculoskeletal quadruped robot driven by PAMs. Through experiments, with tension feedback, the trunk posture oscillated more stably than that without the feedback. Furthermore, over uneven terrain, the running velocity with tension feedback was higher than that without the feedback in the robot experiment. These successful results will lead to more robust musculoskeletal quadruped robots that can be employed in the real-world environment.