Motion control for underactuated robots adaptable to uneven terrain by decomposing body balance and velocity tracking

Body balance and velocity tracking are important for biped robots, especially under-actuated robots, walking on uneven ground. This paper presents a motion control strategy for the torque control of an under-actuated biped robot. In the strategy, we decompose the motion control into body balance control and velocity tracking. The body balance control is used to realize body balance by controlling the body posture and symmetrical movement of the two legs. The velocity tracking is adopted to achieve the desired velocity, where the velocity and acceleration feed back to modify the target angles of the hip joints. With the proposed method, a torque-controlled robot can walk with a balanced body and stable velocity, as validated in experiments conducted for the under-actuated bipedal robot CRANE.