Design and Control of a Bio-Inspired Wheeled Bipedal Robot

Wheeled bipedal robots (WBRs) have the capability to execute agile and versatile locomotion tasks. This article focuses on improving the dynamic performance of WBRs through innovations in both hardware and software development. Inspired by the human barbell squat, a bionic mechanical design is proposed and implemented as shown in Fig. 1, where the torque load could be evenly distributed onto the hip and knee joints to reduce peak torque and alleviate potential overheat, improving the effectiveness of joint motor torques while maintaining a relatively large workspace and maximizing the load capacity. Meanwhile, a novel model-based controller is devised, synthesizing height-variable wheeled linear inverted pendulum (HV-wLIP) model, control Lyapunov function (CLF) and whole-body dynamics for theoretically guaranteed stability and efficient computation. The HV-wLIP surpasses other alternatives in terms of agility by providing a more accurate approximation of wheeled-bipedal locomotion and provide theoretical base for WBR controller design. Experimental results demonstrate that the robot could perform human-like deep squat motion, and is capable of tracking center-of-mass velocity while manipulating base states; furthermore, it exhibits robustness against external disturbances and unknown terrains in the wild.