  Wheeled bipedal robots (WBRs) have the capability to execute agile and
versatile locomotion tasks. This paper 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. It distributes the weight onto its
hip and knee joints to improve the effectiveness of joint motors while
maintaining a relatively large workspace of the base link. 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. Compared with other alternatives, as a more accurate approximation
of the WBR dynamics, the HV-wLIP can enable more agile response and provide
theory basis for WBR controller design. Experimental results demonstrate that
the robot could perform human-like deep squat, and is capable of maintaining
tracking CoM velocity while manipulating base states. Furthermore, it exhibited
robustness against external disturbances and unknown terrains even in the wild.
