Motion and Gesture Compliance Control for High Performance of a Wheeled Humanoid Robot

Humanoid robots have the potential to help or even take the place of humans working in extreme or undesirable environments. Wheeled humanoids are robots that combine the mobility of mobile platforms, and the dexterity of an articulated body with two robotic arms. To perform like a human being, these robots normally are designed with a high center of mass, which makes it challenging to maintain stability while achieving high performance on complex and unpredictable terrain. Inspired from how humans react to balance themselves, a compliance control method is studied to help the wheeled humanoid robot developed at the Robotics Laboratory at Cal State LA achieve high dynamic performance while scouting over uneven terrain. Lagrange-Euler method is used to obtain the dynamic model of the humanoid robot. Then a nonlinear sliding mode compliance controller is derived and proven to ensure asymptotic stability of the humanoid robot while tracking desired reference trajectories. Finally, the performance of the proposed compliance control system is demonstrated using simulation. The results show that the robot successfully tracks a given input while maintaining balance based on the proposed tip-over avoidance algorithm.