Controlling Center of Mass in Humanoid Robot using Sliding Mode Control

Abstract

To successfully realize biped walking process for humanoid robot, a precise mathematical model expressing the dynamic characteristics for the robot is required. In previous works, the lower body of humanoid robot UXA-90 was only given kinematic model, and it was controlled by a traditional PID controller. This leads to inaccuracy in joints' velocities, accelerations when implement the controller on real robot, therefore its performance degrades over time as the dynamic characteristics were not taken into consideration. Hence, a novel controller tracking the joint trajectories based on dynamic model should be given to actually realize biped walking process. In this paper, a mathematical model describing the 12 degree of freedoms (DOFs) dynamic of the humanoid robot's lower body is derived using Euler-Lagrange method. Then, a sliding mode controller (SMC) based on the aforementioned model is used to control the joint trajectories. Finally, the simulation results are investigated through MATLAB to evaluate the effectiveness of the proposed controller.