Trotting control of a quadruped robot using PID-ILC

This paper presents the development of a quadruped robot and introduces its trotting control algorithm. Dynamic control of a four-leg robot is not an easy task. Several attentions are required especially on the stability aspect. During trotting, the quadruped robot is supported only by its two diagonal legs. In this stage, the robot is unstable and easy to fall over. The instability becomes even worse with the presence of external and internal disturbances caused by the movement of legs or body of the robot. The stability of the quadruped robot is achieved by controlling its center of gravity (CoG) trajectory during trotting. The joint trajectory is controlled using hybrid Proportional Integral Derivative - Iterative Learning Control (PID-ILC). The CoG position is controlled based on the trunk attitude. The experimental results reveal that PID-ILC needs only 10 iterations before it can follow the desired path. Trunk attitude is improved three times better by having small pitch and roll angle less than ±3.7 degree.