Tracking Control of Lizard-inspired Single-actuated Robot Utilizing Posture Compensation

—Control System Design and Experiments—

Abstract

The purpose of this study is to implement a trajectory-tracking control system with attitude compensation for a new 1-DOF-driven robot called Lizard-Inspired Single-Actuated Robot (LISA). Previous studies have proposed various morphologies for 1-DOF robots, which present certain challenges. LISA, a multi-legged robot capable of propulsion and turning within a single DOF, overcomes these challenges. In this study, we formulate the kinematics of LISA, considering turning angle, stride length, posture, and turning radius. A unique robot coordinate is defined to derive the kinematics, enabling a symmetric representation of crucial state quantities such as turning angles and link angles. Subsequently, we design the trajectory-tracking control system with attitude compensation, comprising feed forward control, PD control, and attitude compensation control. This control system exhibits the characteristic that, when LISA has a significant attitude error relative to the reference trajectory, the attitude compensator corrects LISA's orientation, while PD control is employed for smaller errors to control LISA's trajectory. This characteristic is achieved by tuning the output ratio of the PD control input to the attitude compensation input. The effectiveness of the designed control system is initially validated through numerical simulations, employing linear and circular trajectories for verification. We also demonstrate that the control system proposed in this paper has a broader stabilization region compared to the conventional LISA control system. Finally, we verify the effectiveness of the designed control system through implementation experiments, confirming its efficacy as a trajectory-following control system for LISA.