Path Following Control of Lizard-Inspired Single-Actuated Robot utilizing Kinematics

The purpose of this paper is to design a path following control system based on the kinematics of the Lizard-Inspired Single-Actuated robot (LISA). LISA is a new type of robot that mimics the quadrupedal walking morphology of lizards with a four-bar linkage mechanism and can realize both propulsion and turning with 1 degree-of-freedom. To achieve this purpose, this paper takes 3 approaches: kinematics formulation, control system design, and numerical simulation. In the kinematics formulation, we formulate LISA’s turning angle, stride length, posture, propulsive direction, curvature, and position coordinate. In control system design, we design a control system that converges not only distance error but also the posture error and control input. Conditional equations that can achieve these 3 control targets are formulated using forward kinematics and reference path functions, and control inputs are obtained by solving the inverse problem. Numerical simulations verify the effectiveness of the designed control system using 3 types of trajectories: linear, circular, and a combination of circular and linear trajectories. As a result, it is confirmed that the designed control system is effective for all 3 types of trajectories and that not only the distance error but also the attitude and control input can be converged.