Control strategy for a snake-like robot based on constraint force and its validation

This paper is concerned with a method for the locomotion of a snake-like robot, and proposes a control strategy based on the friction force between its body and the ground for the robot. It is said that the locomotion of a snake utilizes the friction force between the body and the ground. Our concept of a control system design is that a control law should be based on the friction force as a real snake is. A three- link serial robot is considered as an experimental system, and its mathematical models, both the equation of motion of the robot and the friction, are derived by the projection method proposed by W. Blajer. A snake-like robot has holonomic and nonholonomic constraints. The advantage of the projection method is that it can deal with these different types of constraint simultaneously in the modeling process. The friction model is evaluated by the cost function of the control system design based on state dependent Riccati equations. As a result a derived control law takes the friction effect into account. The effectiveness of the proposed method is verified and evaluated through some numerical simulations.