EXPERIMENTAL AND THEORETICAL EVALUATION OF THE BUOYANCY AND GRAVITY-DRIVEN UNDERWATER ROBOTS

The dynamic model of a new class of underwater robot is derived and th e validity of the model is checked experimentally. Close agreements be tween theory and experiment are attained. The interaction between the buoyancy and gravity forces acting on the robot arm, present in the un derwater environment, is used to generate torques necessary to move th e arm. The mathematical model of a multi-arm robot is developed to def ine the interaction between the dynamics of the moving weight and the robot links under the action of the resisting water drag and other ext ernal forces. The Lagrangian method is used in the formulation of the arm dynamics. The developed dynamic equations serve as means for desig ning the control laws necessary for controlling the position of the di fferent joints of the robots. The study indicates that the buoyancy an d gravity-driven robot can position a payload accurately as well as at a fairly fast speed of response. It is indicated from the theoretical and experimental study that the arm motion is created by a small disp lacement of moving weight on the power screw. Therefore, power require ment of this type of robot is just as enough to overcome the friction between the power screw and the moving weight. This features emphasize the potential of the concept as a viable means for driving underwater robots.