ABSTRACT:

This paper explains the modelling and simulation of manipulator with six degrees of freedom for under water simulator applications. Dynamic simulation has been carried out to obtain the possible trajectories of all degrees of freedom. The legs of the motion platform are made up of UPS joint structure (Universal - Prismatic -Spherical) to achieve six degrees of freedom. Inverse geometric model is developed for calculating the link length variation for different motions such as surge, sway, heave, roll, pitch and yaw. The platform proposed here is of 200 kg payload capacity Force analysis has been carried out for the different joints of the mechanism to select proper actuators. System simulation has been carried out to arrive at configuration and actuator dimensioning to meet specific application requirements such as large displacement heave motion and large angle of tilt for roll, pitch and yaw. This proposed parallel platform can be used to simulate various motions as well as forces acting on AUV (Autonomous Underwater Vehicle), ROV (Remotely Operated Vehicles), offshore and mining structures. This platform can also be used to simulate the behavior and control strategies of underwater robotic manipulator by integrating parallel and serial configurations. Design details, dynamic analysis, and motion simulation results are presented.

INTRODUCTION

Motion simulator of a Parallel manipulator configuration which is being proposed here is known as the Stewart platform has its origin in the design by Stewart of a 6-dof mechanism to simulate flight conditions by generating general motions in space (Stewart, 1965). Later, some of the researchers suggested the use of parallel actuated mechanisms like the flight simulator of Stewart, and built such a manipulator for mechanized work-station and performed some theoretical and numerical study including its mobility analysis and iterative solution of direct kinematics (Hunt, 1978).

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