MODELLING AND SIMULATION OF WIRE ACTUATED ROBOT WITH PAYLOAD

Abstract

ROV-DAKSH, Remotely Operated Vehicle, has a 6 DOF serial link manipulator arm mounted on its base. The configuration of the manipulator arm is in such a way that all the actuators are mounted near its joints thereby increasing the load carried by the actuators at lower links and make the design impractical . Due to this increase in weight, positional accuracy, safety, payload to weight ratio, and the endurance of the robot is greatly reduced. So, a proper design solution becomes necessary to make the design efficient. One of the most efficient ways of decreasing the weight of the robot is by locating all the actuators at the base and actuating the joints of the robot through tendons or wires. Therefore a suitable wire actuation technique can be proposed for driving the joints of the manipulator arm. In this work, features of the ROV-DAKSH and the mechanisms used in it are studied. Wire actuation techniques used in various literature are studied and based on which, an appropriate wire driving mechanism is proposed for the ROV-DAKSH arm. The wire actuated manipulator arm is modelled and both rigid wire drives and elastic cable drives at each joint are discussed in detail. Due to elastic cable low joint torques are needed at the end effectors. Kinematic analysis, including both forward and inverse kinematics, is carried out for the existing manipulator. Trajectory required for simulations are determined. And finally, dynamic analysis is carried out for the rigid wire actuated manipulator and elastic cable actuated manipulator by simulating in MSC ADAMS 2013.2 software. Due to elastic cable drives joint torques is greatly reduced so that payload carrying capacity at the end effector is highly increased. So, the weight to payload ratio is increased which makes the robot more efficient in working conditions.