Helical Interpolation for Welding using Articulated Robotic Arm

Abstract

Robots are flexible, reprogrammable automated machines which are constrained by their physical configuration to perform tasks which are easily programmable considering degrees of freedom of their joints. Robotic hardware that has been used for particular applications can be utilized for new tasks which its structural configuration is not designed by using a customised path planning. This thesis addresses these problems with the RHINO educational robot original software interface that limited the RHINO to tasks suited for a jointed arm configuration only. A new software interface, based on a popular high-level structured language, is introduced which will make the RHINO robot useful for paths which are traditionally not used. Specifically, the inverse kinematics problem is solved for the robot at hand and used in an experiment to calculate on-line the needed position and orientation of the end effector. This important capability was not possible with the commercial original interface of the RHINO. Other advantages of the newly introduced interface; software library units; open the way for more educational benefits of the RHINO in Robotics, Digital Control, Engineering projects, and research. In present scenario, there is a need to have path interpolation for articulated robotic arm so as to follow user defined paths to be useful for inspection, welding & machining operations. This robot is used after adapting its controller to be programmable so that it can generate steps for motors employed at the joints & these motors will further control the joint angles. For more understanding & implementation of the idea, a test case of welding a cylinder liner of an IC engine is taken into account, this process takes place to recondition the worn out engine and it is done by filling material on the inner diameter of cylinder liner. To perform the described task, a consumable electrode used for arc welding is held by end effector which will follow helical path by considering the rate of electrode consumption also. To follow this path by the tool tip, inverse kinematics program is used and output of which is verified by graphical comparison of the achieved & desired path of the electrode. This is further verified & visualised using a Robotic Simulator built in standard mechanism design CAD/CAE package of mechanism design extension in Creo software.