Design and Fabrication of a Robotic Arm for Material Handling

Abstract

The commercial robots are expensive for use in the educational institutions. The operation of them will not leave room for experimentation, which is necessary in an educational institution. Further a large number of components that can be used for building a robot are readily available in the market. Hence this project has been taken up to allow us to build a working robot using as many of the off the shelf components to provide the necessary flexibility. This would make it a low cost robot with enough flexibility for the students to experiment the various functions of the robot. The mechanical component of the manipulator was built with three degrees of freedom, one revolute and two prismatic joints. This configuration is most common to be used as a material-handling device for machine tools. The revolute joint was achieved by making use of a pneumatic rotary table and one prismatic joint is realized by means of a pneumatic cylinder. The second prismatic joint in the Z-direction is achieved by the use of an AC servomotor with a ball screw and linear motion elements to provide for accurate positioning capability. The gripper had been designed for cylindrical components, since this robot was conceived as a material handling unit for a CNC turning center. All the necessary design calculations had been done and the finite element analysis was carried out for the main structure. The control system of the robot was one of the crucial elements. A PC is used as a controller. The motion control was carried out with the help of a motion control card DC2-PC100. It had the ability to control 2 servo and 2 stepper motors in addition to other digital and analogue controls. Several types of sensors and actuators were used for the robot to be fully automatic. The signal conditioning circuitry was designed in house for the interfacing between sensors, actuators and controllers. The control algorithm was developed with the necessary functioning to coordinate all the joint movement as well as gripper manipulation.