New Design of Minimized Torque and Actuators for Industrial Robot Arms

Abstract

Reducing the torque and number of actuators has received great attention because it minimizes both the initial and running costs. This paper introduces a new design for the robot end-effector that reduces the Degree of Freedom (DoF) from 6 to 3. A compressor is employed to generate a vacuum during a vacuum cup. Since atmospheric pressure equalizes itself and the air fills any missing gaps. This pressure moves and pushes against the air outside of the suction cup. This allows pulling and picking up plates of metal or glass in industrial applications. Also, all actuators (three actuators) are installed in the robot base. Then they are linked to a four-bar mechanism to transfer the power to each joint. The four-bar mechanism transfers the power from the actuators to move each joint. Four-bar linkage consists of three rigid moving links connected with the frame. The four-bar mechanism provides rotating and oscillating and relatively high flexibility(high redundant). Installing the actuators in the base makes the arm lighter than the conventional design thus reducing the required torque to operate each joint. The optimization of the robot to select the optimal material and cross-section area is conducted using the Finite Element Method. The torque derivation based on the Lagrange theory is presented. The reduced torque of each joint and total power has been evaluated and compared with the conventional ones. It is observed that the maximum percentage of reduction in the torque occurs at joint 2 (68.1 %) where the torque is reduced from 5.8 Nm to 3.5 Nm for 15 S trajectory time. Besides, it is found that the percentage of reduction depends on the trajectory time, the joint number, and the payload.