Investigation of Driving Torques at the Joints of Industrial ‎Robot Arms based on the Topology Optimization Technique

This paper presents an investigation on the driving torques of industrial robot arm joints using the structural optimization method for Upper Arm (UA) link. The optimal criteria mention reducing the mass of UA link. The static and dynamic analysis problems are considered when robot moves in the vertical plane and in space. Results of these problems are used to perform the optimization of UA link structure. Stress and displacement values in static and dynamic analyses of the optimized link with a weight reduction of 39% and over 45% in volume show that it ensures to meet the set optimal criteria. A mathematical model of 6 degrees of freedom (DOF) robot is established to determine the kinematic and dynamic equations. The inverse kinematic and dynamic problems solving the algorithm of the redundant robot is effectively applied to determine the input values with the given motion trajectory of the end-effector point in the workspace with two different trajectories in a plane and space. The analysis results show that there is a change in driving torque values in a direction favorable for the operation of the joints for any trajectory when the mass of robot reduces. This is also verified by a simple 2DOF robot model presented in the Appendix with three different optimization methods. The reported results have essential implications for application of various topology optimization issues in order to positively change the driving torques at joints while well ensuring the functionality of robot arm.