Limit cycle prediction of robot systems with nonlinear phenomena in the joints

This paper analyses the control of industrial robots with dynamic phenomena at the joints such as friction, backlash and flexibility. The article adopts the describing function (DF) method for the study of stability and the prediction of limit cycles. For the robot, the DF's are evaluated by decoupling the link inertias and considering only the diagonal constant inertial effects. The controllers studied are the first order model and the second order model variable structure controllers. The results show that the best case is the robot system with nonlinear friction, while the worst in the manipulator system with backlash.N/