Velocity and Posture Selection for Torque Optimization in Manipulators with Two-Dimensional Force Requirements

Abstract

This work presents a methodology to perform a combined torque and time optimization for trajectories with particular force requirements. Usually, to reduce the time interval of a trajectory, elevated torques are required, an issue mainly when the mechanism needs to spend part of its energy to apply forces on its environment. In order to find a solution for this problem, an optimization method can be adopted. Here, the procedure is divided in two phases. First, a manipulator posture is chosen to minimize the total applied torques on the robot joints, performed by using a recently developed technique. Afterwards, from the selected posture, a set of possible joint velocities is simulated. The goal of this process is to find a threshold for the time trajectory from which the torque on the robot joints is not largely intensified. The dynamics based on a Lagrangian formulation of a two-link serial arm is applied for the mechanical modeling. By carrying out the analysis, it is possible to relate the robot posture, the velocity and the forces applied on the robot endeffector with the torque on the robot joints, to find an optimal trajectory.