Posture control of redundant manipulators on the norm of task space stiffness optimization

This paper investigates the posture of the manipulator that has redundant DOF similar to human upper extremity. The human arm naturally takes a posture with no wandering although it has one or two DOF redundancy. The authors consider that the posture will be determined in task-oriented, which means that human unconsciously takes a posture of his/her upper extremities, which is suitable for the task that the endpoint is about to do. This study also assumes that all joints are capable to adjust the joint stiffness so that the stiffness of the endpoint in the task space is also adjustable. Hence our study aims to establish the theoretical method to make the manipulator take a posture that provides a stiffness of the endpoint suitable for the task. The new formula for shaping the manipulator's posture to provide a desired stiffness of the endpoint is presented followed by the simulation study to verify it.