Control of a robotic manipulator in the polar coordinate system using a biarticular actuation mechanism

Abstract

The robotic manipulators which are actively interacting with humans should be able to emulate the characteristics and performance of human body systems. Among various approaches to this end, this paper introduces a novel coordination system to control a two link manipulator in a more intuitive and human-friendly way: the polar coordinate system to describe the motions of a two-link manipulator and a biarticular actuation mechanism. The kinematics and dynamics of the two-link manipulator are analyzed utilizing the biarticular actuation mechanism and the polar coordinate system for an effective and convenient expression of the equation of motion inspired by the musculoskeletal structure of humans, which enables the sophisticated and intuitive control of an end-effector of a two-link manipulator. The dynamic equation with the proposed coordinate system and biarticular actuation mechanism is formalized into a state space equation, and the state feedback controller is designed based on the derived state space dynamics (1) to reject undesired dynamic couplings caused by the inherent mechanical structure and (2) to realize the desired dynamic characteristics at the end-effector. As applications of the proposed method, a position tracking controller is designed for the end-effector. In addition, for implementation of the proposed method, a kinematic Kalman filter is utilized for the best estimation of state variables. The experimental verifications of the proposed method are given in this paper.