Tool Position Control of an Upper Limb Exoskeleton for Robot-Assisted Surgery

Abstract

This paper presents a medical robotic system for tool positioning tasks in orthopaedic surgery. The system consists of an 7 DOF upper limb exoskeleton, which is attached to the arm and back of an orthopaedic surgeon, and a real-time control system with an optical tracking camera. The objective is to guide the surgeon during an operation task to follow a predefined trajectory with a surgical tool. Therefore, a control algorithm is introduced to minimize the positioning error between the desired and actual pose (position and orientation) of the tool tip. The required joint velocities for positioning tasks are obtained by solving the inverse kinematic problem of the serial kinematic chain using an extended Jacobian method. For the computation of the Jacobian matrix, a geometric approach is chosen to solve the forward kinematics problem of the manipulator links. The over-determined kinematic system of the redundant robotic manipulator is determined using basic kinematic constraints of the human joint angles. Results of the inverse kinematics solution are evaluated with simulations of positioning trajectories for drilling tasks of the robotic manipulator and show a deviation of the desired path of less than 0.8 mm. The implemented end-effector positioning controller produces satisfactory results and enables future extensions for intuitive human-machine interaction control.