DESIGN, MOTION PLANNING, AND CONTROL OF A SPHERICAL PARALLEL MANIPULATOR WITH COAXIAL INPUT SHAFTS

Abstract

A special class of parallel manipulators, known as spherical parallel manipulators (SPMs), can offer a t hree d egrees-of-freedom ( 3-DOF) p ure rotational motion. Among the various 3-DOF SPMs that have been developed, the most commonly used one is the 3-RRR type SPM. Many applications, such as machining, target tracking, and object stabilization require full-circle or infinite roll rotation from an SPM. Hence, this thesis aims to design a coaxial SPM with an infinite r oll r otation f eature, which could b e used in such applications. The thesis starts with a kinematic analysis of the proposed coaxial SPM model, providing methods and algorithms for obtaining unique solutions to the forward and inverse kinematic problems. Then, it is followed by a numerical estimation of its Cartesian workspace and configuration space ensuring no singular configurations o r c onfigurations wi th li nk co llisions. To pe rform li nk collision checks, a simulation model of the coaxial SPM was created in the CoppeliSim robot simulator for the first t ime. It was found that for the given SPM geometry its maximum tilt is equal to 39∘. Then, a convex approximation of the obtained configuration s pace w as obtained. Subsequently, it was used in a constrained control for external target tracking with joystick, and object stabilization based on the IMU orientation sensor measurements. Results presented in this work are supplemented with examples, and the final prototype of the functional motion control system based on a coaxial SPM structure is presented.