Direct Motion Controlled Robotic Arm

Abstract

Direct motion control, a system by which an operator’s natural motions are mapped directly onto a robotic mimicking agent, has the potential to make robotic operation simpler, more intuitive, and more capable. This thesis involved the design, manufacture, and testing of a prototype of such a direct motion control system. The prototype consisted of a robotic “follower” actuation arm and a sensored, operator-worn “leader” arm. These arms had four degrees of freedom: a finger that opened and closed against a fixed thumb; a wrist that raised and lowered in a “shooing” motion, offset from the vertical so as to more easily hold objects; an elbow that opened and closed in a “chopping” motion; and a shoulder that rotated the arm forward and backward with respect to the body. The elbow and shoulder joints sat in the same plane with vertical rotation axes, modelling a human arm laid flat atop a table, with the wrist and finger enabling motion perpendicular to the upper joints. Four potentiometers were embedded in each arm, which recorded the angular displacements of each joint. Four simultaneously run PID loop control structures managed the four motors of the follower arm to eliminate difference between its position and the position of the leader arm. To focus the project, three specific tasks were chosen: the arm should enable an operator with no prior experience to write their own name, turn the page of a book, and move a raw egg without damaging it. After manufacture, the system was tested on these three tasks. The writing task proved difficult due to the imperfections in the elbow and shoulder joint motions, but an entirely novice operator was able to turn a page and pick-and-place an egg quickly and without error on the first attempt.