A simple, versatile robotic arm for classroom and student laboratory use

Abstract

Robotic arms are indispensable tools in both industry and education. The robotic arm currently used in the MIT class 2.12, Introduction to Robotics, is in need of revision. The arm is heavy, imprecise, bulky, and difficult to customize. The new design presented in this thesis resolves these issues while making the arm more user-friendly and inexpensive enough for classroom use. It uses Hitec HS-805BB hobby servo motors to directly drive each joint. Controlling these motors is effortless with the many commercially available servo motor drivers. Modular construction allows students to change the shape and size of the arm's workspace easily; creating and installing custom linkages is a simple task. Linkages and motor output shafts mount to a common connection shaft with one-sided cut hubs. The radial loads in these shafts are supported by maintenance-free Super Oilite bronze bearings. This robotic arm is better suited for a classroom environment than the current one. It weighs 2.7 pounds; the old one weight 21.2 pounds. Though its workspace and recommended linkage length are about 7% smaller than those of the old design are, it is 87% more precise.

(cont.) It is 60% cheaper with a materials cost of $120 for a two degree of freedom arm. The new motors have 343 oz-in of torque, which is sufficient to handle a 12 oz payload 17 inches from the joint axis or a 16 oz payload at 14 inches. Students will spend less time connecting wires and calibrating sensors. This arm should be a welcome addition to the introductory robotics classroom.