Design and Modeling of a Computer- Controlled Planar Manipulator

Abstract

This paper describes the design of a computer-controlled planar manipulator and the modeling necessary to derive the dynamic equations of motion. The planar manipulator was built as an experimental research device for work in kine matics, dynamics, controls, design, and sensor development. The device consists of three joints and three links with a gripper and operates in a horizontal plane on air bearings. The planar manipulator was instrumented for position, veloc ity, and torque feedback from each joint and is controlled either manually, using a teach pendant, or directly from a computer. A modularity feature was also designed into the robot to allow for interchanging any electromechanical com ponents and to enable structural substitutions for investiga tions into flexibility and vibrations. The completed robot successfully exceeded performance specifications and design criteria.

The next phase of the research focused on the development and evaluation of a computer model designed to simulate the open-loop dynamic behavior of the three-link, three-jointed, high-speed planar manipulator. Describing equations were developed for both the servo actuator and arm dynamics at each joint. Significant terms included were coulomb, viscous, and hysteresis damping; and centripetal, Coriolis, and cou pling inertial effects induced by relative motions of the arm structure. The model used the voltage into the power ampli fiers for each servo drive as the system input, and the joint angular position, velocity, and acceleration as the system output. Results from various inputs including a step-input function, a sinusoidal-input function, and a ramp-input func tion were found to compare closely with experimental data measured from the actual planar manipulator built during the course of the research.