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The RoboArm

Each checker played by the computer is moved over the selected column and dropped by a robot arm (RoboArm) on loan to the college by Goldenrod Research Corp of Spalding, NE. The arm has five degrees of freedom: the base (Motor 1), the shoulder (Motor 2), the elbow (Motor 3), the wrist (Motor 4) and the hand (Motor 5) [1]. The base axis is oriented vertically, allowing of left/right motion for the arm. The shoulder axis is oriented horizontally allowing the ``upper arm'' of movement about the vertical. Approximately of movement toward the rear of the unit and approximately toward the front are allowed. The elbow axis is also oriented horizontally to allow the ``forearm'' to move up or down from the horizontal. Total movement allowed for the elbow is . The wrist axis runs parallel to the forearm, allowing the hand to twist. This axis was not used in this project. The hand motor allows opening and closing of a gripper attachment. All motors in the RoboArm are free-running DC motors.

The robot provides an RS-232 connection for command messages. Each command message to the robot consists of one or more bytes, the first of which is the command byte. For commands which indicate movement (except open and close), a subsequent argument byte is sent representing the number of degrees to move.

Command sequences may be stored in a buffer for later execution. This feature was used for all movements during game play. There is no indication of when a command has been completed, and if a second is sent before the first is finished, the first will be terminated. Consequently, all movement commands necessary to pick up a checker, move it over a column, drop it and then return the arm to the pick-up point are loaded into the buffer and executed as a sequence.



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Brian L. Stuart