Photograph of Phase I Arm at Worcester Regional Science Fair, held at
Worcester Polytechnic Institute. Phase I
was, in several ways, a surprise to many people. It was surprising that the
initial version was completed in less than a month, and it was even more
surprising that it worked. Many thought the idea of attempting to create a
computer-controlled robot arm from scratch was crazy for a 14 year old high
school freshman. However, encouragement from my advisors, parents and friends,
perseverence, and a little bit of luck led to success.
This success and the potential for improvements in the design were primary
motivators for the work that would follow.
||Fall 1989 - Spring 1990
||Wood, steel, carpenter's glue, sheetrock screws, hot glue, nylon
mason's line, duct tape, erector set parts, miscellaneous plumbing
parts, conductive IC foam, lazy susan bearing,
toy truck motor, surplus satellite dish rotator motors, surplus small DC
|Degrees of Freedom
||Three plus grip (rotary base, shoulder, elbow). Semi-spherical work
||Winching nylon line around a pulley on DC motors to raise joints. Gravity
needed to lower joints. Base used a feed-through style winch with
tensioning springs to rotate base on a lazy susan bearing.
||Three potentiometers (one per degree of freedom). Limit switch on
base rotary motion.
||Atari 800XL and Atari 130XE used at different stages of development.
At one point an Atari 800XL had been re-packaged into a
home-made wooden tower case. Atari 1050 and
XF551 floppy drives and ICD SpartaDOS X were used during development.
||Bidirectional joystick ports for digital I/O, paddle controller inputs
for analog-to-digital (ADC). The first version of the interface box was
constructed in a discarded small DEC case. It was a mess of
wires and PC boards. It used reed relays directly driven from the digital
I/O lines of the Atari to drive larger relays, which drove the motors.
The final revision of the external box improved
wiring and reliability considerably, using transistors driving relays
for motor control.
||Written entirely in Turbo BASIC XL on the Atari 8-bit, using both
MyDOS 4.5 and SpartaDOS X (later versions). Provided simple automated
tasks via subroutines (no structured arm task language). Several
diagnostics tools also written.
||Pre-programmed pick-and-place operations with mediocre repeatability,
manual operation via joystick.
This shot shows the Phase I arm gripper holding a wooden block. Note the
ill-fated dual motor design of the gripper. The Phase I arm was entirely
dismantled and an entirely new arm was constructed for Phase II
(several pieces were saved such as the rounded shoulder supports, motors,
The Phase Ic interface box sitting atop an Atari XF551 floppy drive.
An Atari 800XL computer repackaged into a tower case, complete with
|RACS 1.x software intro
||RACS 1.x menu example