HL Robot Arm Construction

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The robot arm Humerus Labor was built in the Kinetics and Electronics lab of the Art and Technology Studies department in the School of the Art Institute of Chicago by Ed Benett and David Juros. The process used was quite intricate. David did a great job in bringing his remarkable fabrication skills and eye for robust design to the project. The main introduction to the purpose and technology of Humerus Labor robot arm project is at HL's front page.

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The base is steel. It supports the gearbox which serves as the waist joint axis.
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The elbow is moved by a ball-screw. This screw is of very good quality. It was bought surplus and cut to length.
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The shoulder axis gearbox is designed to drive loads many times the size of our application. In the robot arm, the large shafts and axles are load bearing supports.
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The flex cable reel under construction.
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The flex cable reel uses a piece of rolled aluminum for its core.
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An adapter ring with a broached keyway.
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This helical beam coupling will compensate for unavoidable misalignment between the drive motor shaft and the gearbox input shaft.
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The elbow joint leadscrew being cut to length. It seemed odd at the time to cut a precision componant on the cutoff saw, but it's hardened steel and there wasn't another way.
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The elbow motor and leadscrew assembly being tested for the first time.
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Uing the metal lathe to drill out an adapter ring.
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Cutting aluminum plate on the compound miter saw.
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The base assembly with the base piece, limit switch actuator. mechanical stop, constant force spring (for backlash mitigation), and the Quick-Grip Screw-Clamp Bushing that attaches the waist gearbox output shaft to the base.
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Some base components including the Quick-Grip Screw-Clamp Bushing, and anti-backlash spring.
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The base drive motor and gearbox mounted on the base plate. The gearbox mounts "upside down". It is supported by its output shaft. The gearbox was chosen based on its bearing's side and thrust load ratings.
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Tapping holes in a bracket.
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The base motor assembly showing the conduit clamp, homing sensor (blue), gearbox, hard limit roller switch, antibacklash spring mount, and servo motor.
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The base motor assembly mounted on the base plate.
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Base motor assembly, nearly complete.
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View from the encoder end of the base servomotor.
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The only outside electrical connections that go into the moving part of the robot are 120 VAC power and a bidirectional RS232 serial data line (Tx, Rx, gnd). The power and data lines pass through the red conduit made of high pressure plastic tubing. Prior to cutting the tubing to finished length, the proper length is being estimated here.
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The robot arm waist can rotate almost 360 degrees. The red conduit allows the rotation without over-flexing or fatiguing the power and data lines.
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The main electronics panel has three PID controllers, one for each motor. Also present are the hard-limit emergency cutoff relays. The serial data link to the outside world is at the bottom of the panel, just to the left of center.

The main introduction to the purpose and technology of Humerus Labor robot arm project is at HL's front page.