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Repairing the Cable Drive of a PHANTOM Omni

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The PHANTOM Omni is a commercially available, six degree-of-freedom haptic device. In our lab, we use these devices for research and instruction, and have found that the cable drive of devices is susceptible to failure. This page describes how to disassemble the Omni and fix the cable drive.

Diagnosing a Cable Drive Failure

In our experience, the cable drive to the distal link of the Omni is the likely culprit. The link may move more freely than the other joints and you may hear a rattle inside the device (a pin which has come free). The joint encoder is mounted on motor shaft. To confirm that the cable drive is disconnected, run the "PHANTOM test" program, move the stylus, and monitor the encoders. If all but the distal link encoder show activity, then the cable drive is probably broken.

Disassembling the PHANTOM Omni

Lay the Omni on its side and remove the eight screws holding the bottom plate to the base.
Bottom plate of the Omni.
Bottom plate of the Omni.
There are three screws along each side and several screws (six in the newer Omnis) that hold the two halves of the base together. A magnetic tipped screwdriver is useful as a couple screws are deeply recessed. Carefully push the ground strap out of the way---they are fragile and will easily rip or break from fatigue if bent too much.
Microprocessor and amplifier boards.
Microprocessor and amplifier boards.
Half of the shell covering the base.
Half of the shell covering the base.
Remove the faceplates by inserting a small screw driver along the edge of the plate and prying free.
Faceplates cover nuts that hold the turret cover in place.
Faceplates cover nuts that hold the turret cover in place.
Two nuts underneath the left and right faceplates hold the left and right turret shells. First remove the LEFT shell (as viewed from the front of the Omni.) Additional screws that are only accessible from inside the turret secure the right shell. Two pliers are needed unless you have a set of very small socket wrenches.
Nut holding the turret cover.
Nut holding the turret cover.
The right turret shell is held by screws that are accessible once the left shell has been removed.
Turret with LEFT shell removed.
Turret with LEFT shell removed.
Turret without covers.
Turret without covers.
Remove the top and bottom arm covers on the first (proximal) link to access the

cable drive for the second (distal) link.

The bottom cover on the arm is held by a screw at the turret end (accessed by lifting the arm). The top cover is held by a  screw at the proximal end of the arm that is accessible after removing the  bottom cover
The bottom cover on the arm is held by a screw at the turret end (accessed by lifting the arm). The top cover is held by a screw at the proximal end of the arm that is accessible after removing the bottom cover
The photos (right) show how the distal-link cable drive should wrap around the post and screw before connecting to the cable-tension spring. We have found that the post can work free over time. To avoid repeatedly fixing the cable drive, replace the post with a screw.
Close-up of the cable drive for the distal link.
Close-up of the cable drive for the distal link.
Close-up of the cable drive for the distal link.
Close-up of the cable drive for the distal link.
This page was last modified 21:34, 8 December 2009.