Mechanical Maintenance
Inspecting for wear and tear
There are three types of wear and tear that might happen to your hand over the course of its use. Settling: Parts and fittings may settle over time. In particular, tendons may stretch slightly, and the spools on the motors may shift, increasing the amount of slack in the system. This can be remedied by re-tensioning the tendons. Hall effect sensors may shift in position slightly. This may be remedied by re-calibrating the joint.
Wearing: In use, some tendons are subject to wear. In particular, wherever a tendon travels over a pulley, it may show signs of wear, appearing slightly fluffy. Normally, this isn’t a problem, but if excessive wear is apparent, then the tendon might need to be changed.
Failing: As many parts of the hand are subject to very high loads at times, it is possible for some parts to fail. The exact symptoms of the failure depend on the particular part in question. Most such failures will need to be fixed by service personnel.
Re-tensioning
From time to time, you may find that the amount of slack in the tendons has increased, causing backlash and deteriorating the control. The tendons can be re-tightened at the motor.
Look at the Motor Layout diagram in this document to find the position of the motor that needs tightening. Using the green hex driver, remove the black motor cover; you can unplug the fan.
Insert the blue hex driver through the hole in the wrist plate, and push it down until you feel it engage with the hex socket in the screw in the motor spool.
Rotate the hex driver clockwise a little way. This will tighten the left tendon, and loosen the right tendon.
Insert the spool-tool into one of the 2mm holes in the top of the spool.
Use the hex driver to loosen the screw. The top of the spool should now be free to rotate.
Use the spool-tool to rotate the top of the spool to the right. You should see the right tendon tighten as you do this.
Re-tighten the bolt using the hex driver.
Broken tendon
Fixing a broken tendon can be easy or extremely difficult depending on the joint involved. Complete instructions for replacing tendons is beyond the scope of this document. Please contact the Shadow Robot Company if this happens support@shadowrobot.com.
Tangled tendon
If a pair of tendons has become extremely slack, then they may become entangled at the spool. If this happens, rotate the motor until they are no longer entangled, and follow the procedure for re-tensioning.
Re-calibrating
The calibration tables in the host allow it to convert from the raw ADC readings sent by the Palm, into real angles in radians required by ROS. It is possible that eventually some joints may need to be re-calibrated. If this is the case, please contact Shadow Robot support@shadowrobot.com,