Finding Motor Offsets for the WAM

After replacing a puck, it is necessary to find two offsets (IOFST and MOFST) using this procedure. IOFST is a "current offset", the current sensor value when zero current is commanded. MOFST is a "motor offset", the offset between the encoder's zero value and the start of an electrical cycle in the motor. The "btutil -f" command will find these two offsets automatically. You can find btutil in the btclient/src/btutil directory.

Please turn on the WAM power and press Shift-Idle on the control pendant before executing btutil commands.

After calibration, you will need to E-STOP then Shift-Idle the WAM in order to load the newly calibrated values.

You should skip down to the instructions for the specific motor you are calibrating now.

Motor 1

Position J1 near the middle of its joint range.

./btutil -f 1

J1 should actively hold position for about 5 seconds, then release. If the puck that controls J1 has an optical encoder, then the joint will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds.

Motor 2

Position J2 near the middle of its range. If the WAM is mounted on the floor, you should balance J2 so that the elbow points toward the ceiling (with the outer link folded down).

./btutil -f 2

Puck 2 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J2 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds. You will want to catch the elbow as it falls. Be ready for J2 to move in either the positive or negative direction.

Motor 3

Position J2 near the middle of its range. If the WAM is mounted on the floor, you should balance J2 so that the elbow points toward the ceiling (with the outer link folded down).

./btutil -f 3

Puck 3 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J2 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds. You will want to catch the elbow as it falls. Be ready for J2 to move in either the positive or negative direction.

Motor 4

Position J4 near the middle of its range. If the WAM is mounted on the floor, you should balance J4 so that the end of the arm points toward the ceiling.

./btutil -f 4

J4 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J4 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds. You will want to catch the outer link as it falls. Be ready for J4 to move in either the positive or negative direction.

Motor 5

Position J5 near the middle of its range.

./btutil -f 5

Puck 5 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J5/6 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds.

Motor 6

Position J6 near the middle of its range.

./btutil -f 6

Puck 6 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J5/6 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds.

Motor 7

Position J7 near the middle of its range.

./btutil -f 7

J7 should actively hold position for about 5 seconds, then release. If that puck has an optical encoder, then J7 will rotate about 30 degrees, else the joint will simply stop holding position after 5 seconds.

Last modified 6 years ago Last modified on Jun 1, 2011, 12:34:45 PM