John Kasunich wrote: > One approach is to consider the power-up state as "acceptable" meaning > "since the motors were free-wheeling a minute ago, there can't be too > much stress in the machine". Record the offset between the two encoder > feedbacks before enabling the amps, and maintain that offset while > moving toward home. The gantry may be a bit out of square, but it won't > get any worse. When one axis hits home, record the position and keep > moving. When the other hits home, record its position and stop (still > keeping the same offset between motors). Then use the two recorded > positions to determine the exact offset between the encoders that will > result in a square gantry. Then move one (or both) motors to that offset. I was hoping to find a solution that could easily be implemented in a few HAL components. I'm not sure how to record the point at which a joint passes the home and index pulse position. I guess you could just let both sides home, using only one home switch, but each side would search for the index pulse independently. After the first side hits the index pulse, it stops, and the second side just comes into better alignment. The index pulses should be adjusted so that with both encoders sitting on the index pulse, the gantry is square. Retaining any reference to the skew from at rest would allow any strains in the machine to skew the orthogonality of the machine when it is homed and running, which sounds undesirable.
Jon ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
