Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Executing Individual Motor Moves
225
Homing Acceleration
The acceleration for homing search moves is controlled by the same parameters – Ixx19 (maximum
acceleration), Ixx20 (acceleration time), and Ixx21 (S-curve time) – as for jogging moves. These are
described in the above section on jogging moves.
acceleration), Ixx20 (acceleration time), and Ixx21 (S-curve time) – as for jogging moves. These are
described in the above section on jogging moves.
Homing Speed
Ixx23 specifies the speed and direction of the homing-search move. If Ixx23 is greater than zero, the pre-
trigger homing-search move will be in positive direction. If it is less than zero, the pre-trigger move will
be in the negative direction. The magnitude of Ixx23 (expressed in counts/msec) controls the speed of
both the pre-trigger and post-trigger moves (should they be long enough to get to this speed).
trigger homing-search move will be in positive direction. If it is less than zero, the pre-trigger move will
be in the negative direction. The magnitude of Ixx23 (expressed in counts/msec) controls the speed of
both the pre-trigger and post-trigger moves (should they be long enough to get to this speed).
Home Trigger Condition
The trigger condition for homing-search moves, as for other triggered moves, is specified by Ixx97,
Ixx24, and Ixx25, as described above in detail. If no trigger is found, the pre-trigger move will continue
indefinitely, or until stopped by an error condition such as hitting overtravel limits.
Ixx24, and Ixx25, as described above in detail. If no trigger is found, the pre-trigger move will continue
indefinitely, or until stopped by an error condition such as hitting overtravel limits.
Post-Trigger Move
Variable Ixx26 specifies the (signed) distance from the trigger-captured position to the end of the post-
trigger move. The units of Ixx26 are 1/16 count. The endpoint of the commanded post-trigger move is
the new motor position zero (the motor’s “home” position). The change of the motor’s reported position
reference occurs at the beginning of the post-trigger move. As soon as this is done, reported positions are
referenced to this new zero position (plus or minus any axis offset in the axis definition statement – if the
axis definition is #1->10000X+3000, the home position will be reported as 3000 counts). Also at this
point, the motor’s “home search in progress” status bit is cleared, and the “home complete” status bit is
set.
trigger move. The units of Ixx26 are 1/16 count. The endpoint of the commanded post-trigger move is
the new motor position zero (the motor’s “home” position). The change of the motor’s reported position
reference occurs at the beginning of the post-trigger move. As soon as this is done, reported positions are
referenced to this new zero position (plus or minus any axis offset in the axis definition statement – if the
axis definition is #1->10000X+3000, the home position will be reported as 3000 counts). Also at this
point, the motor’s “home search in progress” status bit is cleared, and the “home complete” status bit is
set.
If the post-trigger move fails with an error condition, it is not necessary to re-home the motor, as the
home position is already known. A command such as J=0 can move the motor to the home position once
the source of the problem has been cleared up.
home position is already known. A command such as J=0 can move the motor to the home position once
the source of the problem has been cleared up.
If software overtravel limits are used (Ixx13, Ixx14 not equal to zero), they are re-enabled at this time
after having been automatically disabled during the search for the trigger. The trajectory to this new zero
position is then calculated, including deceleration and reversal if necessary. Note that if a software limit
is too close to zero, the motor may not be able to stop and reverse before it hits the limit. In normal
termination, the motor will stop under position control with its commanded position equal to the home
position. If there is a following error, the actual position will be different by the amount of the following
error.
after having been automatically disabled during the search for the trigger. The trajectory to this new zero
position is then calculated, including deceleration and reversal if necessary. Note that if a software limit
is too close to zero, the motor may not be able to stop and reverse before it hits the limit. In normal
termination, the motor will stop under position control with its commanded position equal to the home
position. If there is a following error, the actual position will be different by the amount of the following
error.
Failure to Find Trigger
The pre-trigger move of a homing search will continue indefinitely if it fails to find the trigger condition it
is looking for. Typically, it will be stopped by an overtravel position limit switch or fatal following error
limit at the end of travel in this case. If you want a programmed limit to the length of the pre-trigger
move, you should use an incremental jog-until-trigger command or programmed move-until-trigger, with
the first value specifying the distance to move in the absence of a trigger, and the second the distance
from the trigger to the end of the post-trigger move (replacing Ixx26). Once the post-trigger move is
finished, a HOMEZ command (see below) can be used to set this position to be the motor zero position.
is looking for. Typically, it will be stopped by an overtravel position limit switch or fatal following error
limit at the end of travel in this case. If you want a programmed limit to the length of the pre-trigger
move, you should use an incremental jog-until-trigger command or programmed move-until-trigger, with
the first value specifying the distance to move in the absence of a trigger, and the second the distance
from the trigger to the end of the post-trigger move (replacing Ixx26). Once the post-trigger move is
finished, a HOMEZ command (see below) can be used to set this position to be the motor zero position.