User's Manual

PMAC User Manual
Basic Motor Moves 125
BASIC MOTOR MOVES
Commanding Some Basic Moves for the Motor
Once the motor is defined and basically working, command some basic moves for the motor. Jogging
commands allows the motor to make simple moves, independent of other motors, without writing a
motion program. Use these moves for development, diagnostics, and debugging, but also use them in the
actual application.
Another type of simple motor move is the homing search move. This is a jog-until-trigger type of move,
where PMAC commands the motor to move until it sees a pre-defined trigger. It then brings the motor to
a stop and returns to the trigger position (possibly with an offset), and sets the motor position to zero. A
homing search move should be performed when it is not known where home position is. If there is an
incremental position sensor, the location is not known on power-up. Therefore, the homing search move
is typically the first move done in this type of system. If the home position is known, to return to that
position, there is no need to do a homing search move; simply command a move to the zero position (e.g.,
J=0 or X0)
The trajectories for jogging and homing moves are essentially the same as for linear blended program
moves. The differences are that the move parameters must be specified by I-variables, and that the moves
themselves are started by on-line commands, not by motion programs. These moves are specified directly
to the motor, specified by number, rather than the axis, specified by letter. The moves are described in
unscaled units (all based on counts and milliseconds).
Jogging Move Control
Jog Acceleration
Jog/home acceleration time is specified by Ix20 for motor x, and the S-curve time by Ix21. If Ix20 is less
than two times Ix21, the acceleration time used will be twice Ix21. The acceleration limit for jog/home
moves is set by Ix19 (in counts/msec
2
). If Ix20 and Ix21 are so small that Ix19 would be exceeded, Ix19
controls the acceleration time (without changing the profile shape). To always specify the acceleration by
rate instead of time, simply set the acceleration time parameters small enough that the limiting
acceleration rate parameter is always used.
To specify the acceleration by rate, do not set both acceleration time parameters Ix20 and Ix21 to zero.
This will cause a division-by-zero error in the move calculations that could cause erratic movement. The
minimum acceleration time setting should be Ix20=1 and Ix21=0.
Jog Speed
Jogging speed is specified by Ix22, which is a magnitude of the velocity, in counts per millisecond.
Direction is specified by the jog command itself.
Jog Commands
The commands to jog a motor are on-line (immediate) commands that are motor-specific; they act on the
currently addressed motor.
A jog command to a motor will be rejected if the motor is in a coordinate system currently executing a
motion program, even if the motion program is not commanding that motor to move. PMAC will report
ERR001 if I6 is set to 1 or 3.