User's Manual

PMAC User Manual
136 Basic Motor Moves
Open-Loop Moves
Open-loop moves, as their name implies, do not do closed-loop position control. They open up the servo
loop and just put commands of the specified magnitude on the outputs. Typically, these are used for
diagnostic purposes, but they can also be used in the actual applications.
These moves are executed using the motor-specific O{constant} on-line command, where
{constant} represents the magnitude of the output as a percentage of Ix69, the maximum output
parameter. This command may not be part of a motion program, and it may not be given to a motor when
that motor's coordinate system is executing a motion program, even if it is not moving that motor.
If the motor is not commutated by PMAC, this command creates a constant DC voltage on the single
DAC output for the motor. If the motor is commutated by PMAC, this command sets the magnitude of
the signal that is sinusoidally commutated onto the two DAC outputs for the motor.
To do a variable O-command, define an M-variable to the filter result register (X:$003A, etc.), command
an O0 to the motor to put it in open-loop mode, then assign a variable value to the M-variable. This
technique will even work on PMAC-commutated motors.
The PMAC Executive Program tuning section uses the open-loop moves to allow the user to diagnose and
tune amplifier response.