Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
150
Motor Compensation Tables and Constants
Changing the servo update rate changes the percentage of processor time devoted to the servo tasks,
which can have important implications for lower-priority tasks, such as motion-program and PLC-
program calculations. Refer to the Computational Features section for details on how to evaluate these
changes.
If the servo update time is changed with the jumpers, change global parameter I10 to match the change so
that commanded trajectories are executed at the right speed. I10 does not have to be changed to match
changes in Ixx60 for individual motors.
which can have important implications for lower-priority tasks, such as motion-program and PLC-
program calculations. Refer to the Computational Features section for details on how to evaluate these
changes.
If the servo update time is changed with the jumpers, change global parameter I10 to match the change so
that commanded trajectories are executed at the right speed. I10 does not have to be changed to match
changes in Ixx60 for individual motors.
Types of Amplifiers
Turbo PMAC can interface to a variety of amplifier types. The type of amplifier used for a particular
motor or hydraulic valve has important ramifications for the tuning of the servo loop. Each of the
common types is explained below.
motor or hydraulic valve has important ramifications for the tuning of the servo loop. Each of the
common types is explained below.
Amplifiers for Which Servo Produces Velocity Command
Several types of amplifiers expect a velocity command out of the Turbo PMAC servo loop. The main
types of amplifiers in this class are:
types of amplifiers in this class are:
•
Analog-input velocity-mode servo amplifiers
•
Pulse-and-direction-input amplifiers
•
Hydraulic-valve amplifiers
If the command value from the Turbo PMAC servo loop, regardless of signal type, is a velocity
command, no velocity loop needs to be closed in the Turbo PMAC. With the standard PID loop, this
means that the derivative (D) term Ixx31 can be set to 0.
command, no velocity loop needs to be closed in the Turbo PMAC. With the standard PID loop, this
means that the derivative (D) term Ixx31 can be set to 0.
Analog-Input Velocity-Mode Amplifiers
Analog-input velocity-mode servo amplifiers close a velocity loop in the amplifier using the signal from
the Turbo PMAC as the commanded velocity and sensor feedback for the actual velocity. It is vital that
the amplifier’s velocity loop be tuned properly before attempting to tune the Turbo PMAC’s servo loop
around it.
The velocity loop of a velocity-mode drive must be well tuned with the load that it will drive before the
Turbo PMAC’s position loop is tuned. Because the velocity-loop tuning is load dependent, the amplifier
manufacturer cannot do the final tuning; the machine builder must tune the loop. The velocity step
response must not have any significant overshoot or ringing; if it does, it will not be possible to close a
good position loop around it with Turbo PMAC. The Turbo PMAC Executive Program’s tuning section
has a function called Open-Loop Tuning that can be used to give velocity command steps to the amplifier
and to observe the response plotted on the screen. This makes it easy to tune the amplifier, or to confirm
that it has been well tuned.
the Turbo PMAC as the commanded velocity and sensor feedback for the actual velocity. It is vital that
the amplifier’s velocity loop be tuned properly before attempting to tune the Turbo PMAC’s servo loop
around it.
The velocity loop of a velocity-mode drive must be well tuned with the load that it will drive before the
Turbo PMAC’s position loop is tuned. Because the velocity-loop tuning is load dependent, the amplifier
manufacturer cannot do the final tuning; the machine builder must tune the loop. The velocity step
response must not have any significant overshoot or ringing; if it does, it will not be possible to close a
good position loop around it with Turbo PMAC. The Turbo PMAC Executive Program’s tuning section
has a function called Open-Loop Tuning that can be used to give velocity command steps to the amplifier
and to observe the response plotted on the screen. This makes it easy to tune the amplifier, or to confirm
that it has been well tuned.
Pulse-and-Direction-Input Amplifiers
Pulse-and-direction-input amplifiers interpret each pulse as a commanded position increment. To
generate pulse-and-direction commands, the Turbo PMAC servo loop computes a pulse frequency value
that is sent to pulse-frequency modulation circuitry. This frequency value is effectively a velocity
command.
Amplifiers with this style of interface are of two types – Stepper Drive and Stepper Replacement
Amplifier.
Stepper Drive: There is no position feedback to this drive. Usually, there is no encoder at all for these
motors, so the Turbo PMAC must use the output pulse train as simulated feedback. This requires use of
an encoder channel on Turbo PMAC, even though no encoder is physically connected. If there is an
encoder on the stepper motor, it can be used in either of two ways:
generate pulse-and-direction commands, the Turbo PMAC servo loop computes a pulse frequency value
that is sent to pulse-frequency modulation circuitry. This frequency value is effectively a velocity
command.
Amplifiers with this style of interface are of two types – Stepper Drive and Stepper Replacement
Amplifier.
Stepper Drive: There is no position feedback to this drive. Usually, there is no encoder at all for these
motors, so the Turbo PMAC must use the output pulse train as simulated feedback. This requires use of
an encoder channel on Turbo PMAC, even though no encoder is physically connected. If there is an
encoder on the stepper motor, it can be used in either of two ways: