Hypertherm Phoenix 8.0 - Manual (Page 377)

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Proportional Gain
Proportional Gain correlates to Elastic Stiffness in the control loop. Increasing the
proportional gain increases the static stiffness, but decreases response of the servo loop.
Under proportional loop control the drive system will apply a restoring torque to the
motor in proportion the position error of the axis.
With a Proportional Gain too high, the system will be unstable which will result in
overshoots, and a generally “nervous” and shaky axis. This is also referred to as a “hot”
control loop.
With a proportional gain too low, the system will respond in a loose or sloppy manner.
This can be seen in the test pattern when the outside corners become rounded and the
circle segments do not all meet in the center.
Integral Gain
Integral Gain improves the positioning accuracy of the control loop. Integral gain can be
used to compensate for static friction or gravity. Excessive Integral Gain can result in
system instability.
For most shape cutting machines this parameter should be set to zero (0).
Derivative Gain
Derivative Gain helps to dampen out sudden changes in velocity. The higher the
derivative gain, the slower the response time to the control loop.
For most velocity loop drives this parameter will be set to zero (0).
Feedforward Gain
Feedforward Gain can be used to drive the following error to zero during machine
motion. In all digital control loops there is a finite amount of error that is introduced by
the velocity command. Increasing Feedforward Gain can reduce this introduced error.
Velocity Gain
When using a current loop amplifier, the internal velocity loop in the CNC can be used to
provide dampening without an external tachometer.
Using the internal velocity loop with a current loop amplifier can result in higher static
stiffness, smoother machine motion, and less overshoot.
Skew Error Tolerance
If the Dual Gantry Axis is installed, the user will be prompted for Skew Error Tolerance.
This is the amount of position error allowed between the master and slave gantry drive
axes prior to an error message being displayed.