Hypertherm Phoenix 8.0 - Manual (Page 448)

Motion Overview
441
For example:
4000 RPM Motors x .125 inches per rev = 500 inches per minute
Note: Through test or calculation it is determined that the table moves 1/8 inches per
revolution of the encoder.
With the maximum speed, encoder counts per inch, DAC and encoder polarities
determined and entered into control setups, a simple test of machine motion can be made
in the control Drive Diagnostics screen. This test should be made with the motors
disengaged for safety. This is a basic motion test of the system and does not use gain
terms or the position loop for motion. Refer to the Speeds information in this guide for
more information on this feature.
Gain
Proportional Gain
In a feedback control system, the error term is acted on by the control system and it alters
the output. Proportional gain is amplification of the error term. In a closed loop control
system, this is proportional to the error signal. Thus, the output is proportional gain
multiplied by error.
In most systems, proportional gain is the primary tuning parameter for improving the
response of the position loop.
Integral Gain
Proportional gain cannot completely eliminate error. The system can become unstable if
only proportional gain is used to eliminate error in a system. When the response of a
system is satisfactory, but steady state error is excessive, the error can be further reduced
by increasing system gain only for long term accumulations of error over time. Integral
gain is sometimes used to compensate for static load disturbances like torque loading,
gravity bias, and offset.
Note: Integral gain can cause instability in a system because it has a more instant effect at
the beginning of a move profile. Therefore, it is rarely used for velocity drives. However,
integral gain can provide improved response with current drives. Only small adjustments
to integral gain should be made if indications of steady state error exist. In almost all
applications, this value is set to zero. Use the feed forward gain for closing following
error that occurs during a move profile.
Derivative Gain
Derivative gain responds to the rate of change of the signal and can produce corrections
before the error term becomes large, therefore it is useful in improving the transient
response of a system. Since it opposes change in the controlled output, it can produce a
stabilizing effect by damping a tendency toward oscillation. This is the reason we
promote tuning by following error to the maximum Proportional Gain then setting