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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 control 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.
Encoder Counts per inch
Enter a value that is the number of encoder edges per inch of machine travel. It is possible to enter
fractional encoder units and the control will keep track of these fractions automatically. Encoder
Counts per inch are equal to the resolution of the encoder, multiplied by the encoder revolutions per
inch (based on the machine drive gearing).
For example: The Resolution of a 4X
– 1000 line encoder counts both edges (lines) of channel A and
channel B to equal 4 counts per line multiplied by the 1000 lines per revolution would equal 4000
counts per revolution. If the encoder revolutions per inch to travel is 1:1, we would have 4000
encoder counts per inch of travel.