Differential Gain

Default: 0
Range: 0 to 65535

The Differential Gain field is used to apply a gain based on the rate of change between the target and actual positions. There are two ways to view this.

First, this is a gain multiplied by the current rate of change in the position error. The differential drive, in millivolts is computed as follows:

$image\ebx_1350299206.gif$

$image\ebx_642992483.gif$

where:

Kd=	Differential Gain in mV/[pos-units/ms]
E0=	position error this control loop in position units
E1=	position error last control loop in position units
LoopTime =	RMC Control Loop Time in ms (1 or 2)

A second equivalent way of viewing this parameter is as the gain multiplied by the velocity error. When looked at from this angle, the above equations become the following:

$image\ebx_-709120136.gif$

where:

Kd=	Differential Gain in mV/[pos-units/s]
TarVel =	target velocity in pos-units/s
ActVel =	actual velocity in pos-units/s

Note: The actual drive output may be reduced based on the values of the Extend Feed Forward and Retract Feed Forward.

CAUTION: To avoid oscillation during initial tuning start with values below 10.

Why Bother?

The Differential Gain field will usually be set to zero. Noisy or low-resolution feedback will limit the amount the Differential Gain can be increased.