Delta RMC151 - Manual (Page 1004)

RMC70/150 and RMCTools User Manual
The Output Bias voltage is always added to the Control Output. Use the Output Bias to
compensate for hydraulic valves or other systems that have an offset. To set the Output
Bias, use the Open Loop Rate (10) command to find out how much Control Output is
required to keep the axis from moving. This is called the null drive. Set the Output Bias
parameter to that value.
Note:
Usually there is a null or offset adjustment on the valve or amplifier that can be adjusted so
the null drive is 0.
9.2.2.6.5. Output Deadband
Type: Axis Parameter Register
RMC70 Address: %MDn.42, where n = 12 + the axis number
RMC150 Address: %MDn.42, where n = 24 + the axis number
System Tag: _Axis[n].OutputDeadband, where n is the axis number
How to Find: Axes Parameters Pane, All tab: Output
Data Type: REAL
Units: V
Range: 0 to 10
Default Value: 0 (disabled)
Description
The Output Deadband is the voltage added or subtracted from the Control Output to
compensate for a "deadband" in the system. Some valves or drives do not react to small
changes in output; this effect is termed "dead band". Deadband compensation can be
performed in closed-loop control only. No deadband compensation is performed in open-
loop control.
The Output Deadband works together with the Deadband Tolerance parameter. These are
essential tuning parameters if the system exhibits a deadband. Care must be taken to not
make this value too large or the axis may oscillate. Normally the Output Deadband value
will be less than 2 volts, and often a few hundred millivolts.
Many systems do not require any deadband compensation.
How it Works
The Output Deadband is added to or subtracted from the Control Output (depending on
its sign) so that the Control Output is outside the dead band.
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