Delta MMC120 User Manual download pdf (Page 118)

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number of millivolts added to or subtracted from the drive output (depending on the

direction of travel) so the drive output is outside the dead band.

If a value outside the valid range is entered, the parameter error bit will be set, and the

value will be set to zero.

CAUTION: Do not make this value too large or the drive will oscillate.

Why Bother?

On an axis with overlapped spools or a large amount of static friction, the axis may

oscillate slowly around the COMMAND POSITION. This happens when the axis does

not respond to small changes in drive output. The integrator winds up until the axis

moves and then has too much drive, overshooting the COMMAND POSITION.Theaxis

then winds the integrator down until the axis overshoots the other way. If this happens,

look at the NULL DRIVE.TheNULL DRIVE will oscillate slowly as the axis oscillates.

Notice the peak-to-peak values of the NULL DRIVE oscillation and subtract the

minimum value from the maximum value and then divide the result by two. Enter this

value in the DEAD BAND ELIMINATOR field as a starting point.

A spool that has 10% overlap will require a value of about 1,000 counts.

IN POSITION

Default: 50

Range: 0 to 65535

IN POSITION specifies the size of a window around the COMMAND POSITION.

When the ACTUAL POSITION gets within this window, the In Position bit is set (but

not latched) in the word.

Example:

If an axis COMMAND POSITION is 10,000 and the IN POSITION parameter is 30, the

In Position bit will be set when the ACTUAL POSITION is between 9,971 and 10,029.

The bit will be cleared whenever the ACTUAL POSITION is outside the range.

FOLLOWING ERROR

Default: 250

Range: 0 to 65535

The FOLLOWING ERROR determines how large the difference between the TARGET

POSITION and ACTUAL POSITION can get before the Following Error bit is set in the

word.

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Delta MMC120 User Manual Page 118