Delta Computer Systems VMC 186/40, Manual

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VMC 186/40 Motion Control Module Control Parameters
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Direction (Default: 0) Possible options: 0 and -1
The Direction parameter determines whether the actual position increases or decreases as the transducer counts
increase. A zero produces a direct relation between actual counts and transducer counts while a -1 (65535 or
0FFFFH) results in an inverse relationship between the two counts. The actual position is determined as
follows:
Transducer Counts * Scale
Actual Position =
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XOR Direction + Offset
32768
XOR has the effect of multiplying by -1 when Direction = -1 and multiplying by 1 when Direction =
0.
Note: When the Direction parameter is changed, the sign of the Extend Limit, Retract Limit and Offset must
also be changed. Extending is always the direction which increases transducer counts.
CAUTION: When using the Direction parameter, you must be familiar with the limitations of 16 bit math.
Maximum Position Error (Default: 250)
The Maximum Position Error determines how large the difference between the target position and actual
position can get before the lag error or lead error bits are set in the Status Word . The Maximum Position Error
also limits the proportional term of the drive output due to a position error to:
Proportional Gain * Maximum Position Error
Maximum Proportional Drive =
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100
Proportional Gain represents the Extend or Retract Gain parameters.
At Command Position (Default: 50)
At Command Position specifies the size of a window around the Command Position . When the actual position
gets within this window, the At Command Position bit is set in the Status Word . The size of the window is
expressed in position units.
Near Command Position (Default: 0)
The Near Command Position is similar to the At Command Position . The Near Command Position window
should be wider than the At Command Position window unless the Near Command Position is to be ignored, in
which case it should be set to 0. This parameter is useful in letting the VME controller know the axis is out of
the way of some other equipment. The size of the window is expressed in position units.
Extend Limit (Defaults to actual position on reset)
The Extend Limit specifies the maximum value that the VMC 186/40 will allow as a Command Position .
(When Direction = -1 (65535), this is a minimum value.) Requested positions that exceed this value will be
truncated. The Extend Limit is given in position units.
Note: The Extend Limit must be changed when the Direction, Scale or Offset parameters are changed. Also, on
start-up the Extend Limit defaults to the current position of the axis. New Extend and Retract Limits must be
issued using a 'P' command before the axis will move.