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VIX IM MICROSTEPPER INDEXER DRIVE USER GUIDE
92
Scaling
Using scale allows ‘user-friendly’ settings of distance, velocity and acceleration to be defined
in user units, rather than units required by the drive. For example, using a ViXIM to control a
linear table, it is possible to program distance units directly in mm, velocity in mm per second
(mms
-1
) and acceleration in mm per second/per second (mms
-2
). This is made possible by
measuring one user unit in terms of the number of positional feedback encoder steps. This
measure of Position Encoder/Motor steps per (user) Unit is termed the PEU parameter. For
example, a linear table with base units of 1mm and having an encoder that gives 1 count
every 5µm of travel, results in a PEU of (1mm/5µm) = 200 (PEU must be => 1).
The PEU value is used with the SCALE command and once a PEU value is set this will
determine the units in which acceleration, distance and velocity are measured. In this case,
a base unit of 1mm was chosen, consequently acceleration is measured as 1mm s
-2
,
velocity as 1mm s
-1
and distance in mm.
Individual scaled values of acceleration, distance and velocity can be set using:
SCLA SCaLe Acceleration factor
SCLD SCaLe Distance factor
SCLV SCaLe Velocity factor
For example, to work with distance set in increments of 0.1mm set SCLD as
(base unit)/(desired unit) = 1 mm/0.1 mm = 10. This will require the SCALE command to
take the form:
SCALE1(1,10,1,200)
For more information see the SCALE command.
A, D and V do not have to be in the same units, any combination of units is possible, but
PEU divided by SCLD must result in an integer. This is because the distance moved
requires the following calculation:
D * (PEU/SCLD) steps, which could result in a fractional number of encoder steps that
cannot be resolved by the drive.
Once defined using the SCALE settings command, an application can be simply
programmed in user units, without needing to calculate what units the drive requires.