Motion Control Parameters
TMC 188/40 Motion Control Module
Delta Computer Systems, Inc. 360/254-8688
30
EXTEND FEED FORWARD x SPEED
Feed Forward Drive =
10,000
You can find the appropriate value for EXTEND FEED FORWARD by making a move with the axis
using a SPEED of 10,000. The amount of output drive required to maintain this speed should be
used as the EXTEND FEED FORWARD parameter. If, after the parameter has been set, lag errors
occur, the feed forward is too small or the system response is too slow. If lead errors occur, the feed
forward is too large or the system response is too slow. If the 'F' command is sent after a valid move
(one without overdrive or a null error), the MCM will automatically adjust the EXTEND FEED
FORWARD parameter.
RETRACT FEED FORWARD
(Default: 100)
See EXTEND FEED FORWARD. Used only when retracting.
SCALE
(Default: 32768; Range 0 to 65535)
TIP:
Delta's DCSMON provides an easy way to work with SCALE. Use DCSMON's commands P0
and P1 to help calculate SCALE , OFFSET and DIRECTION.
NOTE:
SCALE is used differently when either the quadrature or analog options are used. If these options
are installed, see Appendix B or C for more information.
In linear position applications, SCALE can be used for two purposes: transducer compensation or
distance translation. Differences in magnetostrictive transducers are compensated by using the
SCALE parameter. Each transducer will indicate a different physical distance for a given
interrogation cycle. Usually, only a small change from the default value is necessary to compensate
the transducer.
A second and more useful feature of SCALE is its ability to translate a fixed physical distance to
usable position units (position units from thousandths to hundreds or vice versa). The translation is
done using a combination of SCALE and recirculation selection (see page 49 for more information on
recirculation).
SCALE can be viewed as the number of position units for every 32768 TRANSDUCER COUNTS.
The SCALE parameter is used to convert TRANSDUCER COUNTS to position units (thousandths of
an inch, tenth of a millimeter, etc.). It is defined as:
Position Units
SCALE =
x 32768
Transducer Count
Linear transducers have a calibration number (typically 9.1 s per inch) and the TMC 188/40 has a
27.75 MHz oscillator for transducer position measurement counters. To determine length per
transducer count for a linear transducer use the following formula:
