Hamilton Sundstrand Company ACT2000 - Manual (Page 43)

The Span is tracked relative to the Home position. If Home position is
based upon a mechanical stop in the user’s system, rather than the
mechanical stop in the actuator, the actual amount of extension possible
(or retraction) will be less than the default Span value of 5.9 inches. This
can create a situation where the DEMAND signal correlates to a position
beyond the design capacity of the actuator. In such a situation, the
actuator will encounter an internal mechanical stop, and increase motor
current to the maximum levels in its attempts to reach the commanded
position. The Maximum Force level of 1000 lbf will soon be reached
without being able to reach the commanded position, which will generate
a Fault. See Figure 3-4 for an example. It may be necessary to reduce the
Span value in the Set-Up parameters to allow for the distance between
the mechanical stop in the user’s system and the mechanical stop in the
actuator.
Interpolation of DEMAND Signal
Linear interpolation of the DEMAND signal in the range between 4 mA
and 20 mA is the default condition, as specified in the Set-Up parameters.
With linear interpolation, a DEMAND signal of 12 mA (midway in range of
DEMAND signal) will correlate to a position at 2.95 inches (midway in the
5.9 inch span). See Figure 3-2 for an illustration of linear interpolation.
A non-linear interpolation table can be created to define positioning at 16
discrete current levels in the DEMAND signal range, but only during Set
Up using the ActWiz Software. See the Section 3.8 for additional details
about Set Up parameters.
Figure 3-2. Actuator Position vs. DEMAND, with default conditions
Home as a Mech. Stop in Actuator
CH. 3: OPERATING THE ACT2000 37