Bimba PCS User Manual
Page 7
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7
FEEDBACK SIGNAL
The feedback signal is a voltage signal from the actuator that corresponds to the
displacement or rotation of the actuator. The feedback signal range is
approximately 0 - 10 VDC.
PTF Note:
The PTF has a fixed electrical rotation span of 340 degrees. This will
affect some of the following adjustments and signals for PTF’s with full
scale rotations of less than 180 degrees.
DEADBAND
The Deadband is a bi-directional band, centered on the commanded position.
Once the actuator is within this zone, the error term will be considered zero and
all valves will be closed. This deadband is measured in volts and can be adjusted
between 0.005 and 0.500 volts. This voltage can be translated to a deadband width
with the following formula:
w =
1
/10V * t
Where:
w = deadband width
V = voltage reading from the PCS
t = full scale travel of the actuator (Note: for PTF rotary actuators
with
total
rotation
less
than 180º, always make t = 180)
The full deadband zone is the deadband width above and below the target
position.
Example
1: If the deadband is set for 20mV (0.02 of a volt) for a 6 inch stroke
cylinder, the width of the deadband zone will be
1
/10 * 0.02 * 6 or ±0.012 of an
inch.
Example 2: If the deadband is set for 20mV (0.02 of a volt) for a 180º actuator,
the width of the deadband zone will be
1
/10 * 0.02 * 180 or ±0.72º.
DECEL RANGE
Once the PCS receives a command signal to move the actuator rod or shaft to a
new position, two of the pneumatic valves are opened causing the actuator to
move toward the desired position. The Decel Range is an adjustable zone outside
the Deadband in which the PCS control begins to slow (decelerate) the actuator
rod. The Decel Range enables the PCS system to accurately position the actuator
inside the Deadband. The Decel Range is measured in volts and can be adjusted
between 0.5 and 13.5 volts. Optimal decel settings vary with the load and
application. However, 1.5 volts is a good default setting for PCS models 1, 2, and
3, and 9 to 11 volts usually works well for PCS models 5, 7, and 8.