Bimba PCS - Manual (Page 20)

www.bimba.com Technical Assistance: 800-44-BIMBA 20
Note: Decel and Deadband adjustments are iterative, and optimum settings
depend upon the application and load. Set the deadband as low as possible for the
greatest positioning accuracy. Set the Decel as low as possible for the greatest
speed. As load inertia increases, the actuator might oscillate (buzz) around the
ending position before coming to a complete stop at the commanded position. If
this happens, simply increase the Deadband or Decel settings, or both, for the
smoothest, fastest, most accurate positioning.
CAUTION! If the DECEL and Deadband adjustments are set too
low, the system may be unstable when subjected to large
transient loads (loads that are 75% of maximum actuator
capability). Check by applying an instantaneous force against
the actuator (i.e., push hard and release quickly). If the system
is not stable, increase the DECEL range or the Deadband. An
unstable system could potentially cause personal harm or
damage to products or machinery.
To optimize the Decel setting, command the actuator to make several long and
short motions, in both increasing and decreasing directions. Watch the LEDs
carefully as the actuator slows to a stop.
Moves in the Increasing Direction (Towards Full Scale)
The green LED will be on while the actuator is moving in the increasing
direction. As the actuator tries to stop at its commanded position, the red LED
may come on or flicker. If so, the Decel Range is too small because the actuator
had to backup before stopping in the Deadband zone. On the other hand, if the
actuator seems to take a long time to stop at its commanded position and the red
LED never comes on, then the Decel Range is too big.
Moves in the Decreasing Direction (Towards Zero)
The red LED will be on while moving in the decreasing direction. As the actuator
tries to stop at its commanded position, the green LED may come on or flicker. If
so, the Decel Range is too small. On the other hand, if the actuator seems to take a
long time to stop at its commanded position and the green LED never comes on,
then the Decel Range is too big. This iterative adjustment can be used to optimize
the PCS for your specific application.
Note: If the DECEL adjustment cannot stabilize the system at
the selected Deadband setting, flow controls may be inserted
into both exhaust ports of the PCS system to reduce the
velocity of the actuator. NEVER install flow controls in the
actuator ports. Flow controls can be adjusted to reduce
velocity until stable controlled motion is achieved. If velocity
cannot be reduced in the application, then increase the
Deadband instead. Start with the Flow Controls in the fully
open position, then adjust them as needed.