how to compensate for dead zone.

I was doing a position control of an actuator having the deadzone. The
dead zone is symmetric with control voltage and requires 1V for
positive velocity and -1V for negative velocity.When i provide athis
offset so to make my system without deadzone and do close loop
control, i see stars. i.e. the offset will be so rapidly changing to
and fro from -1V to 1v as the velocity will be doing so as to track
the position. Anyone with idea to solve this problem.
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The best solution I can see in this is a rather old control technique which has served me well over the years. Change the actuator. If not, get a board which doesn't mind doing fast switching from 1v to -1v, write a position controlller with it, and don't worry about how fast it is moving. You might even consider reducing the activity of the valve by not moving it if the average setpoint is within so many percent of the current value.
More seriously, there are better ways to control a valve than one that makes you see stars. Controlling around a dead zone isn't easy, and is often a waste of time and ingenuity. Dead zones and dead times are often a result of an equipment problem.
Reply to
Herman Family
If the actuator can take it, try imposing a 2 volt dither on top of the normal control signal. Use a frequency that is just low enough so that the actuator just begins to try to follow the dither. I used that technique to successfully implement a closed-loop pressure control using a valve driven by a pneumatic actuator with a dead zone.
-Robert Scott Ypsilanti, Michigan (Reply through newsgroups, not by direct e-mail, as automatic reply address is fake.)
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Robert Scott

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