Re: Bound control system



Fred Marshall wrote:
Vladimir Vassilevsky wrote:

The classic closed loop system tries to minimize the error wrt some
criteria. But what if the requirement is to limit the error to the
bounds (-E,+E) ? So as long as the error is within the bounds, the
control signal should be zero.


This looks like a classical "bang/bang" controller with a dead zone. So, instead of bang/bang you might say bang/off/bang or +1/0/-1.
Then, you might modify the +1 and -1 to have proportional responses instead of +1 or -1 only.

The proportional controller has a steady state error. Besides, there is some deadband in the actuators. So I would like to include the I term.

The Describing Function method of Krylov and Bogolyubov is treated in "Control System Theory", Olle I. Elgerd, McGraw-Hill.

Thank you, I will take a look.

I once used this method to change a control system from bang/bang (100% duty cycle) to bang/off/bang with a huge saving in energy, noise, etc. with under 10% duty cycle. There were just little correcting "blips" in the control signal.

Using the common sense, I got the system working. Looks almost like the error is hard limited at +/- E. However the algorithm is rather ad hoc and not very elegant at all.


Of course, all this is "classical" control theory as compared to "modern" but I've USED the former compared to the latter.

:-)

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
.