exactlyNow if you have thermal mass, warmup times in your heat source, not to mention transport delays of the fluid in the pipe, sensor response time, what ever you do, sort it out first. Fast controller response is meaningless, if the process response time is 20 minutes...
I agree with Dave. Sampling often does not solve the dead time problem.Not when you measure fast.
This isn't so. The derivative may 'speed things up' but the real purpose is to the place closed loop poles. If you place the closed loop poles away from the origin then errors will decay faster.The Smith Predictor is not always effective, and a derivative action to speed things up only work in a narrow range of applications where you have servo controls (robotics and related automation), minimal dead time, instant measurements, and minimal time constants, but generally ineffective in most large plant operations where process stability is manditory.
A heat exchanger is non-linear, not multi dimensional. The dead time is small enough where a Smith Predictor isn't required. It is easy enough to account for the changing gains of a heat exchanger. Most of the time the heat exchanger is controlling at only one temperature so it is easy enough to assume the gain is linear at that point.wait until you turn a controller in a heat exchanger loop, it is a multidimensional universe in that case, beyond pole locations, or even more challenging a steam dearator in a boiler feed water loop, with flow, pressure, drum lever, and emergency feed water...every thing is logical and rational except when you are dealing with phase changes, then "look out."
No, not directly. However, the integrator will compensate if the hysteresis is small. If the hysteresis is a problem then an offset can be added or subtracted from output to compensate depending on the direction of change.does pole placement address valve hysterisis?
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