"Peter Nachtwey" schrieb im Newsbeitrag news:sOadnRRUbtIAervbnZ2dnUVZ snipped-for-privacy@comcast.com...
If you tune power stations you know by experience that this type of steam generator and turbine can be power-incread 10%/minute. Your employer sold for millions of dollars the control sytem that garantees 10%/minutes. The time delays are minutes, not seconds.
u = power target x = power (PV)
On a first try, u is limited to 1%/minute. If all is going smoothly you go to 2%/minute, and so on.
The operator would never have a change to move the plant with a step signal. There will always be a target speed limiter inside the control system.
If finaly power change of 10%/minute is proved and accepted by the staff of the power station my job was done.
What I was basically trying to do you find in the diagram:
V(theoretical) = high (or whatever is possible) Time-compensated(theoretical) = 100% (or whatever is possible)
In the times I tuned power stations with try-and-error method I could reach
10%/minute 'without destroying' power stations.That last diagram you must realy understand: x ~ u c can be 1
This gives you 'linearized' output.
V is nonlinear (valves, pumps, etc.). The integral part of PIDs is worsening time behavior of the loop. You must therefore minimize the integral impact. All these thoughts apply also to your system. In your system I've chosen a filter for example, not a speed limiter.
Peter, you have modified my idea to feedback the total process transfer function in a Matlab test. You should try using feedback the total process transfer function. I have the target signal damped by a filter with T=0.25.
If it works you have the advantage that you or anybody else can change from try-and-error methods to calulate the system in less time, having only one parameter to adjust (filter).
To make it clear: Your result you presented was ok for me. I was just trying to calculate a similar result, and if possible do it slightly better, have better influence to control behavior.
What I'm up to is to find also process transfer functions by good approximation methods and calculate the whole stuff. Calculation is better than just trying.
General note: If PT1 can be controlled by PD why not PT3 by PD3?