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Advanced control theory question.

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JoKKeR

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Hi!

Iv heard that defying problem makes wanted "things" much more accessible. Since im plain lost on my way to solve a problem, because i feel like im missing more than 1 puzzle piece to get where i want to be.
I will try to tell what i want.

The application is central heating system regulator.
The inputs are temperature from outdoor and temperature of heating water measured after valve which is regulated by application + UI inputs (not important).

The output is valve driven by DC motor with reducer. Motor is controlled with DC pulses with period and impulse length modulation.


What iv done to solve the problem?
Iv collected information from old and well working analog device. Visualization purpose graph below.
Iv found a way (equation) to find duty cycle value that changes the polarity of behavior of values T and t1. (table below)
I have written a PID algorithm code. Iv tested it and and i believe is it working as it should.(Iv written this code because i analog device was based on it, im in trouble to explain how).

Tables & Graphs:

**broken link removed**
Table
The duty cycle value which is between values period T - 4s and pos. impulse length t1 - 0,3s. The duty cycle value because it division ling between tease 2 values. By this duty cycle value i can find changing point.


**broken link removed**
Graph based on table.

**broken link removed**
PID. The x axis is sample nr. and y is changed values. This PID got no plant since feedback variable is set manually by varying ADC.



The thing i like to see ... want, is way to link... PID output... to look like values from collected graph based on table.
As much i understand "the thing"... mine only paradox is: If Temp. diff. (error) is more that 0 PID output keeps growing till limits, maybe not linearly but it will? The values from PID output look very different.
The table look like it is discreet, it seems like it is measured by moments and it is solvable by using switch statement or by using equation found by fitting.



I realize that this topic is misplaced because of nature of subject. Im very sorry. :S

Thank you in advance.
 

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