analog PID controller trouble??

[Elits]

Hi all,
i try build analog PID controller using opamp, after finished i test it. when input PID is 0V why the output become 10 volt? how to check if my PID it's work? is there any metode to tuning PID? plese give me some reference? thanks

PS: i test the plant and it works well.

Regards
elits

 

[diemilio]

Could you please post schematic??

diemilio

 

[Elits]

here is the scematic

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[Siniša]

Your "I" and "D" circuit don't have any gain limit or control. What happens is that your "I" circuit has unlimited gain at DC and locks up in either power supply rail depending on offset error. You should probably have fixed arbritrary corner frequencies of "I" and "D" circuits and adjustable gain on all 3 with fixed overall gain of output amp. Circuit as you draw it would never work. Choose corner frequency at natural resonance of your system.
Once circuit is designed properly, it is adjusted in sequence starting with P parameter first to half of value needed for system to start oscillation. Then D to get desired step response and I to get low offset. I and D are usually tweaked after depending on specs you require. Plenty of reference for this on the net.

 

[diemilio]

What Sinisa says its true. You need an extra resistor on the opamp feedback of your I section to fix your DC gain and avoid infinite values (which would make your circuit to saturate to Vcc or -Vcc)

diemilio

 

[Kral]

Elits,
Your integrator input should see the difference between the input and output. In your implementation, it only sees the input. That is why the output is stuck. With zero input, the integrator output does not move. Also, you need a means to initialize (reset) the integrator.
Regards,
Kral