Electro-pneumatic control system and PID control circuit

An electronic PID control circuit for providing fast and accurate closed-loop control of a load, said PID control circuit comprising:

• a command input terminal for receiving a command signal input (V.sub.d) corresponding to a desired output response provided to said load;
• a feedback input terminal for receiving a feedback signal (V.sub.o) corresponding to the actual observed output response provided to said load;
• a control output terminal adapted to produce in response to said command signal input and said feedback signal a control signal output (V.sub.c) for controlling said load, said control signal output being generated substantially in accordance with a predetermined transfer function of said control circuit, said transfer function having the form:
• ##EQU11## where R.sub.1, R.sub.2, R.sub.3, C.sub.1 and C.sub.2 represent component values of individual electrical elements comprising said PID control circuit.

A single op-amp PID control circuit having inherent integrator anti-windup compensation, said PID control circuit comprising:

• a single inverting op-amp having at least one input terminal and at least one output terminal;
• a first electrical impedance coupled between a command input terminal of said PID control circuit and said input terminal of said op-amp and being adapted to deliver to said input terminal of said op-amp a first current that is substantially proportional to a command voltage signal provided to said command input terminal;
• a second electrical impedance coupled between a feedback input terminal of said PID control circuit and said input terminal of said op-amp and being adapted to deliver to said input terminal of said op-amp a second current having at least one component thereof that is substantially proportional to a feedback voltage signal provided to said feedback input terminal and at least another component that is substantially proportional to the derivative of said feedback voltage signal;
• and
• a third electrical impedance coupled between the output terminal of said op-amp and said input terminal of said op-amp and being adapted to deliver to said input terminal of said op-amp a current that is equal and opposite to the sum of the current delivered to said input terminal of said op-amp by said first and said second impedances, said third impedance further comprising an integrating storage element adapted to produce a control voltage signal output on a control output terminal of said PID control circuit that is substantially proportional to the integral of said current delivered to said input terminal of said op-amp by said third electrical impedance.