Prevention of integrator wind-up in PI type controllers
A control system having an integrator component that provides an integrator output signal used to control a load, and a method controlling the same includes conditioning the integrator component during a fraction of the period in which it would tend to otherwise wind-up.
1. A control system for controlling a load, the controller comprising:
a first summer adapted to receive a command signal and a feedback signal, the first summer adapted to generate a system error signal based upon the command signal and the feedback signal;
a proportional gain component adapted to receive the system error signal, the proportional gain component adapted to generate a proportional gain output based upon the system error signal;
a differentiator component adapted to receive one of an input signal based on the command signal or the feedback signal, the differentiator component adapted to generate a differentiated signal based upon the one of the input signal;
a second summer adapted to receive the differentiated signal and the system error signal, the second summer adapted to generate a modified system error signal based upon the differentiated signal and the system error signal;
an integral gain component adapted to receive the modified system error signal, the integral gain component adapted to generate an integrating output signal based upon the modified system error signal; and
a third summer adapted to receive the proportional gain output and the integrating output signal, the third summer adapted to generate a second command signal, the second command signal being utilized to control the load and being based at least in part upon the proportional gain output and the integrating output signal.
2. The control system of claim 1 and further comprising:
a differentiator gain component adapted to receive the system error signal, the differentiator gain component adapted to generate a differentiator output signal based upon the system error signal; and
wherein the third summer is further adapted to receive the differentiator output signal and to generate the second command signal based at least in part upon the differentiator output signal.
3. The control system of claim 1 wherein the differentiated signal is proportional to a rate of change of the one of the input signal.
4. The control system of claim 1 wherein the differentiated signal is scaled.
5. The control system of claim 1 wherein the one of the input signal is based on the command signal.
6. The control system of claim 1 wherein the one of the input signal is based on the feedback signal.
7. The control system of claim 1 wherein the integrating output signal is a result of integrating the modified system error signal.
8. A control system for controlling a load, the control system comprising:
a feedback circuit adapted to provide a feedback signal based on operation of the load;
a first summer adapted to receive a command signal and the feedback signal and generate a system error signal;
a differentiator component adapted to provide a differentiated signal, the differentiator component adapted to receive one of an input signal based on the command signal or the feedback signal;
a second summer adapted to receive the system error signal and the differentiated signal and generate a modified system error signal;
an integral gain component adapted to receive the modified system error signal and provide an integrating output signal used to control the load; and
a proportional gain component adapted to receive the system error signal and to provide a proportional gain output signal used to control the load.
9. The control system of claim 8 wherein the one of the input signal is based on the command signal.
10. The control system of claim 8 and further comprising:
a differentiator gain component adapted to receive the system error signal and to provide a differentiator output signal used to control the load.
11. The control system of claim 10 and further comprising:
a third summer adapted to receive the integrator output signal, the proportional output signal, and the differentiator output signal, the third summer combining the integrator output signal, the proportional output signal, and the differentiator output signal to generate a signal for controlling the load.
12. The control system of claim 8 and further comprising:
a third summer adapted to receive the integrator output signal and the proportional output signal, the third summer combining the integrator output signal and the proportional output signal to generate a signal for controlling the load.
13. The control system of claim 8 and further comprising:
a current feedback scaling circuit that adjusts a gain of the feedback signal.
14. A method for operating a controller used to control a load, the controller comprising an integrator component adapted to provide an integrator output signal for controlling the load, the method comprising:
conditioning the integrator component during a fraction of the period in which it would tend to otherwise wind-up wherein conditioning comprises reverse-charging the integrator component based upon a slew rate or an amplitude to a value less than the value required to maintain a steady-state level desired for the load.
15. The method of claim 14 wherein reverse-charging comprises:
receiving one of an input signal based on a command signal or a feedback signal;
differentiating said input signal;
combining said input signal with a signal based on the command signal; and
providing the combined input signal and the signal based on the command signal to the integrator component.
16. A control system for controlling a load, the controller comprising:
an integrator component adapted to provide an integrator output signal used to control the load; and
a component adapted to reverse-charge the integrator component to a value less than the value required to maintain a steady-state level desired for the load wherein the integrator component is reverse-charged based upon a slew rate.
17. A control system for controlling a load, the controller comprising:
an integrator component adapted to provide an integrator output signal used to control the load; and
a component adapted to reverse-charge the integrator component to a value less than the value required to maintain a steady-state level desired for the load wherein the integrator component is reverse-charged based upon an amplitude.