Feed-forward controller with delayed command input

Data processing: generic control systems or specific application – Generic control system – apparatus or process – Optimization or adaptive control

Reexamination Certificate

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Details

C700S042000, C700S071000

Reexamination Certificate

active

06308106

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to the field of system controllers. More particularly, the present invention relates to system controllers for systems having an inherent delay between a command input and a system output.
It is commonly found in control systems that a phenomenon known as integrator overshoot may occur if compensators having integrators are used with systems having an inherent time delay. A typical control system will have a command input that is summed with a feedback signal to create an error signal. The error signal is applied to an input of a compensator, which usually has an integrator component to drive the error signal to zero. The output of the compensator is applied to the input of the control system. For a system with 100 percent feed-forward, an overshoot may occur following a change in the input command. In particular, due to the inherent delay of the system, an error signal provided to the compensator is generally transiently larger than that needed in order to have the system output track the command signal.
Since overshoot is typically undesirable, there is an ongoing need for a controller that can minimize or reduce the extent and/or duration of overshoot in a control system having an inherent delay.
SUMMARY OF THE INVENTION
A system controller for a controllable system having an inherent time delay includes a delay module that receives a command input and provides a first output signal delayed in time from the command input. A feed-forward module also receives the command input, or a function thereof, and provides a second output signal intended to drive the system to a desired state. A first summer receives the delayed output signal and a feedback signal from the controllable system. The first summer combines the delayed signal and the feedback signal to provide a third output signal. A compensator module receives the third output signal and provides a fourth output signal. A second summer receives the second output signal and the fourth output signal. The second summer combines the second output signal and the fourth output signal to provide an input signal for the controllable system. The modules can be implemented in hardware using conventional analog or digital components. Likewise, a processor can be provided to implement one or all of the modules as software routines.


REFERENCES:
patent: 4195337 (1980-03-01), Bertrand et al.
patent: 4872104 (1989-10-01), Holsinger
patent: 5406474 (1995-04-01), Hansen
patent: 5527238 (1996-06-01), Hrovat et al.
patent: 5587896 (1996-12-01), Hansen et al.
patent: 5623402 (1997-04-01), Johnson

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