Control Theory, in electrical engineering, is a mathematical theory which provides a method for assessing a systems response, or output, for a specific input, and will also determine whether the stability of the system is affected.
The theory relies on the use of circuit and network theories to provide equations which model the performance of the electrical circuits. The idea of modelling electrical circuits dates back to 1827 when G. Ohm first defined the relationship between voltage and current.
An important category of control systems is automatic control systems, which require a feedback signal from the output to a controlling device which provides a self-regulating function (see feedback principle). In general, the controller will compare the output signal to some reference or preset signal, and will take any correcting action necessary to maintain the output within limits defined by the reference.
In 1932, in the USA, H. Nyquist invented a graphical technique which analysed feedback systems and allowed designers to check whether an automatic system would become unstable during operation. The control of electricity supply networks, where the frequency and power outputs of large generating machines must remain within statutory limits, is one modern example of the everyday application of control theory. AC |
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