Introduction to Single-Input Single-Ouput Control Systems

Open-Loop Systems and the Need for Control

Open-loop systems lack feedback and therefore cannot compensate for errors. Prior to the advent of feedback sensors and control theory, man provided the error correction. As the complexity and speed of machines grew people were no longer capable of providing adequate feedback.

Today we have a large variety of feedback sensors for error correction allowing for fully automated control. With control systems comes the ability to make adjustments to a given system parameter at rates well above any human's capability (i.e. a 1 kHz update is reasonable for a automated system and impossible for a person). Higher update rates allow a properly designed system to make corrections faster. These corrections will be tiny since inaccuracies have had little time to accumulate.

Systems Control Techniques

Classical control methods can be categorized into Frequency Domain techniques and Time Domain techniques. Frequency Domain techniques are a suite of analysis and design methodologies that include Root Locus, Pole Placement, Bode Plots, and Nyquist.

Single-Input Single-Output (SISO) control systems are the primary focus of undergraduate control systems courses. Many implementable mechanisms are SISO. An example of an SISO system is a refrigerator's thermostat