# Control

Control

If everything seems under control, you’re just not going fast enough. — Mario Andretti

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## Introduction1

### Dictionary

control : to exercise restraining or directing influence over — Merriam-Webster   See also OneLook

Control (Principia Cybernetica: Dictionary of Cybernetics and Systems)

### Encyclopedia

Control (Encyclopædia Britannica)

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## Foundation

### Theory

Control theory deals with the control of continuously operating dynamical systems in engineered processes and machines. The objective is to develop a control model for controlling such systems using a control action in an optimum manner without delay or overshoot and ensuring control stability.

To do this, a controller with the requisite corrective behaviour is required. This controller monitors the controlled process variable (PV), and compares it with the reference or set point (SP). The difference between actual and desired value of the process variable, called the error signal, or SP-PV error, is applied as feedback to generate a control action to bring the controlled process variable to the same value as the set point. Other aspects which are also studied are controllability and observability. On this is based the advanced type of automation that revolutionized manufacturing, aircraft, communications and other industries. This is feedback control, which is usually continuous and involves taking measurements using a sensor and making calculated adjustments to keep the measured variable within a set range by means of a “final control element”, such as a control valve.

Extensive use is usually made of a diagrammatic style known as the block diagram. In it the transfer function, also known as the system function or network function, is a mathematical model of the relation between the input and output based on the differential equations describing the system. — Wikipedia

### System

Control system is a device, or set of devices, that manages, commands, directs or regulates the behavior of other devices or systems. Industrial control systems are used in industrial production for controlling equipment or machines. There are two common classes of control systems, open loop control systems and closed loop control systems. In open loop control systems output is generated based on inputs. In closed loop control systems current output is taken into consideration and corrections are made based on feedback. A closed loop system is also called a feedback control system. — Wikipedia

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## Innovation

Control engineering is an discipline that applies automatic control theory to design systems with desired behaviors in control environments. The discipline of controls overlaps and is usually taught along with electrical engineering at many institutions around the world. The practice uses sensors and detectors to measure the output performance of the process being controlled; these measurements are used to provide corrective feedback helping to achieve the desired performance. Systems designed to perform without requiring human input are called automatic control systems (such as cruise control for regulating the speed of a car). Multi-disciplinary in nature, control systems engineering activities focus on implementation of control systems mainly derived by mathematical modeling of a diverse range of systems. — Wikipedia

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## Preservation

### History

(Modern) Control theory dates from the 19th century, when the theoretical basis for the operation of governors was first described by James Clerk Maxwell. Control theory was further advanced by Edward Routh in 1874, Charles Sturm and in 1895, Adolf Hurwitz, who all contributed to the establishment of control stability criteria; and from 1922 onwards, the development of PID control theory by Nicolas Minorsky. Although a major application of control theory is in control systems engineering, which deals with the design of process control systems for industry, other applications range far beyond this. As the general theory of feedback systems, control theory is useful wherever feedback occurs. A few examples are in physiology, electronics, climate modeling, machine design, ecosystems, navigation, neural networks, predator–prey interaction, gene expression, and production theory. — Wikipedia

### Library

Subject: Control (Open Library)

Subject: Control (WorldCat)

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## Participation

### Course

Control Courses (edX)

### Occupation

How to Become a Control Systems Engineer (Zippia)

### Event

Control Engineering Conferences (WWW Virtual Library, Department of Engineering, University of Cambridge)

### Document

Control System (USA.gov)

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## Expression

### Humor

Control Engineer Joke (Robert E. Buxbaum)

### Poem

OEDILF: The Omnificent English Dictionary In Limerick Form

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