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Control engineering, also known ascontrol systems engineering and, in some European countries,automation engineering, is anengineering discipline that deals withcontrol systems, applyingcontrol theory to design equipment and systems with desired behaviors in control environments.[1] The discipline of controls overlaps and is usually taught along withelectrical engineering,chemical engineering andmechanical engineering at many institutions around the world.[1]
The practice usessensors and detectors to measure the output performance of the process being controlled; these measurements are used to provide correctivefeedback helping to achieve the desired performance. Systems designed to perform without requiring human input are calledautomatic control systems (such ascruise control for regulating the speed of a car).Multi-disciplinary in nature, control systems engineering activities focus on implementation of control systems mainly derived bymathematical modeling of a diverse range ofsystems.[2]
Modern day control engineering is a relatively new field of study that gained significant attention during the 20th century with the advancement of technology. It can be broadly defined or classified as practical application ofcontrol theory. Control engineering plays an essential role in a wide range of control systems, from simple household washing machines to high-performancefighter aircraft. It seeks to understand physical systems, using mathematical modelling, in terms of inputs, outputs and various components with different behaviors; to use control system design tools to developcontrollers for those systems; and to implement controllers in physical systems employing available technology. Asystem can bemechanical,electrical,fluid,chemical,financial orbiological, and its mathematical modelling, analysis and controller design usescontrol theory in one or many of thetime,frequency andcomplex-s domains, depending on the nature of the design problem.
Control engineering is the engineeringdiscipline that focuses on themodeling of a diverse range ofdynamic systems (e.g.mechanicalsystems) and the design ofcontrollers that will cause these systems to behave in the desired manner.[3]: 6 Although such controllers need not be electrical, many are and hence control engineering is often viewed as a subfield of electrical engineering.
Electrical circuits,digital signal processors andmicrocontrollers can all be used to implementcontrol systems. Control engineering has a wide range of applications from the flight and propulsion systems ofcommercial airliners to thecruise control present in many modernautomobiles.
In most cases, control engineers utilizefeedback when designingcontrol systems. This is often accomplished using aproportional–integral–derivative controller(PID controller) system. For example, in anautomobile withcruise control the vehicle'sspeed is continuously monitored and fed back to the system, which adjusts themotor'storque accordingly. Where there is regular feedback,control theory can be used to determine how the system responds to such feedback. In practically all such systemsstability is important and control theory can help ensure stability is achieved.
Although feedback is an important aspect of control engineering, control engineers may also work on the control of systems without feedback. This is known asopen loop control. A classic example ofopen loop control is awashing machine that runs through a pre-determined cycle without the use ofsensors.
Automatic control systems were first developed over two thousand years ago. The first feedback control device on record is thought to be the ancientKtesibios'swater clock inAlexandria, Egypt, around the third century BCE. It kept time by regulating the water level in a vessel and, therefore, the water flow from that vessel.[3]: 22 This certainly was a successful device as water clocks of similar design were still being made in Baghdad when the Mongolscaptured the city in 1258 CE. A variety of automatic devices have been used over the centuries to accomplish useful tasks or simply just to entertain. The latter includes the automata, popular in Europe in the 17th and 18th centuries, featuring dancing figures that would repeat the same task over and over again; these automata are examples of open-loop control. Milestones among feedback, or "closed-loop" automatic control devices, include the temperature regulator of a furnace attributed toDrebbel, circa 1620, and the centrifugal flyball governor used for regulating the speed of steam engines by James Watt[3]: 22 in 1788.
In his 1868 paper "On Governors",James Clerk Maxwell was able to explain instabilities exhibited by the flyball governor using differential equations to describe the control system. This demonstrated the importance and usefulness of mathematical models and methods in understanding complex phenomena, and it signaled the beginning of mathematical control and systems theory. Elements of control theory had appeared earlier but not as dramatically and convincingly as in Maxwell's analysis.
Control theory made significant strides over the next century. New mathematical techniques, as well as advances in electronic and computer technologies, made it possible to control significantly more complex dynamical systems than the original flyball governor could stabilize. New mathematical techniques included developments in optimal control in the 1950s and 1960s followed by progress in stochastic, robust, adaptive, nonlinear control methods in the 1970s and 1980s. Applications of control methodology have helped to make possible space travel and communication satellites, safer and more efficient aircraft, cleaner automobile engines, and cleaner and more efficient chemical processes.
Before it emerged as a unique discipline, control engineering was practiced as a part ofmechanical engineering andcontrol theory was studied as a part ofelectrical engineering sinceelectrical circuits can often be easily described using control theory techniques. In the first control relationships, a current output was represented by a voltage control input. However, not having adequate technology to implement electrical control systems, designers were left with the option of less efficient and slow responding mechanical systems. A very effective mechanical controller that is still widely used in some hydro plants is thegovernor. Later on, previous to modernpower electronics, process control systems for industrial applications were devised by mechanical engineers usingpneumatic andhydraulic control devices, many of which are still in use today.
David Quinn Mayne, (1930–2024) was among the early developers of a rigorous mathematical method for analysingModel predictive control algorithms (MPC). It is currently used in tens of thousands of applications and is a core part of the advanced control technology by hundreds of process control producers. MPC's major strength is its capacity to deal with nonlinearities and hard constraints in a simple and intuitive fashion. His work underpins a class of algorithms that are probably correct, heuristically explainable, and yield control system designs which meet practically important objectives.[4]
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Acontrol system manages, commands, directs, or regulates the behavior of other devices or systems usingcontrol loops. It can range from a single home heating controller using athermostat controlling a domestic boiler to largeindustrial control systems which are used for controllingprocesses or machines. The control systems are designed via control engineering process.
For continuously modulated control, afeedback controller is used to automatically control a process or operation. The control system compares the value or status of theprocess variable (PV) being controlled with the desired value orsetpoint (SP), and applies the difference as a control signal to bring the process variable output of theplant to the same value as the setpoint.
Forsequential andcombinational logic,software logic, such as in aprogrammable logic controller, is used.[clarification needed]Control theory is a field of control engineering andapplied mathematics that deals with thecontrol ofdynamical systems. The aim is to develop a model or algorithm governing the application of system inputs to drive the system to a desired state, while minimizing anydelay,overshoot, orsteady-state error and ensuring a level of controlstability; often with the aim to achieve a degree ofoptimality.
To do this, a controller with the requisite corrective behavior is required. This controller monitors the controlledprocess variable (PV), and compares it with the reference orset point (SP). The difference between actual and desired value of the process variable, called theerror 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 arecontrollability andobservability. Control theory is used incontrol system engineering to design automation that have revolutionized manufacturing, aircraft, communications and other industries, and created new fields such asrobotics.
Extensive use is usually made of a diagrammatic style known as theblock diagram. In it thetransfer function, also known as the system function or network function, is a mathematical model of the relation between the input and output based on thedifferential equations describing the system.
Control theory dates from the 19th century, when the theoretical basis for the operation of governors was first described byJames Clerk Maxwell.[5] Control theory was further advanced byEdward 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 ofPID control theory byNicolas Minorsky.[6]
Although the most direct application ofmathematical control theory is its use incontrol systems engineering (dealing withprocess control systems forrobotics and industry), control theory is routinely applied to problems both the natural andbehavioral sciences. As the general theory of feedback systems, control theory is useful wherever feedback occurs, making it important to fields likeeconomics,operations research, and thelife sciences.[7]At many universities around the world, control engineering courses are taught primarily inelectrical engineering andmechanical engineering, but some courses can be instructed inmechatronics engineering,[8] andaerospace engineering. In others, control engineering is connected tocomputer science, as most control techniques today are implemented through computers, often asembedded systems (as in the automotive field). The field of control withinchemical engineering is often known asprocess control. It deals primarily with the control of variables in a chemical process in a plant. It is taught as part of the undergraduate curriculum of any chemical engineering program and employs many of the same principles in control engineering. Other engineering disciplines also overlap with control engineering as it can be applied to any system for which a suitable model can be derived. However, specialised control engineering departments do exist, for example, in Italy there are several master in Automation & Robotics that are fully specialised in Control engineering or the Department of Automatic Control and Systems Engineering at the University of Sheffield[9] or the Department of Robotics and Control Engineering at the United States Naval Academy[10] and the Department of Control and Automation Engineering at the Istanbul Technical University.[11]
Control engineering has diversified applications that include science, finance management, and even human behavior. Students of control engineering may start with a linear control system course dealing with the time and complex-s domain, which requires a thorough background in elementary mathematics andLaplace transform, called classical control theory. In linear control, the student does frequency and time domain analysis.Digital control andnonlinear control courses requireZ transformation and algebra respectively, and could be said to complete a basic control education.
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A control engineer's career starts with a bachelor's degree and can continue through the college process. Control engineer degrees are typically paired with an electrical or mechanical engineering degree, but can also be paired with a degree in chemical engineering. According to aControl Engineering survey, most of the people who answered were control engineers in various forms of their own career.[12]
There are not very many careers that are classified as "control engineer", most of them are specific careers that have a small semblance to the overarching career of control engineering. A majority of the control engineers that took the survey in 2019 are system or product designers, or even control or instrument engineers. Most of the jobs involve process engineering or production or even maintenance, they are some variation of control engineering.[12]
Because of this, there are many job opportunities in aerospace companies, manufacturing companies, automobile companies, power companies, chemical companies, petroleum companies, and government agencies. Some places that hire Control Engineers include companies such as Rockwell Automation, NASA, Ford, Phillips 66,Eastman, and Goodrich.[13] Control Engineers can possibly earn $66k annually from Lockheed Martin Corp. They can also earn up to $96k annually from General Motors Corporation.[14] Process Control Engineers, typically found inRefineries and Specialty Chemical plants, can earn upwards of $90k annually.[citation needed]
In India, control System Engineering is provided at different levels with a diploma, graduation and postgraduation. These programs require the candidate to have chosen physics, chemistry and mathematics for their secondary schooling or relevant bachelor's degree for postgraduate studies.[15]
Originally, control engineering was all about continuous systems. Development of computer control tools posed a requirement of discrete control system engineering because the communications between the computer-based digital controller and the physical system are governed by acomputer clock.[3]: 23 The equivalent toLaplace transform in the discrete domain is theZ-transform. Today, many of the control systems are computer controlled and they consist of both digital and analog components.
Therefore, at the design stage either:
The first of these two methods is more commonly encountered in practice because many industrial systems have many continuous systems components, including mechanical, fluid, biological and analog electrical components, with a few digital controllers.
Similarly, the design technique has progressed from paper-and-ruler based manual design tocomputer-aided design and now tocomputer-automated design or CAD which has been made possible byevolutionary computation. CAD can be applied not just to tuning a predefined control scheme, but also to controller structure optimisation, system identification and invention of novel control systems, based purely upon a performance requirement, independent of any specific control scheme.[16][17]
Resilient control systems extend the traditional focus of addressing only planned disturbances to frameworks and attempt to address multiple types of unexpected disturbance; in particular, adapting and transforming behaviors of the control system in response to malicious actors, abnormal failure modes, undesirable human action, etc.[18]
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