What is Control Engineering (CE)? 

Control Engineering is a field of engineering where control techniques and strategies are developed using control theory (CT) to design a controller as per system requirement with desired behavior in the control environment. Generally, this subject is taught to electrical engineering, systems engineering, and mechanical engineering students at many institutes around the world. It is multidisciplinary in nature and actively emphasizes on implementation of a control system (CS) mainly derived by mathematical modeling of various processes input, output, and various components to design a tool to develop the controllers. 

Control engineering plays an important role from simple washing machines to high-performance fighter aircraft. It needs physical knowledge of input-output in various components to design a controller for its apparatus. A Network can be electrical, mechanical, chemical, and biological. Those structures are mathematical-based, a model-based analysis that uses time-domain, frequency domain, and complex s-domain, or else it depends upon the nature of the design. 

Most industrial controls may be classified according to their actions and different integrator: 

• Two-position or one position 
• Proportional (P) 
• Integral (I)  
• Proportional integral (PI)  
• Proportional derivative (PD)  
• Proportional integral derivative (PID)  

Control theory can be classified into two categories 

• Classical  
• Modern  

Classical  

The scope of the classical method is limited to a single-input signal output where this analysis can be carried out in three ways in Time-domain using differential equation 

Complex s-domain with Laplace transform Frequency domain (by converting from the complex s-domain). The solutions to the problems are based on mathematical equations and fundamental science. So it can be said that it is a subfield of engineering science strongly correlated to physics and maths. 

• It was introduced in 1920 - 1950 
• Deals with input-output variables. 
• Well-bloomed robustness concepts (gain / phase / margins). 
• No controllability interference. 
• No Observability interference. 
• No optimality concerns. 
• Well-evolved concepts and very much used in industry. 

Modern  

The limitation of the classical theory is overcomed by modern CT by multiple input multiple outputs. 

• It was developed in 1950 - 1980. 
• Deals with input-output and state variables. 
• Not well-evolved robustness concepts. 
• Controllability can be interference. 
• Observability can be interference. 
• Optimality issues can be incorporated. 
• Slowly gaining popularity in the industry. 

Generally, those CTs are practiced in two ways (including the type of system electrical, hydraulic, mechanical, and thermal dynamical systems) and they are as follows: 

Open-loop  

The command action is autonomous of the desired output response. 

• It is also known as a non-feedback loop CS. 
• The feedback path is not present. 
• Easy to design. 
• It is economical. Optimization is not possible. 
• It consumes less power. 
• Small bandwidth. 
• It is a stable system compared with a close loop scheme. 
• It is inaccurate in comparison with a closed-loop scheme. 

Closed-loop 

The command action is dependent on the desired output response 

• It is also known as a feedback loop CS 
• The feedback path is present 
• Difficult to design 
• It is costly 
• Optimization is possible 
• It consumes more power 
• Large bandwidth 
• It is a less stable set-up compare with an open-loop scheme 
• It is accurate in comparison with an open-loop scheme 

Based on Methodology CE can be Classified as Follows 

• Classical CE 
• Modern CE 
• Linear CE 
• Non-linear CE 
• Adaptive CE 
• Optimal CE 
• Robust CE 
• Game theory   
• Robust CE 

Robust methodology works to decrease the fault occurring in the system by considering parameters like environment, internal and external accuracies, noises, and disturbances which eventually leads to optimization of the system. 

Optimal CE 

In the optimal approach, the prime focus is on cost minimization. The problem is formulated using a mathematical model considering physical and performance limits to diminish the cost function. Thus, optimal control engineering is the finest choice for scheming a system with minimum cost. 

Adaptive CE 

To have accurate results adaptive CE adapts some mechanism like parameter adjustment (which is an additional loop to the existing normal system as shown below figure) for the sway of the controller parameters. 

Nonlinear CE 

This methodology is applicable to non-linear systems where non-linearity cannot be represented by using the ordinary differential function. The main drawback of this CT is that it requires a huge amount of mathematical analysis. 

Game theory 

This method is the combination of robust and optimal CE; the same concept is applied to this method. The problem is encountered against disturbances and noises to reduce the cost function. 

Types of Control  

• Manual 
• Semi-automatic   
• Automatic  
• Local  
• Remote  
• On or Off  
• Step by step  

Software Used in CE Domain

• MATLAB 
• LabVIEW 
• Measurement studio 
• Scilab 
• OCAD PSpice 
• GNU Octave 

Examples

Automobile Steering CS 

In a vehicle, for the direction of travel, the operation comprises the driver, steering mechanism, automobile, and feedback loop measurement visuals. 

Automobile interior cabin temperature CS 

For the comfort of the passenger, luxury vehicles are equipped with an air conditioning device consisting of a controller (thermostat and conditioning unit), Process (Automobile cabin), and Measurement (temperature sensor). 

• A Chemical composition CS 
• A light-seeking CS 
• A Car speed CS 
• NC machine position CS 
• Robot welder 
• An Aircraft flight path sway using GPS 
• Computer-aided technology 

Common Mistakes 

Usually, students and researchers fail to have adequate knowledge of Control engineering which leads to the wrong selection of the methods for their research/project work. 

Context and Applications 

A common use of control theory includes cruise control in a motor vehicle, temperature control in a building, Robotics, chemical concentration in drinking water, speed of a conveyor belt in a process plant, etc. 

CE field has wide applications like in the military, industry, virtually every modern vehicle in the world, Programmable control center (PLC) SCADA in the industrial automation network with the use of HMI displays, for real-time operation in remote terminal units RTU. 

CS is a part of industrial and automation. The types of approach which are popular and regulate those processes include distributed control system (DCS) and supervisory control and data acquisition (SCADA). 

Control systems engineers or Systems engineers make use of Highly integrated software for the simulation of all the applications mentioned above including advanced control applications like motion control, nervous systems, vision systems, and dynamic systems linked with electrical instrumentation, etc. 

Controls Engineer are posted in below sectors like  

• Agriculture  
• Chemical plant
• Pulp and paper mills
• Nuclear power plant  
• Sewage treatment plant  
• Metals in mines  
• Sugar refinery plants
• Quality Inspection
• Boiler control and power plant  
• Environmental control  
• Water treatment plants  
• Food and food processing  
• Pharmaceutical manufacturing