What is a Control System?
A control system can be defined as a mechanism or means whereby the desired response is obtained using given input. Let us take an example to make the meaning of a control system clear. When you press your leg on the accelerator pedal of an automobile, it moves forward. The acceleration is directly proportional to the amount of push you exert. The desired speed can be maintained by controlling pressure on the accelerator pedal. This automobile driving system, which comprises the accelerator, carburetor and the engine, constitutes a control system. There are numerous applications around us where control systems come to play – the washing machine and the dishwater we use at home, the CNC machines and robot arms used in workshops, the lifts that we use at the office, all are governed by underlying circuitry that invariably involves some kind of a control system. From these examples, it should be clear that control systems are not limited to any engineering discipline but are equally applicable to aeronautical, chemical, mechanical, environmental, civil and electrical engineering. In fact, most control systems often blend electrical, mechanical and chemical components. It is worth noting that control systems exist naturally as well. For example, if we become too hot after vigorous exercise, our bodies sweat in order to cool down. And if we shiver in the cold, the brain is sending message to the muscles to tighten and loosen quickly, as this generates heat. We are so accustomed to natural and man-made control systems that we do not even think twice about it.
There are two types of control systems – open loop and closed loop.
Again, let us make the distinction between the two clear with a real-life example. Let’s say there is a traffic junction regulated by signals. In some cases, the lights turn from green to red at a set time automatically, without paying any attention to whether there is any traffic or not. In rush hours, a few of the signals are handled manually by the traffic police. They check the volume of traffic, and then vary the duration of the signal depending upon the volume of the vehicular traffic. The automatic signals are part of an open loop control system and the manual, feedback oriented signals are examples of a closed loop system. A closed-loop control system looks at the current output and alters it to the desired condition; also known as a feedback system.
Control systems can also be classified based on whether they are linear or non-linear. A system is said to be linear if it obeys the principle of homogeneity and principle of superposition. The principle of homogeneity states that the dimensions of each of the terms of a dimensional equation on both sides are the same. The principle of superposition states that a system is linear if the response due to several inputs acting simultaneously is equal to the sum of the responses of each input acting alone. This explanation is quite rudimentary, but should be sufficient to understand what linear systems are. A system is said to be non-linear if either the principle of superposition or homogeneity is not applicable to it. Electrical circuits like amplifiers and filters are examples of linear systems while the triangulation of GPS signals is an example of a non-linear system.
Control systems are the basis of automation and are needed to maintain a process at the required operating conditions safely and effectively.
Designing of Control Systems
Designing control systems involves representing it with a set of different mathematical equations. Called as a mathematical model, they are useful for analysis and design of control systems. The objective of control system design is to construct a system that has a desirable response to standard inputs and conforms to the mathematical model. Designing of modern control systems predominantly use the differential equation model, transfer function model, state space model, the root locus and a few other analysis techniques.
MATLAB for Control Systems
It should be clear by now that while it is easier to intuitively understand what a control system is, actually designing one is quite a challenging task as it involves a lot of mathematics. This is where MATLAB is helpful. MATLAB is one of the most powerful tools in computation, numerical analysis and system design. Its user friendly environment, in addition to its powerful computational kernel and graphical visualization capabilities make it an integral part of the control system design, optimization and implementation. Along with the basic MATLAB command package, several additional toolboxes have been developed for specific purposes that extend MATLAB’s capabilities, two prime examples for control systems being Simulink and Control Systems Toolbox. MATLAB provides algorithms and apps for systematically analyzing, designing, and tuning linear control systems. With MATLAB, it is possible specify a system as a transfer function, state-space, zero-pole-gain, or frequency-response model. Enhancements to MATLAB lets users analyze and visualize system behaviour in the time and frequency domains.
As India and the world move towards automation, control systems will play a pivotal role in the smooth working of machines and gadgets. With MATLAB, you can reduce the design workload and expedite development of efficient control systems.