In the study of engineering, we need to define additional terms are necessary to describe control systems, such as: plant, disturbances, feedback control, and a feedback control system. The following will be given definitions. Then a description of the system is a closed loop and open loop, and also the advantages and shortcomings compared to the open loop control system and a closed loop.
Figure 2.1 Block Diagram Control System General
The term plant is defined as a set of equipment, may consist of several parts of the machine are working together, which is used to perform a particular operation. In this book, every physical object that is controlled (such as heating furnaces, chemical reactors, and spacecraft) called the plant.
The term process (process) according to the Merriam-Webster dictionary defines as the process or the operation of a natural progression that takes place continuously characterized by a row of small sequence changes by way of relatively fixed and go to a particular outcome or end state; or an operation that deliberately, takes place continuously, which consists of several actions or changes are controlled, systematically directed toward a particular outcome or end state. In this book, each controlled operation called process.
An example is the chemical process, economics, and biology. The term system (system) is defined as a combination of several components that work together and perform a particular target. The system is not limited to physical systems. The concept of the system can be used in the abstract and dynamic phenomenon as seen in the economy. Therefore, the term system should be interpreted to state system of physical, biological, economic, and so on.
The term disorders (disturbances) is defined is defined as a signal that tends to have an adverse effect on the price of the system output. If a disturbance is generated in the system, called internally, while external interference generated outside the system and an input.
The term feedback control can be explained as follows. Feedback control refers to an operation, which in the presence of interference, tends to reduce the difference between the output of the system and a reference input and that it was doing based on this difference. Here only interference is expected which is determined so, because of the disruption that can be expected or disorder known to be always compensated in the system.
The term feedback control system. Systems that maintain a specified relationship between output and input some reference, comparing them and using the difference as a control tool called a feedback control system. Examples for this system is room temperature control system. By measuring the actual room temperature and compare it with the reference temperature (desired temperature), thermostat run the heating or cooling, or turn it off in a way that ensures that the room temperature remains at a comfortable temperature does not depend on external circumstances.
A feedback control system is not limited in the fields of engineering, but can also be found in various fields not engineering. The human body, for example, is a feedback control system that is very advanced. Both body temperature and blood pressure kept constant by a feedback tool physiology. In fact, feedback carry out vital functions. He made the human body is relatively insensitive to external interference, so enable it to function properly in a changing field.
As another example, review the control of car speed by a human operator. The driver decides the speed, corresponding to a situation, which is probably the speed limit indicated on a highway or freeway is concerned. This velocity acts as the reference speed.