The term is defined as a system of automatic control system that has a feedback control with reference to the desired input or output can be constant or change slowly over time, have the main task is to maintain actual output is at the desired value by the disruption.
There are many examples of automated control systems, some of which are control room temperature automatically cars, automatic voltage regulator in the power plant with the variation of the electric power load, auto control the pressure and temperature of the chemical process and automatically control the temperature in the room.
Figure 2.2 Block Diagram of the Open Loop Control Systems
The term process control system (process control system) is an automatic control system with the output of magnitude such as temperature, pressure, flow, liquid surface level or pH-called process control system. Process control is widely used in the industry. Control with programs such as controlling temperature furnace with a temperature-controlled furnace according to the instructions that have been programmed in advance is often used on such a system.
Block Diagram Figure 2.3 Closed Loop Control Systems
For example, the program must be arranged in advance can be an instruction to raise the temperature of the furnace to another specified price during a certain time interval the others as well. In the control with such a program, set point is changed in accordance with a predetermined time schedule. Controller (controller) then serves to keep the temperature of the furnace in order to approach the changed set point.
Should be noted that most of the servo process control system as part of an integrated mechanism. The term closed loop control system is often referred to as a feedback control system. Practically and often the terms of feedback control and closed-loop control can be interchangeable use.
In the closed loop control system, an error signal that is working, ie the difference between the input signal feedback signal (which may signal the output itself or function of the output signal and its derivatives), presented to the controller in such a way to reduce errors and bring the system output to the desired value , The term closed loop control always means using feedback control action to reduce system errors.
The term open loop control system can be defined as a system whose output has no effect on the control action is called open-loop control system. In other words, an open loop control system output can not be used as a comparison feedback with feedback. A simple example is the washing machine. Soaking, washing and rinsing in the washing machine is done on the basis of time. This machine does not measure the output signal is the level of cleanliness of clothing.
Servo System
The term Servo System or servomekanisme system is defined as a control system baited and forth with the output of the position, velocity, or acceleration mechanics. Therefore, the term servomekanisme and control systems position (or velocity or acceleration) are synonymous. Servomekanisme widely used in modern industry. Examples of this mechanism servo system is operating an automatic machine tool as a whole or complete, together with instructions programmed, can be achieved by the use of servo systems.
It should be noted that the control system, the output (such as the position of an aircraft in the sky at an automatic landing system) needs to follow a path in space that has been determined, called servo system as well. Other examples include arm-robot control system, in which the robotic arm should follow a certain path in the room that has been determined, and automated aircraft landing systems, the aircraft should follow a path in space that has been determined.