Executive elements

General terms, principle of operation and division of executive elementsThe basic task of the automatic control and regulation system is to act on the controlled object so that its output size approaches the given value. That action often consists in movement of a moving part, for example: a closure for fluid flow, or a moving part of a working part of the machine, either in a given position or at a given speed.The final control elements are actuators. The actuator consists of an amplifier and an executive elements.At its input, it receives a signal from the control part of the system, which it should: 1. amplify, and 2. convert into form suitable for acting on the process. The signal from the control part (regulator) has a low power, it should cause some desired effect: close some valve, increase pressure or temperature, etc.The input part of the actuator is an amplifier that amplifies that signal. The second part of the actuator is the executive elements.The executive elements acts directly on the process – it converts the input quantity into different forms: electrical power into movement, electricity into heat…Depending on the energy used, executive elements can be:- electric,- hydraulic,- pneumatic.As is commonly known, electrical appliances use electricity. Hydraulic devices they use a liquid under pressure (most often oil), and in the case of pneumatic devices, the working fluid is air under pressure or inert gas under pressure. Pneumatic and hydraulic devices are applied because simple construction, relatively small dimensions, high safety and durability, as well as possibilities of high power transmission.According to the method of acting on the process, executive elements are divided into:- continuous and- discrete.Continuous actuators are applied when it is necessary to establish the value of the output signal in a continuous range (Example: dryer – if the temperature of the chamber needs to be increased by a certain percentage the current through the heater should be increased by that percentage, if the time that the material is to be increased carried out in the drying chamber, the speed of the motor that moves the material through the dryer should be reduced).Discrete executive elements are used to control processes, machines and equipment that can have ONLY TWO STATES (1/0, on/off, true/false, object is/is not present, high/low voltage,…).