应用于电气系统的可编程序控制器—外文翻译.doc

附录附录1Programmable designed for electro-pneumatic systems controllerThis project deals with the study of electro-pneumatic systems and the programmable controller that provides an effective and easy way to control the sequence of the pneumatic actuators movement and the states of pneumaticsystem. The project of a specifi c controller for pneumatic applicationsjoin the study of automation design and the control processing of pneumaticsystems with the electronic design based on microcontrollers to implementthe resources of the controller. 1. IntroductionThe automation systems that use electro-pneumatic Technology are formed mainly by three kinds of elements: actuators or motors, sensors or buttonsand control elements like valves.Nowadays, most of the control elements used to execute the logic of the system were substituted by the Programmable Logic Controller(PLC). Sensors and switches are plugged as inputs and the direct control valves for the actuators are plugged as outputs.An internal program executes all the logic necessary to the sequence of the movements, simulatesOther components like counter,timer and control the status of the system.With the use of the PLC,the project wins agility,because it is possible to create and simulate the system as many times as needed.Therefore,timeCan be saved,risk of mistakes reduced and complexity can be increased usingThe same elements.A conventional PLC,that is possible to find on the market from many companies,offers many resources to control not only pneumatic systems, but all kinds of system that uses electrical components. The PLC can be very versatile and robust to be applied in many kinds application of in the industry or even security system and automation of buildings.Because of those characteristics, in some applications the PLC offers to much resources that are not even used to control the system, electro-pneumatic system is one of this kind of application. The use of PLC, especially for small size systems, can be very expensive for the automation project.An alternative in this case is to create a specific controller that can offer the exactly size and resources that the project needs[3,4]. This can be madeusing microcontrollers as the base of this controller.The controller, based on microcontroller, can be very specific and adapted to only one kind of machine or it can work as a generic controller thatcan be programmed as a usual PLC and work with logic that can be changed. All these characteristics depend on what is needed and how much experiencethe designer has with developing an electronic circuit and firmware for microcontroller. But the main advantage of design the controller with the microcontroller is that the designer has the total knowledge of his controller, which makes it possible to control the size of the controller, change the complexity and the application of it. It means that the project gets more independence from other companies, but at the same time the responsibility of the control of the system stays at the designer hands.2. Electro-pneumatic systemOn automation system one can find three basic components mentioned before, plus a logic circuit that controls the system. An adequate technique is neededto project the logic circuit and integrate all the necessary components to execute the sequence of mo vements properly.For a simple direct sequence of movement an intuitive method can be used[1,5], but for indirect or more complex sequences the intuition can generate a very complicated circuit and signal mistakes. It is necessary to use another method that can save time of the project, make a clean circuit, can eliminate occasional signal overlapping and redundant circuits. The presented method is called step-by-step or algorithmic[1,5], it is valid for pneumatic and electro-pneumatic systems and it was used as a base in this work. The method consists of designing the systems based on standard circuits made for each change on the state of the actuators, these changes are called steps.The first part is to design those kinds of standard circuits for each step, the next task is to link the standard circuits and the last part is to connect the control elements that receive signals from sensors, switches and the previous movements, and giv e the air or electricity to the supply lines of each step. In Figs. 1 and2 the standard circuits are drawn for pneumatic and electro-pneumatic system[8]. It is possible to see the relations with the previous and the next steps.3. The method applied inside the controllerhe result of the method presented before is a sequence of movements of the actuator that is well defined by steps. It means that each change on the position of the actuators is a new state of the system and the transition between states is called step. The standard circuit described before helps the designer to define the states of the systems and to define the condition to each change between t。