[通信電子]畢業(yè)設(shè)計(jì)外文資料翻譯-應(yīng)用于電氣系統(tǒng)的可編程控制器plc免費(fèi)下載(參考版)
2024-10-17 16:56本頁(yè)面
【正文】 the system made with microcontroller is an alternative that works in a simple way. 。 4byte: value for the outputs。 2byte: mask for the inputs。 the speed is regulated by a flowing control valve. It was the second step. B and C are examples of actuators working together, while B pushes an object slowly, C repeats its work for some time. When B reaches the final position, C stops immediately its cycle and es back to the initial position. The actuator D is a single acting one with spring return and works together with the back of C, it is the third step. D works making very fast forward and backward movement, just one time. Its backward movement is the fourth step. D could be a tool to make a hole on the object. When D reaches the initial position, A and B return too, it is the fifth step. Fig. 6 shows the first part of the designing process where all the movements of each step should be defined [2]. (A+) means that the actuator A moves to the advanced position and (A?) to the initial position. The movements that happen at the same time are joined together in the same step. The system has five steps. These two representations of the system (Figs. 5 and 6) together are enough to describe correctly all the sequence. With them is possible to design the whole control circuit with the necessary logic ponents. But till this time, it is not a plete system, because it is missing some auxiliary elements that are not included in this draws because they work in parallel with the main sequence. These auxiliary elements give more function to the circuit and are very important to the final application。 each string has the configuration of one step of the process. There are two bytes for the inputs, one byte for the outputs and two more for the other configurations and auxiliary functions of the step. After programming, this sequence of strings is saved inside of a nonvolatile memory of the microcontroller, so they can be read and executed. The controller task is not to work in the same way as a conventional PLC, but the purpose of it is to be an example of a versatile controller that is design for an specific area. A conventional PLC process the control of the system using a cycle where it makes an image of the inputs, execute all the conditions defined by the configuration programmed inside, and then update the state of the outputs. This controller works in a different way, where it read the configuration of the step, wait the condition of inputs to be satisfied, then update the state or the outputs and after that jump to the next step and start the process again. It can generate some limitations, as the fact that this controller cannot execute, inside the program, movements that must be repeated for some time, but this problem can be solved with some external logic ponents. Another limitation is that the controller cannot be applied on systems that have no sequence. These limitations are a characteristic of the system that must be analyzed for each application. 4. Characteristics of the controller The controller is based on the MICROCHIP microcontroller PIC16F877 [6,7] with 40 pins, and it has all the resources needed for this project .It has enough pins for all the ponents, serial munication implemented in circuit, EEPROM memory to save all the configuration of the system and the sequence of steps. For the execution of the main program, it offers plete resources as timers and interruptions. The list of resources of the controller was created to explore all the capacity of the microcontroller to make it as plete as possible. During the step, the program chooses how to use the resources reading the configuration string of the step. This string has two bytes for digital inputs, one used as a mask and the other one used as a value expected. One byte is used to configure the outputs value. One bytes more is used for the internal timer , the analog input or timeout. The EEPROM memory inside is 256 bytes length that is enough to save the string of the steps, with this characteristic it is possible to save between 48 steps （ Table 1） . The controller () has also a display and some buttons that are used with an interactive menu to program the sequence of steps and other configurations. . Interaction ponents For the real application the controller must have some elements to interact with the
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