自動化生產(chǎn)線--外文翻譯-其他專業(yè)(編輯修改稿)
2025-02-24 02:42 本頁面
【文章內(nèi)容簡介】 were developed (circa in 1968) when General Motors Corps, and other automobile manufacturers were experimenting to see if there might be an alternative to scrapping all their hardwired control panel of machine tools and other production equipment during a model changeover. This annual tradition was necessary because rewriting of the panels was more expensive than buying new ones. The automotive panies approached a number of control equipment manufacturers and asked them to develop a control system that would have a longer productive life without major rewriting, but would still be understandable to and repairable by the plant personnel. The new product was named a “programmable controller”. The processor part of the PLC contains a central processing unit and memory. The central processing unit (CPU) is the “traffic direction” of the processor, the memory stores information. Coming into the processor are the electrical signals from the input devices, as conditioned by the input module to voltage levels acceptable to processor logic. The processor scans the state of I/O and updates outputs stored in the memory of the PLC. For example, the processor may be programmed so that if an input connected to a limit switch is true (limit switch closed), then a corresponding output wired to an output module is to be energized. This processor remembers this mand through its memory and pares on each scan to see if that limit switch is, in fact, closed. If it is closed ,the processor energizes the solenoid by turning on the output module. The output device, such as a solenoid or motor starter, is wired to an output module’s terminal, and it receives its shift signal from the processor, in effect, the processor is performing a long and plicated series of logic decisions. The PLC performs such decisions sequentially and in according with the stored program. Similarly, analog I/O allows the processor to make decisions based on the magnitude of a signal, rather than just if it is on or off. For example, the processor may be programmed to increase or decrease the steam flow to a boiler (analog output) based on a parison of the actual temperature in the boiler (analog input ) This is often performed by utilizing the builtin PID (proportional, integral, derivative) capabilities of the processor. Because a PLC is “software based”, its control logic functions can be changed by reprogramming its memory. Keyboard programming devices facilitate entry of the revised program, which can be design to cause an existing machine or process to operate in a different sequence or to different level of, or binations of stimuli. Hardware modifications are needed only if additional, changed, or relocated input/output device are involved. 3. Automated Assembly Assembly in the manifacturing process consists of putting together all the 4 ponent parts and subassemblies of a given product, fastening, performing inspection
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