Automation controllers are the brains of any automation environment. The automation controllers that are used with manufacturing issue instructions to all the devices that are part of the manufacturing process. There are two memory areas in any of the automation controllers: permanent memory where programs are kept when they are not running, and temporary memory, where programs run in order to issue the instructions that are required to make automation work. In its operations the controller will send instructions to an automated device to perform a step in the manufacturing of a product. When that task is completed by the device a message is sent back to the controller to let it know what the result of the completion of that task is. The message may be one that says that the task was completed successfully and the device is now ready for a new instruction. At this point the controller will send a new instruction to the device for its next task to be performed. Sometimes the message that is sent back to the controller is one that says that the task assigned to the device was not completed successfully. Included in the message will be an error code indicating what type of error situation occurred to keep the task from completing as it should. This error code will assist the controller in deciding what instruction it should issue in response to the incomplete task. Depending on the level of severity of the error that has been encountered, the controller may decide to shut down all the automation or it could re-issue an instruction to the device to try the task again and try to get a successful completion or any of a lot of other commands.
Early automation controllers were not as capable as the controllers in use today. Programs that these early devices would run had to be loaded into the device manually before they could be executed to work with other devices. Technology has brought the controller to the point where it is now programmable. User interfaces for building programs are much better and programs can be loaded into programmable automation controllers and executed on-demand. The earlier controllers were called PLC’s (Programmable Logic Controllers) and the later ones are called PAC’s (Programmable Automation Controllers)
The production environment in which the automation controllers must work is often very unpleasant. These devices should be able to run in very hot factories with a high degree of resilience and accuracy. There can be no deviation in their response to the demands of devices with which they converse. In many cases the work requirements for an automation controller is continuous, 24 hours a day, 7 days a week, day in and day out. A high level of mean time before failure is very important. This is the average time that usually occurs before the device will stop working. A company’s continuous existence may totally rest on the automation controller that is running its manufacturing operation, so the length of time that his device should be able to run continuously with no problems should be very long. Periodic routine maintenance should be done on any of the automation controllers that carry should a heavy responsibility. These device should be taken out of the automation process to make sure that they can continue operating at a high level of consistency. A backup controller should be substituted for the primary controller, so that maintenance can be done. In many cases controllers will be upgraded by switching out part of the hardware or software that is used to keep them operating. This also can be done at a maintenance time.
Controllers keep the whole process of automation operating in a safe mode. If there is an error code returned to a controller that warrants for all the automation to stop, the controller has the power to that. In some cases if the controller does not stop automation there could be damage to equipment or personnel. Looking at this scenario you can see the importance of the controller in keeping automation running smoothly. Controllers are decision-making devices that decide how automation should proceed from one operation to the next. Each instruction has to be issued by the controller to perform all the tasks that are required to keep automation running at an optimum pace. It is also important for the controller to be able to handle any error situations of which it is made aware. You have to realize that all these decisions and the issuing of instructions occur at a very high-speed. Controllers are not in conversation with just one device, they must talk to all the devices that are part of the manufacturing automation. The conversation has to happen at such a pace that the instructions for each device in the automation will receive its required instruction prior to the time that the device will need to know what it should do next. You can see the speed constraint that is placed on the automation controller based on the demands that are made on it by the devices that part of the automation environment.
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