Automation

Automated machines can be subdivided into two large categories—open-loop and closed-loop machines, which can then be subdivided into even smaller categories. Open-loop machines are devices that, once started, go through a cycle and then stop. A common example is the automatic dishwashing machine. Once dishes are loaded into the machine and a button pushed, the machine goes through a predetermined cycle of operations: pre-rinse, wash, rinse, and dry, for example. A human operator may have choices as to which sequence the machine should follow—heavy wash, light wash, warm and cold, and so on—but each of these operations is alike in that the machine simply does the task and then stops. Many of the most familiar appliances in homes today operate on this basis. A microwave oven, a coffee maker, and a CD player are examples.

Larger, more complex industrial operations also use open-cycle operations. For example, in the production of a car, a single machine may be programmed to place a side panel in place on the car and then weld it in a dozen or more locations. Each of the steps involved in this process—from placing the door properly to each of the different welds—takes place according to instructions programmed into the machine.