Numerical Control systems simplified.
The following explanation in simplified terms is typical of all Numerical control systems.
First, The numerical control knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it isn't from where it is, or where it is from where it isn't ( whichever is greater), it obtains a difference of deviation.
The N/C system uses deviation to generate corrective commands to drive the system from where it is, to a position where it isn't arriving at the position where it isn't, it is now consequently, the position where it is and is now the position where it wasn't, and it follows the position where it was to the position where it isn't.
In the event the position where it now is, is not the position where it wasn't, the system acquires a variation (Variations are caused by external factors, and the discussion of these factors is not considered to be with in the scope of this explanation), the variation being the difference between where the machine is and where the machine the wasn't. If the variation is considered to be a significant factor, it too may be corrected by the use of parallel digital programming, however, the machine must know where it was, also.
The "thought process" of the system is as follows: Because a variation has modified some of the information which the machine has obtained, it is not sure where it is. However it is sure of where it isn't ( within reason), and it knows where it was. It now subtracts where it should be from where it wasn't ( or vice versa) and by differentiating this from the algebraic difference between its deviation and its variation, which is called error, it computes the correct information to compensate for all factors supplying accurate positioning information.
I hope this simple expanation helps everyone to see how modern CNC controls are making factorys everywhere so productive.
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