Frequency problems
Commande numérique des machines

To give a concrete idea of the problems posed by digital control, especially when compared with analog control, let's consider a first example characterized by high frequencies: an axis controller for robotics. We can give an order of magnitude of the dynamics associated with the different commands and deduce a time diagram (figure 2 a ) showing 6 levels of control. In the real-time computer program executing this task, we can assume that each function is performed by a specialized routine, located at a specific interrupt priority level (for safety reasons, the higher the number, the higher the priority of the task). We can give a typical value for the sampling period associated with each task. For example

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