Why Do Incremental Encoders Do a Reasonably Good Job in Electrical Drives with Digital Control?

The technical requirements of encoders to be used in electrical drives with digital control are not yet completely understood. A main statement of (Kennel, 2005) is that neither high resolution resolvers nor high resolution optical encoders do really provide features that could make them competitive to analogue precision tacho generators. As a result the behaviour of digital speed control can still not be as good as of former analogue speed control. The question is, however, why servo drives with digital speed control in fact are successful - nobody does really worry about any impact of optical encoders, because the performance of servo drives with digital control has indeed improved in comparison to former drives with analogue control. This paper explains the technical reasons for that and hereby contributes to better understanding of speed and position encoders, which still are the technical bottle neck for further improvements in digital drive control