Digital implementation issues of electronic line shafting

Electronic line shafting is a control methodology for reproducing the desirable inter-shaft dynamics of a physical line shaft while adding some features that cannot be achieved with a physical line shaft. There are important challenges that must be addressed before ELS can be implemented. In paper manufacturing and converting, drives sharing a common back plane can be easily clocked together so that the sampling for each drive is synchronized. However, it is difficult and expensive to synchronize every drive in every section. Asynchronous sampling between drives will cause perceived distortion which negatively affects the degree of motion and tension control available. Relative state motion control requires high position information resolution to be able to accurately measure and correct for small differences in motion between shafts. In addressing these issues, ELS can be implemented correctly to achieve much more precise tension and speed control in paper machines.