Closing the motion control loops via industrial ethernet network

This paper deals with a problem of feedback compensator design for motion control loops equipped with industrial Ethernet communication protocols. The main goal of the paper is to choose proper control structures for a supervisory control system which have to deal with the time delay caused by the communication channel and compare the results with a standard cascade control scheme which is implemented directly in a frequency converter. The discrete-time state-space model of the system is derived and several advanced algorithms for time delay compensation are proposed and evaluated by simulations. Finally, the validity of the used methods is verified experimentally with a Yaskawa servo-drive equipped with EtherCat communication protocol. It is shown that proper control structure is able to compensate the effects of communication delay and the results are comparable to direct implementation of the motion control loop in the frequency inverter.