Fieldbus based distributed servo control using LonWorks/IP gateway/web servers

Virtual device network (VDN) is an intelligent integrated form of a device (control) network and IP network. If a fieldbus based distributed control system (DCS) is implemented on a global VDN, efficiency and flexibility can be significantly improved. In this study DCS implemented on the LonWorks/IP VDN is investigated with an example of model reference adaptive control (MRAC) of a geared DC motor. In order to compensate for the network induced uncertain time delay inherently present on VDN, the modified Smith predictor based internal model controller was integrated to MRAC (MRAC–IMC). The effectiveness of the proposed control scheme was tested through experiment. The proposed control scheme exhibited the robustness to noise and external disturbances and the good tracking performance around zero velocity point occurring due to overshoot and stick friction. Result of this study suggests that sophisticated servo control of dynamic systems is possible from a remote client PC on VDN by properly compensating the network delay.