Analysis and compensation of delays in FF H1 fieldbus control loop using model predictive control

In this paper, delays in data acquisition, conversion, and transmission of measurements in Foundation Fieldbus channels are analyzed in detail. The bounds for these delays are established. For measurements used in open-loop applications (e.g. monitoring), proper time calibration of the received signals should be made to consider the delays. However, if the measurements are intended for feedback control purposes, appropriate compensation schemes have to be used to reduce the effects of the delays. Thus, for feedback control, sources of delay for a Foundation Fieldbus (FF) H1 network and DeltaV Distributed Control System (DCS) are identified and analyzed. A model predictive control (MPC) scheme is developed to compensate the delays. The effectiveness of the proposed scheme is demonstrated on a test bench consisting of industrial grade FF H1 devices and a controller under different network parameter configuration (hence, different delays). It is demonstrated that the MPC is a viable solution to compensate network induced delays in industrial control systems.