QoS-based remote control of networked control systems via Profibus token passing protocol

This paper focuses on a quality-of-service (QoS)-based remote control scheme for networked control systems via the Profibus token passing protocol. Typically, token passing experiences random network delay due to uncertainties in token circulation, but the protocol has in-built upper and lower bounds of network delay. Thus, to ensure the control performance of networked control systems via the Profibus token passing protocol, the network delay should be maintained below the allowable delay level. As the network delay is affected by protocol parameters, such as target rotation time, we present here an algorithm for selection of target rotation time using a genetic algorithm to ensure QoS of control information. We also discuss the performance of the QoS-based remote control scheme under conditions of controlled network delay. To evaluate its feasibility, a networked control system for a feedback control system using a servo motor was implemented on a Profibus-FMS network.