Analysis and feedback control of LonWorks-based network systems for automated manufacturing

As the interest in flexible manufacturing systems and computer integrated manufacturing systems increases, the distribution of centralized control systems using industrial control networks is becoming more interesting. We investigate the rate-based traffic control of industrial control networks to improve the performance regarding the throughput fairness and error rates. Especially, we consider the protocol of LonWorks(TM) which consists of all OSI 7-layers and supports various communication media with low cost. Basically, the proposed rate-based traffic control system is closed loop by utilizing the feedback channel errors, which shows improved performance compared with other industrial control networks commonly operating in an open loop. To do this, an additional network node, called the monitoring node, is introduced to check the channel status without increasing the channel load. The proposed control loop is in effect whenever the feedback channel error becomes greater than an admittable value. We demonstrate the improved performance of the controlled network system in view of throughput and fairness measures by implementing the lab-scale network system and through the experimentation upon it.