A Distributed Lonworks Application

The decomposition of a distributed application shows how to implement a decentralized control strategy, following the concepts described in Sections 1.3 and 1.4. A chemo-technical demonstration plant built within the Fraunhofer-Institute IITB (Figure 11-1) is used as an example. This plant includes many processes often performed in chemo-technical plants such as pumping, mixing, heating, cooling and neutralizing. The complete process runs in steps. The plant contains many instruments, but not all are needed for plant control. The plant is about 6 m broad, 3.5 m high, and 1 m deep. The vessels Bl 1 and B12 contain 501. The vessels B21 and B31 contain 100 1. The pump motors consume 550 W at 50 Hz. The flows between the vessels range from 500 1/h to 1200 1/h. All pressures are in the range of 1 bar, with the temperatures ranging from 10 to 50°C. Some of the reaction time requirements are in the range of a few seconds, some are in the range of 10 to 100 ms. Besides the sequential control, there are two closed loop controls for flow as well as two cascaded control loops for temperature.