A good example of the way in which field devices and actuators/sensors work smoothly together can be seen at the Reynolds Tobacco plant in Trier, Germany, where this is achieved through interaction between the Actuator Sensor Interface (AS-I) and
Reynolds Tobacco processes many tons of tobacco per hour. These large quantities require fast and reliable handling with minimum production and maintenance costs. The main requirements placed on the control system are: the greatest possible transparency, high availability, excellent reliability and quality of the automation components used, ease of assembly, all within defined cost parameters.
The AS-I bus system is installed at the lowest level, whereas system communications are handled by the PROFIBUS DP fieldbus. This enables the production units to be assembled as complete modules and electrically tested before being integrated into the master controller. Integration is a quick and easy process, which means units can be installed while the system is in operation. The complete process, from cutting through drying and on to blending, is controlled by a SIMATIC S5-155U, which is connected to the process control level via Ethernet. Data from the production control level is passed to the PLC via the Novell server. The production machines for their part are networked using PROFIBUS DP.
A COROS LSB system is connected to the PLC to coordinate the processing stages, acquire and file production data and transmit the relevant data to the production control level.
PROFIBUS DP handles communications at the process control level. Nine ET 200U stations, two FESTO valve terminals with 14 valves including feedback signals, nine operator panels and 15 converters (Micro Master) with DP interfaces are connected to the S5-155U via the bus. All ET 200U stations are equipped with an AS-I Master CP 2433 to which sensors and actuators are connected.
PROFIBUS and AS-I were beneficial in keeping down the costs of converting to a distributed control architecture. Commissioning times were short and the much smaller wiring loom meant wiring errors were detected more quickly.