Why Network Connectivity on Plant-Floors ?
- Reduces the cabling difficulties (Installation, Maintenance & Troubleshooting) at controllers.
- More accurate signal, because it is transmitted in digital form from sensor to controller.
- To make the plant data available to corporate (and avoiding the manual entry of of data)
- To make use of ERP applications for better optimization of the resources
- Not only the transmission of process variable, but other purposes like Calibration, device diagnostics and asset management are done.
INDUSTRIAL NETWORK STRUCTURE:
Plant-floor Communications
- Proprietary Networks dominated for long; open standards started to emerge.
- Two levels of Networks
- Control level (ex: ProfiBus, FF-HSE, Industrial EtherNet, ControlNet etc.,)
- Device level (ex: CAN, DeviceNet, SDS, AS-I, Seriplex, FF-H1 etc.,)
Popular FieldBuses
- CAN, DeviceNet & CANopen
- ControlNet
- ModBus/TCP
- ProfiBus
- Foundation field bus (H1 and HSE)
- Ethernet/IP etc.,
Chracteristics of Plant-floors Communication
- Real-Time requirements
- Prioritization of data
- Rugged enough to tolerate EMI noise, moisture, vibrations etc.
- Support for periodic and sporadic traffic
- Reliability of transmission
- Fail-Safe
- Required Data Transfer rate
- Easier installation, configuration and Maintenance
Ethernet on Plant-Floors
- Non-deterministic CSMA/CD protocol
- Reliability and ruggedness aspects of commercial Ethernet products
- Difficult to implement at transducer level
- Need of interpreting protocols and applications
Wireless Communication on Plant-floors
- Wi-Fi, BlueTooth and ZigBee are the promising technologies for plant-floor communications.
- Wi-Fi for IP-based surveillance, high-resolution data acquisition and ease of interaction to wired networks. (offers 11 Mbps data rate)
- ZigBee for low-power, low duty-cycle devices. (20-250 Kbps)
- BlueTooth for both voice & data transmitting devices and also for high-speed data acquisition. (720 Kbps)
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