(InGaAs), germanium (Ge), and mercury cadmium telluride (HgCdTe) sensors. Table 1.1 shows the working wavelengths of the IR technology.
Table 1.1 Spectral ranges of infrared technology.
| Infrared technology | Spectral range (μm) | References |
|---|---|---|
| InSb | 0.6–5 | [14] |
| InGaAs | 0.9–1.7 | [14] |
| Ge | 0.8–1.6 | [15] |
| HgCdTe | 1–9.5 | [14] |
Sensor networks are designed after an accurate analysis of the production processes, thus suggesting the correct configurations and connections of possible gateways, routers, and of device combinations. Sensor networks are implemented for point to point, star, extended star, bus, or mesh configuration. In Figure 1.1 are shown the different main network configurations. The design of the network is an important step for the realization of the correct network. The spatial allocation of the production machines and the workflow of the production define the best configuration. The network layout changes with the sensor system: the star or mesh network is typically adopted for sensors, besides the bus layout is suitable for production line connections and for the information system. By considering for example a photovoltaic camp with a high number of panels, it is preferable to realize a ring type fiber optic network linking all electrical string panels. The network also assumes a hybrid configuration, especially when a new network is added and linked to an old one. Table 1.2 lists the main advantages and disadvantages of the different network layouts.
Figure 1.1 Example of network configurations: (a) point to point connection; (b) bus line; (c) ring layout; (d) star connection; (e) tree layout; and (f) node meshing configuration.
Table 1.2 Advantages and disadvantages of network typologies.
| Network type | Advantages | Disadvantages |
|---|---|---|
| Star | The star network manages the whole network by a single node behaving as a master node. Each node of the network can be added, removed, and reconfigured by ensuring the network operations. Network simplicity. Easy identification of errors | For a failure of the central node the whole network is out of order. Bandwidth limitation |
| Bus | Low cost and simple layout. Connection with a simple coaxial or RJ45 cable | For a failure of the bus the whole network is out of order. Additional nodes decrease network velocity. Single direction transmission mode (half duplex) |
| Ring | Bidirectional transmission mode for dual ring typology (full duplex) | Half duplex modality for basic ring configuration. Transmission security (if a node fails the network stops operating) |
| Tree | By adding to the tree network a star and a bus layout, it is possible to allow an easy addition of nodes and a network expansion | If the root node is out of order the whole network fails. Network performance decreases for complex hierarchical layouts |
| Mesh | Reliable and stable network type. Resistance to failure conditions also for complex layouts involving more interconnections | High time for network setting. High computational cost for complex interconnection layouts |
The network typology must be compatible with the network information system of the industry. In this way, the hybrid solutions potentially ensure the best network performances and flexibility. Figure 1.2a shows an example of a hybrid extended star network, constructed by merging an extended star with a mesh network, by showing an example of network reconfiguration in cases of connection failures, where the automatic principle of node commutation is managed by an intelligent algorithm detecting and predicting system failures (example of direct interaction between processing layer and production machine layers). The cases of Figure 1.2b–e are related to a possible configuration of the data transmission of a part of the network of Figure 1.2a. This example highlights the importance of adding nodes to avoid the transmission problem. The solution to add nodes to the local network must be “weighted” with the decrease of performance due to the increased complexity of the new hybrid network. The prediction of possible failures of nodes, allows to change anticipatedly a linking configuration, thus avoiding data interruptions, and preserving production control. In the prediction calculation, sensors play an important role because they detect operation conditions of production lines, status machines and product tracking. In Table 1.3 and Table 1.4 are listed the main specifications of traceability sensors able to detect the product in each production stage, and the main characteristics of transmission protocols, respectively. Solutions for the actuation are the plug and play (P&P) solutions and programmable logic controller (PLC) hardware interfaces. For P&P systems the hardware and software components are downloaded and installed at or before run‐time. The supervisory control and data acquisition (SCADA) [30] systems are able to read production data and transmit the setpoints to the PLCs. SCADA systems typically are implemented to control system architectures by graphical user interfaces (GUIs), and behaving as a supervisor of peripheral devices such as PLC, and proportional integral derivative (PID) controllers interfacing process plant and production machinery. Typically, SCADA adopts visualization tools and synoptic graphics for real‐time data display.
Figure 1.2 Example of hybrid extended star network and failure system reconfiguration for a secure production monitoring: (a) hybrid network structure by extended star and mesh network; (b) normal configuration for data transmission to the manager central node (transmission from node 3 to node 1); (c) example of reconfiguration for an interrupted linking between node 1 (network coordinator) and node 2; (d, e) examples of reconfiguration for interrupted links between node 1 and node 2 and between node 1 and node 4 simultaneously.
Table 1.3 Main specifications of sensors used for traceability.