# A Model for Working Environment Monitoring in Smart Manufacturing
## 3 Model of a System for Monitoring Working Environments in Smart Manufacturing
### Model Description  
As is presented in Figure 1 sensor nodes are deployed at the Perception layer. These nodes can be classified into two categories: \"light\" and \"heavy\" nodes. The general difference between those two types of sensor nodes is in the smaller number of sensors for the \"light\" nodes. The \"heavy\" sensor nodes are designed to be used as fixed wireless sensor nodes, mounted on the walls, with a larger number of sensors, and LCD or OLED displays. The \"light\" sensor nodes are designed as lightweight fixed or wearable devices. Wearable devices can be mounted on helmets and suits or working clothes, or mounted on moving objects/vehicles such as forklifts, carts, and other inner transportation objects. These nodes are planned for deployment in locations without infrastructure and in the hard to reach places. Owing to this, the connectivity of these nodes is achieved with wireless technology. The main building block for the sensor node prototyping was the Arduino/Genuino platform, mainly Arduino/Genuino UNO Rev3 and MEGA 2560 or their clones. Besides these platforms, Texas Instruments development boards such as MSP430 and MSP432, and CC3200 based Launchpads, were used. The system was designed in accordance with a five-layered architecture (Figure 1). In the perception layer the microcontrollers and sensors were deployed; the transport layer mediates between the devices and the core of the system and forwards the collected data to the servers and storages; the middleware layer is responsible for storing, processing, and analyzing data, and servicing the user applications; the application layer provides data to the users of the system; the business layer is designed for the decision making and management of the system, but is it omitted from the figure and it is not covered in the presented system. Figure 1: Five-layered architecture of the working environment monitoring system. Furthermore, considering the connectivity technology, sensor nodes can be classified into three different types of nodes. Those three types are:  
1. WPAN sensor nodes
2. Wi-Fi sensor nodes
3. Ethernet sensor nodes  
WPAN sensor nodes for connectivity use WPAN communication modules. Those modules can be: Digi XBee module for ZigBee and IEEE 802.15.4 technology, RFBee module for proprietary sub 1-GHz technologies, and HM-10 for Bluetooth low energy. Wi-Fi sensor nodes for connectivity used a variant of ESP8266 modules. The Ethernet sensor nodes had the Ethernet shield or Ethernet modules for connectivity. The transport layer serves for connectivity between the transport and application layers. Its primary functions are to enable the connectivity of nodes to the core of the system and to transfer the data collected by the sensors. The communication of WPAN nodes from the perception to the transport layers was realized primarily with WPAN protocols (ZigBee, BLE, or IEEE 802.15.4). In contrast, the communication of the Wi-Fi and Ethernet nodes with the core is directly realized with the Transmission Control Protocol (TCP), or more precisely the MQTT protocol. The MQTT protocol was chosen for the communication between the components within the core of the system. Therefore, the devices for WPAN/TCP conversion with MQTT support should be included in the model, at the edge of the transport layer. The usage of the MQTT protocol assumes that the MQTT broker is used in the core of the system for managing the message publishing and subscription. The usage of Arduino based devices with ESP8266 and Ethernet modules enables support for TCP/MQTT connectivity. So the Arduino base platforms could be used as WPAN/Wi-Fi and WPAN/Ethernet gateways with MQTT support. The architecture of the software components is presented in Figure 2 in more detail. The recommend Arduino board is Mega 2560 and the recommended TI board is CC3200 Launchpad because of the greater number of communication ports and the support for a higher number of communication devices and greater computational power.