# An Action Classification Method for Forklift Monitoring in Industry 4.0 Scenarios
## 1 Introduction  
The term \"Industry 4.0\" was born in 2013 when the German government promoted the \"High-Tech Strategy 2020 Action Plan\" for a planned \"4 th industrial revolution\" [1]. Since then, notable efforts have been carried out toward the implementation of Smart Factories [2] and Smart Warehouses [3]. The underlying concept concerns the integration of industrial technologies with information and communication technologies, which leads to the implementation of a Cyber-Physical-System (CPS) [4]. Each part of the system becomes able to autonomously exchange information, trigger actions and control each other [5]. In other words, a CPS allows the implementation of a digital and intelligent factory in order to promote manufacturing to become more digital, information-led, customized, and green [6]. Furthermore, several enabling technologies have been developed for the Industry 4.0 paradigm, e.g., Internet of Things (IoT) [7], Near-Field Communication (NFC) [8], Radio Frequency Identification (RFID) [9], Wireless Sensor Network (WSN) [10], and Block Chain (BC) [11], to name but a few. The last few years have seen more widespread diffusion of solutions and systems put into practice for the fourth industrial revolution. The aim is to implement an interconnection between production facilities, storage systems, and factory machinery in such a way to allow a real-time interaction between workers, devices and items in the whole supply chain. Consequently, both factory and warehouse facilities may become _smart_. In such a framework, the implementation of a smart warehouse concerns two different aspects. From one side, the possibility of a real-time inventory of items within the warehouse allows the definition of a proper company production-plan based on the market demand, by avoiding excesses of production and warehouse congestion. On the other hand, the development of a location-based system makes sure of not only the awareness of the item presence but also of its position within the warehouse, together with the position of the vehicles employed for procurement operations. It follows the development of lots of additional functionalities such as the optimization of item placement and of the vehicle paths during the loading/unloading operations with a consequent improvement of operator work-quality and safety. The I-READ 4.0 project, funded by Regione Toscana, Italy, fits into this context. In particular, it concerns the implementation of an integrated and autonomous CPS for the automatic management of very large warehouses. The system consists of a network of RFID readers in the Ultra-High-Frequency (UHF) operating band, which are able to automatically collect data from the warehouse pellets equipped with UHF-RFID tags and stored within the tissue-paper warehouse of the Sofidel Italian Company in Porcari, Lucca. Firstly presented in [12], the I-READ 4.0 system consists of two main technological elements: UHF-RFID Smart Gate and UHF-RFID Smart Forklift. The Smart Gates use fixed readers able to detect forklifts/pallets entering or exiting from areas of interest. The Smart Forklifts are equipped with UHF-RFID readers able to auto-localize themselves by exploiting data from UHF-RFID reference tags in the scenario and then localize the tagged pallets in the indoor warehouse. The system is low-cost, reconfigurable, flexible and scalable regardless of several factors, e.g. warehouse sizes, good typology and spatial resolution required for item localization. In this paper, the main idea of the I-READ 4.0 system is a detailed description with particular focus on the UHF-RFID Smart Gate implementation for the forklift action classification. In particular, with the term \"action\", we refer to two particular movements that the forklift can do with respect to a UHF-RFID Gate. The _IN_ action represents the forklift entering a certain area by crossing the gate. The _OUT_ action, instead, refers to a forklift leaving a certain area by crossing the gate.