# An Action Classification Method for Forklift Monitoring in Industry 4.0 Scenarios
## 5 Conclusions  
This paper presented an effective implementation of a UHF-RFID Smart Gate, a fixed identification point placed at warehouse key points for forklift monitoring. Each Smart Gate implements an action classification method that exploits the phase of the backscattering RFID signal to determine the gate crossing direction of the forklifts with respect to the gate. Thanks to an asymmetrical deployment of the reader antenna and the phase acquisition of the signal exchanged by the fixed reader antenna and tags on the forklifts, a scalable and low-cost solution exploiting only one antenna can be used for each gate, with no additional sensors. Performance and method capabilities were investigated through an experimental demonstrator installed in a real warehouse. Data were gathered during the regular operations of the workers. In 100% of cases, the forklift was detected by the RFID gate, and a 98% classification accuracy was achieved when the forklift speed ranged between 0.5 m/s and 1.5 m/s. The accuracy decreases for higher speeds. The proposed method requires short computational time and is therefore suitable for the real-time monitoring of the forklift crossings. For future developments, artificial intelligence techniques will be designed and evaluated to improve classification accuracy even when forklifts are moving at higher speeds.  
Conceptualization, A.M., A.B., P.N.; software, A.M.; methodology, A.M., A.B., P.N., validation, A.M., A.B., M.P., resources, P.N., A.C., writing, A.M., A.B., P.N., review and editing, all authors. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by Regione Toscana (FOR FESR 2014-2020--Line 1 Research and Development Strategic Projects) through the Project IREAD4.0 under Grant CUP 7165.24052017.112000028, and in part by the Italian Ministry of Education and Research (MIUR) in the framework of the CrossLab project (Departments of Excellence). Info: [PERSON] (e-mail: [EMAIL_ADDRESS]).  
The authors wish to thank the company Sofidel S.p.a. for their precious support.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Reference** & **Cost** & **Encumbrance** & **Scalability** & **Architecture** \\ \hline
[16] & High & High & Low & Shielded Gate \\ \hline
[18] & High & High & Low & Shielded Gate \\ \hline
[19] & Medium–High & Medium–High & Low–Medium & Antenna Panels \\ \hline
[22] & Low–Medium & Low–Medium & Medium–High & One reader and two antennas \\ \hline
[23] & Low–Medium & Low–Medium & Medium–High & One reader and two antennas \\ \hline
[24] & Low–Medium & Low–Medium & Medium–High & One reader and two antennas \\ \hline
[26] & Low & Low & High & One reader and one antenna \\ \hline
[28] & Low & Low & High & One reader and one antenna \\ \hline
[33] & Low & Low & Medium & One reader and one antenna \\ \hline
[37] & Low & Low–Medium & Medium & One reader, one antenna, reference tags \\ \hline
[38] & Low & Low–Medium & Medium & One reader, one antenna, reference tags \\ \hline This paper & Low & Low & High & One reader and one antenna \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of the proposed solution with the state-of-the-art.