**2. Materials and Methods**

This study used Scopus (Elsevier's abstract and citation database, Amsterdam, Netherlands), IEEE Xplore (Copyright 2021 IEEE - All rights reserved. A not-for-profit organization IEEE digital library, New York, NY, USA) and Google Scholar (Bibliographic database owned by Google LLC Mountain View, CA, USA) to conduct a systematic search of relevant scientific publications. The literature search presents six sectors: definitions and classifications, robot technology, state of the art, commercial technology, trends, and applications.

This study is a systematic review that searches for topics of service robots in scientific literature. To select and revise relevant papers from each section, the PRISMA approach was used [1], as well as the following criteria:


**Figure 1.** Statistics of the revised literature. A histogram shows the results of several reviewed references: (**a**) number of citations, (**b**) year of publication, and (**c**) impact factor. (**d**) Percentage of literature revised divided into journal papers, conferences, books, technical reports, and others.
