# Trends of Human-Robot Collaboration in Industry Contexts: Handover, Learning, and Metrics
## 2 Human-Robot Collaboration Concepts
### Interaction vs. Collaboration
[5], a distinction between Human-Robot Interaction (HRI) and Human-Robot Collaboration (HRC) is described, using two research works that were mentioned earlier: HRC requires a common goal that is sought by both robot and human working together ([11]); contrarily, in HRI the interaction between the human and the robot does not necessarily entail a common goal, thus falling in the definition of coexistence of [12]. From a different perspective, ref. [6] provides a clear definition of four interaction types: coexistence, synchronised cooperation and collaboration. The term of _coexistence_ characterizes the moment when the human operator and the robot are in the same environment but do not interact with each other; _synchronised_ describes the environment where the human and the robot work in the same space but at different times; _cooperation_ is when the human and robot work on separate tasks, but in the same space at the same time and, lastly, _collaboration_ is used when the human operator and the robot work together on the same task. Following the definitions of [6], when the robot is collaborating with the human, the action of the one has immediate consequences on the other. All this extended literature overview of the definitions about the Human-Robot Interaction and Human-Robot Collaboration concepts are summarized in Table 1.  
With all these perspectives in mind, it is possible to understand the difference and deduce a clear interpretation about this particular topic. For the purpose of this work, \begin{table}
\begin{tabular}{p{42.7 pt} p{341.4 pt}} \hline \hline
**Source** & **Definitions** \\ \hline
[9] & **interaction**: action on someone or something else. \\
**collaboration**: working jointly with someone or something. \\
**collaboration**: working jointly with others or together especially in an intellectual endeavor. \\
[11] & interaction includes collaboration. \\
**interaction**: action on someone else. \\
**collaboration**: working with someone, aiming at reaching a common goal. \\
**collaboration**: robot feature to perform complex tasks with direct human interaction and coordination. \\
**physical interaction**: few nested behaviors that the robot must ensure (collaboration, coexistence and safety). \\
**efficient Human-Robot Collaboration**: robot should be capable of perceiving several communications mechanisms similar to the ones related to human-human interaction. \\
**physical Human-Robot Collaboration**: the moment when human(s), robot(s) and the environment come to contact with each other and form a tightly coupled dynamical system to accomplish a task. \\
**collaborative robot**: able to understand its collaborator's intentions and predict his actions, in order to adapt its behavior in accordance and provide assistance in a wide diversity of tasks. \\
**HRC**: requires a common goal that is sought by both robot and human working together. \\
**HRI**: the interaction between the human and the robot does not necessarily entail a common goal, thus falling in the definition of coexistence. \\
**coexistence**: when the human operator and the robot are in the same environment but do not interact with each other. \\
**synchronised**: when the human and the robot work in the same space but at \\
**cooperation**: when the human and robot work on separate tasks, but in the same space at the same time. \\
**collaboration**: when the human operator and the robot work together on the same task. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Definitions regarding Human-Robot Collaboration and Human-Robot Interaction concepts, from several distinct sources. and for future references, we will address the term of _interaction_ as the communication between two entities. In other words, _interaction_ describes the moment when someone gives any kind of information and someone else reacts accordingly. In a general point of view, _interaction_ could be directly compared to a request-response service.