# Implementation and Evaluation of Dynamic Task Allocation for Human-Robot Collaboration in Assembly
## 1 Introduction
### Human-Robot Collaboration
#### 1.1.2 Classification of Cooperation Levels between Humans and Robots  
Figure 1 shows a classification of cooperation levels between humans and robots into five types--cell, coexistence, synchronized (also sequential cooperation [32]), cooperation, and collaboration--depending on the workspace, the task, and the required safety mechanisms [18; 33]. Cellular operation represents the classical safety fence operation of industrial robots, which is used in fully automated processes, while the other types of collaboration are typically realized with collaborative robot systems.  
A requirement for the implementation of a dynamic task allocation is the existence of a shared workspace, as both the human and the robot must be able to substitute their counterpart and perform the appropriate assembly work when the other is not available. Thus, due to the shared workspace, dynamic task allocation is feasible in the cooperation levels of synchronization, cooperation, and collaboration.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Category** & & [8,24]1  & & [29] & & [30] & & [22]2  \\ \hline \multirow{4}{*}{**Safety**} & \(\bullet\) & Individual risk assessment & \(\bullet\) & _Safe interaction_ & \(\bullet\) & Individual risk assessment & \(\bullet\) & Application of norms in practice \\  & \(\bullet\) & Application of norms in practice & \(\bullet\) & Collaborative operating modes & \(\bullet\) & Safety certifications & \(\bullet\) & Individual risk assessment \\  & \(\bullet\) & Approval through inspecting authority & & operating modes & & are costly and time-consuming & \(\bullet\) & Human’s trust in robot \\ \hline \hline \multirow{4}{*}{**Planning**} & \(\bullet\) & Individual risk assessment & \(\bullet\) & \(\bullet\) & _Performance_ & \(\bullet\) & Limited speed \\  & \(\bullet\) & Identification of suitable & & & & \(\bullet\) & Lack of quality checks \\  & \(\bullet\) & Workplaces design & _Intuitive interfaces_ & \(\bullet\) & _Strategy_ & \(\bullet\) & Cost-effectiveness \\  & \(\bullet\) & **Task allocation among** & \(\bullet\) & _Input modes_ & & expertise and robot programmers in & \(\bullet\) & Identification of suitable \\  & \(\bullet\) & **human and robot** & \(\bullet\) & Input modes & & SMEs & \(\bullet\) & **Task allocation among** \\  & \(\bullet\) & Quantification of effect & _Design methods_ & \(\bullet\) & Fragmentation of & & **humans and robots** \\  & \(\bullet\) & **flexibility** & \(\bullet\) & Task planning and & & human tasks & _Involvement and training_ \\  & \(\bullet\) & Quantification of effect & & **task allocation** & & & \(\bullet\) & Need for training and education of workers \\  & \(\bullet\) & & & & & \(\bullet\) & Involvement of operators \\  & & & & & & & \(\bullet\) & Fear of being replaced \\ \hline \hline \multirow{4}{*}{**Technology**} & \(\bullet\) & \(\bullet\) & _Design methods_ & \(\bullet\) & Handling of & & _Smart technology_ & \(\bullet\) & Intelligent solutions for quality \\  & \(\bullet\) & Control laws & \(\bullet\) & unforeseen errors is & & control & & control \\ \cline{1-1}  & \(\bullet\) & Sensors & & costly & & \(\bullet\) & Flexible robot movement \\ \hline \hline \end{tabular}
\end{table}
Table 1: Key challenges in human–robot collaboration (HRC) identified in the literature and grouped into three categories: safety, planning, and technology. The original categories of challenges proposed by the respective references are indicated in italics. The challenge of task allocation is highlighted in bold in the referenced studies.