## 2 State of Art
### Mobile Manipulators  
Autonomous Mobile Manipulators (AMMs) are composed of the integration of a robotic arm and a mobile robot. The main goal of AMMs is to autonomously move around the manufacturing plant while letting the manipulator execute specific tasks. Some companies have proposed to add mobility to manipulators to extend their functionality and usefulness. Concurrently, several researchers have focused on the same objective. For instance, [PERSON] et al. [17] developed a mobile manipulator as a robot assistant to support the human worker. [PERSON] et al. [15] presented the possibility to adopt AGVs or AMRs equipped with an anthropomorphic manipulator. On another hand, [PERSON] et al. [7] provided a review about Autonomous Industrial Mobile Manipulators (AIMMs), identifying 12 possible application areas: sustainability, configuration, adaptation, autonomy, positioning, manipulation and grasping, robot-robot interaction, human-robot interaction, process quality, dependability, and physical properties. They found out that the biggest obstacles in this field are: dependability (safety), physical properties (economy), and configuration (usability). [PERSON] et al. [18] present a review of the main AMMs and a set of evaluation criteria to assess their performances while [PERSON] et al. [19] present a critical investigation of generic use cases where the AMMs can be applied. [PERSON] et al. [20] present a hardware and software integration of cobot and AGV without taking into account safety aspects. Safety and Control of Mobile Manipulators  
In this context, the main challenge is the integration of cobots and mobile robots, already owned by a generic company, by controlling both the entities without considering them as two separate parts. The challenge refers not only to the scheduling of task processes but especially to the decision-making process which is responsible for both cobot and mobile robot reaction when an unexpected event occurs. Moreover, even though standards provide detailed safety requirements for both industrial manipulators and mobile robots, there is a lack of safety regulation for mobile manipulators. The ISO 10218-1 [21] and ISO 10218-2 [10] provide prescriptions on how to deal with hazards presented by industrial robots and industrial robot systems and their integration into workplaces, whereas the ISO/TS 15066 [16] specializes in collaborative operations. On the other hand, the ISO 3691-4 [22] specifies safety requirements for driver-less industrial trucks and their systems (i.e., AGVs and AMRs). Mobile manipulators are currently not regulated by standards nor guidelines which can assess the new risks related to the integration of the two systems. In this context, many authors have dealt with the identification and analysis of the possible scenarios with the AMM, by providing recommendations and guidelines. [PERSON] et al. [23] identified two possible configurations for a mobile manipulator starting from the possible states of the robotic arm. If the robotic arm always rests during the mobile robot motion, it might be considered as a load and the risk assessment for the total hazard is led by mobile robots standards. Otherwise, when the robotic arm is moving, all three aforementioned standards come to the rescue. Therefore, these scenarios report common situations already considered by the manufacturers of cobots and mobile robots. However, the combination of them presents relevant changes of their working context that needs an additional safety measure provided by a third system that put in communication them. Indeed, it is not clearly nor readily identifiable which safety standard takes precedence when both systems are moving. For this reason, it might be mandatory to take into account special hazardous situations that can occur in industrial robotic applications with mobile manipulators from the beginning [24].