## 4 Discussion and Conclusions  
In this work we presented Float, a novel shoulder exoskeleton designed for the rehabilitation of orthopedic patients. We employed a user-centered design process based on an exploratory phase, a generative phase and a formative phase. The first phase was mainly constituted by interviews to understand all explicit and implicit needs of all the stakeholders involved (mainly patients and therapists). Following this process, during the generative phase, different mockups of Float have been designed, implemented and evaluated by the stakeholders to overcome the limitations of devices currently on the market. In particular, the main limitation of most of the other upper-limb exoskeletons is their reduced workspace, which forces the patient to perform exercises exclusively in a fixed sitting or standing position. This severely limits the range of activities that can potentially be simulated during the rehabilitation. Moreover, visual feedback is usually provided to the patient through a screen placed in front of the machine. However, according to the occupational therapy perspective, simulating purposeful occupations such as daily life tasks or work activities is crucial to support a successful reintegration of the patients in their previous occupations and social roles [18; 19; 20]. Figure 14: Experimental evaluation of the Float exoskeleton performances with respect to the actuator torque-speed envelopes for each joint under a challenging Repeat Trajectory mode exercise. (**A**–**E**) Torque speed for J1–J5. Moreover, it has been demonstrated that prolonged functional deprivation gradually leads to maladaptive neuroplasticity changes, inducing in turn a persistent cycle of decreased use [21; 22; 23]. Conversely, the early introduction of a graded task-oriented motor training contributes to preserve motor programs and motivates the patient to actively participate in therapy, preventing the decline of motor performance caused by limb disuse. Occupation-as-means is therapeutic when the activity has a purpose or goal that makes a challenging demand yet has an expectation of success, especially if using physical objects in an ecologically valid environment (i.e., similar to the real context). Robotics-supported training is receiving growing attention in clinical rehabilitation, particularly in the neurological field. Nevertheless, robotic training is rarely reported as treatment after traumatic shoulder injuries; the few clinical trials conducted to date include robot-assisted exergames consisting of virtual object manipulation in a virtual environment [24]. The development of the Float shoulder exoskeleton is the result of an occupation-focused approach: we indeed hypothesize that an early habilitation to perform specific tasks using common objects in the real physical space can facilitate a more rapid recovery of the quality and effectiveness of upper-limb movements. The innovative mechanical solution to release the device from a fixed position allows the user to receive assistance in complex functional activities, fully integrating the upper limb in the whole-body movements. Float opens up the possibility of carrying out occupational therapy in a large workspace thanks to the polyarticulated arm as detailed in the Results section. This innovation makes it possible to unlock a large number of exercises in the most natural way possible, i.e., without placing the weight of the exoskeleton on the patient. Regarding the control, the implemented friction compensation represents a preliminary solution to guarantee a transparent behavior of the exoskeleton system. The solution proved to be effective and offered a sufficiently transparent behavior when operated by a healthy subject. Nonetheless, it is important to underline that more advanced and complete friction compensation techniques, especially for what concerns the strong non-linearity of harmonic drives, might be implemented to obtain an even better transparency behavior [25].