## 1 Introduction  
In an ever-evolving technological landscape, the development of new technologies demands the availability of rapid and efficient testing procedures. These procedures play a crucial role in expediting the validation process, ensuring the timely introduction of developed technologies to the market. This is essential to prevent the risk of technological obsolescence, which may occur if the testing procedures linger unnecessarily. In the context of rehabilitative robotics, over the past decade, several exoskeletons for upper limb rehabilitation were proposed (Float [1], Alex [2], Armeo [3], CleverArm [4] AnyExo [5], Harmony [6], Aramis [7]). Despite their significant differences, these devices share a common technological foundation: design a device that can be coupled with the human body, closely resembling the physiological movements of the shoulder and scapular complexes. Some unconventional implementation attempts have been presented so far, such as the Limpact [8] hydraulic exoskeleton, which remained in a stage of prototype development. Most of the rehabilitation devices on the market (Armeo Power [3], Harmony [6]), or in an advanced stage of development (Anyexo [5], Float [1]), are equipped with brushless DC motors, harmonic drive transmission and SEAs (Series Elastic Actuators). Several of the aforementioned devices followed a Rapid Control Prototyping (RCP) approach in their early stages of development. Literature offers a variety of platforms for the control design: ARMin [9] runs on MATLAB/Simulink XPC target (now known as Simulink Real-Time), ANYexo runs on a control PC running a Linux operating system and interfaces with the hardware by EtherCAT communication; Harmony is operated by a real-time control system running Linux patched with RT-Preempt and communicatesvia EtherCAT. Furthermore, these exoskeletons share a similar system architecture, with a central control unit overseeing the coordinated actions of various motor control boards distributed throughout the robotic structure. In terms of control strategies, a remarkable consistency can be observed. These systems offer a range of control modes, from precise position control for passive mobilizations to more sophisticated and adaptable approaches like impedance and admittance control, commonly used in rehabilitative robotics to guarantee a compliant human-machine interaction [10]. In the development process of rehabilitative devices, RCP and Hardware In the Loop (HIL) emerge as pivotal approaches, allowing the quick implementation and testing of complex control strategies. RCP approach enables early testing on hardware, even in a prototype stage, allowing for a swift assessment of how the control algorithms perform in a real-world setting. Additionally, RCP facilitates code reusability across different testing platforms, leveraging flexibility in hardware integration. The real-time application allows quick modifications to the control architecture. By combining HIL and RCP, the developed software can be deployed and tested in a realistic environment. This approach allows for an early validation of both hardware and software characteristics, encompassing the testing of potential faults. The synergy between HIL and RCP supports parallel development of hardware and software, with continuous updates and testing. This concurrent approach increases the number of design and test iterations, expediting the definition of final device characteristics and, in turn, reducing time consumption and overall costs. Several platforms are available for RCP and HIL applications.