**1. Introduction**

There is evidence that early and intensive rehabilitation therapies are associated with better functional gains in patients with acquired brain damage [1]. Rehabilitation robots have shown good results in delivering high-intensity therapies and to maximize patients' recovery [2–4]. However, there are some motor functions that cannot be recovered. In this case, assistive robotics have shown good results in assisting patients with acquired brain damage in performing activities of daily living and/or in supporting elderly people in staying active, socially connected, and living independently. Principally, there are two kinds of assistive robotic devices: one of them is based on mobile robot assistants, such as Care-O-bot, PR2, and Tiago, among others; the other one is based on the use of an external robotic arm or a robotic exoskeleton fixed or mounted on a wheelchair.

On the other hand, there is another approach based on the use of: (i) an external robotic arm fixed or mounted on a wheelchair; or (ii) an exoskeleton robotic device. JACO and iARM are two of the most popular external robotic arms fixed or mounted on wheelchairs. Both robotic arms were designed to be mounted on a user's motorized wheelchair; they have six degrees of freedom and can reach objects at a distance of 90 cm [5]. A study on the practical demands of the potential users of external robotic arms and upper limb exoskeletons for assistance with ADLs can be found in [6]. The study concluded that eating

**Citation:** Catalan, J.M.; Blanco, A.; Bertomeu-Motos, A.; Garcia-Perez, J.V.; Almonacid, M.; Puerto, R.; Garcia-Aracil, N. A Modular Mobile Robotic Platform to Assist People with Different Degrees of Disability. *Appl. Sci.* **2021**, *11*, 7130. https://doi.org/10.3390/ app11157130

Academic Editor: Carlos A. Jara

Received: 21 June 2021 Accepted: 29 July 2021 Published: 2 August 2021

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and hairdressing, as well as cleaning, handling food, dressing, and moving nearby items were the ADLs that have received relatively high scores regarding the necessity of external robotic arms. The FRIEND robotic platform is an example of a well-known external robotic arm that assists disabled people in performing ADLs. The FRIEND platform, which belongs to the group of intelligent wheelchair-mounted manipulators, is intended to support disabled people with impairments of the upper limbs in ADLs [7]. On the other hand, dressing, toilet use, transfer, wheelchair control, moving nearby items, and handling food have shown high demand for the necessity of upper limb exoskeletons. Kigachi et al. presented a mechanism and control method of a mobile exoskeleton robot for three-degree-of-freedom upper-limb motion assistance (shoulder vertical and horizontal flexion/extension and elbow flexion/extension motion assistance) [8]. In addition, Meng et al. presented a mobile robotic exoskeleton with six degrees of freedom (DOFs) based on a wheelchair [9].

In this paper, a mobile robotic platform for assisting moderately and severely impaired people in performing daily activities and fully participating in society is presented. The mobile robotic platform was based on an upper limb robotic exoskeleton mounted on a robotized wheel chair. The platform is modular and composed of different hardware components: an unobtrusive and wireless hybrid brain/neural–computer interaction (BNCI) system (electroencephalography (EEG) and electrooculography (EOG)) [10], a physiological signal monitoring system, an electromyography (EMG) system, a rugged, small form-factor, and high-performance computer, a robotized wheelchair, RGB-D cameras, a voice control system, eye-tracking glasses, a small monitor, a robotic arm exoskeleton attached to the wheelchair, and a robotic hand exoskeleton including a mechatronic device to control the pronation/supination of the arm. Moreover, the robotic exoskeleton can be replaced with an external robotic device if needed. The platform has open-source software components as well, such as algorithms to estimate the user's intention based on the hybrid BNCI system, to process the user's physiological reactions, to estimate the indoor location and to navigate, to estimate gaze and to recognize objects, to compute 3D objects and mouth pose, to recognize user activity, and a high-level controller to control the robotic exoskeleton or external robotic device and to control the environment and wheelchair control system. The modularity of the presented mobile robotic platform can be exploited by adapting the multimodal interface to the residual capabilities of the disabled person. In particular, the platform can be mainly adapted to three groups of end users with different residual capabilities:


software, a commercial wearable device for physiological signal monitoring, and RGB depth cameras to sense and understand the environment and context to automatically recognize the abilities necessary for different ADLs.

For users belonging to Groups 1 and 2, a set of application scenarios was identified as possible targets for the AIDE system: drinking tasks, eating tasks, pressing a sensitive dual switch, performing personal hygiene, touching another person, and so on. For users, belonging to Group 3, the identified scenarios were related to communication, the control of home devices, and entertainment.
