Introduction: Individuals with mobility impairments associated with lower limb disabilities often face\nenormous challenges to participate in routine activities and to move around various environments. For many,\nthe use of wheelchairs is paramount to provide mobility and social inclusion. Nevertheless, they still face a\nnumber of challenges to properly function in our society. Among the many difficulties, one in particular stands\nout: navigating in complex internal environments (indoors). The main objective of this work is to propose an\narchitecture based on Mobile Augmented Reality to support the development of indoor navigation systems\ndedicated to wheelchair users, that is also capable of recording CAD drawings of the buildings and dealing with\naccessibility issues for that population. Methods: Overall, five main functional requirements are proposed: the\nability to allow for indoor navigation by means of Mobile Augmented Reality techniques; the capacity to register\nand configure building CAD drawings and the position of fiducial markers, points of interest and obstacles\nto be avoided by the wheelchair user; the capacity to find the best route for wheelchair indoor navigation,\ntaking stairs and other obstacles into account; allow for the visualization of virtual directional arrows in the\nsmartphone displays; and incorporate touch or voice commands to interact with the application. The architecture\nis proposed as a combination of four layers: User interface; Control; Service; and Infrastructure. A proof-ofconcept\napplication was developed and tests were performed with disable volunteers operating manual and\nelectric wheelchairs. Results: The application was implemented in Java for the Android operational system.\nA local database was used to store the test building CAD drawings and the position of fiducial markers and\npoints of interest. The Android Augmented Reality library was used to implement Augmented Reality and\nthe Blender open source library handled the basis for implementing directional navigation arrows. OpenGL\nES provided support for various graphics and mathematical transformations for embedded systems, such as\nsmartphones. Experiments were performed in an academic building with various labs, classrooms and male\nand female bathrooms. Two disable volunteers using wheelchairs showed no difficulties to interact with the\napplication, either by entering touch or voice commands, and to navigate within the testing environment with\nthe help of the navigational arrows implemented by the augmented reality modules. Conclusion: The novel\nfeatures implemented in the proposed architecture, with special emphasis on the use of Mobile Augmented\nReality and the ability to identify the best routes free of potential hazards for wheelchair users, were capable of\nproviding significant benefits for wheelchair indoor navigation when compared to current techniques described\nin the literature.
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