The presence of architectural barriers in public or private buildings represents an important limit for the mobility of wheelchair users. Although norms promote barriers removal, often a complete accessibility cannot be guaranteed due to economic or technical reasons. In such cases, it is necessary to provide disable people with devices able to autonomously climb architectural barriers or obstacles.

Referring to user needs, some requirements for the wheelchair can be defined. Firstly, the user must use it autonomously. Secondly, it should be easy to use, simple in the mechanical and control systems and with limited weight, dimensions, and cost. Finally, also the appearance of the wheelchair must be adequate to guarantee the user acceptability.

In literature, several solutions of stair-climbing wheelchair are proposed. However, none of these completely satisfies the identified requirements.

In this paper, the Wheelchair.q05, an innovative concept for a stair-climbing wheelchair, is presented. This idea has been developed through several years of researches and functional designs. In detail, this work presents the final design for a constructive and real scale prototype.

The proposed wheelchair, thanks to a smart and hybrid locomotion system, is able to move on flat ground and to climb stairs and sidewalks. A triangular shaped frame with a wheel on each corner, connected through an internal epicyclical transmission system, constitutes the locomotion unit. This system provides the traction both for flat ground and stair motion. Moreover, the wheelchair has an idle track that represents the rear contact point during stair-climbing and guarantees only a stable and regular climbing motion. The wheelchair structure is thus constituted by the following functional elements: two locomotion units, the track, the seat and a couple of pivoting wheels connected to floating arms that represents the rear support during flat ground motion and during sidewalks overcoming.

Through a kinematic synthesis, the optimal layout has been defined and the mechanisms that connect the functional elements with the frame have been designed. These mechanisms allow controlling the wheelchair reconfiguration that is necessary to adapt the vehicle to different working conditions.

Moreover, attention has been paid to the user comfort. Thanks to the introduction of a mechanism that controls the seat orientation, the oscillations generated by the motion on stair are compensated and a regular trajectory is guaranteed for the user center of mass.

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