This paper presents a new version of Wheelchair.q, a wheelchair with stair climbing ability. The wheelchair is able to climb single obstacles or staircases thanks to a hybrid wheel-leg locomotion unit with a triple-wheels cluster architecture. The new concept presented in this work represents an improvement respect to previous versions. Through a different arrangement of functional elements, the wheelchair performances in terms of stability and regularity during movement on stair have been increased. In particular, attention has been paid to ensure a regular and comfortable motion for the user during stair climbing operation. For this reason, a cam mechanism has been introduced and designed with the aim to compensate the oscillation generated on the wheelchair frame by the locomotion unit rotation. A design methodology for the cam profile is presented. Moreover, a parametric analysis on the cam profile and on the mechanism dimensions has been conducted with the aim to find a cam profile with suitable dimensions and performances in terms of pressure angle and radius of curvature.

The paper presents a new member of Epi.q robot family, a series of mobile robots with a wheel-legged locomotion and with the ability to overcome obstacles and move on uneven terrains. The particular feature of this robot family is the ability to switch from a wheel locomotion to a leg locomotion without any external active control but only depending on the dynamic conditions. In particular this work deals with the design of the latest prototype developed, analyzing the design and construction phases. This prototype is more powerful than the previous thanks to the possibility to have four driving units instead of two. The robot architecture has been studied in order to be modular. Several robot configurations can be obtained with the same structure and this allows to test how each component affect the overall robot behavior. Moreover the mechanical design is more accurate and reliable respect to previous versions. A sensing system has been introduced with the aim to evaluate the performances of each robot architecture. Finally an on-board processor has been added. This allows the definition of more complex control logics such as the cooperation between a speed control with a torque control in the four driving units configuration. Moreover it increases the smart tasks that the robot is able to perform such as the developing of a remote autonomous control rather than a manual drive by an operator.

In this paper is described a new solution for a stair-climbing wheelchair: a device that allows disabled people to autonomously overcome architectural barriers. The paper presents the evolution of a project introduced in previous works. The aim is to obtain a wheelchair able to move both in structured and unstructured environments and overcome single steps or an entire staircase. The innovative aspect of this work is the introduction of a hybrid solution, with a locomotion system based on wheels and an idle track for the vehicle stability. The locomotion group permits to overcome obstacles through an original architecture based on an epicycloidal transmission. The control logic manages the motors that drive independently the two degrees of freedom of the transmission and allows to switch from an advancing mode to a climbing one. The wheelchair must be able to move in different environments, such as flat ground or stairs, which require different specifications, sometimes in contrast. For this reason the main part of the work regards the design of a reconfiguration mechanism able to prepare the wheelchair for different working conditions. First of all the relative positions between the elements that compose the wheelchair structure in different configuration are studied in order to optimize the performances especially in terms of regularity. Then several possible solutions for the reconfiguration mechanism are presented and qualitatively evaluated, in order to choose the one that satisfy the design specifications.

Introduction: This paper presents the functional design and kinematic synthesis of a recent version of an electric stair-climbing wheelchair. Wheelchair.q: The proposed device represents the latest evolution of the 'Wheelchair.q' project and introduces several improvements over previous designs. This updated solution has greater stability during stair-climbing operation, and it satisfies the safety requirements introduced by ISO 7176-28:2012, "Requirements and test methods for stair-climbing devices". The main improvement presented concerns the regularity of the user trajectory during stair-climbing, which ensures a more comfortable perception. This result has been achieved by introducing a cam mechanism between the frame connected to the locomotion unit and the seat frame, which properly manages the seat orientation. With an appropriate cam profile, it is possible to compensate for the oscillations that are introduced on the wheelchair during the climbing sequence and allow the user to obtain a translational trajectory. Results: The proposed design and its working principle are first described and illustrated through schematic and graphic representations. A brief explanation of the procedure for obtaining the cam profile is also given. Two different architectures for the cam mechanism are then compared, and the advantages and disadvantages for each solution are identified. Finally, the kinematic wheelchair performances are tested through a simulation conducted in the MSC-ADAMS multibody environment. Conclusions: The results obtained with the simulation show the effectiveness of the proposed solution. The wheelchair is able to climb a staircase in a safe and regular way. Following studies will complete the design of the wheelchair with the aim to build a prototype for demonstrating the proposed working principle.

No abstract