The OctoWalker - Design and evaluation of a closed-chain electric powered walking wheelchair for low- and middle-income countries

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Abstract

Background: The lack of access to electric powered wheelchairs for disabled people in low- and middle-income countries, that suit their rural environments, still remains an issue. Current available electric powered wheelchairs that do adapt to these rural environments are expensive and require complex control algorithms.
Objective: The aim of this research is to analyze the feasibility of an electric powered walking wheelchair with an one-degree-of-freedom closed-chain leg mechanism. The electric powered walking wheelchair should provide a solution for low-cost transportation for human adults with lower and upper extremity impairments in the poor road conditions of low- and middle-income countries. A scaled prototype will be designed, build and evaluated with the purpose that it lays the groundwork for future renditions in a true-scaled electric powered walking wheelchair.
Methods: Design requirements were formulated according to the ISO-7176 standards for wheelchairs and conceptual designs were generated, in which a final concept was selected according to the performance criteria. A final design was build and different tests were executed to evaluate the technical specifications and feasibility of the walking wheelchair.
Results: This resulted in the OctoWalker, an 1:3 scaled eight-legged walking wheelchair with a modified Trotbot leg mechanism, two DC motors, timing belt transmission, joystick control and electronic differential. The OctoWalker was able to walk on flat surfaces; steer to the left and right; climb over curb heights of 50 mm; and climb slopes up to 28° without the need of additional sensors and control features to maintain its stability.
Conclusion: The evaluation showed that a true-scaled OctoWalker would have a larger payload (135 kg), step length (675 mm) and speed (4.75 km/h) than currently existing leg-based electric powered wheelchairs. In future studies, improvements for a true-scaled OctoWalker are required in terms of travel range (2.5 km), wheelchair width (789 mm) and weight (140 kg), in order to achieve similar specifications as current stair-climbing and obstacle avoidance electric powered wheelchairs. Nonetheless, the OctoWalker opens up future opportunities for providing low-cost transportation for disabled people in low- and middle-income countries.