Immobility or limited mobility is a large problem across the world, as 19.4 million, or 7.8% of adults ages 18&nbsp; and above are unable to do basic tasks due to mobility restraints caused by disease, chronic conditions, or physical trauma. This immobility takes away from a person’s health, enjoyment of life, and ability to contribute to society. It was identified that there are unmet needs in the medical industry for low-cost assistive devices such as walkers, gait trainers, and wheelchairs with features such as terrain versatility, torso support, a wheelchair feature with sit-to-stand functionality,&nbsp; and easy maintenance. The device design proposed in this paper addresses these needs in a single product with high performance and cost-effective design choices.In this paper we discuss the overall design of a combined walker-wheelchair device. This device is designed for outdoor use as well as indoor by choice of large, inflatable rubber wheels, placement of larger wheels in the front, and use of weather safe materials. It is designed for low resource environments through use of bike wheels and preference of part selection available in a typical bike shop, as bikes are commonly used in both resource and low resource areas of the world. It also enables torso support by its harness. It has sit-to-stand functionality through a trolley system. The system is adjustable due to the inclusion of sliding front axle and seat connections . In this study this design is described further, and is then followed by an analysis of system stability with multiple approaches. This includes analysis of wheel configuration and system stability when hitting a bump and a hole.The analysis was based on simulations performed on a Computer Automated Design (CAD) version of the walker, which were completed using Simwise 4D, given it's unique capabilities for multibody kinematics. A CAD model was created in Creo 6.0, imported into the simulation software, and then parts were created in Simwise 4D and added on to the frame through constraints. This study selected constraints and constraint translational and rotational stiffness based on literature values. A dummy model was created with human dimensions and joint stiffness so to find the behavior of the body when moving with the walker. The forces acting on part connections of high failure risk, such as wheel axles, seat attachment, harness to trolley connections, and any point experiencing a high amount of concentrated force. These forces are compared with yield strength calculations to assure a reasonable safety factor.The paper also further explains how and why the simulations were conducted as they were and how they approximately test for risk of failure and its consequences. The highest impact force experienced at the wheel connections was 20,000 N, which when used with a safety factor of 2, at 40,000 newtons, was still below the limit for the bolts used at the connection. This study shows that this design is both safe and meets an unmet need in the medical industry. It shows that the system does not approach toppling over when hitting a bump or overcoming a hole, and it compares the impact force experienced at these interactions to the limit that the connections within the device can handle safely.

Simulation of a Terrain Versatile Walker-Wheelchair With Torso Support

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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