2022 / Arts et Metiers Institute of Technology

Retractable Exoskeleton Wheel

Foldable wheel mechanism for a multi-mode mobility exoskeleton

Retractable wheel CAD in deployed circular configuration

Overview

Design-office project for a retractable wheel mounted on a mobility exoskeleton with wheelchair, gyropod, and walking-assist modes.

Problem / Context

The wheel had to support the user plus exoskeleton in rolling modes, then retract enough to reduce packaging and avoid ground contact during obstacle crossing in exoskeleton mode.

Role

Team project (bureau d'etude) - Arts et Metiers Institute of Technology

Institution

Arts et Metiers Institute of Technology

Team

Loris Emanuelli and Arts et Metiers BE team

Process

- Studied industrial, military, medical, and mobility exoskeleton references
- Reviewed retractable-wheel concepts and patent constraints
- Defined the need and functional architecture for the wheel subsystem
- Built CAD for a four-segment wheel linked by pivots and central rods
- Checked rods, rivets, and wheel arms under two representative load positions
- Compared manufacturing scenarios for 3D printing and sand casting

Key design decisions

- Used four circular segments so the wheel can form a rolling circle or retract into a compact package
- Maintained position through pivoted rods, rivets, and an electromagnet locking concept
- Focused FEA on geometrically complex parts where hand calculations were not reliable enough
- Selected aluminum sand casting for the production concept based on the cost comparison

Engineering details

- Target load case: about half of a 70 kg user-plus-exoskeleton system per wheel pair
- Two wheel positions analyzed, separated by a 45-degree rotation
- Buckling check gave Fcrit = 2193 N versus a 700 N design load
- ANSYS Workbench APDL used for finite element checks of selected components
- Estimated production cost: 289.99 EUR per wheel before transport and storage

Outcomes

- Defined a functional retractable wheel CAD architecture
- Validated key rods and links against simplified load cases
- Built an industrialization argument around manufacturability, cost, and IP position