Standards and Test Method Development at the REAR Lab
- Design and development of a wheelchair suspension seat
- Development of Standards and Test Methods: Wheelchair Cushion Standards
- Device to Measure Mechanical Work and Efficiency of a Manual Wheelchair
Design and development of a wheelchair suspension seat
The project’s objective was to design and evaluate a seating system that will replace standard wheelchair upholstery. Named the suspension seat, this device supports the body using tension members. This project began in the previous RERC cycle. A company, The PostureWorks, saw the previous prototype and expressed interest in licensing it. They asked the Mobility RERC to re-start refinement of the initial prototype that led to the institution of this project.
Developed and completed the Impact Dampening, Hysteresis and Load deflection tests. These were submited to the ISO. The specific aims of this project are to: 1) continue validation and refinement of the draft ISO heat and moisture vapor test, 2) Investigate the changes in cushion properties with use. This consisted of completing the protocol development and measurement now we are performing data analysis on the obtained data. The third item was Load Distribution Properties in which we designed and built a complaint buttocks model which has a rigid sub-structure and an elastomeric outer shell. The model is capable of measuring stress and strain on the cushion. Currently we are working on assessment of accuracy, creep, and repeatability the model.
This project developed a test device to directly measure the mechanical work and efficiency of propelling a manual wheelchair. The problem definition and design criteria were finalized with input from industry advisors. The general design criteria include the need to measure an occupied wheelchair that is being propelled. Repeatable and reliable test methods require the use of body models or dummies rather than humans. The result was the fabrication of a test device called the Anatomical Model Propulsion System (AMPS), which replaces the human operator and drives the handrims in a manner analogous to human input. From conversations with wheelchair manufacturers, the AMPS anatommy was modelled after the 7176 ISO dummy with a target weight of 100kg and average in size for human male. It applies a tangential force to the ring gear that replaces the handrim through a numerically controlled drive train, producing a propulsion force profile that is programmable and designed to reproduce data from human propulsion studies. AMPS effectiveness was validated by its ability to propel the wheelchair autonomously over defined trajectories. These trajectories include straight motion, turning at a finite radius, and zero radius turn. AMPS ability to measure handrim forces was validated using our instrumented wheelchair wheel that is capable of measuring torque at the wheel axle and the handrim. These simple trajectories test the AMPS control system and will permit simple analytical calculations of KE to compare with ARM measurements. We are in the process of cleaning up the data signals collected which permits accurate energy input into the system and subsequently, the efficiency of the measured chair. This project output will be used to achieve an important outcome, the adoption of this methodology by wheelchair manufacturers and, perhaps, standards organizations.