Multi-speed Ergonomic Wheelchair

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The Minneapolis Adaptive Design & Engineering (MADE) Program has recently developed ergonomic wheelchairs that use a chain drive system to place the hand rims in an ergonomic position while keeping the rear drive wheels posterior for a stable base of support. Our ergonomic wheelchair’s forward hand rim positioning allows for a more efficient push along a longer arc length of the hand rims, without sacrificing wheelchair stability or shoulder ergonomics. The ergonomic wheelchair’s chain drive allows for individualized gear ratios to suit each wheelchair user’s needs; however, we have not yet studied this feature. Thus, the objectives of this proposed work are to (1) explore the effect of different gearing options on Veteran wheelchair user steady-state propulsion efficiency, and (2) develop a multi-speed ergonomic wheelchair allowing for lower gears during difficult situations (initiating movements, moving over carpeting) and higher gears for steady- state movements on flat surfaces. We will recruit 18 Veterans with SCI/D to participate in a cross-over study of the ergonomic wheelchair with three gear ratios (3:2 (low), 1:1 (normal), and 2:3 (high)). We will use two measurement approaches to assess efficiency: (1) work done at the pushrim hubs to move the wheelchair in Joules (J), and (2) the measurement of energy (kCal: kilocalories) expended by the Veteran to move the wheelchair. Similar to miles per gallon in a car, we will calculate distances traveled in meters (m) per energy units (m/J and m/kCal) as our measures of efficiency. We hypothesize that (H1) Higher gear ratios will be more efficient (higher m/J) on hard level terrain than lower gear ratios, (H2) Lower gear ratios will be more efficient (higher m/J) for inclined terrain than higher gear ratios, (H3) Lower gear ratios will be more efficient (higher m/J) for carpeted terrain than higher gear ratios, and (H4) Veterans will be more efficient (higher m/kCal) in moving the wheelchair during the 6MPT on hard level terrain when using higher gear ratios compared with lower gear ratios. In addition to steady-state measures, we will also explore the effects of gearing on propulsion initiation and expect lower gear ratios will be beneficial for initiation on all terrains. We will then recruit 12 Veterans to try a new multi-speed ergonomic wheelchair that has two hand rims per side – one in a lower gear and the other in a higher gear. The proposed system does not require manual or electric shifting between gears. Instead, the Veteran can use the lower gear to initiate movements and then “shift on the fly” by simply pushing on the other hand rim. Veterans will return to the laboratory and provide feedback as the design is iteratively improved. Quantitative and qualitative data will be captured to determine feasibility of this approach and to promote commercialization of the multi-speed ergonomic wheelchair. Throughout the project, our team will work closely with VA’s Technology Transfer Program and the TechLink Center to find an industry partner for this work. Our team has demonstrated the ability to develop rehabilitation products into commercially licensed products. We will follow a similar stage-gate process in this development project to maximize our chances for successful commercialization of the modular multi-speed ergonomic wheelchair.