Design and effects on handrim kinetics of an automatic gear-shifting wheel for manual wheelchairs

Wheelchairs;Mechatronics;Biomechanics

Wineman, Michael ; Hsiao-Wecksler ; Elizabeth T.

关键词: Wheelchairs;    Mechatronics;    Biomechanics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49355/Michael_Wineman.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Of the 3.6 million wheelchair users (WCUs) living in the United States, 61.6% to 89.5% are manual wheelchair users (MWCUs). Shoulder pain is reported by up to 70% of MWCUs at any given time and has been attributed to the high demand, repetitive stresses placed on the shoulders during wheelchair propulsion. Further, up to 78% of MWCUs exhibit neurological evidence of carpal tunnel syndrome. The quality of life that MWCUs experience can be significantly and negatively impacted as a result of these conditions. However, geared wheelchairs have been shown to decrease shoulder pain in MWCUs. Therefore, prototypes of 5-speed automatic gear shifting (AGS) wheels for wheelchairs have been developed. The automatic transmission on the AGS system senses the translational speed of the wheelchair as well as the torque exerted on its handrim by a MWCU and transmits these data wirelessly in order to determine the optimal gear into which it should shift. Methods used to characterize the effectiveness of this design included sensor calibrations, benchtop testing and a full system test of the automatic transmission electronics. Speed and torque calibrations agreed qualitatively with, yet deviated quantitatively from theoretical and modeled conversions. Shift reliability testing showed that the shifting electronics engaged the desired gear 1200 times without failure and that all one-gear shifts had a shifting time between 300-345 ms. Shifting electronics were powered for 26 continuous hours under anticipated daily demands on a single battery charge. However, gearbox lifetime testing showed that each gear failed at its sun gear after at most 173 simulated days of anticipated daily mechanical demands and wear. Considerable noise was found in the automatic transmission’s strain signal; nevertheless, the AGS wheels successfully followed the desired gear determination algorithm during the automatic transmission testing, shifting into the desired gears while receiving 215/218 wireless transmissions sent during testing. A study designed to determine whether geared wheelchairs influence handrim kinetics and wheelchair propulsion across a variety of terrains is also proposed. Data from a pilot subject who travelled at self-selected speeds across a smooth tile surface, 24ft. of padded carpet, and up and down a 15 ft. long ramp with 3.2° grade were analyzed and discussed. Trials were completed in all five gears. Preliminary results showed that travelling across all terrains in lower gears resulted in lower peak torques, while using higher gears typically resulted in higher average translational speeds. The one exception involved travelling across carpet in gear 5, where the subject propelled at a lower translational speed. Work exerted during the carpet and uphill trials were observed to be lowest in gear 2. These preliminary data suggest that geared wheelchairs could reduce shoulder demands during wheelchair propulsion.