Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 113577

113577 - Lever-Based String-Driven Wheelchair With Speed Adjustment 

Wheelchairs are one of the most used mobility-enabling devices used by the physically disabled. The importance of the liberation and freedom that a wheelchair provides to its user cannot be understated. Typically, the drive system of a manually operated wheelchair is often achieved by using a hand-rim on the wheels, through which the user can push the wheels manually, or by using a chain-based pedal system, which enables the user to use the pedals to move the wheelchair. The major drawback of both these systems is that they are not very ergonomic or comfortable for the user. Therefore, improvement in comfort and ease of use of the wheelchair is a very important facet of this design. Moreover, the chain-based system also introduces several losses and friction in the system that reduces the efficiency of the drive and therefore as a result increases the physical effort required by the user.

The purpose of the project String-drive wheelchair is to improve the ergonomics of the manual wheelchair, while also reducing the force required to propel the wheelchair. The string-drive mechanism uses a lever-based system to revise the input from the user, the levers are positioned to the side of the seat in such a way that the user’s hand can naturally rest on it, this increases the comfort of the wheelchair. Further, a Rapid Upper Limb Analysis (RULA) analysis performed in CATIA V5 of this lever mechanism revealed reduced levels of muscle fatigue in the back and lumbar region of the user compared to the existing conventional wheelchair.

The levers actuate a string which is then coupled with a ratcheted freewheel hub mechanism connected to both sides of the wheel hub. This mechanism is tensioned with an industrial-grade elastic band, that recoils the string winding without rotating the wheels. The strings are attached in 2 pivot points on the lever, and this facilitates two strokes for a single arm cycle. The levers are also incorporated with a groove where the pivots can traverse along the axis of the lever to adjust the pivot point according to the speed and torque required using a linear actuator and the speed measured with an accelerometer. A bevel gear setup placed calculatedly between the levers allows the user to operate both levers with a single hand. Steering is incorporated by attaching the support wheels in the front with a tie-rod and controlled with a knob on the lever.

From the calculations and analysis, it is concluded that the string-wheel mechanism requires force nearly 73% lesser when compared to the typical wheelchair drives, such as the hand-pedalled wheelchair. Also, by providing an ergonomic design, the comfort of the user has increased considerably.

Presenting Author: Shanmuga Sundaram K College of Engineering, Guindy-Anna University

Presenting Author Biography: Director of AU-FRG institute in College of Engineering, Guindy-Anna University.
Professor in Department of Mechanical Engineering.

Authors:

Mahmood Khaja Muhieitheen College of Engineering, Guindy-Anna University
Seshaarajesh S College of Engineering, Guindy-Anna University
Jayanand B Anna College of Engineering, Guindy-Anna University
Vickneshvari R M College of Engineering, Guindy-Anna University
Shanmuga Sundaram K College of Engineering, Guindy-Anna University
Nirmal A J L A College of Engineering, Guindy-Anna University