Medical Walker with Integrated Crutch Mechanism
General Electric Energy Steinmetz Award (2014)
Many elderly people and injured people suffer from physical complications that make it difficult or dangerous for them to perform everyday activities, thereby inhibiting their mobility. Some of these activities include walking, standing, and sitting. This thesis focused on designing and building a dual purpose machine that can function as a portable medical walker as well as a standing and sitting aid. The purpose of this is to increase the mobility of independent and resilient people who struggle to move around on their own.
Two Trimesters (20 weeks)
Motion Analysis & Paper Prototype
In the early stages of the design process, it was determined that the crutch mechanism would engage a person at two main points to provide support, stability, and safety. These two contact points were identified to be underneath the armpit and at the center of the hand, similar to where traditional crutches provide support for a user. Using a high speed camera to record video and burst photos, data was obtained by videotaping the sitting and standing motions of various test subjects. I focused my attention on determining the path of the armpit contact point and upper body motion.
A 4-bar parallelogram linkage was created out of paper and tacked to a wall to evaluate the feasibility of a particular design idea. At this stage, I was looking to:
1) Confirm that the linkage would yield a circular motion per the motion analysis study
2) Determine if the design solution was practical to construct
3) Identify different ways to power the linkage that would not be intrusive to the design
3D Model, Final Solution & High-Fidelity Prototype
While maintaining a compact size, the walker/crutch mechanism was designed to ensure stability and ergonomics. Two linear actuators were fixed to the machine via pin joints at calculated locations that allowed the four-bar parallelogram linkages to mimic the natural standing/sitting motion. In addition, the linear actuators were offset from the linkages, which allowed them to extend and retract freely.
The prototype was constructed from 1026 steel tubing and incorporated double locking casters for stability as well as crutch pads for comfort. Two linear actuators with a 10 in. stroke and a 200 lb maximum load rating were used in conjunction with a 12V lead-acid battery and a control box to simultaneously raise and lower the two four-bar parallelogram linkages.