ASSISTIVE TECHNOLOGY

INNOVATION & DESIGN

ENGINEERING

ABOUT

As part of a senior design capstone project, a team of five students and I proposed to create a lower body exoskeleton to assist in walking and STS ( sit to stand ) motion. The idea was proposed because of its social impact capabilities and its necessity in current society. 

PROBLEM:

Most exoskeletons have a heavy price point and are quite sizable. However, it is still a product in demand across many fields, especially medical. Lower body exoskeletons can be used for both rehabilitation and assistance. For people who can't afford the price tag that comes with modern exoskeletons, is there an alternative solution?

INITIAL RESEARCH:

To produce a semi-automated lower body exoskeleton, we first researched into the kinematics of motion for the lower human body. Through mathematical models, the movement of the hip, knees, and ankles can be related during walking motion. In addition, the average maximum values of torque on the knee and hip during walking and STS motion were obtained from documented research articles and adjusted for a weight of approximately 150 lbs. 

PROPOSED SOLUTION:

Our solution was to conceptualize and bring to life an exoskeleton that was significantly cheaper than whats currently on market through the use of 3-D printing methods and cheaper frame materials. 

Unlike other lower body exoskeletons, this form of assistive technology was designed to only support a fraction of the total body weight. The design is focused on patients in need of physical therapy, as well as the elderly who may need help getting up. By only supporting a fraction of the weight, in theory, the exoskeleton would assist in muscle regrowth and physical rehabilitation. To ensure that the exoskeleton was fully automated, flex sensors and encoders would be used in tandem to provide live information about the current position of the user, as well as desired motion. 

RESEARCH:

Upon further research, we realized that in order to implement a semi-automated exoskeleton for walking, we had to utilize machine learning in junction with our sensors. In the duration allotted for this project, our team realized that there was not enough time to master machine learning and subsequently implement it for the assisted walking motion. Consequently, we decided to pursue STS motion and leave walking as a stretch goal. To counter the cost of the necessary motors, this new design incorporated a spring mechanical system to reduce load on the joints sitting down, and provide support rising up. 

INITIAL MANUFACTURING:

Using available 3-D printers, certain components are manufactured using high density infill. Aluminum 6061 T c channel bars are machined to desired size and shape. Aluminum sheet metal is used as a basis for support braces and other components. 

INITIAL TESTING:

3-D printed components were tested for structural integrity. Machined components undergo drop and stress tests to ensure the safety of the user is not compromised. Initial wear tests were conducted and it was determined that design changes need to be made to accommodate for spring strength and structural stability.

SECONDARY DESIGN:

Spring system is updated with cam design and flex sensor attachment designs are implemented. Various components that only held aesthetic purpose were removed to reduce manufacturing and assembly time. Furthermore, certain components were redesigned for symmetry to reduce the total number of unique parts. 

MANUFACTURING:

Once all design changes were accepted, the newly designed components were either machined or 3-D printed. With all the parts produced or purchased, the sub assemblies were put together and then assembled into the exoskeleton. 

FUTURE

While this design was optimized for STS motion, the next steps would be to implement machine learning and adjust the design for walking motion. It would then be tested with patients who are undergoing physical therapy to confirm muscle regrowth capabilities.