ASME Innovative Design Simulation Challenge: Helping Seniors; Rising to the Occasion

By Roger Torda/ASME Public Information

Darshan Sarojini (left) and Akshay Varik show a model and a scale prototype of their bi modal bi-stable chair.

“The elderly lady is our friend’s grandmother,” said Akshay Varik a recent engineering graduate of BMS College of Engineering in Bangalore, India.  He is referring to a photograph showing a woman getting up from a chair with great difficulty. “That really inspired us to take this project forward.”

Akshay and Darshan Sarojini were in Buffalo, New York, for ASME’s inaugural Innovative Design Simulation Challenge. Their project was to simulate a chair that uses the property of bi-modal bi-stability to assist a person in rising to a standing position.

Their research started with a novelty product, a round container with a metal lid that snaps open or closed -- demonstrating “bi stability” in each of the two positions.  

The starting point: a tin lid that demonstrates bi-modal bi-stability.

The team, which included Anirudh Katti, who could not attend the competition, wanted to design a chair with a seat that springs between stable upright and sitting positions, using similar properties as the lid.  Force applied as a person sits down will drive the seat from one position to the other. A light pressure from the side would then trigger the seat to spring back to the upright – a good assist for a disabled person!

The team – which calls itself “Sahai”, or freedom – researched existing products that help people with arthritis or other movement disabilities. They found chairs with electrical actuators or complex hydraulic systems – large and expensive machines beyond the means of many elderly people in India and elsewhere.

To start out, the team simulated the bi-modal, bi stable properties of the lid, specifying beam finite elements and a hinge boundary condition. Darshan was the lead on this stage of the project, using ABAQUS finite element analysis software.

Simulation of Rigid Body moving between two stable states.

Next, the young researchers created an extruded 3D model. The model failed to demonstrate bi-stability, until a roller boundary condition was applied. They found that one particular geometric profile, a “2 cosine” curve, gave consistently good results. Experiments, a literature search, and some tips from their advisor, Prof. H.K. Rangavittal, led to the addition of a stiffening element for improved performance. The team used 3D printing for prototypes to verify the bi-stable behavior experimentally.  

But a chair also needs an easy-to-use activating mechanism. Akshay used ADAMS multibody dynamics software to simulate the system with a bell crank for actuation. This led to a design, and then to a scale model.  

Von Mises stress as prototype moves between bi-stable positions.

Team Sahai won one of two prizes in the Commercial Software category. Their work was cited for Best Impact Simulation for Product Design.

Akshay was in the U.S. for the first time, and was heading to the University of Pennsylvania, to study for a Masters degree in mechanical engineering, specializing in design and manufacturing.

Darshan had been to the U.S. before, to a Society of Automotive Engineers competition in Atlanta. He’s currently working as a project assistant at the Indian Institute of Science in Bangalore and hopes to begin graduate studies in toward a Ph.D. in aerospace engineering next year.  He hopes to develop a full-size prototype for the chair, and then bring it to market.

Scale model prototype of bi-modal, bi-stable chair.

“This was the first real project where we actually got into research,” Darshan said in an interview after the presentation. “It started with research, and then applying research to a design, and actually manufacturing the design and testing it. So we got a complete experience.”

“It was a nice learning [experience], Akshay said.  “When we see products in the market that are high end, these kind of goods are difficult to afford…. To work on such a project where we could help people by making a product economically feasible, this is fantastic…. This probably could be a good 85th birthday gift for my grandmom.”