Simulating Airline Seats to Be More Inclusive with ESI Virtual Seat Solution
Shawn Wasserman posted on September 05, 2017 | 3483 views




Engineers need more human models to simulate the comfort, safety and living space of airline seats. (Image courtesy of ESI Group.)

Everyone can agree that airline seating can get quite enclosed and uncomfortable; especially on long flights.

Triggering a sciatic nerve, for instance, isn’t fun for anyone. However, for differently-abled individuals, or individuals with certain morphologies and ages, the pain can be quite devastating.

Ignoring the needs of these individuals can prevent their travels; a tragedy that is in clear violation of anti-discrimination airline regulations.

To design airline seats that create a comfortable experience for everyone requires human models that fit an assortment of morphologies. Engineers can then use these human models in simulations to assess the comfort and living space of the seats.

ESI Virtual Seat Solution now offers human models that represent typical elderly, differently-abled and larger bodied morphologies.

“Improving comfort for the next generation of seats and taking into consideration the entire population is important for our customers,” said Caroline Borot, industry solutions marketing and business development manager at ESI Group.

How to Assess Seat Comfort and Safety Objectively

Pressure map of an elderly human model sitting in Zodiac Seat Z301 in three different positions: upright during Taxi, Take-off and Landing or TTL (Top); reclined (Middle) and resting on the armrest (Bottom). (Image from ESI publication in AEGATS 2016, 12-14 April 2016, Paris, France.)

Pressure map of an elderly human model sitting in Zodiac Seat Z301 in three different positions: upright during Taxi, Take-off and Landing or TTL (Top); reclined (Middle) and resting on the armrest (Bottom). (Image from ESI publication in AEGATS 2016, 12-14 April 2016, Paris, France.)

It’s quite easy to understand, in theory, how to assess safety. Regulations are set to keep passengers within a range of loads to ensure safety in extreme conditions.

However, how do you measure something as subjective as comfort? Well, you don’t, really.

“Specialists don’t talk about comfort; just discomfort and how to decrease it,” Borot clarified.

In other words, this is a comparison game. There are a handful of seats in the industry that are known to be comfortable. These become the benchmark for comparison in simulations. Engineers then perform real testing or use virtual models with Virtual Seat Solution to simulate pressure maps, living spaces, safety, heat transfer, vibrations and more. The results are then compared to the gold standards in comfort.

Borot adds that there are different measures of comfort. Static comfort relies on the assessments of posture and pressure maps. Dynamic or vibratory comfort assess how much of the aircraft’s vibrations are absorbed by the seat. Thermal comfort assesses how much the seat can maintain a comfortable body heat. Finally, living space defines the volume a passenger has.

“Depending on the seat you will have different expectations,” noted Borot. “From economy to first class, you will expect a different experience. It’s also very different from what you require for pilot seats. Your comfort expectations also depend on the duration of the flight. If you are on a long or overnight haul, you will have different expectations. When engineers have the seat type and aircraft range defined, they know what they are evaluating. You can then start to evaluate the living space and other objective criteria to ensure comfort.”

Now with Virtual Seat Solution, you can also perform these assessments for the elderly, differently-abled and overweight individuals, for whom new human models are now available.

Before the seat is optimized for comfort, engineers must assess its safety for certification. An optimal seat will be comfortable, lightweight and, most importantly, safe.

“When you have a new design, you can use virtual prototypes to pre-certify the seat and replicate what you would do in the testing facility,” said Borot. “Engineers need to ensure that the design will be successful in the testing facility. If unsuccessful, then they will spend a lot of money finding out what went wrong, delaying the time to market.”

To assess comfort, engineers use human models that allow them to better simulate a human’s response to the seat. To assess the seat’s safety, a digital Hybrid II dummy is used.

Pre-certification with ESI Virtual Seat Solution (Image courtesy of ESI Group.)
Pre-certification with ESI Virtual Seat Solution (Image courtesy of ESI Group.)

Importance of As-Built versus As-Designed Digital Prototypes

Virtual Seat Solution gives engineer the ability to simulate the production of the seat before simulating its performance. But why is this

This as-manufactured composite part (right) saw a 20 percent difference in displacement compared to the as-designed model (left). Therefore, it is imperative that engineers perform these simulations with as-built parts. This might entail simulating the production process to gain the correct material properties. (Image courtesy of ESI Group.)

This as-manufactured composite part (right) saw a 20 percent difference in displacement compared to the as-designed model (left). Therefore, it is imperative that engineers perform these simulations with as-built parts. This might entail simulating the production process to gain the correct material properties. (Image courtesy of ESI Group.)

important?

During the manufacturing process, a part will never turn out exactly as it was intended. These imperfections might seem small, but can have catastrophic effects.

“The way that each seat is manufactured can change the material properties and affect performance,” said Borot. “With composites, for example, fiber direction will matter. If you don’t take it into account, you need to add a safety margin, but that means adding weight to a material chosen specifically for its light weight.”

Therefore, before performing simulations on the seat comfort and safety, the engineer must first simulate the manufacturing process of that seat.

Will the cover conform the seat’s foam to an unnatural shape? Will the steel bar have internal stresses that will compromise the structure? Will the fibers in the composite be aligned to the load path?

If you don’t simulate the manufacturing of the part you will never truly know.

How to Build Models of Various Morphologies

Comparing an ESI H2020 Standard Model with the company’s final model for differently abled individuals. (Image courtesy of ESI Group.)

Comparing an ESI H2020 Standard Model with the company’s final model for differently abled individuals. (Image courtesy of ESI Group.)

So, how do you make a human model for simulations? Well, it depends; you can either create a standard based on human scans or modify a standard based on population data.

The initial standards in ESI Virtual Seat Solution were based on real people that represented corresponding percentiles in certain populations. Say male, American, 95th percentile for age, height and build.

“They were then scanned into models with skin, flesh, and organs,” said Borot. “We then did tests with the human and their corresponding avatar. The check was to see if they gave the same results for comfort, be it static, vibration or thermal.”

For the new elderly, larger-bodied and differently-abled models, ESI chose to alter a standard model based on population data. From here, they researched their target populations based on the literature available. This data was then interpolated to tell them how much they needed to change a standard model’s muscle mass, fat mass, bone structure and skin.

For instance, for the differently-abled model, much of the focus was on the lower-body. The standard model that was closest to the end goal morphology was chosen and then modified. Less muscle mass and fibers were included in the model in the lower extremities and the hip-bones changed in shape. All of these changes were made to match the physical changes many paraplegics experience due to their posture and stability restrictions.

Human models library (Image courtesy of ESI Group)

The elderly and overweight models were changed in a similar fashion. The major difference being that changes were made throughout the model, not just the lower body.
Additionally, different starting models were chosen for the elderly and overweight models, respectively. Finally, the elderly model underwent changes to the material property of its bones.

So, what about a differently-abled model for individuals whose muscle mass varies throughout their bodies? That, like older and larger models, could be added in future releases of ESI Virtual Seat Solution.

“We can’t assess the seat comfort for every single person,” conceded Borot. “But this is a first step, allowing seat designers to imagine a new seat and to immediately see the impact of the new seat on a variety of morphologies. It’s a real step forward.”

To learn more about ESI Virtual Seat Solution visit the product website.


ESI Group has sponsored ENGINEERING.com to write this article. All opinions are mine, except where quoted or stated otherwise. —Shawn Wasserman
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