Engineers Develop Chair With 'Sense'
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PURDUE ENGINEERS DEVELOP A CHAIR WITH 'SENSE'
Purdue University /EurekAlert!
Thursday, November 2, 2000
WEST LAFAYETTE, Ind. Purdue University engineers have developed a "sensing
chair" that can determine a person's sitting posture, research that could
lead to numerous applications, from computer-security systems to the design
of more comfortable furniture.
The modified office chair uses software algorithms, or computer
instructions, that interpret information collected by an array of pressure
sensors in the backrest and seat. When tested on 30 people, the chair
demonstrated an overall accuracy of 96 percent in determining whether people
were slouching, leaning in various positions, crossing their legs or sitting
"The chair senses how the pressure is distributed in the seat and the
backrest," said Hong Tan, an assistant professor at Purdue's School of
Electrical and Computer Engineering. "We train the computer to recognize
pressure patterns associated with different seating postures by showing the
computer examples of such patterns."
Lynne A. Slivovsky, a doctoral student working with Tan, will present a
research paper about the work Nov. 9 during the 2000 International
Mechanical Engineering Congress & Exposition, sponsored by the American
Society of Mechanical Engineers in Orlando, Fla.
Special software enables a computer to interpret a person's posture by
analyzing pressure patterns, which are represented by thousands of numbers
fed to the computer by numerous sensing elements, or "sensels," in the
chair. Each time a person sits in the chair, the computer creates precise
"pressure maps" that can distinguish between different people, even if they
are sitting in the same position.
The system is limited in that it is capable only of sensing "static
posture," or how a person is sitting at any one given time.
"Currently, we are working on a dynamic system so that we can see how people
are moving, throughout an eight-hour day, for example," Tan said.
Such an advanced "real-time sitting posture tracking system" would lead to
many applications. Because the system would be able to recognize the
pressure patterns peculiar to specific people, a potential application might
be to verify authorized personnel for computer-security purposes.
A sensing chair also might be used in cars to automatically adjust the
driver's seat according to who is behind the wheel, or to control an
airbag's deployment by adjusting for a person's seating position and weight.
Another potential application could be to improve the ergonomics of
"People come into the showroom, they sit down, they think, 'Oh, this chair
feels great,'" Tan said. "They buy it, and then they return it because after
several hours of sitting in it, it doesn't feel great any more.
"So, chair manufacturers are interested in how to evaluate a chair over an
extended period of time. They want to understand the long-term dynamics of
The chair is most adept at sensing when someone is slouching, correctly
interpreting that posture with an accuracy of 99.8 percent.
"For anybody who wants to do anything related to ergonomics, slouching is
the one posture you probably really want to discourage," said Tan, who
specializes in research focusing on the haptic human-machine interface, or
how machines and people interact through the sense of touch.
Perhaps such a sensing chair might sound a warning beep every time its user
assumed a slouching posture, she said.
Researchers said they were surprised the chair was able to accurately
distinguish between the subtle posture differences of leaning left, crossing
the right leg while leaning left or crossing the right leg without leaning
"We were expecting to see a lot of confusion among those three because they
are so similar," Tan said.
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