Many jobs require that workers remain seated for long stretches of time, such as programming or financial work. However, doing this can have some major drawbacks, including placing pressure on the back (causing back pain) or limiting blood circulation in the legs. On the other hand, maintaining proper posture can relax tense muscles and improve core strength. Based on this, a team at Tohoku University in Japan wanted to make a new type of office chair that actively changes its shape in response to prolonged sitting. Introducing the TiltChair!
The first leg of this project is figuring out when and how a person is sitting. An MPU-6050 accelerometer is mounted just below the seat cushion, and this device is able to measure the inclination angle. On the underside is a BME280 pressure sensor that is responsible for getting if the user is currently sitting down. Finally, an Arduino Uno is used to communicate with both of these sensors over I2C and SPI.
Now that the chair can detect if a person is sitting, along with how, it needs a way to adjust the seating angle. The seat itself is constructed from a lower plate and an upper plate with an inflatable bag between the two. When the angle is to be changed, the Arduino sends a signal to a servo motor that regulates an air compressor to inflate the bag, along with a vacuum pump to help deflate. By using this system, the seat can be raised up to 55 degrees.
After creating the chair, the researchers wanted to do a study on just how effective an automatically-tilted seat is versus a standard one. They set up the test to measure how well the subject can perform various work tasks while sitting at five different angles. And as expected, the lower angles were fine, whereas anything above 35 degrees was quite uncomfortable and caused a small loss in productivity.
Their second test measured how well subjects can respond to changes in seat inclination over time. Finding an optimal degrees per minute rate is very important here, as that determines how quickly the chair should be inflated or deflated. Each subject was able to complete their tasks with no interruptions at rates between five and ten deg/min, but any speeds higher than that caused disruptions. At the fastest speed tested, 80 deg/min, participants felt surprised and even stopped working due to the sudden change.
Overall, the results show that a sufficiently low speed and angle will cause about as many disruptions as a standard chair, with the benefit of encouraging correct posture. It's also great for breaking up prolonged periods of sitting in order to get more blood flowing through the legs.
The team acknowledges that their sample size in the studies was not adequate enough to determine which values are most suitable to the widest range of people. Additionally, other types of office work were not studied, so the impacts of this device are yet unknown. Apart from this, the physical system works well enough, although constant noise from the pump is an issue. It will be interesting to see what new and improved designs come from this early prototype.