Sitting is the most unhealthy position possible for the human body, which has evolved during evolution according to the requirements of straightened, dynamic movement and resting in a supine position. With the proliferation of office work, most workers are forced to spend most of the day in this posture, which can result in long-term health damage. During the pandemic, due to teleworking, this phenomenon came to the fore exponentially, as working conditions at home are usually ergonomically inadequate. By taking regular breaks from exercise and sitting in the right posture, you can minimize the risks.
Under the SmartSeat brand, we have developed an ergonomically designed smart office chair that constantly examines the user’s posture while sitting and alerts you to the correct posture. Thus, the furniture not only makes it possible, but in an educative way promotes the acquisition of the correct posture.
In order to allow stepless tilt adjustment for both the seat and the backrest, as well as the placement of the four pressure measuring sensors, we have developed a new type of mechanical structure for the office chair. The main feature of the mechanics is that the seat and backrest are each placed on an X-shaped flexible sheet metal bracket. The protruding legs of the X-shape provide sufficient flexibility for the pressure stamps placed on them to provide very accurate information about the force acting on the legs and thus the body position of the user sitting in the chair.
A total of eight measuring stamps were placed in the chair and connected to a central processing unit located on the inside of the backrest. The central unit transmits sensor data to the mobile phone application via Bluetooth wireless connection, 2 times per second.
Customizability was an important consideration in the design of the structure. Because users can have very different body sizes, we wanted to allow the seat and backrest to be interchangeable. Backrests of different sizes and designs can be secured with mountable nodes at the ends of the X-shaped metal brackets. In addition to the different sizes (S, M, L) backrests and seats, we also provide users with the possibility of fine adjustment. The backrest can be infinitely adjusted in a vertical movement range of 50 mm and the seat horizontally in a range of 50 mm, so the height of the lumbar support and the front support surface of the seat - below the knee bend - can be precisely adjusted.
In addition to the special customization and adjustment options mentioned above, a gas telescopic height adjustment system typical of modern office chairs as well as vertically and horizontally (back and forth) adjustable armrests have been installed.
IT and data visualization system
Central to the SmartSeat system is the mobile app, which provides communication between the smart chair and the web server responsible for storing data. In addition, it provides the following functions:
- display of weight data measured by pressure measuring sensors on the seat and backrest with an accuracy of 0.1 kg
- visualization of current body position
- assessment of current posture: optimal posture, lateral tilt, forward-backward tilt
- warning in case of prolonged poor posture
- warning to interrupt sedentary work with a rest period
- display statistics based on data stored on the web server
Center of gravity on the seat and backrest in correct posture and poor posture
From the data of the four sensors placed on the chair, the mobile application calculates the center of gravity of the pressure on the seat and the backrest. And the location of these points clearly represents the body position of the user. For example, if we see that there is a high load on the front half of the seat and the top of the backrest, the user is sitting in a reclined position,
the lumbosacral region of the spine bends in a “C” shape instead of a healthy “S” shape.
Once the user logs in to the application and starts using SmartSeat, their body position data is continuously transmitted through the mobile application to the web server where it is stored. These data, after one to two weeks of use, are suitable for analyzing the user's posture and work habits (eg: active period / rest period ratio). The following data can be displayed in the form of application diagrams from the stored data:
- Number of hours spent in sedentary work during the study period
- Average time spent sitting daily
- Sitting map: using the shades of the seat and the backrest, we display which are the most frequently loaded regions - from this it can be deduced in which body position how much time the user spends.
- Ratio of normal, tilted, reclined postures
- Ratio of lateral tilts
- Change in body weight
The primary target group of SmartSeat is users in the computer workplace between the ages of 35 and 65 who either already have a health problem due to an improper session or want to create the most appropriate work environment as preventive.
Due to the high price of a low-value, high-value-added product, we expect mainly corporate customers in addition to private users. Corporate users can use the chair as a medical device with the involvement of an occupational physician. SmartSeat takes approx. is able to build up a database of sitting postures over a one-week period from which the doctor can determine the causes of the symptoms (back pain, neck pain, shoulder pain) and correct them to improve the worker's condition.
Thanks to the unique mechanical solution, our steplessly adjustable office chair with sensors is realized within the framework of the VEKOP-2.1.7-15-2016-00145 project, with the support of the EU and the Government of Hungary.