My work this week centred on further research into our IMU placement, data collection, and calculations for proper integration into PosturePal. We are considering using LSM6DSOX as our IMUs due to their six-axis capability, low power consumption (0.55 mA in their higher-performance mode), and compact size (2.5 mm x 3 mm x 0.83 mm). As Allison mentioned in her weekly report, one potential drawback of these IMUs is that they do not allow for wireless communication, and as a result will integrate either I²C or SPI into our current design. As done in a 2021 research article by Paloschi et al, we will be placing IMUs on the T3, T12, and S1 vertebrae, which in the paper were compared to and validated against a motion capture system to detect poor spinal posture. The T3 and T12 movement and difference were used to capture thoracic changes, while the T12 and S1 were used for the lumbar. However, the research of Paloschi et al did not use a wearable vest for participants when capturing this data and instead placed the IMU’s directly on the skin. As a result, we must and are working to take into account this difference in our design, specifically, how we will test for accurate measurements and worsened posture haptic feedback. One way we are considering to combat this in our design is that instead of integrating the three-axis acceleration and angular velocity given by the LSM6DSOX to calculate the IMU position over time (comparing each sensor’s new position to the location of its old one), we will compare the relative location of each sensor to the others. This way, we can determine if the upper back has curved in comparison to the middle of the spine, and similarly for the lower back. These relative calculations will also guide our calibration phase of PosturePal to identify what the user believes is their “ideal posture”. Specifically, we believe this will help us better meet our requirement of accurately identifying 90% of actual slouches or occurrences of posture worsening over stretching or other movements.
As a result, in our current design process, we believe we are on time and in a good position to complete our design proposal with an updated approach to sensor data calculations and approach. In the next week, my goal is to finalize the positions of these IMUs and the communication protocol they will be using with our MCU and software stack with my teammates to ensure the data we are collecting and the calculations we are performing will best allow for accurate haptic feedback.