Welcome to our ESE senior design project!

An IMU-based Infrastructure for Sway-back Posture Detection Implemented on Raspberry Pi

Studies have found that abnormal loading of the hip is highly related to osteoarthritis, which consequently lead to hip pain [2], an issue that more than 15% of people aged 65 years suffer from [1]. Since abnormal hip load resulting from incorrect postures is one of the major contributors to this problem, we developed a wearable infrastructure that alarms when the user is under a sway-back posture to avoid hyper extension as a solution for chronic hip pain prevention. This infrastructure consists of a wireless IMU (WitMotion BWT901CL) attached to a belt as the sensing unit, and a Raspberry Pi Zero W as the processor that runs a posture detection program in Python 3. Two functionalities were implemented:

1) real-time posture labeling for physical therapist to train the classification algorithm,
2) posture detection to provide feedback to help the user correct sway-back posture.

To develop posture recognition algorithms, we experimented with sensor fusion, dead reckoning and machine learning algorithms. With labeled data that collected from the infrastructure, we applied principal component analysis (PCA) to find most representative features for posture classification. Support vector machine (SVM) was applied with various feature dimensions using ~10,000 data points. The algorithm achieved classification accuracy of 95% for standing properly, 83% for sway-back and 85% for sitting across different subjects. For future work, more complex postures data will be collected for model training.

Team members

Moira Feng

Moira is a senior at Washington University in St. Louis majoring in Electrical Engineering and minoring in Computer Science. She is interested in developing biomedical devices in the future, and she’ll be studying Medical Devices & Systems at UCSD for graduate school.

Ben Wang

Ben is a senior at Washington University in St. Louis studying Electrical Engineering.

Project Advisors

Shantanu Chakrabartty
Department of Electrical Engineering
Division of Biology and Biomedical Sciences
Department of Biomedical Engineering
Department of Computer Science and Engineering

Dan Moran
Associate Professor
Department of Biomedical Engineering


1. D. Rodriguez, “The basics of Hip Pain”, Everyday Health, 2009
2. Lewis, Cara L., Shirley A. Sahrmann, and Daniel W. Moran. “Anterior hip joint force increases with hip extension, decreased gluteal force, or decreased iliopsoas force.” Journal of biomechanics 40, no. 16 (2007): 3725-3731.