1. To develop a secure attachment for data logger and tri-axial accelerometer Replication of a tri-axial accelerometer with the ability to: -Interface with data logger -Attach securely without impeding gait -Adaptable for future modifications We thank Dr. Paul Thompson and Dr. Bryan Heiderscheit for all their guidance throughout the course of this project. We also appreciate Amit Nimunkar’s assistance with circuitry. -Attach Lemo connectors -Package accelerometer to prevent interference with gait -Validate using human subjects -Wireless measurements Detecting Gait Instabilities with Accelerometry Tim Balgemann, Kelvin Ng, Ann Sagstetter, Karissa Thoma Client: Dr. Bryan Heiderscheit / Advisor: Dr. Paul Thompson Department of Biomedical Engineering Cho, C., Kamen. (1998). Detecting Balance Deficits in Frequent Fallers Using Clinical and Quantitative Evaluation Tools. American Geriatrics Society 46, 426. Hausdorff, J.M. (2005). Gait variability: method, modeling and meaning. Journal of NeuroEngineering and Rehabilitation 2, 19. Hausdorff, Jeffrey M., Ladin,Zvi, Wei,Jeanne Y. (1995). Footswitch System For Measurement Of The Temporal Parameters Of Gait. Journal of Biomechanics 28, 347. Figure 1: shows one complete stride in the gait cycle. Abstract Problem Statement Figure 2: Medical Research Ltd. Data logger A device is designed to measure the acceleration of a subject’s center of mass in three dimensions so as to assess gait instability during walking. Results reveal considerable reliability in the ability of the device to detect sharp changes in acceleration, and set the stage for future development in translating accelerometry to instability indication. Motivation Current methods of diagnosing patients that are at high risk of falling is completely dependent on a battery of questions, and is subjective depending on the individual responses. A more definitive method using accelerometry is desired for a greater prevention of life-changing falls. Definition of Gait Figure 3: Triaxial accelerometers with Lemo connectors. Current Product Background Problem Statement -The commercially purchased product is a data logger from Medical Research Ltd. -Uses Analog Devices Accelerometers -Costs ~$5000 Our Design Four Project Components 1. Attachment Belt -Fit waist sizes from 20 to 60 inches -Mounts accelerometer and clips on data logger Figure 6: Circuit diagram of Freescale accelerometer and three op-amps connected via Lemo connectors to Medical Research Ltd. data logger. 2. Data Logger -MIE data logger -8 inputs each with range of 0 to 5V -Physical properties: -72mm x 55mm x 18mm -90 grams including memory card and battery 3. Accelerometer -Freescale tri-axial accelerometer: MMA7261QR2 -Evaluation board: Kit3109MMA7261QE -Maximum output 1.2V -Four G-ranges: 2.5, 3.3, 6.6, 10 -Amplify outputs using Parallax dual op-amps: LM358N 4. Circuit Design -Potentiometers for fine and course adjustment of gain 0-1kΩ, 0-2kΩ -Zener Diode ensures 3.3V to the evaluation board Future Work References Acknowledgments Validation Figure 4: Attachment device Figure 7: Series of sharp oscillations were conducted with accelerometry circuit. Resulting data proved signal was being recorded. Figure 5: Circuit design