Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 52 | Posture & Neck Strain Monitor for Long Study Sessions |
Heet Chauhan Hrishikesh Deshpande Praveen Madan |
Xiyue Zhu | ||
| # Posture & Neck Strain Monitor for Long Study Sessions Team Members: - Hrishikesh Deshpande (hd11) - Praveen Madan (madan7) - Heet Chauhan (heetc2) # Problem Long study or work sessions at a desk make it easy to slip into bad posture without noticing until neck or back pain has already set in. Existing solutions are poorly suited to everyday use - desk mounted cameras are expensive and raise privacy concerns, back braces are bulky and uncomfortable for long wear, and app based posture trackers usually require a subscription and constant phone interaction. Single-sensor clip-on posture devices have also historically been unreliable, since one IMU alone cannot distinguish real slouching from ordinary head movement (like glancing down at a book). We need a small, low cost, standalone device that reliably monitors both posture and neck strain, and gives a quick nudge when the wearer starts slouching, without requiring a phone or subscription to be useful. # Solution We propose a small two-IMU wearable system: one IMU mounted on the glasses (tracking head orientation) and one mounted on the collar/shirt (tracking torso orientation). By comparing the two, the device can compute the actual relative angle between head and torso — a true measure of neck strain and slouching — rather than relying on either sensor alone, which past single-IMU posture devices have struggled with. The glasses-mounted sensor board connects to the main collar-mounted board via a thin wire. During setup, the user calibrates a "neutral" posture baseline while seated normally, and the device monitors deviation of the relative head-to-torso angle from that baseline in real time. If the wearer holds a slouched or strained position past a configurable threshold, the device alerts them via a vibration motor, prompting them to correct their posture. The system is built around three core subsystems: sensing (dual IMU-based relative orientation tracking), processing/control (an STM32 MCU running sensor fusion and threshold logic across both IMUs), and feedback/power (vibration motor, LED, button interface, and battery management). An extra goal could be adding a wireless subsystem (BLE) to log posture data over time to a companion phone app. # Solution Components ## Sensing Subsystem Captures raw motion data from two locations - head and torso - which the processing subsystem fuses into a relative head-to-torso angle estimate. This relative angle is what actually indicates neck strain and slouching, rather than either sensor's absolute orientation alone. - IMU x2: ICM-42670-P (TDK InvenSense, 6-axis accel + gyro, I2C, AD0 pin used to assign distinct addresses for both sensors on one bus) - Small sensor sub-board for the glasses-mounted IMU, connected to the main board via thin wire ## Processing & Control Subsystem Runs sensor fusion on both IMUs' data, computes the relative angle between head and torso orientation, compares that relative angle against the calibrated baseline, tracks how long the wearer has been out of range, and triggers alerts when the threshold is exceeded. Also manages the calibration/mute button input. - MCU: STM32L452RE (STM32L4 series, low-power Cortex-M4) - Tactile push button for calibration/mute ## Feedback Subsystem Alerts the wearer when sustained bad posture or neck strain is detected, with both a discreet (vibration) and noticeable (LED) option. - Vibration motor: Precision Microdrives 306-100 - Status LED (0603 SMD), driven via MOSFET (DMG2305UX) ## Power Subsystem Powers the device for a full day of use in a compact, lightweight form factor and handles battery charging. - Battery: 3.7V LiPo, ~150mAh - Charge IC: MCP73831 (single-cell LiPo linear charger) - Regulator to provide a clean 3.3V rail to MCU and both IMUs ## Wireless Subsystem (Extra Goal) Allows posture and neck strain data to be logged over time and viewed as trends on a companion app, rather than only reacting to current posture. - BLE module: STM32WB55CG or nRF52832 as a discrete BLE co-processor # Criterion For Success - The device detects a sustained relative head-to-torso angle change of at least 15° from the calibrated baseline, held for 10 seconds, and triggers an alert within 1 second, which should be verified with >90% detection rate over 20 trials, including trials with independent head or torso movement alone (e.g., glancing down while seated upright, or shifting torso without tilting the head) that should not trigger a false alert. - The calibration button correctly resets the baseline relative angle, verified by no false alerts for at least 5 minutes after calibration while the wearer stays upright and still. - The device runs continuously on a single charge for at least 8 hours of active monitoring, verified via bench testing. - The fully assembled device (both IMU boards, main PCB, battery, vibration motor, enclosures) weighs no more than 25g total, verified by direct measurement, so that its weight does not shift sensor position or affect calibration during normal wear. - The main PCB fits within a 4cm x 3cm x 1.5cm enclosure, and the glasses-mounted sensor sub-board fits within a 1.5cm x 1cm x 0.5cm enclosure, both measured on the assembled boards. - The alert is reliably noticed by the wearer, verified by at least 8/10 test users noticing it within 3 seconds of triggering. - (Extra Goal) BLE logging has less than 5% data loss over a 30-minute continuous session. |
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