A wireless optical gate and imu system for agility assessment : architecture, synchronization and validation
Brezžični sistem za ocenjevanje agilnosti na osnovi optičnih vrat in kinematičnih senzorjev : arhitektura, sinhronizacija in validacija

english

2025

volume 55, issue 4

agility testing   embedded systems   infrared gates   wearable sensor device   wireless synchronization

Strokovno društvo za mikroelektroniko, elektronske sestavne dele in materiale
(Obvezni izvod spletne publikacije)

Accurate, field-ready timing and motion capture are essential for assessing agility beyond the limits of manual stopwatches. We present a modular measurement system that fuses infrared (IR) optical gates for robust event detection with a trunkworn inertial measurement unit (IMU) for kinematic profiling. Each sensing node is built on an Adafruit Feather M0 Wi-Fi microcontroller and communicates via UDP to a laptop server. Time alignment is accomplished without internet connectivity: the server establishes a relative epoch and executes a triple-handshake broadcast protocol, while timestamps are generated at the edge to avoid latency bias from transport or processing. Module- and device-level characterization shows that IR-receiver processing combined with interrupt service routine latency yields a per-event timestamp error of 0.54 ms ± 0.14 ms (latency ± uncertainty), and local clocks remain stable over the durations relevant to agility trials. In wireless operation, accepted synchronization attempts form tight response clusters in favorable RF conditions, whereas congested environments may require retries; for section times across different gates we therefore report a conservative inter-node uncertainty. End-to-end validation across laboratory, entryhall, and gym venues using the Agility T-test confirms that total test time measured on the same start/finish gate remains below 1 ms error over 10–20 s trials. Synchronized IMU waveforms add explanatory value beyond total and split times by revealing braking, change-of-direction, and re-acceleration phases. The system provides a deployable workflow with substantially improved precision over manual timing. Future work will target more robust synchronization and expanded analytics, including automated phase detection, asymmetry indices, and optional integration with indoor positioning.

06.07.2026