One Way Travel Time Inverted Ultra-Short Baseline Localization for Low-Cost AUV's

Nicholas R. Rypkema, Erin M. Fischell and Henrik Schmidt, MIT, ICRA 2017


I. Introduction:


A) System Hardware

  1. Beacon: Arduino UNO + wave shield connected to GPS unit. GPS Pulse-Per-Second unit triggers playback of 20ms 7-9khz upchirp signal. Played at every GPS second.
  1. AUV Reciever: GPS Unit, Data Aq. Module (DAQ), RPi 3, CSAC, the GPS PPS is used to synchronize the CSAC, which makes the DAQ record at 8000 samples/sec. Delay is estimated during calibration by keeping both together initially.

Note: Accurate timing is the most important component for this system. Without it, OWTT passive ranging is not possible. This allows for multiple vehicles to self localize at each time step making it highly scalable. Without a CSAC it is important for both receiver and beacon to communicate and continuously sync times.

B) Matched Filtering

A method for extracting known wavelets from a noisy signal. Cross correlating the template signal with the recorded signal allows to check for actual peak measurement and weed out outliers.

D) Particle Filter Localization

E) Factor Graph Smoothing

First pose has prior from GPS. Motion model factors connect each node. Beacon is connected via range or range and azimuth factors.

III. Experiments and Results

IV. Conclusions