Sealab Search Robot

Spring 2011

Equip robot and program aquatic platform to:

  • use GPS to follow specified path and navigate to given coordinates

  • autonomously find beacons broadcasting range data

Mission Objective: Find three beacons located on Charles River in 20 minutes.

Practical Implications: Locate stranded persons, give location to search robot to follow.

Team Project for Class 'Design of Electromechanical Robotic Systems'

Team: Ned Burnell, Lauren Chai, Marie McGraw, Mukul Singh, Li Wu

Video (left): our project robot locating the beacon

  • Sensors - Marie McGraw

    Mechanical Design - Lauren Chai, Li Wu

    Acoustic Ranging Algorithm - Ned Burnell, Mukul Singh, Li Wu

    Exploration Behaviors - Ned Burnell, Lauren Chai, Li Wu

    MOOS Architecture - MOOS Architecture

    Team Organization - Ned Burnell, Marie McGraw

Kingfisher M100 Platform - Design strategy for mounting transducer and modem

My contribution: ideate design ideas, prototype, and test strategies

Kingfisher M100 platform came equipped to move and navigate via GPS. It had an onboard computer, batteries, thrusters GPS and compass. For this project, the platform needed an acoustic modem and transducers to ping the beacons After considering multiple options, the team settled on a WHOI Acoustic Modem from Professor Leonard’s Lab.

Design Considerations for mounting the modem and transducers

  • Operating Depth for transducer

  • Drag

  • Weight

  • Stability - Kingfisher was already stern heavy before additions

  • Center of Buoyancy

  • Entanglement Risk - keep sensor cable away from thrusters

Final strategy for attaching transducer and model. Transducer and weight keep cable straight. Weight and equalized cords attached with carabiners keep the cable away from thrusters. Foam blocks offset weight of transducer block.

Two ideas were considered: 1) mount the transducer on an aluminum rod, and 2) mount transducers on cable with weight and equalized cords to keep the cable straight and centered.

Idea #2 was selected because it was

  • easier to transport compared to a long rod

  • more straightforward to attach to the platform

  • lighter - the combined weight of the transducer and added weight was 14 lbs, made neutrally buoyant with the addition of foam blocks.

CAD model of Kingfisher (CAD model and assembly made by Lauren Chai)

Photo from Pool Tests of Kingfisher. During tests, Kingfisher pitched backwards, before sensor attachments. Foam added to transducer to make it neutrally buoyant and avoid pitch instability.