Beagles

General Arrangement

Sub-Teams: Drivetrain, Propulsion, Electrical, Hall & Frame, Dead Man’s Buoy (DMB), Mech Steering, Computer Aided Vision (SubSee), Data Acquisition System (DAQ)

Drivetrain

Inner Shaft

• Driven by input shaft
• Propeller is mounted to end of shaft and rotates with it
• Shaft: ⌀12mm, Al 6061 T6

Outer Shaft

• Driven by input shaft
• Propeller is mounted to end of shaft and rotates with it
• Shaft: ⌀0.875” ID, ⌀0.635” OD, Al 6061 T6

Bevel Gear and Pinion

• Same 5:1 ratio used in previous designs
• Straight-tooth gears were selected
• Limited availability of helical gears in 5:1 ratio
• Insufficient torsional strength of plastic gears
• Material removed from center
• Weight savings
• Integration with spindle and pedals

Purpose: Convert pilot rotary input into dual contra-rotating propeller rotation

Direct Drive System - Latest Model

• A bearing block added to address forces from the gears
• Also addresses the cantilever problem
• New spindle housing to match the length of the spindle
• Important notes to consider after doing some tests

Bearing Block

• Approximate input torque of 30 Nm as reported from last year
• Block tested in combined loading
• Bearing load from radial force component
• Distributed load on shoulder face from axial component
• Minimum factor of safety of 12 when using nylon as material

Propulsion

Fin Prototype Designs

0012 Round

• Greatest lift coefficient
• Full size 30cm in length

0012 Round Cutoff

• Slightly reduced drag (less wingtip vortices)

0012 Round Scaled (⅔ scale)

• Smaller to fit normal 3d printers
• Part snapped in coupler with servo

Electrical

Vision + Data Acquisition: Heads Up Display, Image Processing, and Absolute Orientation Sensor

• New display screen integrated for horizontal orientation
• Fits a thinner, blue robotics enclosure for ease of mounting and known waterproof reliability
• Uses Raspberry Pi 4B for video processing algorithms
• Gathers underwater recordings

Electrical Steering: Motor Control for Mech Steering (Arduino Nano), Hall-effect Joystick, Autonomous and Manual Control Modes

• Joystick (Hardware)

• Joystick (3D Structures)

• Hall-effect PCB inside enclosure
• Joystick with magnet to be mounted to outside of enclosure

• Backup PCB Mount (friction fit)

• Steering PCB

• Similar to last year’s design
  • Power from BMS
  • Buck Converter to regulate 7.5V powering servo
  • Arduino Nano MCU controlling the servo motor and other ports
• What’s new
  • Adapt to the new servo motor (SER-2000)
  • Duration extension of stall current
  • PTC Resettable Fuse (through-hole) for overcurrent protection

Battery Management and Power Delivery: Motor Control for Mech Steering (Arduino Nano), Hall-effect Joystick, Autonomous and Manual Control Modes

• Battery Choice
  • 
  • Selected LiFePO4 (LFP) battery for additional safety consideration.
  • Picked highest capacity cells (15Ah) that would fit in last year’s BMS/Steering enclosure.
  • Purchased four cells with one spare for a 3S battery configuration.
  • Improvement in overall runtime from last year.
• Choice of BMS
  • 
  • Selected off-the-shelf BMS design to reduce complexity.
  • Opted for 9.6V 3S BMS, so we could use last year’s steering board for voltage regulation.
  • BMS board rated at 40A which is well above what the servos would need.
  • Takes up minimal space inside the enclosure allowing easier integration.

Enclosures/Harnessing: Water damage control, connecting everything together, ease of access

BMS/Steering enclosure

• Made out of MDF and 3D printed materials (non-conductive).
• Resistant to movement and secures the batteries.
• Able to be taken out in one piece for ease of maintenance.
• Enough space for thick wire gauges and minimum bend radius.

Elec Waterproof Enclosures Summary

• We used 4 waterproof enclosures for each system.
• One small enclosure for the camera
• One small enclosure for the joystick
• One medium enclosure for the display + raspberry pi
• One large enclosure for the batteries, BMS, steering board, and Arduino Nano
• Each enclosure is bought from Blue Robotics
• In the progress of testing and monitoring using vacuum pressure pump