E. Dobson, A. Pawlica, I. Ren, C. von Spakovsky advised by Prof. Bart-Smith and Prof. Zhu

Bio-Inspired Autonomous Underwater Vehicle Capstone Design Team | Mechanical Engineering | Spring 2018

Dept. of Mechanical & Aerospace Engineering

Background

Our team of four mechanical engineering students was tasked with designing and developing a bio-inspired underwater vehicle. The goal of biomimetic underwater vehicles is to emulate the adaptations of aquatic organisms to improve the performance of current AUV technology. Penguins are flightless birds that have become highly adapted to life in the water. Their torpedo-like bodies are neutrally buoyant and unlike most other birds, penguins produce substantial thrust in both phases of the wingbeat1.

The goal of the design was to reproduce the penguin’s swimming speed and maneuverability by emulating its body structure and wing propulsion mechanism. The design was segmented into three parts, a watertight head and two flooded body sections. These parts were 3-D printed and rubber is used to join the two body sections together to give it passive flexibility.

The Arduino Uno R3 and a Adafruit Motor Shield v2 were used to control two 12V Nema 17 stepper motors and two RC servo motors.

The main body section houses a gear mechanism used to replicate the figure-eight trace produced by penguin wings over their wingbeats. Using two 2-inch nylon gears and 3-D printed linkages affixed to specific positions, we were able to create a figure-eight trace at the intersection of the linkages.2 An aluminum shaft was attached at that point and extended through a hole in the body that acts as a shoulder joint. The external portion of the shaft is inserted into a 3-D printed airfoil-shaped wing.

During normal operation, the actuating gear mechanism is driven at a frequency of 2 Hz which corresponds to a predicted body speed of 0.75 m/s or 1.1 bodylengths/s.3 Wingbeat frequency is varied during other swimming motions such as burst and coast. The design has an estimated turning radius of 0.5 body lengths and an operating time of 1.5 hours.

Power and Control

Design

Actuation Thrust Generation over Wingbeat

CAD overview of design

Head A waterproof head compartment was used to house the microcontroller, batteries, and other electronics. A small window was created at the top to provide a viewpoint for a camera lens. Two 8-pin watertight wiring joints were attached to the backplate of the head compartment.

Feet Two independently operated feet will be affixed to the distal end of the body to control pitch and roll. The feet will be operated by two RC servo motors.

Performance Hui, C. A. (1988). Penguin Swimming. I. Hydrodynamics. Physiological Zoology, 61(4), 333–343. Retrieved from https://www.jstor.org/stable/30161251

Works Cited 1 Bannasch, R. (2008). Functional anatomy of the 'flight' apparatus in penguins. In Mechanics and physiology of animal swimming (pp. 163-192). Cambridge: Cambridge University Press 2 Vagneur, C. (1957). U.S. Patent No. 2,775,899. Washington, DC: U.S. Patent and Trademark Office. 3Hui, C. A. (1988). Penguin Swimming. I. Hydrodynamics. Physiological Zoology, 61(4), 333–343. Retrieved from https://www.jstor.org/stable/30161251

Massare, J. A. (2008). Swimming capabilities of Mesozoic marine reptiles: a review. In Mechanics and physiology of animal swimming (pp. 133-149). Cambridge: Cambridge University Press.

Head Compartment

Wing

Figure-Eight Mechanism

Feet

Body Sections

Rubber