Date: Friday, April 24th, 2026  

Time: 2:00 PM – 4:00 PM ET  

Location: Remote (Zoom)  

Virtual Link: https://gatech.zoom.us/j/95008488072  

Bangyuan Liu  

Robotics Ph.D. Candidate  

School of Mechanical Engineering  

Georgia Institute of Technology  

Committee:  

Dr. Frank L. Hammond III (Advisor) – School of Mechanical Engineering, Georgia Institute of Technology  

Dr. Daniel I. Goldman – School of Physics, Georgia Institute of Technology  

Dr. Alper Erturk – School of Mechanical Engineering, Georgia Institute of Technology  

Dr. Layne R. Churchill – Georgia Tech Research Institute  

Dr. Howie Choset – Robotics Institute, Carnegie Mellon University  

Abstract:  

Maneuverability and adaptability are essential capabilities for underwater robots operating in cluttered and constrained environments, where conventional rigid-body vehicles often struggle. This dissertation investigates a family of soft, modular, non-biomorphic swimming robots that leverage mechanical compliance and underactuated design to achieve robust locomotion and interaction with complex environments without reliance on complex sensing or feedback control. We present a series of robotic systems and experiments that progressively explore the relationship between body morphology, actuation, and body–environment interaction. First, we demonstrate how a minimal actuation architecture enables diverse locomotion behaviors, including a novel roll rotation maneuver that provides full three-dimensional maneuverability. Next, we show that intrinsic morphological features, such as compliant, vertebra-like body structures and passive foldable fins, allow the robot to traverse narrow gaps and complex obstacles through passive mechanical adaptation. Building on these insights, we investigate how body scaling and structural parameters influence locomotion performance, revealing the existence of an effective body compliance regime that balances deformation and force transmission for efficient propulsion. Finally, we introduce an actively controllable fin system that extends morphological adaptability through fluidic actuation, enabling dynamic stiffness modulation and improved environmental interaction. Together, this work establishes a design framework for underwater robots that integrates maneuverability, compliance, and adaptability, offering a pathway toward robust operation in complex real-world aquatic environments.