Semester of Graduation

Summer 2025

Degree

Master of Science in Mechanical Engineering (MSME)

Department

The Department of Mechanical and Industrial Engineering

Document Type

Thesis

Abstract

The need for robotic systems capable of operating in confined, hazardous, or complex environments has driven interest in soft and legged platforms for industrial inspection and structural integrity assessment. This thesis presents the design and fabrication of a tentacle-like, soft-legged hexapod robot, which uses six cable-stiffened, pre-curved, tendon-driven continuum robot (TDCR) legs. These biologically inspired legs are designed to offer a balance between compliance and control, enabling the robot to navigate unstructured terrains and potentially grasp cylindrical structures such as pipes. The design phase involved the development and comparison of multiple leg geometries using CAD modeling and finite element analysis (FEA) to optimize mechanical performance. The final leg design was fabricated using a combination of thermoplastic polyurethane (TPU) for flexibility and polylactic acid (PLA) for structural rigidity. Additional mechanical innovations, including tip-mounted tendon tensioners inspired by guitar tuners, were implemented to control leg stiffness. While the hexapod system was under development, a stiffness characterization study was conducted on a separate 2D tendon-driven robot. A UR5 robotic arm with a custom voltage-based force sensor applied precise displacements while a 3D camera system tracked deformation. Tests were performed under different cable configurations, including actuation-only and various stiffnesses of cosine cable patterns. The results — force-displacement curves, stiffness slopes, and hysteresis loop areas — provided valuable insights into how tendon routing and cable pretension influence stiffness behavior. These experimental methods and findings serve as a reference framework for future stiffness evaluation on the hexapod robot. This work demonstrates a novel approach to integrating stiffness modulation into soft-legged robots and sets the stage for developing fully untethered, terrain-adaptive inspection systems. The hexapod’s modular design, mechanical flexibility, and the foundation laid by earlier stiffness studies contribute to the broader field of soft robotics, especially in applications requiring compliant locomotion and safe interaction with sensitive or irregular environments.

Date

7-14-2025

Committee Chair

Gilbert, Hunter.

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Available for download on Tuesday, July 14, 2026

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