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Embodied Design for Enhanced Flipper-Based Locomotion in Complex Terrains

Nnamdi Chikere, John McElroy, Yasemin Ozkan-Aydin

TL;DR

This work addresses robust, multi-terrain locomotion for bio-inspired flipper-based robots by designing a sea turtle hatchling-inspired quadroped with interchangeable flippers and gait patterns. It combines gait variation, flipper stiffness (soft vs rigid), trajectory correction using an IMU, and terrain-recognition-driven gait adaptation to evaluate performance across sand, rocky, and foam terrains. Key findings show that adaptive gait switching and full engagement of soft flippers generally enhance multi-terrain mobility, with terrain-specific tradeoffs guiding morphology- and gait-choices. The results demonstrate embodied intelligence in soft-robotic design, offering practical implications for environmental monitoring, search-and-rescue, and exploration tasks in complex, real-world environments.

Abstract

Robots are becoming increasingly essential for traversing complex environments such as disaster areas, extraterrestrial terrains, and marine environments. Yet, their potential is often limited by mobility and adaptability constraints. In nature, various animals have evolved finely tuned designs and anatomical features that enable efficient locomotion in diverse environments. Sea turtles, for instance, possess specialized flippers that facilitate both long-distance underwater travel and adept maneuvers across a range of coastal terrains. Building on the principles of embodied intelligence and drawing inspiration from sea turtle hatchings, this paper examines the critical interplay between a robot's physical form and its environmental interactions, focusing on how morphological traits and locomotive behaviors affect terrestrial navigation. We present a bio-inspired robotic system and study the impacts of flipper/body morphology and gait patterns on its terrestrial mobility across diverse terrains ranging from sand to rocks. Evaluating key performance metrics such as speed and cost of transport, our experimental results highlight adaptive designs as crucial for multi-terrain robotic mobility to achieve not only speed and efficiency but also the versatility needed to tackle the varied and complex terrains encountered in real-world applications.

Embodied Design for Enhanced Flipper-Based Locomotion in Complex Terrains

TL;DR

This work addresses robust, multi-terrain locomotion for bio-inspired flipper-based robots by designing a sea turtle hatchling-inspired quadroped with interchangeable flippers and gait patterns. It combines gait variation, flipper stiffness (soft vs rigid), trajectory correction using an IMU, and terrain-recognition-driven gait adaptation to evaluate performance across sand, rocky, and foam terrains. Key findings show that adaptive gait switching and full engagement of soft flippers generally enhance multi-terrain mobility, with terrain-specific tradeoffs guiding morphology- and gait-choices. The results demonstrate embodied intelligence in soft-robotic design, offering practical implications for environmental monitoring, search-and-rescue, and exploration tasks in complex, real-world environments.

Abstract

Robots are becoming increasingly essential for traversing complex environments such as disaster areas, extraterrestrial terrains, and marine environments. Yet, their potential is often limited by mobility and adaptability constraints. In nature, various animals have evolved finely tuned designs and anatomical features that enable efficient locomotion in diverse environments. Sea turtles, for instance, possess specialized flippers that facilitate both long-distance underwater travel and adept maneuvers across a range of coastal terrains. Building on the principles of embodied intelligence and drawing inspiration from sea turtle hatchings, this paper examines the critical interplay between a robot's physical form and its environmental interactions, focusing on how morphological traits and locomotive behaviors affect terrestrial navigation. We present a bio-inspired robotic system and study the impacts of flipper/body morphology and gait patterns on its terrestrial mobility across diverse terrains ranging from sand to rocks. Evaluating key performance metrics such as speed and cost of transport, our experimental results highlight adaptive designs as crucial for multi-terrain robotic mobility to achieve not only speed and efficiency but also the versatility needed to tackle the varied and complex terrains encountered in real-world applications.
Paper Structure (3 sections, 3 equations, 7 figures, 2 algorithms)

This paper contains 3 sections, 3 equations, 7 figures, 2 algorithms.

Table of Contents

  1. Flat Foam Surface Turning:
  2. Rocky Terrain Turning:
  3. Dry Sand Turning:

Figures (7)

  • Figure 1: Biological and robotic sea turtle hatchlings navigating diverse terrains: Sea turtle hatchling (left) and its robotic counterpart (right) are shown traversing dry sand, small and big rocks, wet sand, and vegetation, illustrating the bio-inspired robot's design effectiveness and its capability to adapt to complex environmental conditions.
  • Figure 2: Conceptual framework of the robotic sea turtle: The integrated approach combining biological inspiration with advanced robotics. The leftmost block details the biological aspects that influence the design. The center block describes the robot's embodied intelligence features, including sensor feedback, servo control, and power management. The rightmost block showcases the diverse applications of the robotic sea turtle.
  • Figure 3: Anatomical illustration of the robotic sea turtle: (A) Isometric CAD view, highlighting the rotation axes of the servos for flipper actuation. (B) Front view, showing the lift height of the robot above the ground. (C) Top view, showing the robot's symmetry and flipper arrangement. (D) Electronic components
  • Figure 4: Illustration of gait patterns: (A) Forward Gaits displaying 'All-together' (top row) and 'Diagonal' (bottom row) patterns with corresponding gait cycle diagrams. (B) Turning Gaits exhibiting 'All Flippers Together' (top row) and 'Only Front Flippers' (bottom row) patterns alongside their respective gait cycle diagrams. Each diagram visualizes the flipper contact with the ground (gray) and aerial phase (yellow) throughout the gait cycle. The green arrows indicate the directional movement of the flippers, emphasizing the active propulsion phases of forward and rotational movement.
  • Figure 5: Gait efficiency across varied terrains: The robot's performance with different flipper types (soft all flippers, soft front flippers, rigid all flippers, and rigid front flippers) and gait patterns (diagonal and all-together) across four terrain types: dry sand, rocks and pebbles, wet sand, and flat foam. The best and worst gaits for each flipper and terrain combination are highlighted with green and orange borders, respectively. The trajectory tracking of the robot's Center of Mass (CoM) during locomotion is shown in the blue, orange, and white lines
  • ...and 2 more figures