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WHERE-Bot: a Wheel-less Helical-ring Everting Robot Capable of Omnidirectional Locomotion

Siyuan Feng, Dengfeng Yan, Jin Liu, Haotong Han, Alexandra Kühl, Shuguang Li

TL;DR

This paper addresses the challenge of navigating unstructured environments with minimal sensing by introducing WHERE-Bot, a wheel-less wheel-less helical-ring everting mobile robot. The design uses a Slinky-based loop around a helical hub with a sliding ring and two actuated servos to produce three interacting motions: spiral-rotation (everting), orbiting, and self-rotation, enabling omnidirectional locomotion. A mass-distribution–driven model links the robot’s trajectory to the positions of two concentrated masses, predicting turning behavior and enabling reprogrammable paths without obstacle or boundary sensors. Through modeling and experiments, the authors demonstrate boundary exploration and autonomous-like interactions within square environments, highlighting the potential for soft-robot-inspired boundary exploration on unstructured terrains. Limitations include large coil-hub clearances and reliance on hard, low-friction surfaces, with future work aimed at improving transmission stiffness and material friction to broaden terrain applicability.

Abstract

Compared to conventional wheeled transportation systems designed for flat surfaces, soft robots exhibit exceptional adaptability to various terrains, enabling stable movement in complex environments. However, due to the risk of collision with obstacles and barriers, most soft robots rely on sensors for navigation in unstructured environments with uncertain boundaries. In this work, we present the WHERE-Bot, a wheel-less everting soft robot capable of omnidirectional locomotion. Our WHERE-Bot can navigate through unstructured environments by leveraging its structural and motion advantages rather than relying on sensors for boundary detection. By configuring a spring toy ``Slinky'' into a loop shape, the WHERE-Bot performs multiple rotational motions: spiral-rotating along the hub circumference, self-rotating around the hub's center, and orbiting around a certain point. The robot's trajectories can be reprogrammed by actively altering its mass distribution. The WHERE-Bot shows significant potential for boundary exploration in unstructured environments.

WHERE-Bot: a Wheel-less Helical-ring Everting Robot Capable of Omnidirectional Locomotion

TL;DR

This paper addresses the challenge of navigating unstructured environments with minimal sensing by introducing WHERE-Bot, a wheel-less wheel-less helical-ring everting mobile robot. The design uses a Slinky-based loop around a helical hub with a sliding ring and two actuated servos to produce three interacting motions: spiral-rotation (everting), orbiting, and self-rotation, enabling omnidirectional locomotion. A mass-distribution–driven model links the robot’s trajectory to the positions of two concentrated masses, predicting turning behavior and enabling reprogrammable paths without obstacle or boundary sensors. Through modeling and experiments, the authors demonstrate boundary exploration and autonomous-like interactions within square environments, highlighting the potential for soft-robot-inspired boundary exploration on unstructured terrains. Limitations include large coil-hub clearances and reliance on hard, low-friction surfaces, with future work aimed at improving transmission stiffness and material friction to broaden terrain applicability.

Abstract

Compared to conventional wheeled transportation systems designed for flat surfaces, soft robots exhibit exceptional adaptability to various terrains, enabling stable movement in complex environments. However, due to the risk of collision with obstacles and barriers, most soft robots rely on sensors for navigation in unstructured environments with uncertain boundaries. In this work, we present the WHERE-Bot, a wheel-less everting soft robot capable of omnidirectional locomotion. Our WHERE-Bot can navigate through unstructured environments by leveraging its structural and motion advantages rather than relying on sensors for boundary detection. By configuring a spring toy ``Slinky'' into a loop shape, the WHERE-Bot performs multiple rotational motions: spiral-rotating along the hub circumference, self-rotating around the hub's center, and orbiting around a certain point. The robot's trajectories can be reprogrammed by actively altering its mass distribution. The WHERE-Bot shows significant potential for boundary exploration in unstructured environments.

Paper Structure

This paper contains 15 sections, 7 equations, 10 figures.

Table of Contents

  1. INTRODUCTION
  2. Design and Fabrication
  3. Principle of Motions
  4. Structure of the Robot
  5. Fabrication Method and Material Choice
  6. Multiple rotational motions
  7. Spiral-rotation (Everting Motion)
  8. Orbiting
  9. Self-rotation
  10. Modeling
  11. Locomotion Experiments
  12. Motions Pre-defined by the Initial Mass Distribution
  13. Trajectory Control
  14. Environment Interaction
  15. Conclusion

Figures (10)

  • Figure 1: The WHERE-Bot's motion consists of a spiral-rotating (everting) along the hub circumference, a self-rotating around the hub's center, and an orbiting around a certain point.
  • Figure 2: Structure of the WHERE-Bot. (A) Assembled WHERE-Bot. (B) Components of the robot.
  • Figure 3: Fabrication of a WHERE-Bot. The spring is a "Slinky" toy, and other components, excluding servos and circuits, are 3D-printed.
  • Figure 4: Principle of the spiral-rotation. The axis of the driving coil and some of its adjacent coils transform from a loop into a line, shown in a side view.
  • Figure 5: Demonstration of multiple rotation motions of the WHERE-Bot. (A) Spiral-rotation (everting motion). (B) Orbiting. (C) Self-rotation. (D) Steering module rotation.
  • ...and 5 more figures