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A Sequential Hermaphrodite Coupling Mechanism for Lattice-based Modular Robots

Keigo Torii, Kentaro Uno, Shreya Santra, Kazuya Yoshida

TL;DR

This paper addresses the coupling challenge in lattice-based modular robots for space construction by introducing a shape-matching Sequential Hermaphrodite mechanism that can switch between male and female states, enabling single-sided coupling/decoupling while preserving a flat surface when uncoupled and compatibility with passive interfaces. A 90-degree symmetric cubic-lattice module is designed with 3D-printed PLA parts, a bearing, PCB, and a Dynamixel servo to realize four states (Female Lock/Unlock, Male Unlock/Lock) and a coupling plane on the Female Lock side, including electrical contacts via spring-loaded pins. The mechanism is validated through single-sided coupling/decoupling tests, misalignment tolerance assessments, load-capacity measurements, and fail-safe experiments, demonstrating fast state transitions, robustness to misalignment, and safe operation under partial power. The results expand the design space for heterogeneous modular robots and lay groundwork for assembling such systems with assemblers in extreme environments, with future work focusing on full system integration. This work thus offers a practical pathway toward scalable, reliable space construction using lattice-based modular robots.

Abstract

Lattice-based modular robot systems are envisioned for large-scale construction in extreme environments, such as space. Coupling mechanisms for heterogeneous structural modules should meet all of the following requirements: single-sided coupling and decoupling, flat surfaces when uncoupled, and coupling to passive coupling interfaces as well as coupling behavior between coupling mechanisms. The design requirements for such a coupling mechanism are complex. We propose a novel shape-matching mechanical coupling mechanism that satisfies these design requirements. This mechanism enables controlled, sequential transitions between male and female states. When uncoupled, all mechanisms are in the female state. To enable single-sided coupling, one side of the mechanisms switches to the male state during the coupling process. Single-sided decoupling is possible not only from the male side but also from the female side by forcibly switching the opposite mechanism's male state to the female state. This coupling mechanism can be applied to various modular robot systems and robot arm tool changers.

A Sequential Hermaphrodite Coupling Mechanism for Lattice-based Modular Robots

TL;DR

This paper addresses the coupling challenge in lattice-based modular robots for space construction by introducing a shape-matching Sequential Hermaphrodite mechanism that can switch between male and female states, enabling single-sided coupling/decoupling while preserving a flat surface when uncoupled and compatibility with passive interfaces. A 90-degree symmetric cubic-lattice module is designed with 3D-printed PLA parts, a bearing, PCB, and a Dynamixel servo to realize four states (Female Lock/Unlock, Male Unlock/Lock) and a coupling plane on the Female Lock side, including electrical contacts via spring-loaded pins. The mechanism is validated through single-sided coupling/decoupling tests, misalignment tolerance assessments, load-capacity measurements, and fail-safe experiments, demonstrating fast state transitions, robustness to misalignment, and safe operation under partial power. The results expand the design space for heterogeneous modular robots and lay groundwork for assembling such systems with assemblers in extreme environments, with future work focusing on full system integration. This work thus offers a practical pathway toward scalable, reliable space construction using lattice-based modular robots.

Abstract

Lattice-based modular robot systems are envisioned for large-scale construction in extreme environments, such as space. Coupling mechanisms for heterogeneous structural modules should meet all of the following requirements: single-sided coupling and decoupling, flat surfaces when uncoupled, and coupling to passive coupling interfaces as well as coupling behavior between coupling mechanisms. The design requirements for such a coupling mechanism are complex. We propose a novel shape-matching mechanical coupling mechanism that satisfies these design requirements. This mechanism enables controlled, sequential transitions between male and female states. When uncoupled, all mechanisms are in the female state. To enable single-sided coupling, one side of the mechanisms switches to the male state during the coupling process. Single-sided decoupling is possible not only from the male side but also from the female side by forcibly switching the opposite mechanism's male state to the female state. This coupling mechanism can be applied to various modular robot systems and robot arm tool changers.
Paper Structure (13 sections, 10 figures, 2 tables)

This paper contains 13 sections, 10 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. Gendered
  4. Simultaneous Hermaphrodite
  5. Genderless
  6. Sequential Hermaphrodites
  7. Methodology
  8. Experiments and Discussions
  9. Single-Sided Coupling/Decoupling Tests
  10. Misalignment Tolerance Tests
  11. Load Capability Tests
  12. Fail-Safe System Tests
  13. Conclusions

Figures (10)

  • Figure 1: Heterogeneous structural modules with the proposed coupling mechanism.
  • Figure 2: Exploded view of the proposed coupling mechanism.
  • Figure 3: State transitions of the proposed coupling mechanism in its (a) Female Lock, (b) Female Unlock, (c) Male Unlock, and (d) Male Lock states.
  • Figure 4: State transitions of the proposed coupling mechanism during (1) Single-sided coupling motion, (2) Single-sided decoupling motion from the male side, and (3) Single-sided decoupling motion from the female side.
  • Figure 5: Single-sided coupling motion.
  • ...and 5 more figures