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Rhombot: Rhombus-shaped Modular Robots for Stable, Medium-Independent Reconfiguration Motion

Jie Gu, Yirui Sun, Zhihao Xia, Tin Lun Lam, Chunxu Tian, Dan Zhang

TL;DR

Rhombot introduces a rhombus-shaped deformable lattice MSRR with a central DoF actuator to enable folding along the diagonal. The method hinges on morphpivoting, a four-step primitive—morphing, connection, disconnection, and morphing—that reconfigures topology while preserving inter-module connectivity. The design blends lattice rigidity with chain-like manipulation by using a single deformation DoF and hermaphroditic connectors to achieve stable, medium-independent reconfiguration and reliable docking. The work demonstrates accurate kinematics, robust docking, and practical considerations such as cable tension and friction that influence motion near end ranges.

Abstract

In this paper, we present Rhombot, a novel deformable planar lattice modular self-reconfigurable robot (MSRR) with a rhombus shaped module. Each module consists of a parallelogram skeleton with a single centrally mounted actuator that enables folding and unfolding along its diagonal. The core design philosophy is to achieve essential MSRR functionalities such as morphing, docking, and locomotion with minimal control complexity. This enables a continuous and stable reconfiguration process that is independent of the surrounding medium, allowing the system to reliably form various configurations in diverse environments. To leverage the unique kinematics of Rhombot, we introduce morphpivoting, a novel motion primitive for reconfiguration that differs from advanced MSRR systems, and propose a strategy for its continuous execution. Finally, a series of physical experiments validate the module's stable reconfiguration ability, as well as its positional and docking accuracy.

Rhombot: Rhombus-shaped Modular Robots for Stable, Medium-Independent Reconfiguration Motion

TL;DR

Rhombot introduces a rhombus-shaped deformable lattice MSRR with a central DoF actuator to enable folding along the diagonal. The method hinges on morphpivoting, a four-step primitive—morphing, connection, disconnection, and morphing—that reconfigures topology while preserving inter-module connectivity. The design blends lattice rigidity with chain-like manipulation by using a single deformation DoF and hermaphroditic connectors to achieve stable, medium-independent reconfiguration and reliable docking. The work demonstrates accurate kinematics, robust docking, and practical considerations such as cable tension and friction that influence motion near end ranges.

Abstract

In this paper, we present Rhombot, a novel deformable planar lattice modular self-reconfigurable robot (MSRR) with a rhombus shaped module. Each module consists of a parallelogram skeleton with a single centrally mounted actuator that enables folding and unfolding along its diagonal. The core design philosophy is to achieve essential MSRR functionalities such as morphing, docking, and locomotion with minimal control complexity. This enables a continuous and stable reconfiguration process that is independent of the surrounding medium, allowing the system to reliably form various configurations in diverse environments. To leverage the unique kinematics of Rhombot, we introduce morphpivoting, a novel motion primitive for reconfiguration that differs from advanced MSRR systems, and propose a strategy for its continuous execution. Finally, a series of physical experiments validate the module's stable reconfiguration ability, as well as its positional and docking accuracy.
Paper Structure (19 sections, 7 equations, 8 figures, 2 tables, 1 algorithm)

This paper contains 19 sections, 7 equations, 8 figures, 2 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Related Work
  3. MSRRs with Lattice Attributes
  4. Deformation MSRRs
  5. Comparison with previous MSRRs
  6. Mechanism Design and Electronics
  7. Skeleton and Actuation System
  8. Connector Design
  9. Electronics
  10. Modular Chassis
  11. Motion Analysis
  12. Kinematic Modeling
  13. Reconfiguration Strategy
  14. Experiments
  15. Reconfiguration
  16. ...and 4 more sections

Figures (8)

  • Figure 1: Prototype of Rhombot. (a) Single Module. (b) Lattice Assembly. (c) Chain Assembly.
  • Figure 2: Mechanism Design and Electronics of the Rhombot. (a) Exploded view of the Rhombot’s components. (b) Electronic architecture layout. (c) Actuation system diagram. (d) Pair of hermaphroditic connectors. (e) Modular chassis design. (f) Schematic of the multi-parallelogram linkage mechanism.
  • Figure 3: Two kinematics of Rhombot with configuration representations and reference coordinate frames indicated. (a) Serial connection of four modules. (b) Parallel connection of four modules.
  • Figure 4: Demonstration of a morphpivoting operation with three Rhombots.
  • Figure 5: Kinematic Accuracy of Rhombot's Chain Form.
  • ...and 3 more figures