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mCLARI: a shape-morphing insect-scale robot capable of omnidirectional terrain-adaptive locomotion in laterally confined spaces

Heiko Kabutz, Alexander Hedrick, Parker McDonnell, Kaushik Jayaram

TL;DR

mCLARI addresses the challenge of rapid, shape-adaptive locomotion in lateral confinements at insect scale by leveraging an exoskeleton-inspired passive body compliant design. It combines four piezoelectric, two-DoF leg modules in a closed kinematic chain to enable passive shape morphing during locomotion, achieving omnidirectional movement in confined spaces. The work reports a 60% size and 38% mass reduction from CLARI while maintaining about 80% of the actuation power, and demonstrates a top unconstrained speed of 60 mm/s with the novel ability to traverse narrow gaps and 90° corners. This approach promises significant impact for search-and-rescue and exploration tasks, and lays groundwork for onboard sensing, autonomous decisions, and active shape control in future iterations.

Abstract

Soft compliant microrobots have the potential to deliver significant societal impact when deployed in applications such as search and rescue. In this research we present mCLARI, a body compliant quadrupedal microrobot of 20mm neutral body length and 0.97g, improving on its larger predecessor, CLARI. This robot has four independently actuated leg modules with 2 degrees of freedom, each driven by piezoelectric actuators. The legs are interconnected in a closed kinematic chain via passive body joints, enabling passive body compliance for shape adaptation to external constraints. Despite scaling its larger predecessor down to 60 percent in length and 38 percent in mass, mCLARI maintains 80 percent of the actuation power to achieve high agility. Additionally, we demonstrate the new capability of passively shape-morphing mCLARI - omnidirectional laterally confined locomotion - and experimentally quantify its running performance achieving a new unconstrained top speed of 3 bodylengths/s (60 mms-1). Leveraging passive body compliance, mCLARI can navigate through narrow spaces with a body compression ratio of up to 1.5x the neutral body shape.

mCLARI: a shape-morphing insect-scale robot capable of omnidirectional terrain-adaptive locomotion in laterally confined spaces

TL;DR

mCLARI addresses the challenge of rapid, shape-adaptive locomotion in lateral confinements at insect scale by leveraging an exoskeleton-inspired passive body compliant design. It combines four piezoelectric, two-DoF leg modules in a closed kinematic chain to enable passive shape morphing during locomotion, achieving omnidirectional movement in confined spaces. The work reports a 60% size and 38% mass reduction from CLARI while maintaining about 80% of the actuation power, and demonstrates a top unconstrained speed of 60 mm/s with the novel ability to traverse narrow gaps and 90° corners. This approach promises significant impact for search-and-rescue and exploration tasks, and lays groundwork for onboard sensing, autonomous decisions, and active shape control in future iterations.

Abstract

Soft compliant microrobots have the potential to deliver significant societal impact when deployed in applications such as search and rescue. In this research we present mCLARI, a body compliant quadrupedal microrobot of 20mm neutral body length and 0.97g, improving on its larger predecessor, CLARI. This robot has four independently actuated leg modules with 2 degrees of freedom, each driven by piezoelectric actuators. The legs are interconnected in a closed kinematic chain via passive body joints, enabling passive body compliance for shape adaptation to external constraints. Despite scaling its larger predecessor down to 60 percent in length and 38 percent in mass, mCLARI maintains 80 percent of the actuation power to achieve high agility. Additionally, we demonstrate the new capability of passively shape-morphing mCLARI - omnidirectional laterally confined locomotion - and experimentally quantify its running performance achieving a new unconstrained top speed of 3 bodylengths/s (60 mms-1). Leveraging passive body compliance, mCLARI can navigate through narrow spaces with a body compression ratio of up to 1.5x the neutral body shape.
Paper Structure (15 sections, 8 figures, 1 table)

This paper contains 15 sections, 8 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. Morphological Intelligence embodied in exoskeleton compliance
  3. mCLARI: Design, Fabrication and Characterization
  4. Platform Overview
  5. Scaling Down Flexures, Actuators & Transmissions
  6. Actuation Characterization
  7. Transmission Characterization
  8. Modular leg mechanics
  9. Robot Performance
  10. Experimental setup
  11. Unconstrained Locomotion
  12. Omni-directionality
  13. Confined terrain navigation
  14. Complex Cluttered Terrain Locomotion
  15. Conclusion and Future Work

Figures (8)

  • Figure 1: mCLARI (left) alongside the previous larger version CLARI (right). mCLARI measures a neutral body length of 20 mm, and weighs 0.97 g.
  • Figure 2: mCLARI body compliance configurations under environmental constraints. Robot body shape aspect ratios and directions of motion under compression. Neutral body length 20m m, with a maximum length of 24m m and width 16m m body shape combination.
  • Figure 3: mCLARI system shown with a penny (19 mm diameter) for scale. Each of the leg modules is equipped with an individual pin header for wire connections.
  • Figure 4: Characterization of mCLARI bimorph piezoelectric actuators (a) Free tip deflection of piezoelectric actuators compared to theoretical math model. (b) Single sided block force of piezoelectric actuators compared to theoretical math model.
  • Figure 5: Mechanism of single leg module. (a) Actuator connecting to the leg tip across a spherical five-bar linkage. (b) Magnified view of the leverage distances for the input of actuation.
  • ...and 3 more figures