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A Decapod Robot with Rotary Bellows-Enclosed Soft Transmissions

Yiming He, Yuchen Wang, Yunjia Zhang, Shuguang Li

TL;DR

The paper addresses the challenge of controlling soft, untethered robots with minimal hardware by introducing a valveless rotary bellows-driven transmission (R-BESTS) that converts a single servo input into coordinated leg swings. Through a closed pneumatic system and a timing belt to enforce opposite phases, the design achieves alternating tripod gaits for walking and turning, while a PET-based reinforcement skeleton and geometry control the actuation sequencing. The work presents fabrication methods, a geometric model of actuation, and experimental validation demonstrating 1.75 cm/s walking speed, 15 cm turning radius, and 90 minutes of untethered operation with a 200 g payload on varied terrains. The approach reduces valves, tubing, leakage, noise, and energy waste, enabling more compact and reliable soft robots with potential applicability to other morphologies and tasks.

Abstract

Soft crawling robots exhibit efficient locomotion across various terrains and demonstrate robustness to diverse environmental conditions. Here, we propose a valveless soft-legged robot that integrates a pair of rotary bellows-enclosed soft transmission systems (R-BESTS). The proposed R-BESTS can directly transmit the servo rotation into leg swing motion. A timing belt controls the pair of R-BESTS to maintain synchronous rotation in opposite phases, realizing alternating tripod gaits of walking and turning. We explored several designs to understand the role of a reinforcement skeleton in twisting the R-BESTS' input bellows units. The bending sequences of the robot legs are controlled through structural design for the output bellows units. Finally, we demonstrate untethered locomotion with the soft robotic decapod. Experimental results show that our robot can walk at 1.75 centimeters per second (0.07 body length per second) for 90 min, turn with a 15-centimeter (0.6 BL) radius, carry a payload of 200 g, and adapt to different terrains.

A Decapod Robot with Rotary Bellows-Enclosed Soft Transmissions

TL;DR

The paper addresses the challenge of controlling soft, untethered robots with minimal hardware by introducing a valveless rotary bellows-driven transmission (R-BESTS) that converts a single servo input into coordinated leg swings. Through a closed pneumatic system and a timing belt to enforce opposite phases, the design achieves alternating tripod gaits for walking and turning, while a PET-based reinforcement skeleton and geometry control the actuation sequencing. The work presents fabrication methods, a geometric model of actuation, and experimental validation demonstrating 1.75 cm/s walking speed, 15 cm turning radius, and 90 minutes of untethered operation with a 200 g payload on varied terrains. The approach reduces valves, tubing, leakage, noise, and energy waste, enabling more compact and reliable soft robots with potential applicability to other morphologies and tasks.

Abstract

Soft crawling robots exhibit efficient locomotion across various terrains and demonstrate robustness to diverse environmental conditions. Here, we propose a valveless soft-legged robot that integrates a pair of rotary bellows-enclosed soft transmission systems (R-BESTS). The proposed R-BESTS can directly transmit the servo rotation into leg swing motion. A timing belt controls the pair of R-BESTS to maintain synchronous rotation in opposite phases, realizing alternating tripod gaits of walking and turning. We explored several designs to understand the role of a reinforcement skeleton in twisting the R-BESTS' input bellows units. The bending sequences of the robot legs are controlled through structural design for the output bellows units. Finally, we demonstrate untethered locomotion with the soft robotic decapod. Experimental results show that our robot can walk at 1.75 centimeters per second (0.07 body length per second) for 90 min, turn with a 15-centimeter (0.6 BL) radius, carry a payload of 200 g, and adapt to different terrains.

Paper Structure

This paper contains 17 sections, 4 equations, 11 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. DESIGN AND FABRICATION
  3. Working principle of the R-BESTS
  4. Fabrication of the R-BESTS
  5. Hardware implementation
  6. CHARACTERIZATIONS OF THE ROBOT
  7. Control of the actuation sequencing
  8. Twisting of the input bellows unit
  9. Locomotion strategy and control
  10. EXPERIMENTS AND RESULTS
  11. Basic Motion Performance
  12. Walking
  13. Turning
  14. Demonstration of locomotion skills
  15. Path following
  16. ...and 2 more sections

Figures (11)

  • Figure 1: The untethered soft decapod robot with the R-BESTS.
  • Figure 2: The working principle of a transmission system consisting of piston (a), two connected balloons (b), and the R-BESTS (c).
  • Figure 3: Overview of the fabrication process of the R-BESTS. (a) Three-dimensional schematic diagram. (b) After heat-pressing, the R-BESTS forms a flat laminated structure. Upon inflation, the pair of input bellows units expand.
  • Figure 4: Exploded view of the robot.
  • Figure 5: The electronics and pneumatics of the soft crawling robot. (a) Embedded electronic components in the robot. (b) Pneumatic channels for alternating tripod gait.
  • ...and 6 more figures