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A Chain-Driven, Sandwich-Legged Quadruped Robot: Design and Experimental Analysis

Aman Singh, Bhavya Giri Goswami, Ketan Nehete, Shishir N. Y. Kolathaya

TL;DR

Legged robots enable traversal of unstructured terrain, motivating accessible research testbeds. This work presents a chain-driven, sandwich-legged quadruped as a mid-size platform designed to improve locomotion, reliability, and manufacturability, with a target weight of approximately 25 kg and a cost under $8000. The design introduces a quasi-direct-drive actuator, a dual-motor hip-knee arrangement, a sandwiched leg, and a sheet-metal torso built with laser cutting and 3D printing to achieve low cost and rapid fabrication, complemented by cable strain reliefs, thermal management, and safety limits for robust actuation. Hardware experiments demonstrate trot and crawl gaits on flat and inclined terrain, validating the platform as a practical, scalable research testbed with clear avenues for future improvements.

Abstract

This paper introduces a chain-driven, sandwich-legged, mid-size quadruped robot designed as an accessible research platform. The design prioritizes enhanced locomotion capabilities, improved reliability and safety of the actuation system, and simplified, cost-effective manufacturing processes. Locomotion performance is optimized through a sandwiched leg design and a dual-motor configuration, reducing leg inertia for agile movements. Reliability and safety are achieved by integrating robust cable strain reliefs, efficient heat sinks for motor thermal management, and mechanical limits to restrict leg motion. Simplified design considerations include a quasi-direct drive (QDD) actuator and the adoption of low-cost fabrication techniques, such as laser cutting and 3D printing, to minimize cost and ensure rapid prototyping. The robot weighs approximately 25 kg and is developed at a cost under \$8000, making it a scalable and affordable solution for robotics research. Experimental validations demonstrate the platform's capability to execute trot and crawl gaits on flat terrain and slopes, highlighting its potential as a versatile and reliable quadruped research platform.

A Chain-Driven, Sandwich-Legged Quadruped Robot: Design and Experimental Analysis

TL;DR

Legged robots enable traversal of unstructured terrain, motivating accessible research testbeds. This work presents a chain-driven, sandwich-legged quadruped as a mid-size platform designed to improve locomotion, reliability, and manufacturability, with a target weight of approximately 25 kg and a cost under $8000. The design introduces a quasi-direct-drive actuator, a dual-motor hip-knee arrangement, a sandwiched leg, and a sheet-metal torso built with laser cutting and 3D printing to achieve low cost and rapid fabrication, complemented by cable strain reliefs, thermal management, and safety limits for robust actuation. Hardware experiments demonstrate trot and crawl gaits on flat and inclined terrain, validating the platform as a practical, scalable research testbed with clear avenues for future improvements.

Abstract

This paper introduces a chain-driven, sandwich-legged, mid-size quadruped robot designed as an accessible research platform. The design prioritizes enhanced locomotion capabilities, improved reliability and safety of the actuation system, and simplified, cost-effective manufacturing processes. Locomotion performance is optimized through a sandwiched leg design and a dual-motor configuration, reducing leg inertia for agile movements. Reliability and safety are achieved by integrating robust cable strain reliefs, efficient heat sinks for motor thermal management, and mechanical limits to restrict leg motion. Simplified design considerations include a quasi-direct drive (QDD) actuator and the adoption of low-cost fabrication techniques, such as laser cutting and 3D printing, to minimize cost and ensure rapid prototyping. The robot weighs approximately 25 kg and is developed at a cost under \$8000, making it a scalable and affordable solution for robotics research. Experimental validations demonstrate the platform's capability to execute trot and crawl gaits on flat terrain and slopes, highlighting its potential as a versatile and reliable quadruped research platform.

Paper Structure

This paper contains 20 sections, 9 figures.

Table of Contents

  1. INTRODUCTION
  2. DESIGN
  3. Simplified Design
  4. QDD Actuator
  5. Design for efficient manufacturing
  6. Enhancement of Locomotion Capability
  7. Sandwiched Leg Design
  8. Dual Motor Design
  9. Reliability and safety of actuation system
  10. Cable Strain Relief
  11. Thermal Management
  12. Safety Limits
  13. ELECTRONICS AND CONTROL ARCHITECTURE
  14. RESULTS
  15. Design Principles Results
  16. ...and 5 more sections

Figures (9)

  • Figure 1: Chain-driven, Sandwich-legged quadruped robot shown standing on the ground.
  • Figure 2: Robot Dimensions: (a) Isometric view of the robot: The torso in made up of two sheet metal parts (yellow and green), with two plastic parts (white and inside the torso) joinging them (b) Top view, (c) Front View, (d) Side view
  • Figure 3: QDD Actuator: (a) Details of the actuator design; (b) Cross-section view of actuator; (c) Manufactured actuator
  • Figure 4: Torso Diagram: (a) Details of Torso design (b) Exploded view of Torso
  • Figure 5: (a) Joints and Actuator Axes; (b) Details of Leg Design; (c) Details of Thigh Link:①a, ①b: Al Sheets; ②a, ②b: Central spacers; ③a, ③b: Upper spacers; ④a, ④b: Thigh strength plates; ⑤a, ⑤b: Knee bearings; ⑥a, ⑥b: Knee bearing blocks; ⑦: Knee bolt; ⑧: Knee nut; ⑨: Sprocket support shaft; ①0: Support shaft fastener; (d) Details of Shank Link: ①1a, ①1b: Shank Al-sheets; ①2a, ①2b: Shank strength plates; ①3a, ①3b: Knee sprocket couplings; ①4: Knee driven sprocket; ①5: Shank spacer; ①6: Foot.
  • ...and 4 more figures