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DIABLO: A 6-DoF Wheeled Bipedal Robot Composed Entirely of Direct-Drive Joints

Dingchuan Liu, Fangfang Yang, Xuanhong Liao, Ximin Lyu

TL;DR

The paper tackles balancing and locomotion for a direct-drive wheeled bipedal robot by introducing DIABLO, a 6-DoF platform that forgoes gearboxes. It derives a 2D inverted-pendulum model and designs an LQR balance controller plus a comprehensive motion controller to handle height, roll, yaw, and split-angle dynamics, validating the approach via simulations and a real prototype. Key contributions include the hardware-software integration of direct-drive joints, the 2D model-based control framework, and demonstrated stability and mobility on flat, inclined, and spacewalk-like terrains. The work highlights the practical impact of high-bandwidth, low-friction direct-drive actuation for efficient, robust wheel-legged robots and outlines future directions toward whole-body control and expanded locomotion tasks.

Abstract

Wheeled bipedal robots offer the advantages of both wheeled and legged robots, combining the ability to traverse a wide range of terrains and environments with high efficiency. However, the conventional approach in existing wheeled bipedal robots involves motor-driven joints with high-ratio gearboxes. While this approach provides specific benefits, it also presents several challenges, including increased mechanical complexity, efficiency losses, noise, vibrations, and higher maintenance and lubrication requirements. Addressing the aforementioned concerns, we developed a direct-drive wheeled bipedal robot called DIABLO, which eliminates the use of gearboxes entirely. Our robotic system is simplified as a second-order inverted pendulum, and we have designed an LQR-based balance controller to ensure stability. Additionally, we implemented comprehensive motion controller, including yaw, split-angle, height, and roll controllers. Through expriments in simulations and real-world prototype, we have demonstrated that our platform achieves satisfactory performance.

DIABLO: A 6-DoF Wheeled Bipedal Robot Composed Entirely of Direct-Drive Joints

TL;DR

The paper tackles balancing and locomotion for a direct-drive wheeled bipedal robot by introducing DIABLO, a 6-DoF platform that forgoes gearboxes. It derives a 2D inverted-pendulum model and designs an LQR balance controller plus a comprehensive motion controller to handle height, roll, yaw, and split-angle dynamics, validating the approach via simulations and a real prototype. Key contributions include the hardware-software integration of direct-drive joints, the 2D model-based control framework, and demonstrated stability and mobility on flat, inclined, and spacewalk-like terrains. The work highlights the practical impact of high-bandwidth, low-friction direct-drive actuation for efficient, robust wheel-legged robots and outlines future directions toward whole-body control and expanded locomotion tasks.

Abstract

Wheeled bipedal robots offer the advantages of both wheeled and legged robots, combining the ability to traverse a wide range of terrains and environments with high efficiency. However, the conventional approach in existing wheeled bipedal robots involves motor-driven joints with high-ratio gearboxes. While this approach provides specific benefits, it also presents several challenges, including increased mechanical complexity, efficiency losses, noise, vibrations, and higher maintenance and lubrication requirements. Addressing the aforementioned concerns, we developed a direct-drive wheeled bipedal robot called DIABLO, which eliminates the use of gearboxes entirely. Our robotic system is simplified as a second-order inverted pendulum, and we have designed an LQR-based balance controller to ensure stability. Additionally, we implemented comprehensive motion controller, including yaw, split-angle, height, and roll controllers. Through expriments in simulations and real-world prototype, we have demonstrated that our platform achieves satisfactory performance.
Paper Structure (14 sections, 23 equations, 9 figures, 2 tables)

This paper contains 14 sections, 23 equations, 9 figures, 2 tables.

Table of Contents

  1. INTRODUCTION
  2. RELATED WORK
  3. SYSTEM DESCRIPTION
  4. Mechanism
  5. Hardware
  6. Software
  7. MODELING
  8. CONTROLLER DESIGN
  9. Balance Controller Design
  10. Comprehensive Motion Controller Design
  11. EXPERIMENT VERIFICATION
  12. Experiment in Simulation
  13. Experiment in Real-world Prototypes
  14. CONCLUSION AND FUTURE WORK

Figures (9)

  • Figure 1: A novel 6-DoF wheeled bipedal robot composed entirely of direct-drive joints. (A) DIABLO keeping balance on flat ground. (B) DIABLO maintaining balance involving body tilt and non-horizontal orientation of the head. Accompanying video is available at https://youtu.be/mm0XruFvZ4U
  • Figure 2: Mechanical structure of DIABLO
  • Figure 3: The exploded parts diagram of M1502D motor
  • Figure 4: Overview of the software framework
  • Figure 5: DIABLO's coordinate system and dynamic analysis diagram of simplified model (A) DIABLO's coordinate system. (B) Illustration of the simplified model in a 2D planar environment along with the dynamic analysis diagram.
  • ...and 4 more figures