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Design, Contact Modeling, and Collision-inclusive Planning of a Dual-stiffness Aerial RoboT (DART)

Yogesh Kumar, Karishma Patnaik, Wenlong Zhang

TL;DR

This work addresses the challenge of enabling agile, collision-tolerant flight in cluttered environments by introducing DART, a dual-stiffness aerial robot that switches between rigid and flexible post-collision modes. A novel 3D collision model based on linear complementarity systems (LCS) is developed to predict post-collision dynamics and support collision-inclusive trajectory planning, complemented by a recovery controller that generates post-collision setpoints from external-force estimates. The authors characterize post-collision behavior via drop tests, validate the LCS model in flight, and demonstrate mode selection and pre-collision velocity optimization for collision-inclusive trajectories. Results show accurate prediction of peak contact forces and demonstrated planning capabilities, highlighting the potential for improved safety and performance in contact-rich aerial tasks. The work lays a foundation for planning and control frameworks that leverage collisions, with future work on planning algorithms and low-level controller refinements to further exploit the dual-stiffness design.

Abstract

Collision-resilient quadrotors have gained significant attention given their potential for operating in cluttered environments and leveraging impacts to perform agile maneuvers. However, existing designs are typically single-mode: either safeguarded by propeller guards that prevent deformation or deformable but lacking rigidity, which is crucial for stable flight in open environments. This paper introduces DART, a Dual-stiffness Aerial RoboT, that adapts its post-collision response by either engaging a locking mechanism for a rigid mode or disengaging it for a flexible mode, respectively. Comprehensive characterization tests highlight the significant difference in post collision responses between its rigid and flexible modes, with the rigid mode offering seven times higher stiffness compared to the flexible mode. To understand and harness the collision dynamics, we propose a novel collision response prediction model based on the linear complementarity system theory. We demonstrate the accuracy of predicting collision forces for both the rigid and flexible modes of DART. Experimental results confirm the accuracy of the model and underscore its potential to advance collision-inclusive trajectory planning in aerial robotics.

Design, Contact Modeling, and Collision-inclusive Planning of a Dual-stiffness Aerial RoboT (DART)

TL;DR

This work addresses the challenge of enabling agile, collision-tolerant flight in cluttered environments by introducing DART, a dual-stiffness aerial robot that switches between rigid and flexible post-collision modes. A novel 3D collision model based on linear complementarity systems (LCS) is developed to predict post-collision dynamics and support collision-inclusive trajectory planning, complemented by a recovery controller that generates post-collision setpoints from external-force estimates. The authors characterize post-collision behavior via drop tests, validate the LCS model in flight, and demonstrate mode selection and pre-collision velocity optimization for collision-inclusive trajectories. Results show accurate prediction of peak contact forces and demonstrated planning capabilities, highlighting the potential for improved safety and performance in contact-rich aerial tasks. The work lays a foundation for planning and control frameworks that leverage collisions, with future work on planning algorithms and low-level controller refinements to further exploit the dual-stiffness design.

Abstract

Collision-resilient quadrotors have gained significant attention given their potential for operating in cluttered environments and leveraging impacts to perform agile maneuvers. However, existing designs are typically single-mode: either safeguarded by propeller guards that prevent deformation or deformable but lacking rigidity, which is crucial for stable flight in open environments. This paper introduces DART, a Dual-stiffness Aerial RoboT, that adapts its post-collision response by either engaging a locking mechanism for a rigid mode or disengaging it for a flexible mode, respectively. Comprehensive characterization tests highlight the significant difference in post collision responses between its rigid and flexible modes, with the rigid mode offering seven times higher stiffness compared to the flexible mode. To understand and harness the collision dynamics, we propose a novel collision response prediction model based on the linear complementarity system theory. We demonstrate the accuracy of predicting collision forces for both the rigid and flexible modes of DART. Experimental results confirm the accuracy of the model and underscore its potential to advance collision-inclusive trajectory planning in aerial robotics.

Paper Structure

This paper contains 16 sections, 8 equations, 10 figures.

Table of Contents

  1. Introduction
  2. Design and Fabrication
  3. Structural Design
  4. Arm-locking Mechanism
  5. Drone Components and Assembly
  6. System Characterization
  7. Collision Model using Linear Complementarity Systems
  8. Description of Recovery Controller
  9. LCS Formulation for Collision Model
  10. Collision Model Applications
  11. Determining Pre-collision Velocity
  12. Mode Selection
  13. Experimental Results
  14. Collision Model Validation In-flight
  15. Validation for Mode Selection
  16. ...and 1 more sections

Figures (10)

  • Figure 1: DART is a dual-mode variable stiffness quadrotor that adapts its post-collision response by switching between rigid and flexible modes. The figure demonstrates how this capability, along with a new collision response model, enables the generation of collision-inclusive paths.
  • Figure 2: (a) Top-view (b) Arms mounted on bearings and interconnected using extension springs (c) Bottom-view (d) Locking mechanism
  • Figure 3: (a) The kinematic model for the cam mechanism. (b) The motion model for DART, described as a 3D spring-damper system.
  • Figure 4: (a) Front-view and (b) Side-view, showing initial and maximum flexed configurations of DART during the drop test from 0.2m height (c) UR5 holding DART for drop test
  • Figure 5: Position ($x^\dagger$) and velocity ($\dot{x}^\dagger$) vs time from drop test experiments
  • ...and 5 more figures