Abstract

The multilinked or modular structure is one of the state-of-the-art topics in aerial robot field. One type of the multilinked aerial robot called DRAGON containing a two degree-of-freedom (DoF) force vectoring apparatus in each link has been developed in our previous work to augment both maneuvering and manipulation ability. However, several types of invalid robot poses, which are due to the mechanical structure, the previous control method and the interrotor aerodynamic interference, significantly reduce the region of deformation. Thus, enhanced modeling and control methods are necessary to overcome these problems. In this letter, we first develop an integrated thrust and vectoring control method with a rigorous allocation to solve the control singularity. Second, we present a vectoring configuration planning method, which solves the mechanical singularity by locking one of the axes in the two DoF vectoring apparatus. Finally, we propose an estimation method and an active compensation control regarding the aerodynamic interference to improve the flight stability. In the end, simulation studies and experiments involving the hovering and deformation along a vertical plane are performed to evaluate the whole modeling and control framework.

Highlights

  • T HE aerial deformability achieved by a multilink or modular aerial robot demonstrates the advanced potential in maneuvering [1]–[3] and manipulation [4]–[6]

  • Compared to the link module composed from eight propellers in [1], [5], a more compact link design containing two DoF roll-pitch vectoring apparatus is presented in our previous work [7], and the multilinked aerial robot called DRAGON which connects the link modules with two DoF actuated joints is developed

  • A quad-type DRAGON is used in this work, of which the detailed specification is presented in our previous work [7]

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Summary

INTRODUCTION

T HE aerial deformability achieved by a multilink or modular aerial robot demonstrates the advanced potential in maneuvering [1]–[3] and manipulation [4]–[6]. A control framework for one DoF force vectoring apparatus in [10] first obtains the desired wrench in the Centerof-Gravity (CoG) frame, linearly allocates it to the desired vectored force in each rotor as intermediate terms, and converts to the desired thrust and vectoring angles. Based on this framework, an improved control method is developed for two.

Wrench Generated By Two DoF Vectoring Apparatus
Dynamics Approximation
Wrench PID Control
Control Allocation
Unstable Case of Two DoF Roll-Pitch Vectoring
Optimization of Locked Roll Vectoring Angle
Control Allocation With Locked Roll Vectoring Angles
External Wrench Estimation
Interference Acting Point Estimation
Interference Wrench Filter
Implementation Details
Robot Platform
Simulation Studies
Experimental Results
CONCLUSION
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