Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Design and Control of a VTOL Aerial Vehicle Tilting its Rotors Only with Rotor Thrusts and a Passive Joint

Takumi Ito, Riku Funada, Mitsuji Sampei

TL;DR

The paper tackles designing a VTOL UAV that tilts its rotors through rotor thrusts via a passive joint, avoiding extra actuators to reduce weight. It develops a combined rotor-wrench and aerodynamics model, establishes cruisability conditions with a key rank constraint, and introduces a four-component controller that separates body control from tilting via an exact linearization approach and LQR design. The tilt controller leverages a two-input rotor thrust framework, enabling forward acceleration while keeping angle of attack near equilibrium, and the control allocation scheme ensures feasible rotor commands to realize the desired body wrench and joint torque. Simulation results corroborate the transition from hover to cruise, showing controlled tilt and stable cruise speed with constrained aerodynamic variation, underscoring the practical impact of a lighter, actuator-light VTOL design.

Abstract

This paper presents a novel VTOL UAV that owns a link connecting four rotors and a fuselage by a passive joint, allowing the control of the rotor's tilting angle by adjusting the rotors' thrust. This unique structure contributes to eliminating additional actuators, such as servo motors, to control the tilting angles of rotors, resulting in the UAV's weight lighter and simpler structure. We first derive the dynamical model of the newly designed UAV and analyze its controllability. Then, we design the controller that leverages the tiltable link with four rotors to accelerate the UAV while suppressing a deviation of the UAV's angle of attack from the desired value to restrain the change of the aerodynamic force. Finally, the validity of the proposed control strategy is evaluated in simulation study.

Design and Control of a VTOL Aerial Vehicle Tilting its Rotors Only with Rotor Thrusts and a Passive Joint

TL;DR

The paper tackles designing a VTOL UAV that tilts its rotors through rotor thrusts via a passive joint, avoiding extra actuators to reduce weight. It develops a combined rotor-wrench and aerodynamics model, establishes cruisability conditions with a key rank constraint, and introduces a four-component controller that separates body control from tilting via an exact linearization approach and LQR design. The tilt controller leverages a two-input rotor thrust framework, enabling forward acceleration while keeping angle of attack near equilibrium, and the control allocation scheme ensures feasible rotor commands to realize the desired body wrench and joint torque. Simulation results corroborate the transition from hover to cruise, showing controlled tilt and stable cruise speed with constrained aerodynamic variation, underscoring the practical impact of a lighter, actuator-light VTOL design.

Abstract

This paper presents a novel VTOL UAV that owns a link connecting four rotors and a fuselage by a passive joint, allowing the control of the rotor's tilting angle by adjusting the rotors' thrust. This unique structure contributes to eliminating additional actuators, such as servo motors, to control the tilting angles of rotors, resulting in the UAV's weight lighter and simpler structure. We first derive the dynamical model of the newly designed UAV and analyze its controllability. Then, we design the controller that leverages the tiltable link with four rotors to accelerate the UAV while suppressing a deviation of the UAV's angle of attack from the desired value to restrain the change of the aerodynamic force. Finally, the validity of the proposed control strategy is evaluated in simulation study.
Paper Structure (18 sections, 2 theorems, 27 equations, 16 figures)

This paper contains 18 sections, 2 theorems, 27 equations, 16 figures.

Table of Contents

  1. INTRODUCTION
  2. Notation
  3. MODELING
  4. Overview of the Vehicle
  5. Equation of Motion
  6. Transformation of the Rotor Thrusts
  7. Aerodynamic Force
  8. REALIZABILITY OF THE CRUISE FLIGHT
  9. Realizability Analysis
  10. Planning of $\alpha$ and $\chi$
  11. CONTROLLER
  12. Position Controller for Hovering Phase
  13. Position Controller for the Other Phases
  14. Attitude Controller
  15. Control Allocation
  16. ...and 3 more sections

Key Result

Lemma 1

The proposed UAV achieves a cruise flight if and only if the following two conditions are satisfied.

Figures (16)

  • Figure 1: Topview of the proposed UAV.
  • Figure 2: Sideview of the proposed UAV.
  • Figure 3: Flight modes considered in this paper.
  • Figure 4: The relationship of the forces at the equilibrium point.
  • Figure 5: The curve satisfying cruisability conditions.
  • ...and 11 more figures

Theorems & Definitions (5)

  • Remark 1
  • Definition 1: Cruise flight
  • Lemma 1: Cruisability check
  • Theorem 1
  • proof