Research Papers

Twisting and Tilting Rotors for High-Efficiency, Thrust-Vectored Quadrotors

[+] Author and Article Information
Matthew J. Gerber

Mechatronics and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of California Los Angeles,
Los Angeles, CA 90095
e-mail: gerber211@ucla.edu

Tsu-Chin Tsao

Mechatronics and Controls Laboratory,
Department of Mechanical and
Aerospace Engineering,
University of California Los Angeles,
Los Angeles CA 90095
e-mail: ttsao@ucla.edu

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANISMS AND ROBOTICS. Manuscript received March 1, 2018; final manuscript received August 15, 2018; published online October 1, 2018. Assoc. Editor: David J. Cappelleri.

J. Mechanisms Robotics 10(6), 061013 (Oct 01, 2018) (7 pages) Paper No: JMR-18-1057; doi: 10.1115/1.4041261 History: Received March 01, 2018; Revised August 15, 2018

A mechanism consisting of twisting and tilting joints is introduced to provide omnidirectional thrust-vectoring capabilities to a quadrotor system. This mechanism eliminates mechanical constraints and kinematic singularities to provide full directional authority to all four individual thrust vectors. The presented system fully decouples position and attitude dynamics to overcome the intrinsic maneuverability limitations of traditional multirotors while maximizing thrust efficiency over its entire configuration space. This paper presents a mathematical model of the system, introduces a control method for position and attitude tracking, and presents numerical simulation results that demonstrate the system benefits.

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Fig. 1

Shown is (a) the mechanism design of the omnidirectional propeller arm with (b) the twisting motion and (c) the tilting motion. The mechanism is devoid of mechanical constraints and provides full directional authority (4π sr) to the generated thrust (ti).

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Fig. 2

Shown is a model of the quadrotor system with coordinate frames and system inputs. The model includes 12 inputs (α, β, and ω¯) and accounts for an offset center of mass (Oc).

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Fig. 3

Shown is a diagram of the control architecture. The controller exploits the thrust-vectoring capability of the system to decouple the position and attitude dynamics and maps the resulting control wrench to the 12 controllable inputs via inverse kinematics.

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Fig. 4

Trajectory 1: Complete, on-point rotation. This trajectory represents an infeasible maneuver for a traditional multirotor and its successful execution by the presented system demonstrates the ability to (1) vector the thrust directions (arrows) to track an arbitrary rotation without affecting position and to (2) account for an offset center of mass (large dot).

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Fig. 5

Trajectory 1: Twist and tilt angles during the on-point rotation. Letters indicate snapshots in time corresponding to Fig. 4.

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Fig. 6

Trajectory 1: Propeller spinning velocities during the on-point rotation. The magnitudes never reach saturation, are equally distributed between propellers, and–regardless of body attitude–are approximately equal to the minimum required to counteract gravity.

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Fig. 7

Trajectory 2: Trajectory to align to a wall with three externally applied destabilizing forces. The system is able to vector its thrusts to cancel the applied forces and regain the desired trajectory.

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Fig. 8

Trajectory 2: The left column shows positional displacements and the right column shows angular displacements for the duration of the trajectory. For clarity, the angular displacements are presented as the standard roll (ϕB), pitch (θB), and yaw (ψB) angles in FB.



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