298 research outputs found
Multi-Agent Reinforcement Learning for the Low-Level Control of a Quadrotor UAV
This paper presents multi-agent reinforcement learning frameworks for the
low-level control of a quadrotor UAV. While single-agent reinforcement learning
has been successfully applied to quadrotors, training a single monolithic
network is often data-intensive and time-consuming. To address this, we
decompose the quadrotor dynamics into the translational dynamics and the yawing
dynamics, and assign a reinforcement learning agent to each part for efficient
training and performance improvements. The proposed multi-agent framework for
quadrotor low-level control that leverages the underlying structures of the
quadrotor dynamics is a unique contribution. Further, we introduce
regularization terms to mitigate steady-state errors and to avoid aggressive
control inputs. Through benchmark studies with sim-to-sim transfer, it is
illustrated that the proposed multi-agent reinforcement learning substantially
improves the convergence rate of the training and the stability of the
controlled dynamics.Comment: 8 pages, 6 figures, 3 table
Control Synthesis for an Underactuated Cable Suspended System Using Dynamic Decoupling
This article studies the dynamics and control of a novel underactuated
system, wherein a plate suspended by cables and with a freely moving mass on
top, whose other ends are attached to three quadrotors, is sought to be
horizontally stabilized at a certain height, with the ball positioned at the
center of mass of the plate. The freely moving mass introduces a 2-degree of
underactuation into the system. The design proceeds through a decoupling of the
quadrotors and the plate dynamics. Through a partial feedback linearization
approach, the attitude of the plate and the translational height of the plate
is initially controlled, while maintaining a bounded velocity along the and
directions. These inputs are then synthesized through the quadrotors with a
backstepping and timescale separation argument based on Tikhonov's theorem
Survey on Aerial Multirotor Design: a Taxonomy Based on Input Allocation
This paper reviews the impact of multirotor aerial vehicles designs on their abilities in terms of tasks and system properties. We propose a general taxonomy to characterize and describe multirotor aerial vehicles and their design, which we apply exhaustively on the vast literature available. Thanks to the systematic characterization of the designs we exhibit groups of designs having the same abilities in terms of achievable tasks and system properties. In particular, we organize the literature review based on the number of atomic actuation units and we discuss global properties arising from their choice and spatial distribution in the designs. Finally, we provide a discussion on the common traits of the designs found in the literature and the main future open problems
Advanced Feedback Linearization Control for Tiltrotor UAVs: Gait Plan, Controller Design, and Stability Analysis
Three challenges, however, can hinder the application of Feedback
Linearization: over-intensive control signals, singular decoupling matrix, and
saturation. Activating any of these three issues can challenge the stability
proof. To solve these three challenges, first, this research proposed the drone
gait plan. The gait plan was initially used to figure out the control problems
in quadruped (four-legged) robots; applying this approach, accompanied by
Feedback Linearization, the quality of the control signals was enhanced. Then,
we proposed the concept of unacceptable attitude curves, which are not allowed
for the tiltrotor to travel to. The Two Color Map Theorem was subsequently
established to enlarge the supported attitude for the tiltrotor. These theories
were employed in the tiltrotor tracking problem with different references.
Notable improvements in the control signals were witnessed in the tiltrotor
simulator. Finally, we explored the control theory, the stability proof of the
novel mobile robot (tilt vehicle) stabilized by Feedback Linearization with
saturation. Instead of adopting the tiltrotor model, which is over-complicated,
we designed a conceptual mobile robot (tilt-car) to analyze the stability
proof. The stability proof (stable in the sense of Lyapunov) was found for a
mobile robot (tilt vehicle) controlled by Feedback Linearization with
saturation for the first time. The success tracking result with the promising
control signals in the tiltrotor simulator demonstrates the advances of our
control method. Also, the Lyapunov candidate and the tracking result in the
mobile robot (tilt-car) simulator confirm our deductions of the stability
proof. These results reveal that these three challenges in Feedback
Linearization are solved, to some extents.Comment: Doctoral Thesis at The University of Toky
Design and control of next-generation uavs for effectively interacting with environments
In this dissertation, the design and control of a novel multirotor for aerial manipulation is studied, with the aim of endowing the aerial vehicle with more degrees of freedom of motion and stability when interacting with the environments. Firstly, it presents an energy-efficient adaptive robust tracking control method for a class of fully actuated, thrust vectoring unmanned aerial vehicles (UAVs) with parametric uncertainties including unknown moment of inertia, mass and center of mass, which would occur in aerial maneuvering and manipulation. The effectiveness of this method is demonstrated through simulation. Secondly, a humanoid robot arm is adopted to serve as a 6-degree-of-freedom (DOF) automated flight testing platform for emulating the free flight environment of UAVs while ensuring safety. Another novel multirotor in a tilt-rotor architecture is studied and tested for coping with parametric uncertainties in aerial maneuvering and manipulation. Two pairs of rotors are mounted on two independently-controlled tilting arms placed at two sides of the vehicle in a H configuration to enhance its maneuverability and stability through an adaptive robust control method. In addition, an impedance control algorithm is deployed in the out loop that modifies the trajectory to achieve a compliant behavior in the end-effector space for aerial drilling and screwing tasks
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