239 research outputs found
Nonlinear Feedback Control of Axisymmetric Aerial Vehicles
We investigate the use of simple aerodynamic models for the feedback control
of aerial vehicles with large flight envelopes. Thrust-propelled vehicles with
a body shape symmetric with respect to the thrust axis are considered. Upon a
condition on the aerodynamic characteristics of the vehicle, we show that the
equilibrium orientation can be explicitly determined as a function of the
desired flight velocity. This allows for the adaptation of previously proposed
control design approaches based on the thrust direction control paradigm.
Simulation results conducted by using measured aerodynamic characteristics of
quasi-axisymmetric bodies illustrate the soundness of the proposed approach
Enhancing VTOL Multirotor Performance With a Passive Rotor Tilting Mechanism
This article discusses the benefits of introducing a simple passive mechanism to enable rotor tilting in Vertical Take-Off and Landing (VTOL) multirotor vehicles. Such a system is evaluated in relevant Urban Air Mobility (UAM) passenger transport scenarios such as hovering in wind conditions and overcoming rotor failures. While conventional parallel axis multirotors are underactuated systems, the proposed mechanism makes the vehicle fully actuated in SE(3), which implies independent cabin position and orientation control. An accurate vehicle simulator with realistic parameters is presented to compare in simulation the proposed architecture with a conventional underactuated VTOL vehicle that shares the same physical properties. In order to make fair comparisons, controllers are obtained solving an optimization problem in which the cost function of both systems is chosen to be equivalent. In particular, the control laws are Linear-Quadratic Regulators (LQR), which are derived by linearizing the systems around hover. It is shown through extensive simulation that the introduction of a passive rotor tilting mechanism based on universal joints improves performance metrics such as vehicle stability, power consumption, passenger comfort and position tracking precision in nominal flight conditions and it does not compromise vehicle safety in rotor failure situations
Geometric Surface-Based Tracking Control of a Quadrotor UAV
New quadrotor UAV control algorithms are developed, based on nonlinear
surfaces composed of tracking errors that evolve directly on the nonlinear
configuration manifold, thus inherently including in the control design the
nonlinear characteristics of the SE(3) configuration space. In particular,
geometric surface-based controllers are developed and are shown, through
rigorous stability proofs, to have desirable almost global closed loop
properties. For the first time in regards to the geometric literature, a region
of attraction independent of the position error is identified and its effects
are analyzed. The effectiveness of the proposed "surface based" controllers are
illustrated by simulations of aggressive maneuvers in the presence of
disturbances and motor saturation.Comment: 2018 26th Mediterranean Conference on Control and Automation (MED
Global configuration stabilization for the VTOL aircraft with strong input coupling
Trajectory tracking and configuration stabilization for the vertical takeoff and landing (VTOL) aircraft has been so far considered in the literature only in the presence of a slight (or zero) input coupling (i.e., for a small ε). In this paper, our main contribution is to address global configuration stabilization for the VTOL aircraft with a strong input coupling using a smooth static state feedback. In addition, the differentially flat outputs for the VTOL aircraft are automatically obtained as a by-product of applying a decoupling change of coordinates
Asymptotic Vision-Based Tracking Control of the Quadrotor Aerial Vehicle
This paper proposes an image-based visual servo (IBVS) controller for the 3D translational
motion of the quadrotor unmanned aerial vehicle (UAV). The main purpose of this paper is to
provide asymptotic stability for vision-based tracking control of the quadrotor in the presence
of uncertainty in the dynamic model of the system. The aim of the paper also includes the use
of
ow of image features as the velocity information to compensate for the unreliable linear
velocity data measured by accelerometers. For this purpose, the mathematical model of the
quadrotor is presented based on the optic
ow of image features which provides the possibility
of designing a velocity-free IBVS controller with considering the dynamics of the robot. The
image features are de ned from a suitable combination of perspective image moments without
using the model of the object. This property allows the application of the proposed controller
in unknown places. The controller is robust with respect to the uncertainties in the transla-
tional dynamics of the system associated with the target motion, image depth and external
disturbances. Simulation results and a comparison study are presented which demonstrate the
e ectiveness of the proposed approach
Control of VTOL Vehicles with Thrust-direction Tilting
An approach to the control of a VTOL vehicle equipped with complementary
thrust-direction tilting capabilities that nominally yield full actuation of
the vehicle's position and attitude is developed. The particularity and
difficulty of the control problem are epitomized by the existence of a maximal
thrust-tilting angle which forbids complete and decoupled control of the
vehicle's position and attitude in all situations. This problem is here
addressed via the formalism of primary and secondary objectives and by
extending a solution previously derived in the fixed thrust-direction case. The
proposed control design is also illustrated by simulation results involving a
quadrotor UAV with all propellers axes pointing in the same monitored tilted
direction
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