32,892 research outputs found
Geometric control of particle manipulation in a two-dimensional fluid
Manipulation of particles suspended in fluids is crucial for many applications, such as precision machining, chemical processes, bio-engineering, and self-feeding of microorganisms. In this paper, we study the problem of particle manipulation by cyclic fluid boundary excitations from a geometric-control viewpoint. We focus on the simplified problem of manipulating a single particle by generating controlled cyclic motion of a circular rigid body in a two-dimensional perfect fluid. We show that the drift in the particle location after one cyclic motion of the body can be interpreted as the geometric phase of a connection induced by the system's hydrodynamics. We then formulate the problem as a control system, and derive a geometric criterion for its nonlinear controllability. Moreover, by exploiting the geometric structure of the system, we explicitly construct a feedback-based gait that results in attraction of the particle towards the rigid body. We argue that our gait is robust and model-independent, and demonstrate it in both perfect fluid and Stokes fluid
Benchmarking End-to-end Learning of MIMO Physical-Layer Communication
End-to-end data-driven machine learning (ML) of multiple-input
multiple-output (MIMO) systems has been shown to have the potential of
exceeding the performance of engineered MIMO transceivers, without any a priori
knowledge of communication-theoretic principles. In this work, we aim to
understand to what extent and for which scenarios this claim holds true when
comparing with fair benchmarks. We study closed-loop MIMO, open-loop MIMO, and
multi-user MIMO and show that the gains of ML-based communication in the former
two cases can be to a large extent ascribed to implicitly learned geometric
shaping and bit and power allocation, not to learning new spatial encoders. For
MU-MIMO, we demonstrate the feasibility of a novel method with centralized
learning and decentralized executing, outperforming conventional zero-forcing.
For each scenario, we provide explicit descriptions as well as open-source
implementations of the selected neural-network architectures.Comment: 6 pages, 8 figures, conference pape
Reach Control on Simplices by Piecewise Affine Feedback
We study the reach control problem for affine systems on simplices, and the
focus is on cases when it is known that the problem is not solvable by
continuous state feedback. We examine from a geometric viewpoint the structural
properties of the system which make continuous state feedbacks fail. This
structure is encoded by so-called reach control indices, which are defined and
developed in the paper. Based on these indices, we propose a subdivision
algorithm and associated piecewise affine feedback. The method is shown to
solve the reach control problem in all remaining cases, assuming it is solvable
by open-loop controls
Coherent versus measurement feedback: Linear systems theory for quantum information
To control a quantum system via feedback, we generally have two options in
choosing control scheme. One is the coherent feedback, which feeds the output
field of the system, through a fully quantum device, back to manipulate the
system without involving any measurement process. The other one is the
measurement-based feedback, which measures the output field and performs a
real-time manipulation on the system based on the measurement results. Both
schemes have advantages/disadvantages, depending on the system and the control
goal, hence their comparison in several situation is important. This paper
considers a general open linear quantum system with the following specific
control goals; back-action evasion (BAE), generation of a quantum
non-demolished (QND) variable, and generation of a decoherence-free subsystem
(DFS), all of which have important roles in quantum information science. Then
some no-go theorems are proven, clarifying that those goals cannot be achieved
by any measurement-based feedback control. On the other hand it is shown that,
for each control goal, there exists a coherent feedback controller
accomplishing the task. The key idea to obtain all the results is system
theoretic characterizations of BAE, QND, and DFS in terms of controllability
and observability properties or transfer functions of linear systems, which are
consistent with their standard definitions.Comment: 21 pages, 10 figures, to appear in Physical Review
Automatic crosswind flight of tethered wings for airborne wind energy: modeling, control design and experimental results
An approach to control tethered wings for airborne wind energy is proposed. A
fixed length of the lines is considered, and the aim of the control system is
to obtain figure-eight crosswind trajectories. The proposed technique is based
on the notion of the wing's "velocity angle" and, in contrast with most
existing approaches, it does not require a measurement of the wind speed or of
the effective wind at the wing's location. Moreover, the proposed approach
features few parameters, whose effects on the system's behavior are very
intuitive, hence simplifying tuning procedures. A simplified model of the
steering dynamics of the wing is derived from first-principle laws, compared
with experimental data and used for the control design. The control algorithm
is divided into a low-level loop for the velocity angle and a high-level
guidance strategy to achieve the desired flight patterns. The robustness of the
inner loop is verified analytically, and the overall control system is tested
experimentally on a small-scale prototype, with varying wind conditions and
using different wings.Comment: This manuscript is a preprint of a paper accepted for publication on
the IEEE Transactions on Control Systems Technology and is subject to IEEE
Copyright. The copy of record is available at IEEEXplore library:
http://ieeexplore.ieee.org
Algebraic geometric methods for the stabilizability and reliability of multivariable and of multimode systems
The extent to which feedback can alter the dynamic characteristics (e.g., instability, oscillations) of a control system, possibly operating in one or more modes (e.g., failure versus nonfailure of one or more components) is examined
Quantum Internal Model Principle: Decoherence Control
In this article, we study the problem of designing a Decoherence Control for
quantum systems with the help of a scalable ancillary quantum control and
techniques from geometric control theory, in order to successfully and
completely decouple an open quantum system from its environment. We
re-formulate the problem of decoherence control as a disturbance rejection
scheme which also leads us to the idea of Internal Model Principle for quantum
control systems which is first of its kind in the literature.
It is shown that decoupling a quantum disturbance from an open quantum
system, is possible only with the help of a quantum controller which takes into
account the model of the environmental interaction. This is demonstrated for a
simple 2-qubit system wherein the effects of decoherence are completely
eliminated. The theory provides conditions to be imposed on the controller to
ensure perfect decoupling. Hence the problem of decoherence control naturally
gives rise to the quantum internal model principle which relates the
disturbance rejecting control to the model of the environmental interaction.
Classical internal model principle and disturbance decoupling focus on
different aspects viz. perfect output tracking and complete decoupling of
output from external disturbances respectively. However for quantum systems,
the two problems come together and merge in order to produce an effective
platform for decoherence control. In this article we introduce a seminal
connection between disturbance decoupling and the corresponding analog for
internal model principle for quantum systems.Comment: Submitted to IEEE Transactions on Automatic Control, Mar 15 2010. A
basic introduction appeared in 46th IEEE CDC 2007. Acknowledgements: The
authors would like to thank the Center for Quantum Information Science and
Technology at Tsinghua University, R.-B. Wu, J. Zhang, J.-W. Wu, M. Jiang,
C.-W. Li and G.-L. Long for their valuable comments and suggestion
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