11,692 research outputs found
An extension of the quickened display for manual control
It is very difficult (or even impossible) for a human to control plants of third order or more with little or no damping by just knowing the instantaneous error. It has been shown that adding first and/or higher order derivatives to the error signal and displaying the combined signal are effective in facilitating human control over such plants. This signal quickening technique by Birmingham and Taylor is further extended to incorporate the future trajectory variation into the displayed signal so as to minimize the tracking error. A method for tuning free parameters in ordinary and extended quickening is established by applying discrete-time optimal control. Experimental results for a triple integrator plant indicate the effectiveness of the proposed method to achieve high quality tracking
Proofs of Control of a Quadrotor and a Ground Vehicle Manipulating an Object
This paper focuses on the control of a cooperative system composed of an
Unmanned Aerial Vehicle (UAV) and an Unmanned Ground Vehicle (UGV) manipulating
an object. The two units are subject to input saturations and collaborate to
move the object to a desired pose characterized by its position and
inclination. The dynamics are derived using Euler-Lagrange method. A
pre-stabilizing control law is proposed where the UGV is tasked to deploy the
object to a certain position whereas the UAV adjusts its inclination. In
particular, a proportional-derivative control law is proposed for the UGV, and
a cascade control approach is used for the UAV, where the inner loop controls
the attitude of the UAV and the outer loop stabilizes the inclination of the
object. Then, we prove the stability of the points of equilibrium using small
gain arguments. To ensure constraints satisfaction at all times, a reference
governor unit is added to the pre-stabilizing control scheme. Finally,
numerical results combined with experimental results are provided to validate
the effectiveness of the proposed control scheme in practice.Comment: 16 pages, 7 figure
Analytical developments for definition and prediction of USB noise
A systematic acoustic data base and associated flow data are used in identifying the noise generating mechanisms of upper surface blown flap configurations of short takeoff and landing aircraft. Theory is developed for the radiated sound field of the highly sheared flow of the trailing edge wake. An empirical method is also developed using extensive experimental data and physical reasonings to predict the noise levels
Use of Devolved Controllers in Data Center Networks
In a data center network, for example, it is quite often to use controllers
to manage resources in a centralized man- ner. Centralized control, however,
imposes a scalability problem. In this paper, we investigate the use of
multiple independent controllers instead of a single omniscient controller to
manage resources. Each controller looks after a portion of the network only,
but they together cover the whole network. This therefore solves the
scalability problem. We use flow allocation as an example to see how this
approach can manage the bandwidth use in a distributed manner. The focus is on
how to assign components of a network to the controllers so that (1) each
controller only need to look after a small part of the network but (2) there is
at least one controller that can answer any request. We outline a way to
configure the controllers to fulfill these requirements as a proof that the use
of devolved controllers is possible. We also discuss several issues related to
such implementation.Comment: Appears in INFOCOM 2011 Cloud Computing Worksho
Coronal heating in multiple magnetic threads
Context. Heating the solar corona to several million degrees requires the
conversion of magnetic energy into thermal energy. In this paper, we
investigate whether an unstable magnetic thread within a coronal loop can
destabilise a neighbouring magnetic thread. Aims. By running a series of
simulations, we aim to understand under what conditions the destabilisation of
a single magnetic thread can also trigger a release of energy in a nearby
thread. Methods. The 3D magnetohydrodynamics code, Lare3d, is used to simulate
the temporal evolution of coronal magnetic fields during a kink instability and
the subsequent relaxation process. We assume that a coronal magnetic loop
consists of non-potential magnetic threads that are initially in an equilibrium
state. Results. The non-linear kink instability in one magnetic thread forms a
helical current sheet and initiates magnetic reconnection. The current sheet
fragments, and magnetic energy is released throughout that thread. We find
that, under certain conditions, this event can destabilise a nearby thread,
which is a necessary requirement for starting an avalanche of energy release in
magnetic threads. Conclusions. It is possible to initiate an energy release in
a nearby, non-potential magnetic thread, because the energy released from one
unstable magnetic thread can trigger energy release in nearby threads, provided
that the nearby structures are close to marginal stability
- …