2,740,280 research outputs found
Multirobot heterogeneous control considering secondary objectives
Cooperative robotics has considered tasks that are executed frequently, maintaining the
shape and orientation of robotic systems when they fulfill a common objective, without taking
advantage of the redundancy that the robotic group could present. This paper presents a proposal
for controlling a group of terrestrial robots with heterogeneous characteristics, considering primary
and secondary tasks thus that the group complies with the following of a path while modifying its
shape and orientation at any time. The development of the proposal is achieved through the use
of controllers based on linear algebra, propounding a low computational cost and high scalability
algorithm. Likewise, the stability of the controller is analyzed to know the required features that have
to be met by the control constants, that is, the correct values. Finally, experimental results are shown
with di erent configurations and heterogeneous robots, where the graphics corroborate the expected
operation of the proposalThis research was funded by Corporación Ecuatoriana para el Desarrollo de la Investigación
y Academia–CEDI
Smart microgrids and virtual power plants in a hierarchical control structure
In order to achieve a coordinated integration of distributed energy resources in the electrical network, an aggregation of these resources is required. Microgrids and virtual power plants (VPPs) address this issue. Opposed to VPPs, microgrids have the functionality of islanding, for which specific control strategies have been developed. These control strategies are classified under the primary control strategies. Microgrid secondary control deals with other aspects such as resource allocation, economic optimization and voltage profile improvements. When focussing on the control-aspects of DER, VPP coordination is similar with the microgrid secondary control strategy, and thus, operates at a slower time frame as compared to the primary control and can take full advantage of the available communication provided by the overlaying smart grid. Therefore, the feasibility of the microgrid secondary control for application in VPPs is discussed in this paper. A hierarchical control structure is presented in which, firstly, smart microgrids deal with local issues in a primary and secondary control. Secondly, these microgrids are aggregated in a VPP that enables the tertiary control, forming the link with the electricity markets and dealing with issues on a larger scale
On the Impact of Wireless Jamming on the Distributed Secondary Microgrid Control
The secondary control in direct current microgrids (MGs) is used to restore
the voltage deviations caused by the primary droop control, where the latter is
implemented locally in each distributed generator and reacts to load
variations. Numerous recent works propose to implement the secondary control in
a distributed fashion, relying on a communication system to achieve consensus
among MG units. This paper shows that, if the system is not designed to cope
with adversary communication impairments, then a malicious attacker can apply a
simple jamming of a few units of the MG and thus compromise the secondary MG
control. Compared to other denial-of-service attacks that are oriented against
the tertiary control, such as economic dispatch, the attack on the secondary
control presented here can be more severe, as it disrupts the basic
functionality of the MG
Study of vortex valve for medium temperature solid propellants
Fluid state vortex valve secondary injection control system shows considerable promise for future application to solid propellant rocket engine thrust vector control. The single axis injection system tested would be capable of providing secondary injection thrust vector control using 2000 deg F gas
Distributed Secondary Frequency Control through MTDC Transmission Systems
In this paper, we present distributed controllers for sharing primary and
secondary frequency control reserves for asynchronous AC transmission systems,
which are connected through a multi-terminal HVDC grid. By using Lyapunov
arguments, the equilibria of the closed-loop system are shown to be globally
asymptotically stable. We quantify the static errors of the voltages and
frequencies, and give upper bounds for these errors. It is also shown that the
controllers have the property of power sharing, i.e., primary and secondary
frequency control reserves are shared fairly amongst the AC systems. The
proposed controllers are applied to a high-order dynamic model of of a power
system consisting of asynchronous AC grids connected through a six-terminal
HVDC grid.Comment: arXiv admin note: text overlap with arXiv:1409.801
Control Function Assisted IPW Estimation with a Secondary Outcome in Case-Control Studies
Case-control studies are designed towards studying associations between risk
factors and a single, primary outcome. Information about additional, secondary
outcomes is also collected, but association studies targeting such secondary
outcomes should account for the case-control sampling scheme, or otherwise
results may be biased. Often, one uses inverse probability weighted (IPW)
estimators to estimate population effects in such studies. However, these
estimators are inefficient relative to estimators that make additional
assumptions about the data generating mechanism. We propose a class of
estimators for the effect of risk factors on a secondary outcome in
case-control studies, when the mean is modeled using either the identity or the
log link. The proposed estimator combines IPW with a mean zero control function
that depends explicitly on a model for the primary disease outcome. The
efficient estimator in our class of estimators reduces to standard IPW when the
model for the primary disease outcome is unrestricted, and is more efficient
than standard IPW when the model is either parametric or semiparametric
Optimized Hierarchical Power Oscillations Control for Distributed Generation Under Unbalanced Conditions
Control structures have critical influences on converter-interfaced
distributed generations (DG) under unbalanced conditions. Most of previous
works focus on suppressing active power oscillations and ripples of DC bus
voltage. In this paper, the relationship between amplitudes of the active power
oscillations and the reactive power oscillations are firstly deduced and the
hierarchical control of DG is proposed to reduce power oscillations. The
hierarchical control consists of primary and secondary levels. Current
references are generated in primary control level and the active power
oscillations can be suppressed by a dual current controller. Secondary control
reduces the active power and reactive power oscillations simultaneously by
optimal model aiming for minimum amplitudes of oscillations. Simulation results
show that the proposed secondary control with less injecting negative-sequence
current than traditional control methods can effectively limit both active
power and reactive power oscillations.Comment: Accepted by Applied Energ
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