307 research outputs found
Modified Implicit Discretization of the Super-Twisting Controller
In this paper a novel discrete-time realization of the super-twisting
controller is proposed. The closed-loop system is proven to be globally
asymptotically stable in the absence of a disturbance by means of Lyapunov
theory. Furthermore, the steady-state error in the disturbed case is computed
analytically and shown to be independent of the parameters. The steady-state
error only depends on the sampling time and the unknown disturbance. The
proposed discrete-time controller is compared to previously published
discrete-time super-twisting controllers by means of the controller structure.
In extensive simulation studies the proposed controller is evaluated
comparative to known controllers. The continuous-time super-twisting controller
is capable of rejecting any unknown Lipschitz-continuous perturbation.
Furthermore, the convergence time decreases, if any of the gains is increased.
The simulations demonstrate that the systems closed in the loop with each of
the known controllers lose one of these properties, introduce
discretization-chattering effects, or do not yield the same accuracy level as
with the proposed controller. The proposed controller, in contrast, is
beneficial in terms of the above described properties of the continuous-time
super-twisting controller
COST Action IC1402 Runtime Verification beyond Monitoring
International audienceIn this paper we report on COST Action IC1402 which studies Run-time Verification approaches beyond Monitoring. COST Actions are funded by the European Union and are an efficient networking instrument for researchers, engineers and scholars to cooperate and coordinate research activities. This COST action IC1402 lasted over the past four years, involved researchers from 27 different European countries and Australia and allowed to have many different working group meetings, workshops and individual visits
Staggered flux and stripes in doped antiferromagnets
We have numerically investigated whether or not a mean-field theory of spin
textures generate fictitious flux in the doped two dimensional -model.
First we consider the properties of uniform systems and then we extend the
investigation to include models of striped phases where a fictitious flux is
generated in the domain wall providing a possible source for lowering the
kinetic energy of the holes. We have compared the energetics of uniform systems
with stripes directed along the (10)- and (11)-directions of the lattice,
finding that phase-separation generically turns out to be energetically
favorable. In addition to the numerical calculations, we present topological
arguments relating flux and staggered flux to geometric properties of the spin
texture. The calculation is based on a projection of the electron operators of
the model into a spin texture with spinless fermions.Comment: RevTex, 19 pages including 20 figure
Tip- and laser-based 3D nanofabrication in extended macroscopic working areas
The field of optical lithography is subject to intense research and has gained enormous improvement. However, the effort necessary for creating structures at the size of 20 nm and below is considerable using conventional technologies. This effort and the resulting financial requirements can only be tackled by few global companies and thus a paradigm change for the semiconductor industry is conceivable: custom design and solutions for specific applications will dominate future development (Fritze in: Panning EM, Liddle JA (eds) Novel patterning technologies. International society for optics and photonics. SPIE, Bellingham, 2021. https://doi.org/10.1117/12.2593229). For this reason, new aspects arise for future lithography, which is why enormous effort has been directed to the development of alternative fabrication technologies. Yet, the technologies emerging from this process, which are promising for coping with the current resolution and accuracy challenges, are only demonstrated as a proof-of-concept on a lab scale of several square micrometers. Such scale is not adequate for the requirements of modern lithography; therefore, there is the need for new and alternative cross-scale solutions to further advance the possibilities of unconventional nanotechnologies. Similar challenges arise because of the technical progress in various other fields, realizing new and unique functionalities based on nanoscale effects, e.g., in nanophotonics, quantum computing, energy harvesting, and life sciences. Experimental platforms for basic research in the field of scale-spanning nanomeasuring and nanofabrication are necessary for these tasks, which are available at the Technische Universität Ilmenau in the form of nanopositioning and nanomeasuring (NPM) machines. With this equipment, the limits of technical structurability are explored for high-performance tip-based and laser-based processes for enabling real 3D nanofabrication with the highest precision in an adequate working range of several thousand cubic millimeters
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