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Lernfabrik
(2016)
Die Einführung von cyberphysischen Systemen in der Fertigung wird die Arbeitsbedingungen und Prozesse genauso wie Geschäftsmodelle stark verändern. In der Praxis kann eine wachsende Diskrepanz zwischen Großunternehmen und KMU beobachtet werden. Genau diese Diskrepanz soll die im Folgenden präsentierte Lernfabrik überbrücken, die Unternehmen eine Plattform zum Probieren bietet, die Möglichkeit zur Ausbildung von Studenten und Mitarbeitern schafft und Beratungsangebote bereithält. Zur Umsetzung wird ein integriertes, offenes und standardisiertes Automatisierungskonzept vorgestellt, das einzelne Geräte, ganze Produktionslinien bis hin zu höheren Automatisierungssystemen umfasst und auch eine Community bereitstellt sowie zur Umsetzung neuer Geschäftsmodelle dient.
Error correction coding based on soft-input decoding can significantly improve the reliability of flash memories. Such soft-input decoding algorithms require reliability information about the state of the memory cell. This work proposes a channel model for soft-input decoding that considers the asymmetric error characteristic of multi-level cell (MLC) and triple-level cell (TLC) memories. Based on this model, an estimation method for the channel state information is devised which avoids additional pilot data for channel estimation. Furthermore, the proposed method supports page-wise read operations.
Generalized concatenated (GC) codes with soft-input decoding were recently proposed for error correction in flash memories. This work proposes a soft-input decoder for GC codes that is based on a low-complexity bit-flipping procedure. This bit-flipping decoder uses a fixed number of test patterns and an algebraic decoder for soft-input decoding. An acceptance criterion for the final candidate codeword is proposed. Combined with error and erasure decoding of the outer Reed-Solomon codes, this bit-flipping decoder can improve the decoding performance and reduce the decoding complexity compared to the previously proposed sequential decoding. The bit-flipping decoder achieves a decoding performance similar to a maximum likelihood decoder for the inner codes.
This work proposes a construction for low-density parity-check (LDPC) codes over finite Gaussian integer fields. Furthermore, a new channel model for codes over Gaussian integers is introduced and its channel capacity is derived. This channel can be considered as a first order approximation of the additive white Gaussian noise channel with hard decision detection where only errors to nearest neighbors in the signal constellation are considered. For this channel, the proposed LDPC codes can be decoded with a simple non-probabilistic iterative decoding algorithm similar to Gallager's decoding algorithm A.
Digitale Signaturen zum Überprüfen der Integrität von Daten, beispielsweise von Software-Updates, gewinnen zunehmend an Bedeutung. Im Bereich der eingebetteten Systeme kommen derzeit wegen der geringen Komplexität noch überwiegend symmetri-sche Verschlüsselungsverfahren zur Berechnung eines Authentifizierungscodes zum Einsatz. Asym-metrische Kryptosysteme sind rechenaufwendiger, bieten aber mehr Sicherheit, weil der Schlüssel zur Authentifizierung nicht geheim gehalten werden muss. Asymmetrische Signaturverfahren werden typischerweise zweistufig berechnet. Der Schlüssel wird nicht direkt auf die Daten angewendet, sondern auf deren Hash-Wert, der mit Hilfe einer Hash-funktion zuvor berechnet wurde. Zum Einsatz dieser Verfahren in eingebetteten Systemen ist es erforder-lich, dass die Hashfunktion einen hinreichend gro-ßen Datendurchsatz ermöglicht. In diesem Beitrag wird eine effiziente Hardware-Implementierung der SHA-256 Hashfunktion vorgestellt.
Comparison and Identifiability Analysis of Friction Models for the Dither Motion of a Solenoid
(2018)
In this paper, the mechanical subsystem of a proportional solenoid excited by a dither signal is considered. The objective is to find a suitable friction model that reflects the characteristic mechanical properties of the dynamic system. Several different friction models from the literature are compared. The friction models are evaluated with respect to their accuracy as well as their practical identifiability, the latter being quantified based on the Fisher information matrix.
This paper focuses on the multivariable control of a drawing tower process. The nature of the process together with the differences in measurement noise levels that affect the variables to be controlled motivated the development of a new MPC algorithm. An extension of a multivariable predictive control algorithm with separated prediction horizons is proposed. The obtained experimental results show the usefulness of the proposed algorithm..
This paper describes an early lumping approach for generating a mathematical model of the heating process of a moving dual-layer substrate. The heat is supplied by convection and nonlinearly distributed over the whole considered spatial extend of the substrate. Using CFD simulations as a reference, two different modelling approaches have been investigated in order to achieve the most suitable model type. It is shown that due to the possibility of using the transition matrix for time discretization, an equivalent circuit model achieves superior results when compared to the Crank-Nicolson method. In order to maintain a constant sampling time for the in-visioned-control strategies, the effect of variable speed is transformed into a system description, where the state vector has constant length but a variable number of non-zero entries. The handling of the variable transport speed during the heating process is considered as the main contribution of this work. The result is a model, suitable for being used in future control strategies.
This work introduces new signal constellations based on Eisenstein integers, i.e., the hexagonal lattice. These sets of Eisenstein integers have a cardinality which is an integer power of three. They are proposed as signal constellations for representation in the equivalent complex baseband model, especially for applications like physical-layer network coding or MIMO transmission where the constellation is required to be a subset of a lattice. It is shown that these constellations form additive groups where the addition over the complex plane corresponds to the addition with carry over ternary Galois fields. A ternary set partitioning is derived that enables multilevel coding based on ternary error-correcting codes. In the subsets, this partitioning achieves a gain of 4.77 dB, which results from an increased minimum squared Euclidean distance of the signal points. Furthermore, the constellation-constrained capacities over the AWGN channel and the related level capacities in case of ternary multilevel coding are investigated. Simulation results for multilevel coding based on ternary LDPC codes are presented which show that a performance close to the constellation-constrained capacities can be achieved.
The computational complexity of the optimal maximum likelihood (ML) detector for spatial modulation increases rapidly as more transmit antennas or larger modulation orders are employed. Hence, ML detection may be infeasible for higher bit rates. This work proposes an improved suboptimal detection algorithm based on the Gaussian approximation method. It is demonstrated that the new method is closely related to the previously published signal vector based detection and the modified maximum ratio combiner, but can improve the detection performance compared to these methods. Furthermore, the performance of different signal constellations with suboptimal detection is investigated. Simulation results indicate that the performance loss compared to ML detection depends heavily on the signal constellation, where the recently proposed Eisenstein integer constellations are beneficial compared to classical QAM or PSK constellations.