Large animal lightning accidents - determining possible injury mechanisms by simulations :
Großtier-Blitzunfälle - Ermittlung möglicher Schädigungsmechanismen durch Simulationen. - In: 14. VDE Blitzschutztagung, (2021), S. 136-142
Modulation-function-based finite-horizon sensor fault detection for salient-pole PMSM using parity-space residuals. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 7, S. 61-66
An online model-based fault detection and isolation method for salient-pole permanent magnet synchronous motors over a finite horizon is proposed. The proposed approach combines parity-space-based residual generation and modulation-function-based filtering. Given the polynomial model equations, the unknown variables (i.e. the states, unmeasured inputs) are eliminated resulting in analytic redundancy relations used for residual generation. Furthermore, in order to avoid needing the derivatives of measured signals required by such analytic redundancy relations, a modulation-function-based evaluation is proposed. This results in a finite-horizon filtered version of the original residual. The fault detection and isolation method is demonstrated using simulation of various fault scenarios for a speed controlled salient motor showing the effectiveness of the presented approach.
https://doi.org/10.1016/j.ifacol.2021.08.335
Modulating function based fault diagnosis using the parity space method. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 7, S. 268-273
A model-based method for the detection and estimation of faults in dynamic systems is proposed. The method is based on the combination of the parity space approach and the modulating function framework for estimation. The parity space method is employed as an efficient geometric procedure determining null subspaces for annihilating unknown terms and formulating residuals. With the modulating functions technique the dynamic relation from output differentiation is reformulated as an algebraic expression. This substantially reduces the noise sensitivity of the output derivatives required. The design allows for the robust fault detection and isolation also for some nonlinear systems. The robustness of the approach is demonstrated on a nonlinear model of a four-tank process.
https://doi.org/10.1016/j.ifacol.2021.08.370
Long-term dependency slow feature analysis for dynamic process monitoring. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 3, S. 421-426
Industrial processes are large scale, highly complex systems. The complex flow of mass and energy, as well as the compensation effects of closed-loop control systems, cause significance cross-correlation and autocorrelation between process variables. To operate the process systems stably and efficiently, it is crucial to uncover the inherent characteristics of both variance structure and dynamic relationship. Long-term dependency slow feature analysis (LTSFA) is proposed in this paper to overcome the Markov assumption of the original slow feature analysis to understand the long-term dynamics of processes, based on which a monitoring procedure is designed. A simulation example and the Tennessee Eastman process benchmark are studied to show the performance of LTSFA. The proposed method can better extract the system dynamics and monitor the process variations using fewer slow features.
https://doi.org/10.1016/j.ifacol.2021.08.278
A novel attitude representation in view of spacecraft attitude reconstruction using temperature data. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 14, S. 500-505
There are various different attitude representations that describe the orientation of a rigid body in space and allow the transformation between different coordinate systems. Among others, they differ in number of variables, uniqueness of the representation and their continuity. However, in spite of some of them being based on angles, none of them constitutes a simple representation of an angle between two arbitrary vectors. We tackle this issue by proposing a novel attitude representation that directly incorporates the desired angle. The usefulness of this representation is demonstrated in the attitude reconstruction from temperature data, which then leads to an order reduction of a non-linear system.
https://doi.org/10.1016/j.ifacol.2021.10.404
Dynamic extension for adaptive backstepping control of uncertain pure-feedback systems. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 14, S. 307-312
An adaptive backstepping algorithm is developed for a class of uncertain systems in pure-feedback form. The control is based on a dynamic state feedback that allows to compensate for parametric uncertainties which enter linearly into the system. As possible in the nominal case, a dynamic extension of just order one is required, in addition to the dynamics of the identifiers for the adaptation. The regularity of the control law only requires standard assumptions.
https://doi.org/10.1016/j.ifacol.2021.10.371
Energy shaping and partial feedback linearization of mechanical systems with kinematic constraints. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 19, S. 243-248
Traditionally, the energy shaping for mechanical systems requires the elimination of holonomic and nonholonomic constraints. In recent years, it was argued that such elimination might be unnecessary, leading to a possible simplification of the matching conditions in energy shaping. On the other hand, the partial feedback linearization (PFL) approach has been widely applied to unconstrained mechanical systems, but there is no general result for the constrained case. In this regard, this paper formalizes the PFL for mechanical systems with kinematic constraints and extends the energy shaping of such systems by including systems with singular inertia matrix and non-workless constraint forces, which can arise from the coordinate selection and PFL. We validated the proposed methodology on a 5-DoF portal crane via simulation.
https://doi.org/10.1016/j.ifacol.2021.11.085
Direct current stimulation of the entire visual pathway does not affect the full field electroretinogram. - In: Brain stimulation, ISSN 1876-4754, Bd. 14 (2021), 6, S. 1674-1675
https://doi.org/10.1016/j.brs.2021.10.274
Quantitative robustness analysis of model following control for nonlinear systems subject to model uncertainties. - In: IFAC-PapersOnLine, ISSN 2405-8963, Bd. 54 (2021), 14, S. 167-172
We investigate a model following control (MFC) design for nonlinear minimumphase systems subject to model uncertainties. The model following control architecture is a two degrees-of-freedom structure consisting of two control loops. The model control loop (MCL) includes a nominal model of the process. The design of the process control loop (PCL) is based on the error system resulting from the nominal design and the actual process. Both control loops are designed using (partial) feedback linearisation. We analyse the robustness in view of the norm of the uncertainty and the region of attraction compared to a single-loop (partial) feedback linearisation control. It turns out that the proposed approach is able to stabilize significantly larger uncertainties, shows better tracking performance, and exhibits a larger region of attraction (based on a quadratic Lyapunov function).
https://doi.org/10.1016/j.ifacol.2021.10.347
What is in the KGQA benchmark datasets? Survey on challenges in datasets for question answering on knowledge graphs. - In: Journal on data semantics, ISSN 1861-2040, Bd. 10 (2021), 3/4, S. 241-265
Question Answering based on Knowledge Graphs (KGQA) still faces difficult challenges when transforming natural language (NL) to SPARQL queries. Simple questions only referring to one triple are answerable by most QA systems, but more complex questions requiring complex queries containing subqueries or several functions are still a tough challenge within this field of research. Evaluation results of QA systems therefore also might depend on the benchmark dataset the system has been tested on. For the purpose to give an overview and reveal specific characteristics, we examined currently available KGQA datasets regarding several challenging aspects. This paper presents a detailed look into the datasets and compares them in terms of challenges a KGQA system is facing.
https://doi.org/10.1007/s13740-021-00128-9