Control Design for Interval Type-2 Fuzzy Systems Under Imperfect Premise Matching

Abstract—This paper focuses on designing interval type-2 (IT2) control for nonlinear systems subject to parameter uncertainties. To facilitate the stability analysis and control synthesis, an IT2 TS fuzzy model is employed to represent the dynamics of nonlinear systems of which the parameter uncertainties are captured by IT2 membership functions characterized by the lower and upper membership functions. A novel IT2 fuzzy controller is proposed to perform the control process, where the membership functions and number of rules can be freely chosen and different from those of the IT2 T-S fuzzy model. Consequently, the IT2 fuzzymodel- based (FMB) control system is with imperfectly matched membership functions, which hinders the stability analysis. To relax the stability analysis for this class of IT2 FMB control systems, the information of footprint of uncertainties, and the lower and upper membership functions are taken into account for the stability analysis. Based on the Lyapunov stability theory, some stability conditions in terms of linear matrix inequalities are obtained to determine the system stability and achieve the control design. Finally, simulation and experimental examples are provided to demonstrate the effectiveness and the merit of the proposed approach

Accurate Bolt Tightening using Model-Free Fuzzy Control for Wind Turbine Hub Bearing Assembly

"In the modern wind turbine industry, one of the core processes is the assembly of the bolt-nut connections of the hub, which requires tightening bolts and nuts to obtain well-distributed clamping force all over the hub. This force deals with nonlinear uncertainties due to the mechanical properties and it depends on the final torque and relative angular position of the bolt/nut connection. This paper handles the control problem of automated bolt tightening processes. To develop a controller, the process is divided into four stages, according to the mechanical characteristics of the bolt/nut connection: a Fuzzy Logic Controller (FLC) with expert knowledge of tightening process and error detection capability is proposed. For each one of the four stages, an individual FLC is designed to address the highly non-linearity of the system and the error scenarios related to that stage, to promptly prevent and avoid mechanical damage. The FLC is implemented and real time executed on an industrial PC and finally validated. Experimental results show the performance of the controller to reach precise torque and angle levels as well as desired clamping force. The capability of error detection is also validated.

Aerodynamic and Aeroacoustic Performance of Small UAV Propellers in Static Conditions

The proliferation of small multi-rotor UAVs in commercial, recreational, and surveillance spheres has garnered significant interest in the noise produced by these vehicles. The current research aims to study the relationship between the aerodynamic performance and acoustic characteristics of small-scale UAV propellers. Three commercially available propellers for the DJI Phantom 2/3 UAV were selected for preliminary development and validation of an aeroacoustic experimental test setup and associated data reduction methods. Propeller thrust, torque, and power measurements were recorded at static conditions. Upon successful validation of the test bench, acoustic measurements were taken at the propeller disk’s upstream and in-plane locations. The power spectral density of these acoustic signals was estimated using the modified periodogram (Welch’s) method to identify frequency content and calculate sound pressure levels (SPLs) at each of the observation locations. Additionally, time-frequency analysis verified the periodogram results and identified possible sources of transient noise at static thrust. These methods found the nonrotor noise to be a major contributor to the SPL at higher frequencies and the propeller noise dominating the SPL spectra at the lower frequencies. Experimental thrust, torque, power, and sound pressure level (SPL) data were then compared for each propeller to identify relationships between aerodynamic performance and acoustic characteristics with variations in propeller geometry and blade loading

Perspektive zur Höherauslastung des Verteilernetzes mit Gleichstrom (DC): (Stand: 28.03.2023)

Die klimapolitisch bedingte Transformation des elektrischen Energiesystems, bei gleichzeitiger Elektrifizierung sämtlicher Sektoren, führt zu einem deutlich gesteigertem Bedarf an Verteilnetzkapazitäten. Der Ausbau der elektrischen Infrastruktur kann jedoch nicht zuletzt aufgrund komplizierter und verzögerter Genehmigungsverfahren mit dem Integrationstempo neuer Erzeuger und Lasten mithalten. Eine Höherauslastung der Bestandsnetze könnte eine zusätzliche schnell umsetzbare Abhilfe bieten, um den Netzausbaubedarf zu reduzieren oder zeitlich in die Zukunft zu verlagern. Dabei bietet vor allem die Gleichstromtechnologie vielseitige und vielversprechende Lösungsansätze zur Höherauslastung von Verteilnetzen. Dieses Positionspapier gibt einen Überblick über technologische und methodische Ansätze zur Höherauslastung von Bestandsnetzen mit dem Fokus auf der Gleichstromtechnologie. Dabei werden wesentliche betriebliche und physikalische Vorteile der Gleichstromtechnik erläutert und in zwei exemplarischen Fallstudien demonstriert. Dadurch wird der Einsatz der Gleichstromtechnologie als sinnvolle Ergänzung zum herkömmlichen Verteilnetzausbau nachgewiesen

On Security Guidelines and Policy Compliance: Considering Users’ Need for Autonomy

Recent studies raise the concern that the regular communication of security guidelines and policies and their updates is not always the best option for organizations to protect information system\u27s security. Users show symptoms of being frustrated or overwhelmed by security guidelines and consequently either ignore policies or actively pursue workarounds. Our aim is first, to understand the affective states of employees being confronted with security-related guidelines and the reasons for negative emotions. Second, we develop a communication strategy for security policies that avoids negative affective states and reduces the chance of security policies being ignored or worked around to foster compliance. In this paper, we introduce a framework by connecting the theories of security fatigue, psychological reactance, and the elaboration likelihood model. Our framework moreover considers different strategies to communicate security guidelines or policies. Finally, we draft an experimental setup to empirically evaluate our research model

Fusing biomedical multi-modal data for exploratory data analysis

Martin C, Deters H grosse, Nattkemper TW. Fusing biomedical multi-modal data for exploratory data analysis. In: Kollias S, ed. ARTIFICIAL NEURAL NETWORKS - ICANN 2006, PT 2. Vol 4132. Berlin, Heidelberg: SPRINGER-VERLAG BERLIN; 2006: 798-807.Data analysis in modern biomedical research has to integrate data from different sources, like microarray, clinical and categorical data, so called multi-modal data. The reef SOM, a metaphoric display, is applied and further improved such that it allows the simultaneous display of biomedical multi-modal data for an exploratory analysis. Visualizations of microarray, clinical, and category data are combined in one informative and entertaining image. The U-matrix of the SOM trained on microarray data is visualized as an underwater sea bed using color and texture. The clinical data and category data are integrated in the form of fish shaped glyphs. The resulting images are intuitive, entertaining and can easily be interpreted by the biomedical collaborator, since specific knowledge about the SOM algorithm is not required. Visual inspection enables the detection of interesting structural patterns in the multi-modal data when browsing through and zooming into the image. Results of such an analysis are presented for the van't Veer data set

Model-Based Self-Tuning PI Control of Bolt-Nut Tightening for Wind Turbine Bearing Assembly

"One of the core steps of the assembly of wind turbines is the assembly of the bearings on the wind turbine hub. The hub can contain up to 128 bolt connections to install the bearing blades: nuts need to be precisely tightened to ensure a uniformly distributed clamping force as well as avoiding assembly errors, e.g. nut misalignments. The bolt-nut connection is a non-linear system with uncertainties making it difficult to design a numerical model and PI Gains. This paper presents a novel two-stage Proportional-Integral (PI) controller with assembly error detection capability for bolt tightening process. It is based on the combination of a numerical model (offline training) and a genetic algorithm (GA) for online training on the physical bolt system. Since the model does not include all non-linearity and uncertainties of the physical plant (here the bolt-nut connection), it is used at first to estimate the range of the PI values; followed by a fine tuning of the values online by the GA.