Uwe G. Kühnapfel

Endoscopic surgery training using virtual reality and deformable tissue simulation

Abstract Surgical training systems based on virtual reality (VR) and simulation techniques for tissue deformation may represent a more cost-effective and efficient alternative to traditional training methods. Additionally, VR is a technology that can teach surgeons new procedures and can determine their level of competence before they operate on patients. At Forschungszentrum Karlsruhe (FZK), a virtual reality training system for minimally invasive surgery (MIS), based on the simulation software KISMET, has been developed. An overview of the current state of development for the “Karlsruhe Endoscopic Surgery Trainer” is presented. For quick and easy creation of surgical scenes containing deformable anatomical organ models, the spline-based modeller KisMo has been developed, which generates beside the geometry also a spatial mass–spring network of the objects for the elastodynamic simulation in KISMET. The MIS trainer provides several surgical interaction modules for deformable objects like grasping, application of clips, cutting, coagulation, injection and suturing. Additionally, it is possible to perform irrigation and suction in the operation area. Active deformable objects are used for the morphodynamic simulation of the stomach and the intestines. Furthermore, a hierarchical pulse simulation in virtual arterial vessel trees has been realized, which enables the palpation of the pulse with a force-feedback device. The pulse simulation is coupled with an arterial bleeding simulation, which gets activated by injuries of arteries and stopped by application of clips. The simulation system has been applied to minimally invasive surgery training in gynaecology and laparoscopy. Special attention is addressed to elastodynamically deformable tissue models and geometric modelling techniques for graphical real-time performance.

Data processing of high-rate low-voltage distribution grid recordings for smart grid monitoring and analysis

Power networks will change from a rigid hierarchic architecture to dynamic interconnected smart grids. In traditional power grids, the frequency is the controlled quantity to maintain supply and load power balance. Thereby, high rotating mass inertia ensures for stability. In the future, system stability will have to rely more on real-time measurements and sophisticated control, especially when integrating fluctuating renewable power sources or high-load consumers like electrical vehicles to the low-voltage distribution grid.In the present contribution, we describe a data processing network for the in-house developed low-voltage, high-rate measurement devices called electrical data recorder (EDR). These capture units are capable of sending the full high-rate acquisition data for permanent storage in a large-scale database. The EDR network is specifically designed to serve for reliable and secured transport of large data, live performance monitoring, and deep data mining. We integrate dedicated different interfaces for statistical evaluation, big data queries, comparative analysis, and data integrity tests in order to provide a wide range of useful post-processing methods for smart grid analysis.We implemented the developed EDR network architecture for high-rate measurement data processing and management at different locations in the power grid of our Institute. The system runs stable and successfully collects data since several years. The results of the implemented evaluation functionalities show the feasibility of the implemented methods for signal processing, in view of enhanced smart grid operation.

Ein Ansatz zur automatisierten Erstellung umfangreicher und komplexer Simulationsmodelle für elektrische Übertragungsnetze aus OpenStreetMap-Daten

Zusammenfassung Lastfluss-Simulationen in Stromnetzen stellen die Grundlage für regelungstechnische Analysen dar, auch und gerade für Smart Grids der Zukunft. Die Generierung und die Verwaltung von komplexen und umfangreichen Stromnetzmodellen mit Berücksichtigung variabler regionaler Modellgranularität ist eine große Herausforderung, zumal die manuelle Erstellung aufgrund der enormen Datenmenge sehr schwer durchzuführen ist. Im vorliegenden Beitrag wird ein Ansatz zur automatisierten Generierung von Stromnetzmodellen ausschließlich aus OpenStreetMap-Daten, frei verfügbaren öffentlichen und amtlichen Datenbanken sowie Geo-Webdiensten vorgestellt. Eine neue Methode zur Generierung von dynamischen Lasten basierend auf Voronoi-Geopartitionierung unter Berücksichtigung der Netztopologie wird zudem ausgearbeitet. Ein erstes, voll automatisiert erstelltes Stromnetzmodell für das Übertragungsnetz in Baden-Württemberg wird mit dynamischer Lastflusssimulation evaluiert.

One year high rate low voltage recording - Devices, methods and results

Power system management currently advances from rigid to flexible and requires highly sophisticated monitoring and control in the future. In order to contribute to a more detailed analysis and to provide a fundamental database for simulation and investigation we developed the recording device EDR (Electrical Data Recorder). Synchronized continuous high rate captures of low voltage time series are stored in a central database without any data reduction. Since more than one year we already record voltage transient information from the KIT campus power supply. We checked the device for accuracy, for reliability and developed methods for large scale data storage and for use with simulation. In this paper we present these devices and methods, as well the improvements, derived from the experiences we gathered in our studies. We conclude that the EDR provides high accuracy and precision; our data storage and retrieval methods are fast and appropriate; but available simulation tools need improvements. The system is now ready for productive use in the low voltage supply grid.

Preparing the electrical data recorder for comparative power network measurements

As the power system management currently advances from rigid to flexible, highly sophisticated monitoring and control is required in the future. By developing the Electrical Data Recorder (EDR) and preparing the device for comparative tests in low voltage power network at multiple locations we intend to contribute to a more detailed analysis and to provide a fundamental database for simulation and investigation. Using EDR devices, high rate captures of low voltage time series are acquired synchronously and are stored in a central large database without any information reduction. We performed extensive tests according to the IEC 61000-4-30 standard in order to assure the comparability of the measured values. Special attention was paid to the synchronization for achieving temporal coincidence of values measured at different locations. We developed methods for large scale data storage and interfaces for 3rd party simulation packages. In this paper we present the preparation of the device and the test procedures as well as the results. We report on the methods we already provide for data management and analysis. We conclude that the EDR provides sufficient accuracy and precision for comparative tests; our data storage and retrieval methods are fast and reliable; and we did not find 3rd party simulation tools appropriate for our needs, yet. However, the measurement system is ready for productive use in the low voltage supply grid.

A Matlab-Based Simulation Tool For The Analysis Of Unsymmetrical Power System Transients In Large Networks

This paper presents an extendable Matlab-based phasortime domain toolbox for modeling, simulation and analysis of unsymmetrical power system transients in large networks. Unlike most of the existing transient stability simulators which represent the transmission network on a per phase positive sequence basis, the new simulation function introduced in this paper is based on the symmetrical component technique which employs the three sequence networks. This representation allows consideration of network imbalances in order to include a wide range of disturbances during transient stability studies. The main aim of this paper is to describe the model details of the power system components required for unsymmetrical transients analysis and the solution methodology in the introduced simulation function. The performance of the simulation function is tested using standard IEEE test network models and the promising results are positively compared to respective results in DIgSILENT PowerFactory in terms of accuracy.

Poster Abstract: Implementation of an extended generator subsystem in OpenModelica and comparative analysis with DIgSILENT PowerFactory

Mathematical modeling is a key step in the analysis of power system stability. In view of model accuracy, this process should include all relevant details that affect the transient behavior of the power system. To this aim, an extension of the generator subsystem model is introduced in OpenModelica by adding a new turbine-governor model. Taking advantage of the multi-domain modeling property of OpenModelica, two libraries are coupled to interconnect the mechanical and electrical domains of the generator subsystem. The new generator subsystem is tested using the standard IEEE 9-Bus test feeder and the simulation results in OpenModelica are furthermore compared to respective results in DIgSILENT PowerFactory. The new generator subsystem model is integrated into the validated 20 kV power grid model of KIT-Campus North and respective results are presented for abrupt load changes.

Entwicklung eines Bewertungssystems für Virtual Reality-Simulatoren in der Chirurgie

Zusammenfassung Chirurgische Fertigkeiten im Bereich der minimal invasiven Chirurgie können an Virtual Reality-Simulatoren geübt werden. Für ein zielgerichtetes Training ist die Bewertung der Übungsausführung wichtig. Deshalb werden neue Methoden zur Entwicklung eines Bewertungssystems für die automatisierte Beurteilung von Trainierenden eingeführt. Zwei Studien haben die Eignung des neuen Konzeptes gezeigt. Abstract Currently, essential skills for minimal access surgery can be practised on a virtual reality-simulator outside the operating room. For effective training, it is important to assess the training process. Therefore, new methods are introduced to develop an assessment system for an automated evaluation of trainees. Two different studies demonstrate the quality of the new concept.