No abstract

Wireless capsule endoscopy (WCE) is a powerful tool for medical screening and diagnosis, where a small capsule is swallowed and moved by means of natural peristalsis and gravity through the human gastrointestinal (GI) tract. The camera-integrated capsule allows for visualization of the small intestine, a region which was previously inaccessible to classical flexible endoscopy. As a diagnostic tool, it allows to localize the sources of bleedings in the middle part of the gastrointestinal tract and to identify diseases, such as inflammatory bowel disease (Crohn's disease), polyposis syndrome, and tumors. The screening and diagnostic efficacy of the WCE, especially in the stomach region, is hampered by a variety of technical challenges like the lack of active capsular position and orientation control. Therapeutic functionality is absent in most commercial capsules, due to constraints in capsular volume and energy storage. The possibility of using body-exogenous magnetic fields to guide, orient, power, and operate the capsule and its mechanisms has led to increasing research in Magnetically Guided Capsule Endoscopy (MGCE). This work shortly reviews the history and state-of-art in WCE technology. It highlights the magnetic technologies for advancing diagnostic and therapeutic functionalities of WCE. Not restricting itself to the GI tract, the review further investigates the technological developments in magnetically guided microrobots that can navigate through the various air-and fluid-filled lumina and cavities in the body for minimally invasive medicine.

The use of flexible endoscopes is the standard screening method for the upper gastrointestinal tract today. Disadvantages for the patient, due to the insertion process and often applied sedation, can be overcome with wireless capsule endoscopy (WCE). But WCE is not suited for the stomach as it can not guarantee a complete screening having no active guidance. With the magnetically guided capsule endoscopy (MGCE) a novel minimal invasive screening method for the gastrointestinal tract is being developed. With its current focus on the human stomach comes the need for a navigation and control method that is specialized for this application and its constraints. We present a new method for screening a waterfilled stomach with 10 functions for basic capsule movements, special maneuvers and mode-changes. Its evaluation was done in a clinical study consisting of 53 patient and volunteer cases. The individual evaluation of each function included a statistical analysis and an operators' survey. The functions proved sufficient to reach all parts of the stomach and to acquire close-up views of the mucosa.

No abstract

mittels Transformation auf ,,Nichtlineare Beobachternormalform" stellt eine geradlinige Verallgemeinerung des aus der linearen Theorie bekannten Luenberger-Beobachter-Verfahrens auf den nichtlinearen, zeitvarianten Fall dar: Der Beobachter wird in den transformierten Zuslatulsvariablen derart angesetzt, daß eine lineare, zeitinvariante, homogene Fehlerdifferentialgleichung resultiert, der mittels Polvorgabe ein gewünschtes Zeitverhalten aufgeprägt werden kann. Der Entwurf wird in zwei Schritten durchgeführt und erfordert keine Linearisierung, ist allerdings auf eine gewisse Klasse nicht linearer, zeitvarianter Systeme beschränkt.The observer design by transformation into the ,,Nonlinear Observer Canonical Form" comprises a straightforward generalization of the Luenberger-observer-method, as it is known from linear systems, to the nonlinear time-variant case: The observer is set up in the transformed state-variables in such a manner that a linear time-invariant homogeneous differential equation of the observer-error results, for which a desired time-response can be prescribed by poleassignment. The design is carried out in two steps and requires no linearization but is restricted to a certain class of nonlinear time-variant systems.

No abstract

No abstract

No abstract