Thesis (M.S.)--Ohio University, August, 2000. / Title from PDF t.p.

This thesis addresses the path planning problem for Autonomous Underwater Vehicles (AUVs) using homotopy classes to provide topological information on how paths avoid obstacles. Looking for a path within a homotopy class constrains the search into a specific area of the search space, speeding up the computation of the path. Given a workspace with obstacles, the method starts by generating the homotopy classes. Those which probably contain lower cost solutions are determined by means of a lower bound criterion before computing a path. Finally, a path planner uses the topological information of homotopy classes to generate a few good solutions very quickly. Three path planners from different approaches have been proposed to generate paths for the homotopy classes obtained. The path planning is performed on Occupancy Grid Maps (OGMs) improved with probabilistic scan matching techniques. The results obtained with synthetic s scenarios and with real datasets show the feasibility of our method. / Aquesta tesi aborda el problema de la planificació de camins per a Vehicles Submarins Autònoms (AUVs) mitjançant la utilització de classes d'homotopia per a proporcionar informació topològica de com els camins eviten els obstacles. Calcular un camí dins d'una classe d'homotopia permet limitar l'espai de cerca accelerant-ne el càlcul de la solució. Donat un workspace amb obstacles, el mètode primer genera les classes homotòpiques. Aquelles classes que probablement contenen les solucions de menor cost s'identifiquen per mitjà d'una heurística sense haver-ne de calcular el camí al workspace. Finalment, un planificador de camins utilitza la informació topològica de les classes d'homotopia per generar solucions segons les classes seleccionades molt ràpidament. El mètode de planificació de camins s’aplica sobre Mapes d’Occupació de Graella (OGMs) millorats amb tècniques de scan matching probabilístic. Els tests i resultats obtinguts tan en escenaris sintètics com en datasets reals mostren la viabilitat del nostre mètode.

Zielsetzung dieser Arbeit ist die Vorstellung des klinischen Aufbaus und des Arbeitsablaufs eines robotischen Assistenzsystems für bildgeführte Interventionen in einem konventionellen Magnetresonanztomographen (MRT), sowie die Beurteilung der Genauigkeit und der klinischen Erfahrungen bei perkutanen Biopsien in verschieden Körperregionen. Material und Methoden: Das MR- kompatible, servopneumatische robotische Assistenzsystem lässt sich mit dem Patienten in die 60- cm Gantry eines Standard- MR- Scanners fahren. Die Genauigkeit des Systems wurde anhand von Nadelpunktionen (n= 25) in einem Phantommodell ermittelt. Perkutane diagnostische Biopsien wurden bei sechs Patienten durchgeführt. Ergebnisse: Für eine Interventionstiefe zwischen 29 und 95 mm wurde eine 3-DGenauigkeit von 2,2 +/- 0,7 mm (Intervall 0,9- 3,8 mm) bestimmt. Patienten mit einem BMI bis zu ≈30 kg/m2 konnten mit dem System punktiert werden. Die klinischen Arbeitsschritte werden anhand der Fallbeispiele dargestellt. Die mittlere Interventionszeit betrug 44 Minuten (Intervall 36 – 68 Minuten). Zusammenfassung: Die Punktion verschiedener Körperregionen ist mit Hilfe des robotischen Assistenzsystems in einem geschlossenen MRT erfolgreich und sicher möglich. Die Genauigkeit des Systems ist vergleichbar mit anderen Assistenzsystemen in der Literatur und genügt den klinischen Anforderungen. Eine kürzere Interventionszeit ist mittels einer Optimierung der einzelnen Arbeitsschritte möglich.:Einleitung 1 Publikation 5 Titelseite mit Abstract 6 Einleitung Publikation (Introduction) 7 Material und Methoden (Materials and Methods) 8 Robotisches Assistenzsystem (Robotic Assistance System) 8 Phantommessung (Phantom Experiment) 9 Patientenauswahlkriterien (Patient Selection Criteria) 11 Magnetresonanztomographie (MRI) 11 Biopsiedurchführung (Biopsy Procedure) 12 Ergebnisse (Results) 13 Phantommessung (Phantom Experiment) 13 Klinische Fälle (Clinical Experience) 14 Weichteilbiopsie kleines Becken (Soft-Tissue Biopsy in the Lesser Pelvis) 14 Weichteilbiopsie iliakaler Lymphknoten (Soft-Tissue Biopsy in Iliac Lymph Node) 15 Knochenbiopsie rechtes Femur (Bone Biopsy in Right Femur) 16 Knochenbiopsie Beckenkamm (Bone Biopsy in Iliac Crest) 17 Abszessaspiration (Abscess Aspiration) 18 Weichteilbiopsie Leber (Soft-Tissue Biopsy in the Liver) 19 Diskussion (Discussion) 22 Danksagungen (Acknowledgments) 25 Literaturverzeichnis Publikation (References) 25 Interpretation und Bewertung 30 Zusammenfassung 35 Literaturverzeichnis 39 Tabellenverzeichnis 46 Abbildungsverzeichnis 46 Erklärung über die eigenständige Abfassung der Arbeit 47 Lebenslauf und wissenschaftlicher Werdegang 48 Danksagung 49 Anlagen Anlage 1 Aufklärungsbogen zur Studie 50 Anlage 2 Einverständniserklärung 54 Anlage 3 Zertifikat des Assistenzsystems 57 durch TÜV- Süd

This thesis proposes and evaluates a new cooperative guidance law called General Vector Explicit - Impact Time and Angle Control Guidance (GENEX-ITACG). The motivation for GENEX-ITACG came from an explicit trajectory shaping guidance law called General Vector Explicit Guidance (GENEX). GENEX simultaneously achieves design specifications on miss distance and terminal missile approach angle while also providing a design parameter that adjusts the aggressiveness of this approach angle. Encouraged by the applicability of this user parameter, GENEX-ITACG is an extension that allows a salvo of missiles to cooperatively achieve the same objectives of GENEX against a stationary target through the incorporation of a cooperative trajectory shaping guidance law called Impact Time and Angle Control Guidance (ITACG). ITACG allows a salvo of missile to simultaneously hit a stationary target at a prescribed impact angle and impact time. This predetermined impact time is what allows each missile involved in the salvo attack to simultaneously arrived at the target with unique approach angles, which greatly increases the probability of success against well defended targets. GENEX-ITACG further increases this probability of kill by allowing each missile to approach the target with a unique approach angle rate through the use of a user design parameter. The incorporation of ITACG into GENEX is accomplished through the use of linear optimal control by casting the cost function of GENEX into the formulation of ITACG. The feasibility GENEXITACG is demonstrated across three scenarios that demonstrate the ITACG portion of the guidance law, the GENEX portion of the guidance law, and finally the entirety of the guidance law. The results indicate that GENEX-ITACG is able to successfully guide a salvo of missiles to simultaneously hit a stationary target at a predefined terminal impact angle and impact time, while also allowing the user to adjust the aggressiveness of approach.

Thesis (M.S.)-- Air Force Institute of Technology. / The original document contains color images.

Guidance is defined as the determination of a strategy for following a nominal path in the presence of o-nominal conditions, disturbances and uncertainties, and the strategy employed is called a guidance law. Variants of Proportional Navigation (PN), such as True Proportional Navigation (TPN) and Pure Proportional Navigation (PPN), have been studied extensively in the literature on tactical missile guidance. In the absence of target maneuvers, in a linear interceptor guidance problem, TPN was shown to be optimal. However, the standard PN class of guidance laws per se does not show good performance against maneuvering targets, and was found to be eective in intercepting a maneuvering target only from a restrictive set of initial geometries. Also, since these guidance laws were eectively designed for lower speed targets, they show a degraded performance when applied against higher speed targets. However, in the current defense scenario, two classes of agile targets, which are capable of continuous maneuver, and/or of much higher speed than the interceptor, are a reality. This thesis presents analysis of several variants of PN class of guidance laws against these two classes of agile targets. In the literature, an augmentation of the TPN guidance law, termed as Augmented Proportional Navigation (APN), was shown to be optimal in linearized engagement framework. The present work proposes an augmentation of the PPN guidance law, which is more realistic than TPN for an aerodynamically controlled interceptor, and an-alyzes its capturability in fully nonlinear framework, and develops sauciest conditions on speed ratio, navigation gain and augmentation parameter to ensure that all possible initial engagement geometries are included in the capture zone when applied against a target executing piecewise continuous maneuver. The thesis also obtains the capture zone in the relative velocity space for augmented PPN guidance law. In the literature, a novel guidance law was proposed for the interception of higher speed targets in planar engagement by using a negative navigation gain instead of the standard positive one, and was termed as Retro-PN. It was shown that even though the Retro-PN guided interceptor takes more time than PN guided one in achieving successful interception, Retro-PN performs significantly better than the classical PN law, in terms of capturability, lateral acceleration demand, and closing velocity, when used against higher speed targets. The thesis analyzes Retro-PN guidance law in 3-D engagement geometries to yield the complete capture zone of interceptors guided by Retro-PN guidance philosophy, and derives necessary and sucient conditions for the capture of higher speed non-maneuvering targets with and without a constraint on finiteness of lateral acceleration. Terminal impact angle control is crucial for enhancement of warhead eectiveness. In the literature, this problem has been addressed mostly in the context of targets with lower speeds than the interceptor. The thesis analyzes the performance of a composite PN guidance law, that uses standard PPN and the Retro-PN guidance laws based on initial engagement geometry and requirement of impact angle, against higher speed non-maneuvering targets. Then, to expand the set of achievable impact angles, it proposes a modified composite PN guidance scheme, and analyzes the same. For implementation of many modern guidance laws, a good estimate of time-to-go is essential. This requirement is especially severe in case of impact time constrained en-gagement scenarios. To this end, an ecient and fast time-to-go estimation algorithm for generic 3-D engagement is required. Two time-to-go estimation algorithms are presented and analyzed in this work for the engagement of a PPN or Retro-PN guided interceptor and a higher speed target. The first one is a closed form approximation of time-to-go in terms of range, nominal closing speed and an indicator of heading error, and the second one is a numerical recursive time-to-go estimation algorithm. To improve the odds of intercepting an intelligent target and destroying it, a salvo attack of two or more interceptors could be considered as a viable option. Moreover, this simultaneous salvo attack can also be further improved in eciency by incorporating the shoot-look-shoot approach in making a decision about launching interceptors. This can be considered as the first step towards a layered defense system, which has been described in the literature as a potentially eective strategy against short range or long range ballistic threat. To this end, the present work proposes two PPN and Retro-PN based guidance strategies for achieving simultaneous salvo attack on a higher speed non-maneuvering target. For the implementation of the same the numerical recursive time-to-go estimation technique proposed in this work is utilized