Title page for ETD etd-02092007-152020

Type of Document Dissertation
Author Gadre, Aditya Shrikant
Author's Email Address agadre@vt.edu
URN etd-02092007-152020
Title Observability Analysis in Navigation Systems with an Underwater Vehicle Application
Degree PhD
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Stilwell, Daniel J. Committee Chair
Kachroo, Pushkin Committee Member
Reed, Jeffrey Hugh Committee Member
Saunders, William R. Committee Member
Woolsey, Craig A. Committee Member
  • Autonomous Underwater Vehicles
  • Underwater Range Navigation
  • Uniform Observability
  • Finite-time Uniform Observability
  • Limiting Systems
Date of Defense 2007-01-26
Availability unrestricted
Precise navigation of autonomous underwater vehicles (AUV) is one of the most important challenges in the realization of distributed and cooperative algorithms for marine applications. We investigate an underwater navigation technology that enables an AUV to compute its trajectory in the presence of unknown currents in real time and simultaneously estimate the currents, using range or distance measurements from a single known location. This approach is potentially useful for small AUVs which have severe volume and power constraints.

The main contribution of this work is observability analysis of the proposed navigation system using novel approaches towards uniform observability of linear time-varying (LTV) systems. We utilize the notion of limiting systems in order to address uniform observability of LTV systems. Uniform observability of an LTV system can be studied by assessing finite time observability of its limiting systems. A new definition of uniform observability over a finite interval is introduced in order to address existence of an observer whose estimation error is bounded by an exponentially decaying function on the finite interval. We also show that for a class of LTV systems, uniform observability of a lower dimensional subsystem derived from an LTV system is sufficient for uniform observability of the LTV system.

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