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- Nicholas R. Fischer, Rushikesh Kamalapurkar, Warren E. Dixon
- IEEE Trans. Automat. Contr.
- 2013

- Nicholas R. Fischer, Zhen Kan, Rushikesh Kamalapurkar, Warren E. Dixon
- IEEE Trans. Automat. Contr.
- 2014

A saturated controller is developed for a class of uncertain, second-order, nonlinear systems which includes time-varying and nonlinearly parameterized functions with bounded disturbances using a continuous control law with smooth saturation functions. Based on the robust integral of the sign of the error (RISE) control methodology, the developed controller… (More)

- Ashwin P. Dani, Nicholas R. Fischer, Warren E. Dixon
- IEEE Trans. Automat. Contr.
- 2012

A reduced order nonlinear observer is proposed for the problem of “structure and motion (SaM)” estimation of a stationary object observed by a moving calibrated camera. In comparison to existing work which requires some knowledge of the Euclidean geometry of an observed object or full knowledge of the camera motion, the developed reduced order observer only… (More)

Autonomous and remotely operated marine vehicles such as ships and submarines are becoming a key component in several aspects of maritime industry and defense. This paper explores the development of a nonlinear controller for a fully actuated autonomous underwater vehicle (AUV) using a robust integral of the sign of the error (RISE) feedback term with a… (More)

A reduced-order nonlinear observer is developed to estimate the distance from a moving camera to a feature point on a static object (i.e., range identification), where full velocity and linear acceleration feedback of the calibrated camera is provided. The contribution of this work is to develop a global exponential range observer which can be used for a… (More)

- Nicholas R. Fischer, Devin Hughes, Patrick Walters, Eric M. Schwartz, Warren E. Dixon
- IEEE Transactions on Robotics
- 2014

This study focuses on the development of a nonlinear control design for a fully-actuated autonomous underwater vehicle (AUV) using a continuous robust integral of the sign of the error control structure to compensate for system uncertainties and sufficiently smooth bounded exogenous disturbances. A Lyapunov stability analysis is included to prove semiglobal… (More)

- Nicholas R. Fischer, L Pinggera, Viktor Weichbold, D Dejaco, Joachim Schmutzhard, G. Widmann
- AJNR. American journal of neuroradiology
- 2015

BACKGROUND AND PURPOSE
Localization of the electrode after cochlear implantation seems to have an impact on auditory outcome, and conebeam CT has emerged as a reliable method for visualizing the electrode array position within the cochlea. The aim of this retrospective study was to evaluate the frequency and clinical impact of scalar dislocation of various… (More)

- Ashwin P. Dani, Zhen Kan, Nicholas R. Fischer, Warren E. Dixon
- CDC-ECE
- 2011

A state observer is designed for estimating the structure of a moving object with time-varying velocities seen by a moving camera. A nonlinear unknown input observer strategy is used where the object’s velocity is considered as an unknown input to the perspective dynamical system. The object is assumed to be moving on a ground plane. The downward-looking… (More)