Tamer Inanc

Optimal trajectory generation in ocean flows

In this paper it is shown that Lagrangian Coherent Structures (LCS) are useful in determining near optimal trajectories for autonomous underwater gliders in a dynamic ocean environment. This opens the opportunity for optimal path planning of autonomous underwater vehicles by studying the global flow geometry via dynamical systems methods. Optimal glider paths were computed for a 2-dimensionaI kinematic model of an end-point glider problem. Numerical solutions to the optimal control problem were obtained using Nonlinear Trajectory Generation (NTG) software. The resulting solution is compared to corresponding results on LCS obtained using the Direct Lyapunov Exponent method. The velocity data used for these computations was obtained from measurements taken in August, 2000, by HF-Radar stations located around Monterey Bay, CA, USA.

Mixed Time/Frequency-Domain Based Robust Identification

In this paper we propose a new robust identification framework that combines both frequency and time-domain experimental data. The main result of the paper shows that the problem of obtaining a nominal model consistent with the experimental data and bounds on the identification error can be recast as a constrained finite-dimensional convex optimization problem that can be efficiently solved using Linear Matrix Inequalities techniques. This approach, based upon a generalized interpolation theory, contains as special cases the Caratheodory-Fejer (purely time-domain) and Nevanlinna- Pick (purely frequency-domain) problems. The proposed procedure interpolates the frequency and time domain experimental data while restricting the identified system to be in an a priori given class of models, resulting in a nominal model consistent with both sources of data. Thus, it is convergent and optimal up to a factor of two (with respect to central algorithms).

An LMI approach to control oriented identification of LPV systems

This paper proposes a control oriented identification framework for a class of linear parameter-varying (LPV) systems, that takes into account both the dependence of part of the model on time-varying parameters as well as the possible existence of a nonparametric component. The main result of the paper shows that the problems of establishing consistency of the data and of obtaining a nominal model for these systems can be recast as a linear matrix inequality feasibility problem that can be efficiently solved. These results are illustrated with a practical example arising in the context of active vision.

An Autonomous Mobile Robotics Testbed: Construction, Validation, and Experiments

This paper describes design and construction of an Autonomous Mobile Robotics Systems Testbed in detail. The testbed is an indoor experimental platform for developing and validating theoretical as well as practical research work in identification, coordinative and cooperative control, trajectory generation, computational intelligence, and sensing for multiple autonomous mobile robotics systems. It provides a designated space for multiple mobile robots while tracking their position and orientation in real-time using an overhead vision system. Several problems encountered in developing the testbed such as multi-camera color consistency, radial lens distortion, hat pattern design are clearly addressed. The testbed is analyzed for its performance and several experiments with ER1 mobile robots are presented.

H/sub 2/ control with time-domain constraints: theory and an application

In this paper, we study the problem of minimizing the H/sub 2/ norm of a given transfer function subject to time-domain constraints on the time response of a different transfer function to a given test signal. The main result of this paper shows that this problem admits a minimizing solution in R~H~/sub 2/. Moreover, rational solutions with performance arbitrarily close to optimal can be found by constructing families of approximating problems. Each one of these problems entails solving a finite-dimensional quadratic programming problem whose dimension can be determined before hand. These results are illustrated and experimentally validated by designing a controller for an active vision application.

A new approach to unwrap a 3-D fingerprint to a 2-D rolled equivalent fingerprint

For many years, fingerprints have been captured by pressing a finger against a paper or hard surface. This touch-based fingerprint acquisition introduces some problems such as distortions and deformations in the acquired images, which arise due to the contact of the fingerprint surface with the sensor platen, and degrades the recognition performance. A new touch-less fingerprint technology has been recently introduced to the market, which can address the problems with the contact-based fingerprint systems. In this paper, we propose a new algorithm for unwrapping the acquired 3-D scan of the subjects finger into a 2-D rolled equivalent image. Therefore, The resulting image can be matched with the conventional 2-D scans; it also can be used for matching unwrapped 3-D fingerprints among themselves with the 2-D fingerprint matching algorithms. The algorithm is based on curvature analysis of the 3-D surface. The quality of the resulting image is evaluated and analyzed using NIST fingerprint image software.

Robust controller design for active vision systems

Recent hardware developments have rendered controlled active vision a viable option for a broad range of problems, spanning applications as diverse as intelligent vehicle highway systems, MEMS microassembly and assisting individuals with disabilities. However, realizing this potential requires having a framework for synthesizing robust active vision systems, capable of moving beyond carefully controlled environments. In this paper we show how recently developed robust identification and control synthesis techniques can be brought to bear on the problem. These results are experimentally validated using a Bisight robotic head.

Fast Structured Nuclear Norm Minimization With Applications to Set Membership Systems Identification

Set membership identification seeks to obtain models amenable to be used in a robust control framework. While under suitable assumptions this problem is convex, existing methods lead to high order models. As we show in this note, this difficulty can be avoided by recasting the problem as a structured nuclear norm minimization. To solve this problem, we propose a computationally efficient first order algorithm that requires performing only a combination of thresholding and eigenvalue decomposition steps. Finally, since the optimization is carried out only over sequences compatible with the output responses of stable systems, the identified model is guaranteed to be stable.

NTGsim: A graphical user interface and a 3D simulator for nonlinear trajectory generation methodology

NTGsim: A graphical user interface and a 3D simulator for nonlinear trajectory generation methodology Nonlinear Trajectory Generation (NTG), developed by Mark Milam, is a software algorithm used to generate trajectories of constrained nonlinear systems in real-time. The goal of this paper is to present an approach to make NTG more user-friendly. To accomplish this, we have programmed a Graphical User Interface (GUI) in Java, using object oriented design, which wraps the NTG software and allows the user to quickly and efficiently alter the parameters of NTG. This new program, called NTGsim, eliminates the need to reprogram the NTG algorithm explicitly each time the user wishes to change a parameter.

Shape Analysis of the Human Brain: A Brief Survey

The survey outlines and compares popular computational techniques for quantitative description of shapes of major structural parts of the human brain, including medial axis and skeletal analysis, geodesic distances, Procrustes analysis, deformable models, spherical harmonics, and deformation morphometry, as well as other less widely used techniques. Their advantages, drawbacks, and emerging trends, as well as results of applications, in particular, for computer-aided diagnostics, are discussed.