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IEEE Conference on Nanotechnology

作者： C.T. Kelley D.L. Woolard P. Zhao M. Kerr M.I. Lasater Department of Mathematics Center for Research in Scientific Computation USA U.S. Army Research Office U. S. Army Research Laboratory NC USA Electrical and Computer Engineering Department North Carolina State University Raleigh NC USA

ISBN: (纸本)0780375386

We present theoretical results on instability processes in nanoscale tunneling structures that were obtained from a computationally improved physics-based simulator. The results were obtained from a numerical implementation of the Wigner-Poisson electron transport model upon a parallel-computing platform. These investigations considered various forms of multi-barrier resonant tunneling structures (RTSs) and they were used to test the robustness of the new modeling code. This improved modeling tool is shown to be fast and efficient with the potential to facilitate complete and rigorous studies of this time-dependent phenomenon. This is important because it will allow for the study of RTSs embedded in realistic circuit configurations. Hence, this advanced simulation tool will allow for the detailed study of RTS devices coupled to circuits where numerical simulations in time and iterative numerical optimization over the circuit parameters are required. Therefore, this work will enable the future study of RTS-based circuits operating at very high frequencies.

关键词： Numerical simulation Nanoscale devices Nanostructures Physics computing computational modeling Electrons Resonant tunneling devices Circuit testing Robustness Circuit simulation

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Vision-guided flight stability and control for micro air vehicles

Vision-guided flight stability and control for micro air veh...

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IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： S.M. Ettinger M.C. Nechyba P.G. Ifju M. Waszak Dept. of Electr. & Comput. Eng. Florida Univ. Gainesville FL USA Department of Electrical and Computer Engineering University of Florida Gainesville FL USA Department of Aerospace Engineering Mechanics and Engineering University of Florida Gainesville FL USA Dynamics and Control Branch NASA-Langley Research Center Hampton VA USA

Substantial progress has been made recently towards designing, building and test-flying remotely piloted Micro Air Vehicles (MAVs) and small UAVs. We seek to complement this progress in overcoming the aerodynamic obstacles to flight at very small scales with a vision-guided flight stability and autonomy system, based on a robust horizon detection algorithm. In this paper, we first motivate the use of computer vision for MAV autonomy, arguing that given current sensor technology, vision may be the only practical approach to the problem. We then describe our statistical vision-based horizon detection algorithm, which has been demonstrated at 30 Hz with over 99.9% correct horizon identification. Next, we develop robust schemes for the detection of extreme MAV attitudes, where no horizon is visible, and for the detection of horizon estimation errors, due to external factors such as video transmission noise. Finally, we discuss our feedback controller for self-stabilized flight, and report results on vision-based autonomous flights of duration exceeding ten minutes.

关键词： Unmanned aerial vehicles Robust stability Detection algorithms Buildings Testing Aerodynamics computer vision Noise robustness Estimation error Adaptive control

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A Markov process using curvature for filtering curve images 3rd

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3rd International Workshop on Energy Minimization Methods in computer Vision and Pattern Recognition, EMMCVPR 2001

作者： August, Jonas Zucker, Steven W. Center for Computational Vision and Control Departments of Electrical Engineering and Computer Science Yale University 51 Prospect Street New HavenCT06520 United States

ISBN: (纸本)3540425233

A Markov process model for contour curvature is introduced via a stochastic differential equation. We analyze the distribution of such curves, and show that its mode is the Euler spiral, a curve minimizing changes in curvature. To probabilistically enhance noisy and low contrast curve images (e.g., edge and line operator responses), we combine this curvature process with the curve indicator random field, which is a prior for ideal curve images. In particular, we provide an expression for a nonlinear, minimum mean square error filter that requires the solution of two elliptic partial differential equations. Initial computations are reported, highlighting how the filter is curvature-selective, even when curvature is absent in the input. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Markov processes

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Multivariable MRAC using high frequency gain matrix factorization

Multivariable MRAC using high frequency gain matrix factoriz...

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IEEE Conference on Decision and control

作者： A.K. Imai R.R. Costa Liu Hsu Gang Tao P. Kokotovic Department of Electrical Engineering COPPE/UFRJ Rio de Janeiro Brazil Department of Electrical and Computer Engineering University of Virginia Charlottesville VA USA Center of Control Engineering and Computation University of California Santa Barbara CA USA

A MIMO (multiple-input, multiple-output) analog to the well-known Lyapunov-based SISO (single-input, single-output) design of MRAC (model-reference adaptive control) has been recently introduced by L. Hsu et al. (2001). The new design utilizes a control parametrization derived from a factorization of the high-frequency gain matrix K/sub p/=SDU, where S is symmetric positive-definite, D is diagonal and U is unity upper-triangular. Only the signs of the entries of D or, equivalently, the signs of the leading principal minors of K/sub p/, were assumed to be known. However, the result was restricted to plants with (vector) relative degree one. In this paper, we extend the MRAC for more general plants with relative degree greater than one. We present three possible factorizations of K/sub p/ and the resulting update laws.

关键词： Frequency MIMO Symmetric matrices Transfer functions Artificial intelligence control engineering control engineering computing Analog computers Adaptive control Linear systems

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Lyapunov-based adaptive control of MIMO systems

Lyapunov-based adaptive control of MIMO systems

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American control Conference (ACC)

作者： Liu Hsu R. Costa A.K. Imai P. Kokotovic Department of Electrical Engineering COPPE/UFRJ Rio de Janeiro Brazil Â‡ Center for Control Engineering and Computation University of California Santa Barbara CA

The design of model-reference adaptive control (MRAC) for MIMO linear systems has not yet been achieved, in spite of significant efforts, the completeness and simplicity of its SISO counterpart. One of the main obstacles has been the generalization of the SISO assumption that the sign of the high-frequency gain is known. Here we overcome this obstacle and present a MIMO analog to the well known Lyapunov-based MRAC SISO design. Our algorithm makes use of a new control parametrization derived from a factorization of the high-frequency gain matrix K/sub p/=SDU, where S is symmetric positive definite, D is diagonal, and U is unity upper triangular. Only the signs of the entries of D or, equivalently, the signs of the leading principal minors of K/sub p/, are assumed to be known.

关键词： Adaptive control MIMO Linear systems Frequency Transmission line matrix methods Symmetric matrices Visual servoing Upper bound control engineering control engineering computing

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Modeling and control of robot manipulators

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Automatica 2001年第10期37卷 1681-1682页

作者： Marco de Oliveira Mo Jamshidi Autonomous Control Engineering Center The University of New Mexico Albuquerque NM USA Department of Electrical and Computer Engineering The University of New Mexico Albuquerque NM USA

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Discrete time model predictive control design using Laguerre functions

Discrete time model predictive control design using Laguerre...

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American control Conference (ACC)

作者： Liuping Wang Center for Integrated Dynamics and Control Department of Electrical and Computer Engineering University of Newcastle Callaghan NSW Australia

In the design of model predictive controller (MPC), the traditional approach of expanding the projected control signal uses the forward operator to obtain the linear-in-the-parameters relation for predicted output. In this paper, by using a performance specification on the exponential change rate of the projected control signal, a more appropriate expansion, related to Laguerre networks, is introduced. It is shown that the number of terms used in the optimization procedure can be reduced to a fraction of that required by the usual procedure in the case of rapid sampling, and as a result, the numerical condition of the optimization algorithm can be significantly improved. Furthermore, the proposed algorithm is easy to tune for closed-loop performance with two explicit tuning parameters. By relaxing the constraint on the exponential change rate of the control signal and allowing arbitrary complexity in describing the trajectory, the proposed approach becomes equivalent to the traditional approach in MPC design.

关键词： Predictive models Predictive control Signal design Sampling methods Trajectory Industrial control electrical equipment industry Polynomials Australia Signal sampling

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Time delay and power control in spread spectrum wireless networks

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IFAC Proceedings Volumes 2001年第23期34卷 159-164页

作者： Aly I. El-Osery Chaouki Abdallah Mo Jamshidi Autonomous Control Engineering Center (ACE) The University of New Mexico Albuquerque NM 87131 USA Electrical & Computer Engineering Department The University of New Mexico Albuquerque NM 87131 USA

Delay in the computation of the signal-to-interference ratio in communication systems is unavoidable. In the the case of mobile communication, delay is a very critical problem due the fast variation of the communication channel and the need for effective, fast and accurate power control. In this paper we present our approach to dealing with the delay in mobile communication systems as well as our controller to achieve and maintain the desired signal quality. We will concentrate on the code division multiple access (CDMA) systems.

关键词： Power control CDMA

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Delay-dependent guaranteed cost control for uncertain state-delayed systems

Delay-dependent guaranteed cost control for uncertain state-...

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American control Conference (ACC)

作者： Young Sam Lee Young Soo Moon Wook Hyun Kwon Engineering Research Center for Advanced Control and Instrumentation School of Electrical Engineering and Computer Sciene Seoul National University Seoul South Korea

This paper concerns delay-dependent guaranteed cost control via memoryless state feedback controllers for a class of linear state-delayed systems with norm-bounded time-varying parametric uncertainties. New delay-dependent conditions for the existence of the guaranteed cost controller are presented in terms of matrix inequalities for both nominal state-delayed systems and uncertain state-delayed systems. An algorithm involving convex optimization is proposed to design a controller achieving a suboptimal guaranteed cost such that the system can be stabilized for all admissible uncertainties. Through numerical examples, it is shown that the proposed method can even give a lower guaranteed cost than the delay-independent method.

关键词： Delay Costs control systems Linear feedback control systems Uncertainty State feedback Time varying systems Linear matrix inequalities Design optimization Algorithm design and analysis

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Delay-dependent robust H/sub /spl infin// control for uncertain systems with time-varying state-delay

Delay-dependent robust H/sub /spl infin// control for uncert...

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IEEE Conference on Decision and control

作者： Young Sam Lee Young Soo Moon Wook Hyun Kwon Kwan Ho Lee Engineering Research Center of Advanced Control and Instrumentation School of Electrical Engineering and Computer Science Seoul National University Seoul South Korea

The paper concerns a problem of robust H/sub /spl infin// control for uncertain systems with time-varying state-delay. A delay-dependent robust H/sub /spl infin// controller is presented in terms of matrix inequalities. An algorithm involving convex optimization is proposed to find a suboptimal maximal delay such that the closed-loop system with the designed controller is asymptotically stable and guarantees the H/sub /spl infin// norm bound for all admissible uncertainties. Numerical examples are presented to show that the proposed results are less conservative than the existing results.

关键词： Delay Robustness Robust control control systems Uncertain systems Time varying systems Linear matrix inequalities Design optimization Algorithm design and analysis Uncertainty

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