Murti V. Salapaka

SISO controller design to minimize a positive combination of the l 1 and the H 2 norms

norm under a specified level. The problem is analyzed for the discrete-time, single-input single-output (SISO), linear-time invariant case. It is shown that an optimal solution always exists. Duality theory is employed to show that any optimal solution is a finite impulse response sequence, and an a priori bound is given on its length. Thus, the problem can be reduced to a finite-dimensional convex optimization problem with an a priori determined dimension. Finally, it is shown that, in the region of interest of the

Performance Evaluation for ML Sequence Detection in ISI Channels with Gauss Markov Noise

\cal{H}

Architectures for Distributed Controller With Sub-Controller Communication Uncertainty

_2

Damping mechanisms in dynamic mode atomic force microscopy applications

constraint level, the optimal is unique and continuous with respect to changes in the constraint level.

Constructive control of quantum-mechanical systems

Microcantilevers that thermally sense the topography of the sample with the ability of electrostatic actuation enable a highly parallel implementation where multiple cantilevers scan the media. Microcantilevers with integrated sensors are used for a variety of applications viz. calorimetry, thermal dip pen lithography, thermal metrology, room temperature chemical vapor deposition in addition to high density data storage application. The dynamics of these cantilevers is governed by a complex interplay of mechanical, thermal, electrostatic and interatomic forces. Such dynamics are analyzed in this paper for operating conditions that are practical for high density data storage applications (¿ Tb=in2) and imaging. Models for a thermo-mechanical cantilever that are tractable for real-time applications as well as a comprehensive characterization of the relevant physical effects and methods for identifying model parameters are developed. The efficacy of the paradigm developed is proven by a comparison with experimental data.

Stability and sensitivity analysis of periodic orbits in tapping mode atomic force microscopy

In this paper we address the problem of synthesizing controllers that have to be implemented distributively and have structure. The effect of sub-controller to sub-controller communication noise on stability and performance is considered. Using an observer based controller parameterization, we provide suitable stabilizing sub-controller architectures that directly take into account the effect of communication noise on performance. In particular, the overall performance optimization can be cast as a convex problem in the Youla-Kucera parameter Q. Similar results hold for banded controller structures, i.e., when there is also a delay in the subsystem to subsystem communication

Exact topology reconstruction of radial dynamical systems with applications to distribution system of the power grid

This work deals with a model for repeated impacts of a mass attached to a spring with a massive, sinusoidally vibrating table. This model has been studied in an attempt to understand the cantilever-sample dynamics in atomic force microscopy. In this work, we have shown that for some values of the frequency of the vibrating table, there are countably many orbits of arbitrarily long periods and the system is sensitive to the initial conditions with which the experiments are conducted.

Viability and analysis of implementing only voltage-power droop for parallel inverter systems

This paper addresses the problem of output voltage regulation for multiple DC-DC converters connected to a grid, and prescribes a robust scheme for sharing power among different sources. Also it develops a method for sharing 120 Hz ripple among DC power sources in a prescribed proportion, which accommodates the different capabilities of DC power sources to sustain the ripple. We present a decentralized control architecture, where a nested (inner-outer) control design is used at every converter. An interesting aspect of the proposed design is that the analysis and design of the entire multi-converter system can be done using an equivalent single converter system, where the multi-converter system inherits the performance and robustness achieved by a design for the single-converter system. Another key aspect of this work is that the voltage regulation problem is addressed as a disturbance-rejection problem, where unknown load current is viewed as an external signal, and thus, no prior information is required on the nominal loading conditions. The control design is obtained using robust optimal-control framework. Case studies presented show the enhanced performance of prescribed optimal controllers.

Design of a constant force clamp and estimation of molecular motor motion using modern control approach

In this paper the design of controllers that incorporate structural and multiobjective performance requirements is considered. The control structures under study cover nested, chained, hierarchical, delayed interaction and communications, and symmetric systems. Such structures are strongly related to several modern-day and future applications including integrated flight propulsion systems, platoons of vehicles, micro-electromechanical systems, networked control, control of networks, production lines and chemical processes. It is shown that the system classes presented have the common feature that all stabilizing controllers can be characterized by convex constraints on the Youla-Kucera parameter. Using this feature, a solution to a general optimal performance problem that incorporates time domain and frequency domain constraints is obtained. A synthesis procedure is provided which, at every step, yields a feasible controller together with a measure of its performance with respect to the optimal performance. Convergence to the optimal performance is established. An example of a multi-node network congestion control problem is provided that illustrates the effectiveness of the developed methodology.