Alterations of Structures and Functions of Useful Proteins : Cholesterol Oxidase and Human Metallothionein

This paper overviews a series of the authors’ recent contributions to dynamic quantizer design for control. The problem considered here is to find a dynamic quantizer such that the resulting quantized system is an optimal approximation of an ideal unquantized system.We show here a fundamental solution to this problem and briefly review several results toward real applications

Low-Energy Brane-World Effective Actions and Partial Supersymmetry Breaking

As part of a programme for the general study of the low-energy implications of supersymmetry breaking in brane-world scenarios, we study the nonlinear realization of supersymmetry which occurs when breaking N=2 to N=1 supergravity. We consider three explicit realizations of this supersymmetry breaking pattern, which correspond to breaking by one brane, by one antibrane or by two (or more) parallel branes. We derive the minimal field content, the effective action and supersymmetry transformation rules for the resulting N=1 theory perturbatively in powers of kappa = 1/M_{Planck}. We show that the way the massive gravitino and spin-1 fields assemble into N=1 multiplets implies the existence of direct brane-brane contact interactions at order O(kappa). This result is contrary to the O(kappa^2) predicted by the sequestering scenario but in agreement with recent work of Anisimov et al. Our low-energy approach is model independent and is a first step towards determining the low-energy implications of more realistic brane models which completely break all supersymmetries.Comment: Latex, 29 Page

Performance of multistep finite control set model predictive control for power electronics

The performance of direct model predictive control (MPC) with reference tracking and long prediction horizons is evaluated through simulations, using the current control problem of a variable speed drive system with a voltage source inverter as an illustrative example. A modified sphere decoding algorithm is used to efficiently solve the optimization problem underlying MPC for long horizons. For a horizon of five and a three- level inverter, for example, the computational burden is reduced by four orders of magnitude, compared to the standard exhaustive search approach. This work illustrates the performance gains that are achievable by using prediction horizons larger than one. Specifically, for long prediction horizons and a low switching frequency, the total harmonic distortion of the current is significantly lower than for space vector modulation, making direct MPC with long horizons an attractive and computationally viable control scheme

Controllability of discrete-time networked control systems with try once discard protocol

This paper investigates controllability of discrete-time Networked Control Systems. The distinguishing feature is that the network imposes scheduling. The network is characterized by a dynamic protocol and different types of additional processing capabilities, as determined by available technology. For NCS with general nonlinear plants we present general controllability results. Finally, for NCS with linear plants we extend ideas motivated by NCS architectures with static protocols to state corresponding controllability results

Uniform Global Asymptotic Stability of Networked Control Systems affected with packet dropouts and scheduling issues

We focus on Networked Control Systems where the network induces two communication issues: one of them is packet dropouts while the other is scheduling. To mitigate the corresponding undesirable effects, such as instability or deteriorated performance, we use a protocol and controller co- design method. In particular, we adopt a deterministic Model Predictive Control (MPC) framework. We establish Uniform Global Asymptotic Stability (UGAS) by assuming a finite bound on the number of consecutive packet dropouts and appropriate modifications to standard MPC stability-related assumptions. We show UGAS through finding an appropriate Lyapunov candidate function.<br/

Adaptive control of the nonlinear dynamic behavior of the cantilever-sample system of an atomic force microscope

The paper presents a model reference adaptive control (MRAC) of first and second order to control the nonlinear dynamics of an atomic force microscope (AFM) cantilever, which is operated in contact mode. The AFM is a powerful tool to measure the topography of a sample at the scale of a few nanometers, where a small sharp tip supported in a micro cantilever scans the surface. In the contact mode the sample's topography is obtained by using the closed-loop control that holds the tip sample force constant. The nonlinear dynamics of the tip-sample system is very complex with different kinds of nonlinear forces that act between the tip and the sample. Here the dominated force depends on the distance tip-sample. In the present work we use a modified Hertz model to describe the nonlinear force when the distance tip-sample is less than 1 nm. First the complex nonlinear tip-sample system is controlled with a nonlinear MRAC of 1st order and after with a nonlinear MRAC of 2nd order. The results of both control strategies were compared in order to see which one gives a better control perfomance. Here a stability proof for both MRAC methods is present. A variety of simulation results are presented to demonstrate the efficacy of the proposed methods. The procedure is general and can be applied to any nonlinear system

To wait or to drop: On the optimal number of retransmissions in wireless control

The dimensioning of wireless communication protocols for networked control involves a non-trivial trade-off between reliability and delay. Due to the lossy nature of wireless communications, there is a risk that sensor messages will be dropped. The end-to-end reliability can be improved by retransmitting dropped messages, but this comes at the expense of additional delays. In this work, we determine the number of re-transmissions that strikes the optimal balance between communication reliability and delay, in the sense that it achieves the minimal expected linear-quadratic loss of the closed-loop system. An important feature of our framework is that it accounts for the random delays and possible losses that occur when lossy communication is combatted with re-transmissions. The resulting controller dynamically switches among a set of infinite-horizon linear-quadratic regulators, and is simple to implement. Various simulations are carried out to highlight the trade-off between reliability and delay

A jump filter for uncertain dynamic systems with dropouts

In this work, we consider a state estimation problem for linear uncertain discrete-time systems over a network with dropouts. The uncertainty of the plant model is described by a norm-bounded time-varying parameter that affects the system matrix. We design a jump filter that minimizes an upper bound of the trace of the state estimation error covariance for all possible parameter uncertainties and whose gains are selected from a precalculated finite set depending on the possible measurement reception scenarios. The presented procedure allows us to relate the complexity of the jump filter to the achievable estimation performance