Output Filter Aware Optimization of the Noise Shaping Properties of {\Delta}{\Sigma} Modulators via Semi-Definite Programming

The Noise Transfer Function (NTF) of {\Delta}{\Sigma} modulators is typically designed after the features of the input signal. We suggest that in many applications, and notably those involving D/D and D/A conversion or actuation, the NTF should instead be shaped after the properties of the output/reconstruction filter. To this aim, we propose a framework for optimal design based on the Kalman-Yakubovich-Popov (KYP) lemma and semi-definite programming. Some examples illustrate how in practical cases the proposed strategy can outperform more standard approaches.Comment: 14 pages, 18 figures, journal. Code accompanying the paper is available at http://pydsm.googlecode.co

Continuous Order Identification of PHWR Models Under Step-back for the Design of Hyper-damped Power Tracking Controller with Enhanced Reactor Safety

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.In this paper, discrete time higher integer order linear transfer function models have been identified first for a 500 MWe Pressurized Heavy Water Reactor (PHWR) which has highly nonlinear dynamical nature. Linear discrete time models of the nonlinear nuclear reactor have been identified around eight different operating points (power reduction or step-back conditions) with least square estimator (LSE) and its four variants. From the synthetic frequency domain data of these identified discrete time models, fractional order (FO) models with sampled continuous order distribution are identified for the nuclear reactor. This enables design of continuous order Proportional-Integral-Derivative (PID) like compensators in the complex w-plane for global power tracking at a wide range of operating conditions. Modeling of the PHWR is attempted with various levels of discrete commensurate-orders and the achievable accuracies are also elucidated along with the hidden issues, regarding modeling and controller design. Credible simulation studies are presented to show the effectiveness of the proposed reactor modeling and power level controller design. The controller pushes the reactor poles in higher Riemann sheets and thus makes the closed loop system hyper-damped which ensures safer reactor operation at varying dc-gain while making the power tracking temporal response slightly sluggish; but ensuring greater safety margin.This work has been supported by Department of Science and Technology (DST), Govt. of India, under the PURSE programme

Robust adaptive sampled-data control of a class of systems under structured nonlinear perturbations

Cataloged from PDF version of article.A robust adaptive sampled-data feedback stabilization scheme is presented for a class of systems with nonlinear additive perturbations. The proposed controller generates a control input by using high-gain static or dynamic feedback from nonuniform sampled values of the output. A simple adaptation rule adjusts the gain and the sampling period of the controller

Nonlinear and sampled data control with application to power systems

Sampled data systems have come into practical importance for a variety of reasons. The earliest of these had primarily to do with economy of design. A more recent surge of interest was due to increase utilization of digital computers as controllers in feedback systems. This thesis contributes some control design for a class of nonlinear system exhibition linear output. The solution of several nonlinear control problems required the cancellation of some intrinsic dynamics (so-called zero dynamics) of the plant under feedback. It results that the so-dened control will ensure stability in closed-loop if and only if the dynamics to cancel are stable. What if those dynamics are unstable? Classical control strategies through inversion might solve the problem while making the closed loop system unstable. This thesis aims to introduce a solution for such a problem. The main idea behind our work is to stabilize the nonminimum phase system in continuous- time and undersampling using zero dynamics concept. The overall work in this thesis is divided into two parts. In Part I, we introduce a feedback control designs for the input-output stabilization and the Disturbance Decoupling problems of Single Input Single Output nonlinear systems. A case study is presented, to illustrate an engineering application of results. Part II illustrates the results obtained based on the Articial Intelligent Systems in power system machines. We note that even though the use of some of the AI techniques such as Fuzzy Logic and Neural Network does not require the computation of the model of the application, but it will still suer from some drawbacks especially regarding the implementation in practical applications. An alternative used approach is to use control techniques such as PID in the approximated linear model. This design is very well known to be used, but it does not take into account the non-linearity of the model. In fact, it seems that control design that is based on nonlinear control provide better performances

Analysis and design of ΣΔ Modulators for Radio Frequency Switchmode Power Amplifiers

Power amplifiers are an integral part of every basestation, macrocell, microcell and mobile phone, enabling data to be sent over the distances needed to reach the receiver’s antenna. While linear operation is needed for transmitting WCDMA and OFDM signals, linear operation of a power amplifier is characterized by low power efficiency, and contributes to unwanted power dissipation in a transmitter. Recently, a switchmode power amplifier operation was considered for reducing power losses in a RF transmitter. A linear and efficient operation of a PA can be achieved when the transmitted RF signal is ΣΔ modu- lated, and subsequently amplified by a nonlinear device. Although in theory this approach offers linearity and efficiency reaching 100%, the use of ΣΔ modulation for transmitting wideband signals causes problems in practical implementation: it requires high sampling rate by the digital hardware, which is needed for shaping large contents of a quantization noise induced by the modulator but also, the binary output from the modulator needs an RF power amplifier operating over very wide frequency band. This thesis addresses the problem of noise shaping in a ΣΔ modulator and nonlinear distortion caused by broadband operation in switchmode power amplifier driven by a ΣΔ modulated waveform. The problem of sampling rate increase in a ΣΔ modulator is solved by optimizing structure of the modulator, and subsequent processing of an input signal’s samples in parallel. Independent from the above, a novel technique for reducing quan- tization noise in a bandpass ΣΔ modulator using single bit quantizer is presented. The technique combines error pulse shaping and 3-level quantization for improving signal to noise ratio in a 2-level output. The improvement is achieved without the increase of a digital hardware’s sampling rate, which is advantageous also from the perspective of power consumption. The new method is explored in the course of analysis, and verified by simulated and experimental results. The process of RF signal conversion from the Cartesian to polar form is analyzed, and a signal modulator for a polar transmitter with a ΣΔ-digitized envelope signal is designed and implemented. The new modulator takes an advantage of bandpass digital to analog conversion for simplifying the analog part of the modulator. A deformation of the pulsed RF signal in the experimental modulator is demonstrated to have an effect primarily on amplitude of the RF signal, which is correctable with simple predistortion

Characterization of Model-Based Detectors for CPS Sensor Faults/Attacks

A vector-valued model-based cumulative sum (CUSUM) procedure is proposed for identifying faulty/falsified sensor measurements. First, given the system dynamics, we derive tools for tuning the CUSUM procedure in the fault/attack free case to fulfill a desired detection performance (in terms of false alarm rate). We use the widely-used chi-squared fault/attack detection procedure as a benchmark to compare the performance of the CUSUM. In particular, we characterize the state degradation that a class of attacks can induce to the system while enforcing that the detectors (CUSUM and chi-squared) do not raise alarms. In doing so, we find the upper bound of state degradation that is possible by an undetected attacker. We quantify the advantage of using a dynamic detector (CUSUM), which leverages the history of the state, over a static detector (chi-squared) which uses a single measurement at a time. Simulations of a chemical reactor with heat exchanger are presented to illustrate the performance of our tools.Comment: Submitted to IEEE Transactions on Control Systems Technolog

Regelungstheorie

The workshop “Regelungstheorie” (control theory) covered a broad variety of topics that were either concerned with fundamental mathematical aspects of control or with its strong impact in various fields of engineering