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GLOBAL INTERNAL STABILIZABILITY DOES NOT IMPLY GLOBAL EXTERNAL STABILIZABILITY FOR SMALL SENSOR DISTURBANCES

IEEE TRANSACTIONS ON AUTOMATIC control 1995年第12期40卷 2119-2122页

作者： FREEMAN, R Center for Control Engineering and Computation Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

It was shown in [1] that for control-affine nonlinear systems, global asymptotic stabilizability via continuous state feedback implies global input-to-state stabilizability with respect to actuator disturbances. We show that the analogous result for sensor disturbances does not hold: we construct a second-order system which admits a continuous memoryless globally asymptotically stabilizing state feedback controller but for which no such controller can prevent finite escape times from every initial condition in the presence of small sensor disturbances.

关键词： Asymptotic stability Actuators Sensor systems control systems Nonlinear systems Nonlinear control systems State feedback Robust stability control theory Working environment noise

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Tracking controllers for Systems Linear in the Unmeasured States *

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IFAC Proceedings Volumes 1995年第14期28卷 577-582页

作者： R.A. Freeman P.V. Kokotović Center for Control Engineering and Computation Dept. of Electrical and Computer Engineering University of California Santa Barbara CA 93106 Telephone: (805) 893-4691

For nonlinear systems in extended strict feedback form, where unmeasured states enter linearly, we construct dynamic partial state feedback controllers that achieve the global asymptotic tracking of given reference tr... 详细信息

关键词： Nonlinear systems global tracking dynamic partial state feedback

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Backstepping Design with Nonsmooth Nonlinearities *

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IFAC Proceedings Volumes 1995年第14期28卷 435-440页

We develop tools for backstepping with Lyapunov functions and control laws which are locally Lipschitz but not differentiable. We use Clarke’s generalized gradient and its associated calculus to show that the locally Lipschitz backstepping construction is essentially the same as the differentiable one. Our recursive method is constructive and yields an explicit expression for the control law.

关键词： Backstepping nonsmooth Lyapunov functions generalized gradient

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Error feedback loop linearizes direct digital synthesizers 29

Error feedback loop linearizes direct digital synthesizers

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29th Asilomar Conference on Signals, Systems and computers, ACSSC 1995

作者： Hanis, Fred Mcknight, Bill Electrical and Computer Engineering San Diego State University San DiegoCA92182-0309 United States Naval Research and Development Command Control and Ocean Systems Center San DiegoCA92152-2485 United States

ISBN: (纸本)0818673702

The fidelity of a signal formed by recalling samples of a sinusoid from a look-up table and converting these sample amplitudes to a waveform in a digital-to-analog converter (DAC) is affected by both the phase and amplitude quantization of the process. The length and width of the look-up table affect the signal's phase angle resolution and the signal's amplitude resolution respectively. These resolution limits are equivalent to time base jitter and to amplitude quantization of the signal and add spectral modulation lines and a white broad-band noise floor to the signal's spectrum. These undesired spectral terms can be controlled by the use of noise shaping to spectrally alter the structure of the quantization noise related to limited table length and width. © 1995 IEEE.

关键词： Digital to analog conversion

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A dual-mode algorithm for blind equalization of qam signals: cadama 29

A dual-mode algorithm for blind equalization of qam signals:...

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29th Asilomar Conference on Signals, Systems and computers, ACSSC 1995

作者： Axford, R.A. Milstein, L.B. Zeidler, J.R. Communications Department Control and Ocean Surveillance Center RDTE Division Naval Command San DiegoCA921 52-5001 United States Department of Electrical and Computer Engineering University of Califomia at San DiegoCA92093 United States

ISBN: (纸本)0818673702

The misadjustment exhibited by the constant modulus algorithm (CMA) can be excessive when it is used for blind equalization of QAM signals, thus degrading the performance of decision-directed carrier recovery algorithms. This paper introduces a hybrid blind equalization algorithm, the CMA-assisted decision adjusted modulus algorithm (CADAMA), that exhibits reductions in misadjustment on the order of 18 to 25 dB for higher order QAM constellations. CADAMA employs CMA to perform initial adjustment of the equalizer, and switches to decision adjusted modulus algorithm (DAMA) mode when the amplitude equalization has been sufficiently accomplished. DAMA is based on a phase-blind cost function that goes to zero at each ring of the QAM constellation. © 1995 IEEE.

关键词： Blind equalization

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First passage risk-sensitive criterion for stochastic evolutions

First passage risk-sensitive criterion for stochastic evolut...

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American control Conference (ACC)

作者： C.D. Charalambous J.L. Hibey Measurement and Control Engineering Research Center College of Engineering Idaho State University Pocatello ID USA Department of Electrical and Computer Engineering Old Dominion University Norfolk VA USA

The purpose of this paper is to investigate in an infinite dimensional space, the first passage problem with a risk-sensitive performance criterion, and to illustrate the asymptotic behavior of the associated value function, as related to differential games arising in robust control theory. The model of interest is described by a controlled stochastic evolution with small Wiener noise intensity. The Wiener and state processes take values in infinite dimensional Hilbert spaces. The objective is to control the evolution of the state process, so as to keep it in some compact set G. By using a logarithmic transformation, it is shown that in the limit as the small noise parameter, /spl epsiv//spl rarr/0, the risk-sensitive value function converges to the value of a deterministic differential game. In the limit as the risk parameter, /spl theta//spl rarr/0, the risk-sensitive value function converges to the value function corresponding to the mean escape time problem. In addition, a lower bound on the first escape time is derived which is slightly different from the known bound for finite dimensional systems. The magnitude of the lower bound derived here, increases as /spl theta/ increases, thus robustness is achieved.

关键词： Stochastic processes Hilbert space Equations Electric variables measurement control engineering Educational institutions Game theory Robust control Stochastic resonance Robustness

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Preisach modeling of piezoceramic and shape memory alloy hysteresis

Preisach modeling of piezoceramic and shape memory alloy hys...

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IEEE Conference on control Technology and Applications (CCTA)

作者： D. Hughes J.T. Wen Control Laboratory for Mechanical Structures (CLaMS) Center for Advanced Technology in Automation Robotics & Manufacturing Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY USA

Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test data for a multi-sheet piezoceramic actuator (made of lead zirconate titanate) attached to a flexible beam are presented and are seen to be very consistent with the two Preisach model properties. The commanded parameter is the sheet transverse electric field while the measured parameter is an approximately colocated strain induced in the beam. Equivalent data for a Nitinol SMA wire muscle, attached to the same beam, are also presented. The input and output parameters are the SMA current and a beam strain respectfully. The minor loop and wiping out evidence is less strong than that of the piezoceramic case, but encouraging. In all experiments the quasi-steady state responses were generated in order to avoid exciting beam flexible modes which would complicate the analysis.

关键词： Piezoelectric materials Shape memory alloys Hysteresis Strain measurement Shape control Open loop systems Testing Actuators Titanium compounds Electric variables measurement

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Synthesized passive feedback control of sensor-rich smart structures-experimental results

Synthesized passive feedback control of sensor-rich smart st...

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IEEE Conference on control Technology and Applications (CCTA)

作者： P. Akella J.T. Wen Control Laboratory for Mechanical Structures Department of Electrical Computer and Systems EngineeringCenter for Advanced Technology in Automation Robotics & Manufacturing Rensselaer Polytechnic Institute RPI Troy NY USA

Passivity based controllers are used in structural control due to their inherent robustness properties. These controllers require sensor/actuator collocation. In this paper, we consider the design of a "squaring down" matrix which renders a system passive by using a linear combination of all collocated and non-collocated sensor/actuator pairs. The design uses experimental transfer functions and does not require the knowledge of the system model. The problem of finding the squaring down matrix is cast as a solution to a set of linear matrix inequalities (LMIs) subject to some additional performance considerations. The design procedure of the squaring down matrix assumes that velocity information is available from the sensors which is not generally the case. We show that the squaring down matrix can be implemented without the use of such velocity information. We provide experimental results gathered from the single link flexible beam setup in the C/sub La/MS laboratory at RPI to show that implementation of passive loops without velocity measurements provides very good results.

关键词： Feedback control Linear matrix inequalities Intelligent sensors control system synthesis Robust control Sensor systems Hydraulic actuators Transfer functions Laboratories Economic indicators

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Error feedback loop linearizes direct digital synthesizers

Error feedback loop linearizes direct digital synthesizers

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Asilomar Conference on Signals, Systems & computers

作者： F. Harris B. McKnight Electrical and Computer Engineering San Diego State University San Diego CA USA Naval Research and Development Command Control and Ocean Systems Center San Diego CA USA

关键词： Feedback loop Synthesizers Quantization Signal resolution Noise shaping Table lookup Signal processing Digital-analog conversion Jitter Amplitude modulation

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The transversal and lattice multiple modulus algorithms for blind equalization of QAM signals

The transversal and lattice multiple modulus algorithms for ...

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MILCOM, Military Communications Conference

作者： R.A. Axford L.B. Milstein J.R. Zeidler RDTE Division Naval Command Control and Ocean Surveillance Center San Diego CA USA Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA

The most popular algorithm for blind equalization of QAM signals is the constant modulus algorithm (CMA). However, because the CMA cost function is not matched to constellations with signal points on multiple radii, CMA can exhibit excessive misadjustment for QAM signals. This paper develops an alternative to CMA, the multiple modulus algorithm (MMA), which is based on stochastic gradient minimization of a cost function that goes to zero at each radius of the QAM constellation. For the applicable QAM constellations, MMA exhibits significantly reduced misadjustment compared to CMA. A lattice implementation of MMA is also presented.

关键词： Lattices Blind equalizers Quadrature amplitude modulation Cost function Constellation diagram Stochastic processes Minimization methods Phase shift keying Oceans Surveillance

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