Preface, Notations 1.Introduction to Time-Delay Systems I.Frequency-Domain Approach 2.Systems with Commensurate Delays 3.Systems withIncommensurate Delays 4.Robust Stability Analysis II.Time Domain Approach 5.Systems with Single Delay 6.Robust Stability Analysis 7.Systems with Multiple and Distributed Delays III.Input-Output Approach 8.Input-output stability A.Matrix Facts B.LMI and Quadratic Integral Inequalities Bibliography Index

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Stability of Time-Delay Systems

This paper presents control and coordination algorithms for groups of vehicles. The focus is on autonomous vehicle networks performing distributed sensing tasks where each vehicle plays the role of a mobile tunable sensor. The paper proposes gradient descent algorithms for a class of utility functions which encode optimal coverage and sensing policies. The resulting closed-loop behavior is adaptive, distributed, asynchronous, and verifiably correct.

Coverage control for mobile sensing networks

A most critical and important issue surrounding the design of automatic control systems with the successively increasing complexity is guaranteeing a high system performance over a wide operating range and meeting the requirements on system reliability and dependability. As one of the key technologies for the problem solutions, advanced fault detection and identification (FDI) technology is receiving considerable attention. The objective of this book is to introduce basic model-based FDI schemes, advanced analysis and design algorithms and the needed mathematical and control theory tools at a level for graduate students and researchers as well as for engineers.

Model-based Fault Diagnosis Techniques: Design Schemes, Algorithms, and Tools

Differential-Difference Equations. By Richard Bellman and Kenneth L. Cooke. Pp. xvi, 465. 1963. (Academic Press)

This paper provides a new stability criterion for systems with time-invariant uncertain delays. Based on an improved upper bound for the inner product of two vectors, a new delay-dependent robust stability criterion is derived, which is shown by an example less conservative than existing stability criteria.

A delay-dependent stability criterion for systems with uncertain time-invariant delays

Active magnetic bearing (AMB) actuators support rotors without friction but require feedback control for stabilization and performance. We address the application of modern control techniques such as LQG/LTR, H/spl infin/, and QFT to AMB systems. We also introduce a novel method called adaptive forced balancing (AFB) which solves the problem of synchronous vibration caused by mass unbalance. Simulation and experimental results are included to show the performance of AFB as applied to single-end AMB suspensions (SISO systems). Finally, AFB with frequency tracking and its generalization for double-end AMB suspensions (MIMO systems) are briefly explored. >

Magnetic bearing control systems and adaptive forced balancing

A design method for a robust controller including a new type of observer called the proportional integral observer (PI observer) is proposed. The new observer differs from the conventional one by an integration path which provides additional degrees of freedom. This freedom can be used to make the observer-based controller design less sensitive to parameter variation of the system. It is shown that some of the difficulties that may arise in the exclusive pursuit of a design for the conventional observer-based controller from the point of view of system robustness are resolved in a straightforward manner using the PI observer. A systematic robustness recovery procedure is described for the PI observer-based controller design which asymptotically achieves the same loop transfer functions as the full-state feedback control implementation. A design example is included and the effectiveness of our method is illustrated by simulation results.

Robust control system design with a proportional integral observer

In this paper we study the stability properties of linear time-invariant delay systems. The specific notion under consideration is asymptotic stability independent of delay. As an attempt to achieve a compromise between the complexity and tightness of various stability tests, we present a number of sufficient stability conditions which improve several previously available sufficient conditions and which are also much easier to verify than the known necessary and sufficient conditions. >

On sufficient conditions for stability independent of delay

SUMMARY This paper applies the proportional-integral (PI) observer in connection with loop transfer recovery (LTR) design for continuous-time systems. We show that a PI observer makes it possible to obtain time recovery, i.e., exact recovery for t -+ -, under mild conditions. Based on an extension of the LQG/LTR method of proportional (P) observers, a systematic LTR design method is derived for the PI observer. Our recovery design method allows time recovery and frequency (normal) recovery to be done independently. Furthermore, we give explicit expressions for the recovery error when asymptotic recovery cannot be obtained. A design example demonstrates the advantages of time recovery in the nonminimum phase case. Since the appearance of the papers by Doyle and Steinsv6 dealing with loop transfer recovery (LTR), many papers have been written on this topic for both continuous- and discrete-time systems. The reason for the current research effort is that one is required to (a) provide LTR design with low gain, (b) consider the trade-off between the level of LTR and the necessary gain, which in turn relates to fundamental trade-offs in control system design, (c) handle nonminimum phase systems, (d) achieve recovery at both the plant input and output, and (e) provide a parallel treatment for discrete-time systems. Recent works, including Lee and Chen,’ Okada er ~l.,’~.’~ NiemaM er ~1.,’~~’~ Shafai et al.” and Saekil’ concentrated on these issues; and both observer-based controllers and general compensator structures were proposed. The applied observer types have been, in most cases, full-order or minimal-order observers, but more general observer architectures have also been used in LTR design. Beale and Shafai3 introduced the proportional-integral (PI) observer in LTR design. A PI observer is an observer with an integrating effect which takes care of the asymptotic time behaviour. The

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Ltr design of proportional-integral observers

This paper considers the design of a proportional integral observer (PIO) for simultaneous disturbance attenuation and fault detection. Unlike the proportional observer, an integral observer alone suffices to achieve good convergence and filtering properties when sensor noise is present in the system. On the other hand, a proportional integral observer makes it possible to decouple the modeling uncertainties while estimating the states and faults with satisfactory convergence properties. We show that a generalized PIO structure, a proportional integral fading observer, facilitates the design procedure for achieving the above goal.

Bahram Shafai

Papers

Magnetic bearing control systems and adaptive forced balancing

Robust control system design with a proportional integral observer

On sufficient conditions for stability independent of delay

Ltr design of proportional-integral observers

Simultaneous disturbance attenuation and fault detection using proportional integral observers