Network-Based Control

Leader

Prof. Qing-Long Han, School of Computing Sciences

Members

Dr. Xian-Ming Zhang (Senior Postdoctoral Research Fellow)

Dr. Yu-Long Wang (Postdoctoral Research Fellow)

Ke Ding, PhD Candidate

Anthony Greening, PhD Candidate

Yi Hu, PhD Candidate

Qiang Lu, PhD Candidate

Xin Ma, PhD Candidate

Dawei Zhang, PhD Candidate

External Funding

Activities

1. Stability of delay-differential systems of neutral type

This research considers the stability problem of linear delay-differential systems of neutral type that exist in practical systems such as the distributed networks containing lossless transmission lines, and population ecology. A discretized Lyapunov functional approach will be developed. The resulting stability criteria will be formulated in the form of a linear matrix inequality (LMI). For nominal systems, the analytical results will be approached with fine discretization. For uncertain systems, the new approach will be much less conservative. Numerical examples will show significant improvement over approaches in the literature.

2. On robust stability of uncertain time-delay systems

The robust stability of time-delay systems has been widely investigated in the last two decades. The practical examples of time-delay systems include engineering, communications and biological systems. The existence of delay in a practical system may induce instability, oscillation and poor performance. This research will consider the robust stability of uncertain time-delay systems. The uncertainty under consideration is a quadratic dissipative one that contains a norm-bounded uncertainty, a positive real uncertainty and an uncertainty satisfying the so-called integral quadratic constraints as special cases. Note that a norm-bounded uncertainty only considers the gain of the uncertainty regardless of its phase, where a positive real uncertainty only characterizes the phase allowing for an arbitrary gain. Clearly, the norm-bounded and positive real characterizations are conservative if information on both gain and the phase of the uncertainty is available. The project will develop a stability criterion based on discretized Laypunov functional method and will cover the some existing results in the literature as a special case.

3. Robust H-inf synthesis and filtering of uncertain time-delay systems

This research is concerned with the problem of robust H-inf synthesis and filtering problem for linear uncertain time-delay systems. Based on Lyapunov functional approach, we will develop some methods for synthesizing robust H-inf state and dynamic output feedback control laws which guarantee the stability of the closed-loop system and reduces, to a prescribed level, the effect of disturbance input on the controlled output. Some sufficient criteria will be proposed in terms of linear matrix inequalities (LMIs). Examples will show the effectiveness of the approach.

4. Robust H-inf control of uncertain descriptor time-delay systems

This research will investigate the robust H-inf control problem of uncertain descriptor time-delay systems. Firstly, based on the decomposition-free method, robust stability criteria will be proposed. The regularity and nonimpulsiveness problems will be analysed simultaneously. Then we will also extend the discretized Laypunov functional method to this kind of system. A practical computational criterion will be given. The derived stability criteria are expressed in terms of a set of LMIs.

Based on a generalized Lyapunov function and matrix analysis technology, memoryless linear H-inf controller and H-2 controller design methods will be proposed. Mixed H-2/H-inf control will also be considered based on a solution of an optimisation problem including control of chaos.

5. Robust fault-tolerant control of uncertain time-delay systems

This research is concerned with robust fault-tolerant control for linear time-delay systems with actuator and/or sensor failures. The stability criteria will be formulated in the form of linear matrix inequalities (LMIs). The new design procedure will be proposed. Numerical examples will show the effectiveness of the approach

Selected Publications 

Q.-L. Han, "A discrete delay decomposition approach to stability of linear retarded and neutral systems," Automatica, vol. 45, no. 2, pp. 517-524, February 2009.

Q.-L. Han, "Improved stability criteria and controller design for linear neutral systems," Automatica, vol. 45, no. 8, pp. 1948-1952, August 2009.

  X.-M. Zhang and Q.-L. Han, "New Lyapunov-Krasovskii functionals for global asymptotic stability of delayed neural networks," IEEE Transactions on Neural Networks, vol. 20, no. 3, pp. 533-539, March 2009.

Q.-L. Han, D. Mehdi, and D. Han, "Master-slave synchronization of Lur'e systems with general sector-bounded nonlinearities," International Journal of Bifurcation and Chaos, vol. 19, no. 2, pp. 517-529, February 2009.

M. Zhong and Q.-L. Han, "Fault tolerant master-slave synchronization for Lur'e systems using time-delay feedback control," IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 56, no. 7, pp. 1391-1404, July 2009.

X.-M. Zhang and Q.-L. Han, "A delay decomposition approach to delay-dependent stability for linear systems with time-varying delays," International Journal of Robust and Nonlinear Control, vol. 19, no. 17, pp. 1922-1930, November 2009 (Published Online: Mar 27 2009 6:38AM DOI: 10.1002/rnc.1413).

X.-M. Zhang and Q.-L. Han, "A less conservative method for designing  filters for linear time-delay systems," International Journal of Robust and Nonlinear Control, vol. 19, no. 12, pp. 1376-1396, August 2009.