Guest editorial: Special issue on communications, information processing and control using chaos
✍ Scribed by Hasler, Martin; Vandewalle, Joos
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 28 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0098-9886
No coin nor oath required. For personal study only.
✦ Synopsis
In the engineering community, it took a long time for it to be generally accepted that chaotic behaviour may well be found in many devices, such as electronic circuits, adaptive systems, etc. As a consequence, it became important to develop methods that permitted the exclusion of chaos. However, researchers at the forefront of non-linear circuits and systems theory realized that the rich dynamics of chaos could be used to perform functions of engineering relevance. The most advanced applications of chaotic behaviour can be found at present in communications and control. The papers in this special issue give a good account of what the current problems are and how far research has been able to go. It also shows how lively this research area is, and the reader will be convinced that these are interesting topics to work on. Indeed, we are only at the beginning, and there are many more open problems than solved ones.
To scan the issue, it appears that most papers address the problem of transmitting information using chaotic signals. The motivations to do this are two-fold. On the one hand, to some extent the information is hidden in chaos, and on the other hand the spectrum of the transmitted signal is broadband and therefore the transmission is in principle more robust against interference and fading. However, the current chaos communication techniques still fall short of the competing cryptographic and spread spectrum techniques. Each contribution to chaos communications in this issue tries to improve either the privacy or the robustness of the transmission, or simply proposes some new circuits for the transmitter}receiver pair*such as in the paper by Storace et al. In this work, a new chaotic circuit based on a hysteretic element is used for an inverse system approach to transmission. The paper by Grassi et al. proposes increasing privacy by using hyperchaotic systems. Their system is based on synchronization by error feedback and transmission of information using chaotic masking. The paper by Rulkov et al. addresses the problem of a communication channel whose frequency band is too narrow to accommodate the chaotic signals. Their method aims at either transmitting only a "ltered version or at transforming the chaos generator such that the chaotic signal is adapted to the bandwidth of the channel, without losing the synchronization between the transmitter and the receiver. A method that should improve performance against additive perturbations in the channel is the chaotic FM modulation discussed in the paper of Volkovskii et al.
The issue of separating the noise from the chaotic signal is discussed in the paper of Dedieu and Kisel. Using a priori information, attractive low-cost on line noise cleaning techniques are developed. In the paper of Galias it is successfully shown that local Lyapunov exponents can be used for characterizing synchronization of continuous time as well as discrete time chaotic systems. Based on the observed strong correlation between local Lyapunov exponents and the behavior of coupled chaotic systems, three new synchronization criteria are developed and shown to be e!ective in the presence of noise.
There are two papers that fall into the category of control of chaos. In this discipline, the purpose is to control a chaotic system such that the chaos is replaced by periodic behaviour, using the intrinsic properties of chaos as much as possible in order to avoid &brute-force control'. The paper by Suykens et al. applies the support vector machine method to design a state feedback controller. The paper by Batlle et al. uses the time-delay feedback method to stabilize the desired periodic solution in buck converters in power electronics. This chaos control method allows the extension of the application range of the circuit to parameter regions that usually would result in undesirable chaotic behaviour.
Finally, the paper of Leenaerts is not linked to chaotic behaviour, but to &wave' propagation in lattices of di!usively coupled bistable circuits. It shows that the phenomenon of propagation failure can be advantageously used to realize completely new A/D converters.