Complex chaotic systems are of great significance in practical applications such as encryption, secure communication, random sequence, key design, signal processing, and signal detection. Therefore, it is significant and necessary to control and analyze the complexity of chaotic systems.

Over the course of several years, more and more attention has been focused on new control methods to improve the complexity of different chaotic systems. Generally, the complexity of a chaotic system is evaluated by the Lyapunov exponent, frequency spectrum, random entropy, topological structure, multistability, etc. At present, many new analytical techniques to increase the complexity of chaotic system are proposed. However, there are still various theoretical and technical issues which should be investigated in such subjects.

This Special Issue aims to introduce and discuss new results, new methods, and new applications for complexity control and complexity analysis of nonlinear systems. We welcome original research and review articles relating to the themes of this special issue.

Potential topics include but are not limited to the following:

• High-dimensional hyperchaotic systems with multiple positive Lyapunov exponents
• Chaotic or hyperchaotic systems with large Lyapunov exponent
• Chaotic or hyperchaotic systems with wide frequency spectrum
• Fractional chaotic systems with high complexity and multistability
• Chaotification of linear or nonlinear systems
• Chaos, chimeras and spiral waves in biological systems
• Melkinov analysis and chaos in mechanical systems
• Complexity analysis and complexity measurement of chaotic time series
• Dynamical degradation of digital chaos
• Multi-scroll or multi-wing chaotic attractors
• Multistability, self-excited, and hidden attractors in chaotic systems
• Chaos-based image encryption, sound encryption, and sound steganography
• Chaos-based cryptosystem and secure communications
• Chaotic signal processing and detection