Fengling Han

Generating 3-D multi-scroll chaotic attractors: A hysteresis series switching method

This paper introduces a systematic method-a hysteresis series switching approach-for generating multi-scroll chaotic attractors from a three-dimensional linear autonomous system, including 1-D n-scroll, 2-D nxm-grid scroll, and 3-D nxmxl-grid scroll chaotic attractors. The chaos generation mechanism is studied by analyzing the system trajectories and the hysteresis switching dynamics of the controlled chaotic systems are explored. Moreover, a two-dimensional Poincare return map is rigorously derived. This map and its maximum Lyapunov exponent are applied to verifying the chaotic behaviors of the generated 3-D multi-scroll chaotic attractors.

On nonsingular terminal sliding-mode control of nonlinear systems

This paper proposes a method to overcome the singularity problem of terminal sliding-mode control systems. The system behaviors in both the reaching phase and the ideal sliding-mode are analyzed. A global nonsingular terminal sliding-mode control strategy for nonlinear systems is developed and it is shown that the proposed control strategy can eliminate the singularity, while guaranteeing the finite-time reachability of the systems to the terminal sliding-mode surface and the finite-time convergence of the systems towards the origin along the terminal sliding-mode surface.

Chattering free full-order sliding-mode control

In conventional sliding-mode control systems, the sliding-mode motion is of reduced order. Two main problems hindering the application of the sliding-mode control are the singularity in terminal sliding-mode control systems and the chattering in both the conventional linear sliding-mode and the terminal sliding-mode control systems. This paper proposes a chattering-free full-order terminal-sliding-mode control scheme. Since the derivatives of terms with fractional powers do not appear in the control law, the control singularities are avoided. A continuous control strategy is developed to achieve the chattering free sliding-mode control. During the ideal sliding-mode motion, the systems behave as a desirable full-order dynamics rather than a desirable reduced-order dynamics. A systematic design method of full-order sliding-mode control for nonlinear systems is presented, which allows both the chattering and singularity problems to be resolved. Simulations validate the proposed chattering free full-order sliding-mode control.

On the cluster consensus of discrete-time multi-agent systems

Nowadays, multi-agent systems (MAS) are ubiquitous in the real world. Consensus is a fundamental natural phenomenon. Over the past decade, consensus of MAS has received increasing attention from various disciplines. This paper aims to further investigate a novel kind of cluster consensus of MAS with several different subgroups. Based on Markov chains and nonnegative matrix analysis, two novel cluster consensus criteria are obtained for MAS with fixed and switching topology, respectively. Furthermore, numerical simulations are also given to validate the effectiveness of these proposed criteria. The proposed cluster consensus criteria have some potential applications in real world engineering systems.

High-Order Terminal Sliding-Mode Observer for Parameter Estimation of a Permanent-Magnet Synchronous Motor

This paper proposes a terminal sliding-mode (TSM) observer for estimating the immeasurable mechanical parameters of permanent-magnet synchronous motors (PMSMs) used for complex mechanical systems. The observer can track the system states in finite time with high steady-state precision. A TSM control strategy is designed to guarantee the global finite-time stability of the observer and, meanwhile, to estimate the mechanical parameters of the PMSM. A novel second-order sliding-mode algorithm is designed to soften the switching control signal of the observer. The effect of the equivalent low-pass filter can be properly controlled in the algorithm based on requirements. The smooth signal of the TSM observer is directly used for the parameter estimation. The experimental results in a practical CNC machine tool are provided to demonstrate the effectiveness of the proposed method.

A fingerprint based bio-cryptographic security protocol designed for client/server authentication in mobile computing environment

With fast evolution of mobile devices and mobile network, the need of protecting user sensitive information locally and performing secure user authentication remotely become evermore increasing. Bio-cryptography is emerging as a powerful solution which can combine the advantages of conventional cryptography and biometric security. In this paper, we present an efficient bio-cryptographic security protocol designed for client/server authentication in current mobile computing environment, with a reasonable assumption that server is secure. In this protocol, fingerprint biometric is used in user verification, protected by a computationally efficient Public Key Infrastructure (PKI) scheme, Elliptic Curve Cryptography (ECC). The genuine fingerprint information is hidden in the feature vault which is the mixture of genuine and chaff features. Fingerprint features are not only used for biometric verification but also for cryptographic key generation. Our security analysis shows that the proposed protocol can provide a secure and trustworthy authentication of remote mobile users over insecure network. Experimental results on public domain database show an acceptable verification performance. We also tested the computational costs and efficiency of our protocol on the CLDC emulator using Java ME (previous J2ME) programming technology. The simulation results prove that the proposed protocol suits current mobile environment. Copyright

Fingerprint images encryption via multi-scroll chaotic attractors

This paper proposes a chaotic fingerprint images encryption approach. An image of a fingerprint is encrypted via a two-dimensional (2D) chaotic sequence obtained from multi-scroll chaotic attractors. Initial values of the chaotic attractors are served as the private key, which can be generated from the pixel distribution of the binary images of the captured fingerprints. Due to the dynamic uncertainties in the acquisition process of fingerprint images, the keys generated from the pixel value distribution are virtually random. With the elaborately designed 2D chaotic sequence, the encrypted fingerprint images have balanced 0-1 ratio and ideal nonlinearity. Only with the valid private key can the images of fingerprint be recovered. Simulation results and 2D-DFT validate this chaotic encryption approach.

A chaos-based encryption technique to protect ECG packets for time critical telecardiology applications

Electrocardiography (ECG) signal is popularly used for diagnosing cardiovascular diseases (CVDs). However, in recent times ECG is being used for identifying person. As ECG signals contain sensitive private health information along with details for person identification, it needs to be encrypted before transmission through public media. Moreover, this encryption must be applied with minimal delay for authenticating CVD patients, as time is critical for saving CVD affected patient’s life. Within this paper, we propose the usage of multi-scroll chaos to encrypt ECG packets. ECG packets are being encrypted by the mobile phones using the chaos key by patients’ subscribed in tele-cardiology applications. On the other hand, doctors and hospital attendants receive the encrypted ECG packets, which can be decrypted using the same chaos key. Using the techniques described in this paper, end-to-end security can be applied to wireless tele-cardiology application, with minimal processing. Our experimentation with 12 ECG segments shows that with multi-scroll chaos implementation, CVD patients remain completely unidentified, upholding patients’ privacy and preventing spoof attacks. Most importantly, the proposed method is 18 times faster than permutation-based ECG encoding, 25 times faster than wavelet-based ECG annonymization techniques and 31 times faster than noise-based ECG obfuscation techniques, establishing the proposed technique as the fastest ECG encryption system according to the literature. Copyright

An alignment free fingerprint fuzzy extractor using near-equivalent Dual Layer Structure Check (NeDLSC) algorithm

Biometric techniques provide a feasible solution for protecting personal information at a high security level. However, biometric features themselves demand protection. As a promising method, fuzzy extractor seamlessly binds a cryptographic key to biometric features, in order to prevent both keys and features being exposed to attackers. Some related research has been done in this area however three major issues are still unsolved, which are : 1) Feature alignment 2) Verification accuracy. 3) Information leakage. In this paper, an alignment-free fingerprint fuzzy extraction scheme is proposed. To eliminate the alignment process, we use the minutia local structure features which has been proved to be stable, discriminative, rotation and shift free. The Dual Layer Structure Check (DLSC) verification scheme is base on the minutia local structure and it achieves a high verification performance. In this paper, we proposed a near-equivalent version of DLSC (NeDLSC) that can be directly employed by the existing bio-cryptographic constructions. Then a new fuzzy extractor scheme which is on the basis of NeDLSC is demonstrated. The preliminary experiments on publicly-available database FVC2002 shows a high verification accuracy.

Mobile device access control: an improved correlation based face authentication scheme and its Java ME application

This paper investigates face authentication based access control solutions for camera‐equipped mobile devices. A new hierarchical correlation based face authentication (HCFA) scheme is proposed, which suits resource‐constrained mobile devices such as mobile phones and personal digital assistants. The idea of HCFA is conducting a partial correlation output peak analysis (analyze the relationship between each cross‐correlation output peak generated from selected sub‐regions of a face), in conjunction with conventional direct cross‐correlation methods. The experimental results on the public domain database demonstrate that the proposed scheme achieved better performance than that of the conventional direct correlation based schemes. Furthermore, HCFA was implemented on the Nokia S60 CLDC emulator using Java ME (previously J2ME) programming technology in order to test the applicability and implementability. The test results show that the proposed algorithm is implementable on mobile devices. It not only shortens processing time but also reduces resource demand significantly, compared with the direct correlation algorithms. Copyright