非线性系统有限时间受限控制

Any realistic system is restricted in one form or another. One of the restrictions is the lack of sensors and actuators. This paper addresses the problem of restricted control of nonlinear systems with a finite time approach. Important results are obtained on the design of controllers for stabilizing nonlinear systems in a finite time. Practical issues on control implementation are also discussed. The proposed design method is validated through its application to a Lorenz chaotic system

Two characterizations of switched nonlinear systems with average dwell time

This note aims to establish the fast switching condition with average dwell time satisfying an upper bound. Important results are obtained on the behaviour of switched nonlinear dynamical systems. In specific, this note contributes in the following three aspects: (1) establish the condition of fast switching of switched nonlinear systems; (2) obtain the condition of arbitrary switching stability of switched nonlinear dynamical systems using a weak Lyapunov functions approach; and (3) prove the necessity of the average dwell time condition associated with the conventional multiple Lyapunov functions’ framework

非线性系统的限制有限时间控制

Any realistic system is restricted in one form or another. One of the restrictions is the lack of sensors and actuators. This paper addresses the problem of restricted control of nonlinear systems with a finite time approach. Important results are obtained on the design of controllers for stabilizing nonlinear systems in a finite time. Practical issues on control implementation are also discussed. The proposed design method is validated through its application to a Lorenz chaotic system

Meet-in-the-Middle Attack on 8 Rounds of the AES Block Cipher under 192 Key Bits

The AES block cipher has a 128-bit block length and a user key of 128, 192 or 256 bits, released by NIST for data encryption in the USA; it became an ISO international standard in 2005. In 2008, Demirci and Selccuk gave a meet-in-the-middle attack on 7-round AES under 192 key bits. In 2009, Demirci et al. (incorrectly) described a new meet-in-the-middle attack on 7-round AES under 192 key bits. Subsequently, Dunkelman et al. described an attack on 8-round AES under 192 key bits by taking advantage of several advanced techniques, including one about the key schedule. In this paper, we show that by exploiting a simple observation on the key schedule, a meet-in-the-middle attack on 8-round AES under 192 key bits can be obtained from Demirci and Selccuk\u27s and Demirci et al.\u27s work; and a more efficient attack can be obtained when taking into account Dunkelman et al.\u27s observation on the key schedule. In the single-key attack scenario, attacking 8 rounds is the best currently known cryptanalytic result for AES in terms of the numbers of attacked rounds, and our attack has a dramatically smaller data complexity than the currently known attacks on 8-round AES under 192 key bits

Model-based acceleration control of turbofan engines with a Hammerstein-Wiener representation

Acceleration control of turbofan engines is conventionally designed through either schedule-based or acceleration-based approach. With the widespread acceptance of model-based design in aviation industry, it becomes necessary to investigate the issues associated with model-based design for acceleration control. In this paper, the challenges for implementing model-based acceleration control are explained; a novel Hammerstein-Wiener representation of engine models is introduced; based on the Hammerstein-Wiener model, a nonlinear generalized minimum variance type of optimal control law is derived; the feature of the proposed approach is that it does not require the inversion operation that usually upsets those nonlinear control techniques. The effectiveness of the proposed control design method is validated through a detailed numerical study

Two Iterative algorithms for the matrix sign function based on the adaptive filtering technology

In this paper, two new efficient algorithms for calculating the sign function of the large-scale sparse matrix are proposed by combining filtering algorithm with Newton method and Newton Schultz method respectively. Through the theoretical analysis of the error diffusion in the iterative process, we designed an adaptive filtering threshold, which can ensure that the filtering has little impact on the iterative process and the calculation result. Numerical experiments are consistent with our theoretical analysis, which shows that the computational efficiency of our method is much better than that of Newton method and Newton Schultz method, and the computational error is of the same order of magnitude as that of the two methods.Comment: 18 pages,12 figure

FMI-Based Multi-Domain Simulation for an Aero-Engine Control System

The simulation of an aero-engine control system involves numerous disciplines due to its complex functions and architecture, which generally consist of mechanical, hydraulic and electrical, and electronic systems. For each discipline, the modeling and simulation are usually dependent on different commercial software and tools, which makes the simulation, integration, and verification of system-level models very difficult. To meet this challenge, a multi-domain co-simulation method based on the Functional Mock-up Interface (FMI) standard is proposed to integrate models developed by different software or tools. The simulation and testing results demonstrate that multi-disciplinary model integration and cross-platform simulation based on the FMI standard can be realized for an aero-engine control system, which lays a foundation for high-fidelity control system design, simulation, integration, and testing

Design and Verification of Aeroengine Rotor Speed Controller Based on U-LADRC

Due to the harsh working environment, engine electronic controller (EEC) has limited computing power. Many advanced control algorithms are difficult to be applied in practice because of complexity of calculation. In this paper, a novel aeroengine transient-speed controller with low algorithm complexity is designed by combining linear parameter varying (LPV) model with U-control theory. Aiming at restraining bad performance influence caused by possible disturbance in cruise, linear active disturbance rejection control (LADRC) compensation is integrated as the U-LADRC controller. This new controller is verified in both the digital simulation platform and hardware-in-the-loop (HIL) platform. The experimental results of the HIL platform show that the U-LADRC control algorithm meets the real-time performance of the EEC in the actual aeroengine. It has good transition state control performance and good steady-state antidisturbance ability, which ensures the smooth operation of the engine in the steady state and has a good practical application prospect