线性自抗扰控制系统的鲁棒稳定性

针对线性自抗扰控制系统,研究了模型参数不确定情况下的鲁棒稳定性问题.首先给出对象为非自治模型时该系统的H∞判据.然后针对线性误差模型的状态矩阵只在某一行存在不确定参数的情况,基于奇异值理论,得到H∞判据的一种新的等价描述,把H∞范数约束转化为对奈奎斯特图的约束.之后为了降低新判据在实际应用中的保守性,对不确定性矩阵的分解方式进行优化.在此基础之上提出了一种新的方法,用于计算时变参数不确定性的最大边界,为线性自抗扰控制器设计提供理论依据.数值实例表明该方法不仅保守性小,而且计算简单.     

Fault-tolerant control of delta operator systems with actuator saturation and effectiveness loss

This paper studies the problem of robust fault-tolerant control against the actuator effectiveness loss for delta operator systems with actuator saturation. Ellipsoids are used to estimate the domain of attraction for the delta operator systems with actuator saturation and effectiveness loss. Some invariance set conditions used for enlarging the domain of attraction are expressed by linear matrix inequalities. Discussions on system performance optimisation are presented in this paper, including reduction on computational complexity, expansion of the domain of attraction and disturbance rejection. Two numerical examples are given to illustrate the effectiveness of the developed techniques.     

ADRC Law of Spacecraft Rendezvous and Docking in Final Approach Phase

This article addresses the high-precision coordinated control problem of spacecraft autonomous rendezvous and docking, which couple the relative position and attitude in the final approach phase. The coupled dynamics equations of the tracking-target spacecrafts is derived by using dual quaternions. Then, a cascade Active Disturbance Rejection Controller is proposed, by which the extended state observer and nonlinear error feedback law is designed, the virtual value on which the actual control volume tracking is calculated to ensure the finite time convergence of the relative position and attitude tracking errors in spite of parametric uncertainties and external disturbances. Finally, numerical simulations are performed to demonstrate that the proposed approaches, which can avoid the coupling effect and restrain the interference, can track the target spacecraft in a relatively short period of time, and the control precision can satisfy the requirements of docking.     

跳变系统在给定时间内的有限频段H∞控制

本文针对特定频段的干扰信号,为多模态跳变系统设计给定时间控制器,在给定时间内设法使各模态轨迹在期望范围受限运动,且具有更强的干扰抑制能力.所提控制方案不仅从时间角度为降低跳变系统控制器设计的保守性提供了思路,频段信息的引入也从频率角度降低了设计结果的保守性.仿真示例验证了所提算法的有效性以及优越性.     

气动人工肌肉关节的自抗扰控制

气动人工肌肉关节系统是一个强非线性时变自平衡2阶系统,鉴于传统控制方法难以克服控制精度、调节速度和稳定性之间的矛盾,设计了一种2阶自抗扰控制器.采用3阶扩张状态观测器实时估计未建模型部分及外界扰动,对系统进行线性补偿,并利用非线性反馈机制提高控制效率,在保证稳定性的前提下,提高调节速度和控制精度,使得系统的稳态精度小于...     

On the two-degree-of-freedom Wiener–Hopf optimal design with tracking and disturbance rejection constraints

In this paper, the design of the two-degree-of-freedom optimal Wiener–Hopf controller with asymptotic tracking and disturbance rejection constraints is studied. Based on the solvability conditions and the solution parameterization of Diophantine equations over the stable rational fractional ring M(s), the disturbance rejection problem in the general case is solved. A simple cost function is defined to reflect the transient performance of control signal caused by deterministic signals. Finally, the design of the two-degree-of-freedom optimal Wiener–Hopf controller is presented.     

Performance Analysis of Periodic Control for l1 and l∞ Disturbance Rejection

This paper presents a performance analysis of discrete time periodically time varying controllers for the rejection of l_p specific and uniform disturbances. Earlier results on l₂ performance are extended to l₁ and l_∞ performance to present a unified treatment of l_p performance for all p ε [1, ∞]. For a given linear time varying periodic controller, a linear time invariant controller is constructed and necessary and sufficient conditions are presented under which the linear time invariant controller gives strictly better l_p disturbance rejection performance than the time varying periodic controller.     

A self-recovery fragile watermarking scheme for image authentication with superior localization

To address the problems of the inferior localization and high probability of false rejection in existing self-recovery fragile watermarking algorithms, this paper proposes a new self-recovery fragile watermarking scheme with superior localization, and further discusses the probability of false rejection （PFR） and the probability of false acceptance （PFA） of the proposed scheme. Moreover, four measurements are defined to evaluate the quality of a recovered image. In the proposed algorithm, the original image is divided into 2×2 blocks to improve localization precision and decrease PFR under occurrence of random tampering. The PFR under occurrence of region tampering can be effectively decreased by randomly embedding the watermark of each block in conjunction with a novel method of tamper detection. Compared with the current self-recovery fragile watermarking algorithms, the proposed scheme not only resolves the tamper detection problem of self-embedding watermarking, but also improves the robustness against the random tampering of self-embedding watermarking. In addition, the subjective measurements are provided to evaluate the performance of the self-recovery watermarking schemes for image authentication.     

Output regulation of two-time-scale hyperbolic PDE systems

This paper addresses the output regulation of flow systems described by a class of two-time-scale nonlinear PDE systems. Within the framework of singular perturbation, the reduced-order slow model comprised of first-order PDEs coupled with ODEs is obtained. Based on the numerical approximation technique and the solvability of an inertial manifold, the finite-dimensional nonlinear model with nonlinear input is developed in this paper. Extending from the geometric control method, the non-distributed nonlinear controller can be synthesized. A combination of the state-space internal model control scheme, the reduced observer-based controller can asymptotically attenuate the effect of external disturbances. Finally, the developed methodologies are successfully applied to the development of a PFR system asscociated with the cooling coil apparatus.     

重复控制系统中非周期扰动的抑制

为了改善重复控制系统中的扰动抑制性能,提出一种基于曲率模型的扰动估计新方法.该方法的主要特点是扰动的估计值直接与重复控制规则结合也不影响重复控制系统的稳定性.仿真结果显示该方法可以有效地抑制扰动.