无拖曳卫星的推进器不确定下鲁棒控制器设计

以低轨环境下无拖曳卫星控制器设计为研究对象,对于给定结构的无拖曳卫星,考虑推进器增益存在不确定时的鲁棒控制器设计。首先,简要介绍无拖曳卫星的概念及原理;之后,对带有不确定性的无拖曳卫星控制系统进行分析与建模,并对其进行LFT不确定性建模,最后利用μ分析和D-K迭代设计出满足鲁棒性能的鲁棒控制器。仿真结果说明鲁棒控制器的有效性。     

约束条件下的舵鳍联合减摇控制研究

舵鳍联合减摇是一种新型减摇方法。在已有研究文献的基础上,基于输入输出线性化的鲁棒控制器设计方法,针对某集装箱船设计舵鳍联合减摇控制器,并重点研究舵速、鳍速限制对减摇效果与航向保持效果的影响,探讨舵速与鳍速之间的制约关系。仿真结果表明鳍速越低、舵速越高则减摇效果越好,但舵速、鳍速均有一上限值,超过上限值后,舵速、鳍速变化对减摇效果及航向保持效果的进一步改善不再明显。     

基于T-S模型的双时变时滞不确定系统的鲁棒H∞容错控制

为了解决系统在含有执行器局部或者完全失效故障情况下的鲁棒H∞容错控制问题, 针对一类状态和控制输入同时存在时变时滞的不确定非线性系统, 采用T-S模糊模型来描述, 利用并行分布补偿（PDC）算法设计了模糊状态反馈控制器, 结合Lyapunov稳定性理论给出了保证该模糊容错控制系统渐近稳定的充分条件, 不但保证了系统输出的鲁棒稳定性, 而且能够满足给定的鲁棒H∞性能指标。最后通过MATLAB仿真对比系统中有外部干扰和无外部干扰情况下的系统输出曲线, 验证了所提出方法的可行性。     

Controller design for nonlinear systems using the Contoured Robust Controller Bode plot

In this paper, we develop the Contoured Robust Controller Bode (CRCBode) plot and demonstrate its use in the design of robust controllers for nonlinear single‐input single‐output (SISO) systems. The CRCBode plot shows contours (level sets) of a robust performance quantity on the Bode magnitude and phase plots of the controller. An iterative frequency domain loop‐shaping design approach is employed to eliminate all intersections of the controller frequency response with certain ‘forbidden regions,’ indicating that a standard SISO robust stability and performance criterion is satisfied. Nonlinearities are accounted for by avoiding the maximum forbidden regions over a structured uncertainty set consisting of linearizations of the system dynamics about several operating points. We demonstrate this technique by designing and experimentally verifying a flow‐rate controller for a butterfly‐valve based liquid cooling system, which is robust to valve nonlinearities and flow disturbances. Finally, we compare this compensator with one generated using an automated H _∞ synthesis algorithm and discuss the advantages of the CRCBode approach. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantized output feedback stabilization of uncertain systems with input nonlinearities via sliding mode control

This paper is concerned with the quantized output feedback stabilization problem for a class of uncertain systems with nonsmooth nonlinearities in the actuator device via sliding mode control schemes. It is assumed that system signals are quantized before being transmitted through communication channels. First, a dynamical compensator is developed to estimate unmeasurable system state. Then a sliding surface, in the augmented space using the system output and the estimated state, is proposed, and an adaptive sliding mode control scheme with a static adjustment law of the quantization parameter is established. It is shown that the proposed quantized feedback control strategy is able to tackle parameter uncertainty, external disturbances, and nonsymmetric input nonlinearity simultaneously and guarantees the reachability of the sliding modes of the uncertain system. Finally, an example is given to verify the validity of the theoretical results. Copyright © 2012 John Wiley & Sons, Ltd.     

A generalized robust H ∞ filtering for singular Markovian jump systems and its applications

In this paper, a generalized robust H _∞ filtering method is proposed for a class of singular Markovian jump systems, whose generality is mainly embodied that the desired filter could bear perturbances in terms of uncertainties on its parameter matrices. Firstly, an LMI condition of robust mode‐dependent filter is developed. Based on the given result, a new approach to mode‐independent H _∞ filter is presented, which establishes a direct connection between mode‐dependent and mode‐independent filters. Secondly, when the transition rate matrix is with elementwise bounded uncertainties or partially unknown, sufficient conditions of such robust mode‐dependent and mode‐independent filters are all developed within LMI frameworks. Finally, a numerical example is used to demonstrate the effectiveness of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd.     

A quantitative feedback solution to the multivariable tracking error problem

This paper introduces a novel solution for the multi‐input multi‐output (MIMO) quantitative feedback theory control design problem with tracking error specifications. Looking for a minimum controller overdesign, the technique finds new controller quantitative feedback theory bounds based on necessary and sufficient conditions for the existence of suitable associated prefilter matrix elements. It improves previous approaches to the subject and includes (i) the possibility of a free selection of the nominal plant, (ii) a less conservative application of the Schwartz inequality to decisively reduce the potential controller overdesign, (iii) a methodology to design independently the elements of the prefilter matrix, and (iv) a scope of application to both sequential and nonsequential MIMO controller design methods. The benefits of the new control design technique are illustrated by means of two examples. The first one, a standard 2 × 2 MIMO problem, is provided for comparison purposes with previous approaches. The second example, included as a major control challenge, deals with a well‐known demanding distillation column benchmark problem. Copyright © 2013 John Wiley & Sons, Ltd.     

Robust consensus for uncertain multi‐agent systems with discrete‐time dynamics

This paper investigates robust consensus for multi‐agent systems with discrete‐time dynamics affected by uncertainty. In particular, the paper considers multi‐agent systems with single and double integrators, where the weighted adjacency matrix is a polynomial function of uncertain parameters constrained into a semialgebraic set. Firstly, necessary and sufficient conditions are provided for robust consensus based on the existence of a Lyapunov function polynomially dependent on the uncertainty. In particular, an upper bound on the degree required for achieving necessity is provided. Secondly, a necessary and sufficient condition is provided for robust consensus with single integrator and nonnegative weighted adjacency matrices based on the zeros of a polynomial. Lastly, it is shown how these conditions can be investigated through convex programming by exploiting linear matrix inequalities and sums of squares of polynomials. Some numerical examples illustrate the proposed results. Copyright © 2013 John Wiley & Sons, Ltd.     

Robust adaptive control for a class of cascaded nonlinear systems with applications to space interception

This paper proposes a robust H _∞ ‐based adaptive backstepping control scheme for the output stabilization of a special class of cascaded nonlinear systems. This kind of systems possess the feature that the first sub‐equation is a linear perturbed system, whereas the rest ones perform a general semi‐strict feedback form. Different from the conventional backstepping design approach, the special cascaded structure ensures to introduce the H _∞ technique to the backstepping procedure such that both the robust performance and the robust stability can be simultaneously guaranteed. Within the Lyapunov framework, the proposed control scheme is proved to guarantee (i) the uniformly ultimate boundedness of the system signals with a bound that can be made arbitrarily small by suitably choosing control parameters; (ii) asymptotic output stabilization as long as the uncertain nonlinearities and external disturbances vanish; and (iii) ‐performance of the closed‐loop system. A space interception scenario is utilized to demonstrate the effectiveness of the proposed control scheme. Copyright © 2013 John Wiley & Sons, Ltd.     

PROCESS CONTROL PERSPECTIVE FOR PROCESS ANALYTICAL TECHNOLOGY: INTEGRATION OF CHEMICAL ENGINEERING PRACTICE INTO SEMICONDUCTOR AND PHARMACEUTICAL INDUSTRIES

FDA's Process Analytical Technology (PAT) initiative provides an unprecedented opportunity for chemical engineers to play significant roles in the pharmaceutical industry. In this article, the authors provide their perspectives on (1) the need for chemical engineering principles in pharmaceutical development for a thorough process understanding; (2) applications of chemical engineering principles to meet the challenges from the semiconductor and pharmaceutical industries; and (3) the integration of chemical engineering practice into the semiconductor and pharmaceutical industries to achieve process understanding and the desired state of quality-by-design. A real-world case study from the semiconductor industry is presented to demonstrate how a classic chemical engineering concept, mixing homogeneity, can be implemented by inducing forced flow to ensure an excellent copper electrochemical plating process performance and to improve product quality substantially. Further, a case study of brake system design is discussed with the concept of Dr. Taguchi's robust engineering design to illustrate how quality-by-design can be achieved through appropriate experimental design, in conjunction with the discussion on the concept of quality-by-design in pharmaceuticals. Third, a case study of freeze-dried sodium ethacrynate is presented to demonstrate the vital importance of controlling the processing factors to achieve the desired product stability. Finally, the problems of the current pharmaceutical manufacturing mode, the opportunities and engineering challenges during implementation of PAT in the pharmaceutical industry, and the role of chemical engineering in implementation of PAT is discussed in detail.