磁悬浮直线电动机H∞鲁棒控制器及其蚁群算法优化设计

磁悬浮永磁直线电动机在结构上取消了机械传动的中间环节,具有磁悬浮和直接驱动的特点.针对磁悬浮永磁直线电动机由于悬浮高度不同,在磁悬浮和直接驱动运行过程中存在自身参数摄动和外界干扰突出的问题,设计基于蚁群算法的H_∞鲁棒控制器,以保证系统对这些不确定性具有良好的鲁棒性.建立包含磁悬浮永磁直线电动机参数摄动和外界干扰的状态空间模型.推导出无须满足正则条件约束的Riccati不等式,给出H_∞鲁棒控制器的解析表达式.针对H_∞控制器中加权矩阵选择的困难,采用蚁群算法对加权矩阵进行寻优.最后在MATLAB环境下对控制系统进行仿真研究.仿真实验表明基于蚁群算法的磁悬浮永磁直线电动机控制系统的性能比优化前有较明显改善,说明该方法的可行性和有效性.     

基于改进快速鲁棒性特征的导弹视频特征匹配

利用电视制导导弹视频图像确定导弹落点,从而开展精确目标毁伤评估研究,是目前全新的一种评估手段。图像特征匹配是利用视频图像确定导弹落点的关键步骤。针对导弹视频图像的特点及其作战应用,在特征匹配阶段,依据准确性和实时性两个原则,对快速鲁棒性特征算法做了两方面的改进:一是限制特征点提取区域,定义了图像区域限制算子;二是限制特征点数量,利用算法阈值和随机抽样一致性算法对特征点进行限制。实验结果表明,提出的算法对典型视频片段进行处理,较原算法在匹配时间上平均减少12.6%,匹配准确率平均提升13.4%,较尺度不变特征变换算法匹配时间平均提升了74.9%,同时,有效消除伪匹配点。通过对三段视频进行测试仿真,改进算法在整体上较原算法的匹配时间加快14.9%,且通用性较强,适用于视频图像的特征点匹配。     

A robust estimation approach for uncertain systems with perturbed measurements

This paper deals with state estimation problem for uncertain continuous‐time systems. A numerical treatment is proposed for designing interval observers that ensures guaranteed upper and lower bounds on the estimated states. In order to take into account possible perturbations on the system and its outputs, a new type of interval observers is introduced. Such interval observers consist of two coupled general Luenberger‐type observers that involve dilatation functions. In addition, we provide an optimality criterion in order to find optimal interval observers that lead to tight interval error estimation. The proposed existence and optimality conditions are expressed in terms of linear programming. Also, some illustrative examples are given. Copyright © 2015 John Wiley & Sons, Ltd.     

The Nyquist stability criterion in the Nichols chart

The Nyquist stability criterion is a widely used technique for determining in the complex s‐plane the stability of a dynamical system with feedback. This paper presents a practical and comprehensive method to compute the Nyquist stability criterion directly in the Nichols (magnitude/phase) chart. The proposed method also gives guidelines to design controllers to stabilize unstable plants when dealing with frequency domain techniques like the quantitative feedback theory robust control. Copyright © 2015 John Wiley & Sons, Ltd.     

Robust Input Covariance Constraint Control for Uncertain Polytopic Systems

In this paper, the robust input covariance constraint (ICC) control problem with polytopic uncertainty is solved using convex optimization with linear matrix inequality (LMI) approach. The ICC control problem is an optimal control problem that optimizes the output performance subjected to multiple constraints on the input covariance matrices. This control problem has significant practical implications when hard constraints need to be satisfied on control actuators. The contribution of this paper is the characterization of the control synthesis LMIs used to solve the robust ICC control problem for polytopic uncertain systems. Both continuous‐ and discrete‐time systems are considered. Parameter‐dependent and independent Lyapunov functions have been used for robust ICC controller synthesis. Numerical design examples are presented to illustrate the effectiveness of the proposed approach.     

Robust‐Adaptive Control Strategies for a Time Delay Bioelectrochemical Process Using Interval Observers

The paper addresses the design and the analysis of adaptive and robust‐adaptive control strategies for a complex recycled wastewater treatment bioprocess. The design procedures are developed under the realistic assumptions that the bacterial growth rates are unknown and the influent flow rates are time‐varying and uncertain, but some lower and upper bounds of these uncertainties are known. The proposed control structures are achieved by combining a linearizing control law with an appropriately (asymptotic or interval based) state observer and with a parameter estimator used for on‐line estimation of unknown kinetics. These approaches are applied to a complex time delay bioprocess resulting from the association of a recycling bioreactor with an electrochemical reactor. Numerical simulations are performed in order to validate the proposed algorithms.     

Robust stability and stabilization of uncertain linear positive systems via integral linear constraints: L1‐gain and L∞‐gain characterization

Copositive linear Lyapunov functions are used along with dissipativity theory for stability analysis and control of uncertain linear positive systems. Unlike usual results on linear systems, linear supply rates are employed here for robustness and performance analysis using L₁‐gain and L_∞‐gain. Robust stability analysis is performed using integral linear constraints for which several classes of uncertainties are discussed. The approach is then extended to robust stabilization and performance optimization. The obtained results are expressed in terms of robust linear programming problems that are equivalently turned into finite dimensional ones using Handelman's theorem. Several examples are provided for illustration. Copyright © 2012 John Wiley & Sons, Ltd.     

Modeling and robust discrete LQ repetitive control of electrically driven robots

Discrete linear quadratic control has been efciently applied to linear systems as an optimal control.However,a robotic system is highly nonlinear,heavily coupled and uncertain.To overcome the problem,the robotic system can be modeled as a linear discrete-time time-varying system in performing repetitive tasks.This modeling motivates us to develop an optimal repetitive control.The contribution of this paper is twofold.For the frst time,it presents discrete linear quadratic repetitive control for electrically driven robots using the mentioned model.The proposed control approach is based on the voltage control strategy.Second,uncertainty is efectively compensated by employing a robust time-delay controller.The uncertainty can include parametric uncertainty,unmodeled dynamics and external disturbances.To highlight its ability in overcoming the uncertainty,the dynamic equation of an articulated robot is introduced and used for the simulation,modeling and control purposes.Stability analysis verifes the proposed control approach and simulation results show its efectiveness.     

On finite-time stability and stabilization of nonlinear port-controlled Hamiltonian systems

The finite-time stability and stabilization of nonlinear port-controlled Hamiltonian(PCH)systems are investigated in this paper,and a number of new results are proposed.Firstly,by exploiting the Hamiltonian structural properties,a proper form of the Hamiltonian function is obtained,based on which a finite-time stability criterion is then presented for a class of Hamiltonian systems.Secondly,using the obtained stability criterion and the so-called"energy shaping plus damping injection"technique,the continuous finite-time stabilization problem is studied for the PCH system,and several global stabilization results are provided.Finally,the continuous robust finite-time stabilization of the PCH system with external disturbances is investigated,and two results on designing global robust finite-time stabilizers are obtained.Study of several examples with numerical simulations shows that the control design approach developed in this paper works very well.     

A Robust Controller for A 3‐DOF Flexible Robot with a Time Variant Payload

This article describes a new control scheme designed for a three degree of freedom (3‐DOF) flexible robot. The control scheme consists of two multi variable control loops. The inner loop is the motor's position control system, while the outer loop controls the robot tip's position, thus canceling vibrations which are originated by the structural flexibility of the manipulator during movement. As it will be shown, the outer control loop is robust to payload variations. The outer loop performance is based on a perfect cancelation of the inner loop dynamics. The effects of not achieving such perfect cancelation are also studied, and rules for designing a robust controller in this case are developed. Simulations assuming different payloads have been carried out with successful results for trajectory tracking. Trajectory tracking with a variable payload is also achieved.