一类仿射非线性系统的自适应神经网络输出反馈变结构控制

本文研究了一类仿射非线性系统的输出反馈控制问题. 在介绍文献[4~6]的基础上, 提出一种基于神经网络参数化技术的自适应变结构输出反馈控制方案, 该方案能够避免使用严格正实(SPR)条件, 它不仅能够保证收缩条件的可行性, 而且还可以分析闭环系统的稳态和暂态的一致有界性, 并能够对观测增益和控制参数的选取进行清楚地分析.     

不确定系统D稳定与方差约束的鲁棒H∞可靠控制

研究了一类不确定系统区域稳定和方差约束的鲁棒H∞可靠控制器的设计方法,其目的是通过设计状态反馈控制器,使闭环系统的极点被配置在给定的圆盘中,同时,当有外生扰动,以及所有可能的不确定及其敏感执行器失效的时候,依然能满足闭环传递函数H∞范数有界和稳态方差的约束.借助于LMI和凸优化技术,给出了控制器存在的充分条件及其解析式.最后,通过一个仿真例子,说明该方法的可行性.     

基于积分二次约束时滞不确定系统的H∞可靠性控制

把基于积分二次约束H∞可靠性控制方法引入状态与时滞不确定系统。通过LMI方法导出无扰动时滞系统具有二次约束H∞可靠性控制的时滞依赖标准,降低有关判定系统鲁棒稳定性条件的保守性。通过推导获得参数与时滞不确定系统的时滞依赖标准。通过数例说明所得结论。     

一类非线性参数化系统自适应重复学习控制

针对一类高阶非线性参数化系统, 利用分段积分机制, 提出了一种新的自适应重复学习控制方法. 该方法结合反馈线性化, 可以处理参数在一个未知紧集内周期性快时变的非线性系统, 通过引进微分-差分混合型参数自适应律, 设计了一种自适应控制策略, 使广义跟踪误差在误差平方范数意义下渐近收敛于零, 通过构造Lyapunov泛函, 给出闭环系统收敛的一个充分条件. 实例仿真结果说明了该方法的可行性.     

一类不确定非线性系统的停息时间可调的有限时间镇定

研究了一类带有零动态不确定非线性系统有限时间镇定问题, 给出了具有更强实用性的停息时间可调的有限时间稳定控制设计方法. 基于有限时间稳定的Lyapunov理论和反推技术, 给出了停息时间可调有限时间稳定控制器的设计步骤. 所设计的状态反馈控制器使得闭环系统全局有限时间稳定, 且停息时间可调整, 特别是当系统初始值已知时, 停息时间可以任意调节. 仿真例子验证了本文的主要结论.     

Robust output feedback learning control for induction motor servo drives

This paper addresses the output feedback tracking control problem for induction motor servo drives with mechanical uncertainties: rotor angle, rotor speed and stator currents are assumed to be available for feedback. A robust adaptive learning control is designed under the assumption that the reference profile for the rotor angle is periodic with known period: it ‘learns’ the periodic disturbance signal by identifying the Fourier coefficients of any truncated approximation; ??₂ and ??_∞ transient performances are guaranteed in the ‘learning phase’. It is shown that, for any motor initial condition belonging to an arbitrary given compact set, by properly setting the control parameters: (i) the rotor position and flux modulus tracking errors exponentially converge to residual sets, which may be arbitrarily reduced by increasing the number of terms in the truncated Fourier series; (ii) when the unknown periodic disturbance can be represented by a finite Fourier series, the rotor position and flux modulus tracking errors exponentially converge to zero. As in field oriented‐control, the control algorithm generates references for the magnetizing flux component and for the torque component of the stator current leading to significant simplifications for current‐fed motors. Copyright © 2008 John Wiley & Sons, Ltd.     

Switching contact task control in hydraulic actuators: Stability analysis and experimental evaluation

A switching contact task control for hydraulic actuators is proposed. The controller is built upon three individually designed control laws for three phases of motion: (1) position regulation in free space, (2) impact suppression and stable transition from free to constrained motion and (3) force regulation in sustained‐contact motion. The position and force control schemes are capable of asymptotic set‐point regulation in the presence of actuator friction and without the complexity of sliding mode or adaptive control techniques. The intermediate impact control scheme is included for the first time to dampen the undesirable impacts and dissipate the impact energy that could potentially drive the whole system unstable. The solution concept and the stability of the complete switching control system are analyzed rigorously using the Filippov's solution concept and the concept of Lyapunov exponents. Both computer simulations and experiments are carried out to demonstrate the efficacy of the designed switching control law. Copyright © 2009 John Wiley & Sons, Ltd.     

Analytical formulation to compute QFT bounds: The envelope method

This paper describes an analytical formulation to compute quantitative feedback theory (QFT) bounds in one‐degree‐of‐freedom feedback control problems. The new approach is based on envelope curves and shows that a QFT control specification can be expressed as a family of circumferences. Then, the controller bound is defined by the envelope curve of this family and can be obtained as an analytical function. This offers the possibility of studying the QFT bounds in an analytical way with several useful properties. Gridding methods are avoided, resulting in a lower computational effort procedure. The new formulation improves the accuracy of previous methods and allows the designer to calculate multivalued bounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Output feedback variable structure control of uncertain linear systems in the presence of actuator dynamics

A new output feedback variable structure control scheme is developed based on a novel passivity idea. This scheme may practically stabilize a class of higher‐relative‐degree uncertain linear systems, and realize output tracking and disturbance attenuation as well. The controller is composed of linear filters and a single relay, without employing real‐time exact differentiators. Under this framework, we also explain how actuator dynamics affect the closed loop behavior. A simulation example shows the simplicity and efficiency of this method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society