基于多面体描述系统的鲁棒非线性预测控制

针对一类具有持续有界扰动的离散时间非线性系统, 提出一种基于多面体描述系统的鲁棒非线性模型预测控制策略. 首先利用泰勒级数构造多面体描述系统包裹原系统. 其次, 对该多面体描述系统构造鲁棒终端不变集和仿射输入型预测控制律. 进一步, 利用离散系统的输入状态实际稳定性(Input-to-state practical stability, ISpS)概念证明了闭环系统的鲁棒稳定性. 最后, 通过仿真验证了本结果的有效性.     

Set invariance under output feedback: a set-dynamics approach

The article offers a framework to define and analyse the notion of invariance with respect to output feedback under non-parametric disturbances. The motivation is that the straightforward generalisation of the definition of invariance under state feedback to the output feedback framework, namely relying only on feedback from the output, does not yield a useful notion. Our model follows standard feedback invariance considerations with, however, a crucial modification that is needed when only an observation of the state, rather than the state itself, is available. The model incorporates information gathered by the controller during the process; this is in similarity with the observer-based dynamics model; however our framework represents the information within a set dynamics. The evolution of the resulting information sets determines invariant sets and attractors of the state dynamics. The framework in this article is discrete-time control systems. We offer an analysis of the notion with results on existence of, and convergence to, output feedback invariant sets; illustrative examples related to potentially practical feedback rules are exhibited.     

The invariance property of control systems with imperfect relay elements

We consider the problem of ensuring the invariance property for a linear stationary system with relay controls. In the case of perfect relays, wide-class exogenous disturbances are compensated theoretically on the basis of sliding mode theory. Existing imperfections of relay elements make it impossible to implement a perfect sliding mode; thus, the closed-loop system has dynamics in a zero neighborhood of the given variety. This causes undesirable oscillations in a steady-state mode (“chattering”), leading to missed invariance with respect to exogenous and parametric disturbances. This paper solves the problem of ensuring invariance under imperfect relay elements and involves two approaches. The first one allows for making the relay characteristic close to that of the perfect counterpart (by means of increasing the feedback amplification coefficient); consequently, the chattering problem is eliminated. The second approach proceeds from the high-frequency modulation principle and performs regularization of relay switchings; using the linearization effect for the relay characteristics, the second approach guarantees the invariance property.     

线性切换系统的积分不变性原理

将积分不变性原理进行推广, 用来讨论线性切换系统的稳定性. 作为LaSalle不变性原理的推广, 文中推广的积分不变性原理无需构造Lyapunov函数, 而是利用系统输出的可积性, 讨论线性切换系统输出为零的状态集合的稳定性. 另外, 讨论了切换系统状态集合稳定性与切换信号之间的关系. 利用线性切换系统的可观测性, 讨论了系统平衡点的渐近稳定性. 数值例子说明了文中方法的有效性.     

An off-line cursive handwriting recognition system

Describes a complete system for the recognition of off-line handwriting. Preprocessing techniques are described, including segmentation and normalization of word images to give invariance to scale, slant, slope and stroke thickness. Representation of the image is discussed and the skeleton and stroke features used are described. A recurrent neural network is used to estimate probabilities for the characters represented in the skeleton. The operation of the hidden Markov model that calculates the best word in the lexicon is also described. Issues of vocabulary choice, rejection, and out-of-vocabulary word recognition are discussed     

Invariant Aircraft Control Under Wind Disturbances

A method is developed for compensating the effect of wind disturbances on the flight path of an aircraft. Computer modeling of the method is performed. An approach is considered based on methods of the theory of absolute nonlinear invariance. The results of computer modeling of the method developed for compensating the influence of turbulent atmosphere on the flight of an aircraft are presented with a view to comparing its efficiency with that of an existing method for compensating the influence of turbulent atmosphere. The use of the conception of aircraft control based on the theory of absolute nonlinear invariance in designing automatic control systems will make it possible to implement an efficient method for flight control under uncertainty and external disturbances that has advantages over existing methods and will provide the comfort of passengers and safety of flights.     

基于多模型混合的广义最小方差控制性能评估

针对实际工业过程中控制系统经常会受到时变扰动的影响,致使针对单一扰动模型设计的性能评估方法不再适用于时变扰动控制系统的问题,提出了基于多模型混合的广义最小方差控制性能评估方法．该方法综合考虑被控对象输出方差与控制器输出方差的两个指标,同时提出了一种“判断—加权”的控制器设计策略．首先,在任一时间段选取使广义输出方差最小的控制器,并判断其与上一时间段采用的控制器是否一致;然后,在此基础上采用多模型混合思想进行控制器设计,并将其作用下的广义输出方差作为性能评估的基准．通过乙烯裂解炉仿真,验证了本文所述方法在时变系统性能评估中的有效性．     

Output feedback control for rigid-body attitude with constant disturbances

In this article, the control problem of rigid-body attitude under constant disturbances without angular-velocity measurement is solved by the combination of the immersion and invariance methodology and the dynamic scaling technique. Two observers, which are respectively for estimating the angular velocity and the disturbance, are constructed by utilising the immersion and invariance method. The mismatched term arising from the observers is dominated by the high-gain injection. The control law is a simple proportional-derivative controller plus a disturbance compensation term, where the estimates of the angular velocity and the disturbance from observers are used for feedback directly. The overall closed-loop system is shown to be almost globally asymptotically stable under easy choices of some control parameters. Finally, simulations are conducted to demonstrate the effectiveness of the proposed control scheme.     

伺服系统中抑制非线性扰动的有限维重复控制方法

针对一类具有严重非线性扰动的伺服系统,提出一种有限维重复控制方法以实现高精度的信号跟踪.所考虑的扰动与系统输出间存在未知非线性关系,仅设其满足连续里普希斯条件,便可处理大多数实际情况.应用不动点原理,给出了所提出方法有效的充分条件,该条件也是应用基于系统周期不变性的学习控制方法的必要条件.在稳定的闭环系统中,利用H阶有限维重复控制器,可实现参考信号前H次谐波的渐近跟踪.仿真结果证明了方法的有效性.     

Robust Adaptive Model Tracking for Distributed Parameter Control of Linear Infinite-dimensional Systems in Hilbert Space

This paper is focused on adaptively controlling a linear infinite-dimensional system to track a finite-dimensional reference model. Given a linear continuous-time infinite-dimensional plant on a Hilbert space with disturbances of known waveform but unknown amplitude and phase, we show that there exists a stabilizing direct model reference adaptive control law with the properties of certain disturbance rejection and robustness. The plant is described by a closed, densely defined linear operator that generates a continuous semigroup of bounded operators on the Hilbert space of states. The central result will show that all errors will converge to a prescribed neighborhood of zero in an infinitedimensional Hilbert space. The result will not require the use of the standard Barbalat0s lemma which requires certain signals to be uniformly continuous. This result is used to determine conditions under which a linear infinite-dimensional system can be directly adaptively controlled to follow a reference model. In particular, we examine conditions for a set of ideal trajectories to exist for the tracking problem. Our results are applied to adaptive control of general linear diffusion systems described by self-adjoint operators with compact resolvent.      

A New Adaptive Sliding Mode Control of Uncertain Nonlinear Systems

In this paper, a new adaptive sliding mode control is proposed to control nonlinear systems with parametric uncertainties and matched and unmatched external disturbances. The proposed method first combines immersion and invariance (I&I) adaptive scheme with sliding mode control (SMC), which preserves the advantages of the two methods. The proposed method is different from the approach of combining the backstepping adaptive scheme and sliding mode control in the parameter estimation law, which allows for prescribed dynamics to be assigned to the estimation error and is easier to tune. Finally, the method is applied to control a class of power systems, and simulation results show the advantages of the proposed method.     

面向彩色图像的尺度和旋转不变性特征提取方法及应用

提出一种面向彩色图像的尺度和旋转不变性特征提取方法,并在真实的场景识别中进行了应用。该方法是先对给定彩色图像的各组成平面分别进行Radon变换,然后对得到的Radon变换系数矩阵进行尺度不变性处理,接着对处理后的Radon变换系数矩阵用频率B样条小波进行1维小波变换,在所得到的脊波系数矩阵中计算均值和方差的同时,采用线性回归模型提取在不同的颜色组成平面下所有频率子波段之间的关系属性,最后将得到的特征进行旋转不变性处理,从而得到所提出的尺度和旋转不变性特征。在3个数据库上进行了实验,结果表明本文方法可靠有效。     

Adaptive Proportional-Derivative Sliding Mode Control Law With Improved Transient Performance for Underactuated Overhead Crane Systems

In this paper, an adaptive proportional-derivative sliding mode control (APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties, and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved. The Lyapunov techniques and the LaSalle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.      

Nonlinear H ∞ control of a Quadrotor (UAV), using high order sliding mode disturbance estimator

A nonlinear H _∞ output feedback controller is proposed and coupled to a high-order sliding mode estimator to regulate an UAV in the presence of the unmatched perturbations. The plant to be controlled is a Quadrotor helicopter described by nonlinear dynamics with plant uncertainties due to the variations of inertia moments and payload operation. A robust state estimation is considered under model uncertainties as well as external/measurement disturbances. Performance issues of the controller are illustrated in a simulation study made for an UAV prototype.     

Time-domain input-output representations of linear systems

A non-oriented matrix pencil model containing internal and external variables is shown to possess properties useful for modelling and design of linear dynamical systems. Three of these properties are trivial inversion, invariance under a useful class of operations, and simple decomposition using easily-implemented row and column operations. Realizations of state-space and polynomial operator models are given, then a definition of system dimension and a minimal-reduction algorithm. A new time-domain canonical form compatible with polynomial operator systems is described. Examples of the use of the model in algebraic design problems are given.     

Design of a control algorithm for objects with parametric uncertainty,disturbances, and input signal saturation

We design a control algorithm for objects under parametric uncertainty, external bounded disturbances, and saturation of the controlled signal. We assume that the object model is described by a linear dynamical system with arbitrary relative degree and several inputs and outputs. The developed algorithm provides approximate tracking of the output of the control object for a reference signal. We obtain sufficient stability conditions for the closed system that depend on object parameters, reference model, and the controller. We show modeling results that illustrate the operation of the developed scheme.     

Auto-tuning and adaptive control of sheet metal forming

This paper describes the design and implementation of automatic controller tuning and model reference adaptive control (MRAC) to improve part quality in stamping and extends previous work on a manually-tuned fixed-gain process controller. Automatic tuning is described with a discussion of implementation issues in the presence of plant disturbances. Design of a direct MRAC, whose controller gains are continuously adjusted to accommodate changes in process dynamics and disturbances, is investigated, including simulation-based robustness analysis of the adaptation law and a consideration of constrained estimation in the recursive least squares algorithm to address practical implementation issues. The performance of the MRAC process controller designed through simulation is experimentally validated. Good tracking of the reference process variable (i.e., punch force), and significant part quality improvement in the presence of disturbances, is achieved.     

分数阶奇异系统的Lie对称性与守恒量

对称性与守恒量可以简化动力学问题从而进一步求出力学系统的精确解,这样更加有利于研究动力学行为.分数阶模型相比于整数阶模型,能够描述复杂系统的动力学过程,因此在分数阶模型下研究对称性与守恒量是不可或缺的.首先介绍两个分数阶奇异系统,一个系统包含混合整数和Caputo分数阶导数,另一个系统仅含Caputo分数阶导数.由两个分数阶奇异系统分别给出两个分数阶固有约束,并给出对应的分数阶约束Hamilton方程.然后,基于微分方程在无限小变换下的不变性,给出了分数阶约束Hamilton方程Lie对称性的定义,导出了相应的确定方程,限制方程和附加限制方程.第三,建立并证明了两个分数阶约束Hamilton系统的Lie对称性定理,得到了相应的分数阶约束Hamilton系统的Lie守恒量.在特定条件下,本文所得结果可以退化为整数阶约束Hamilton系统的Lie守恒量.最后通过两个算例来说明此结果的应用.     

有界扰动下异质车辆队列分布式鲁棒经济预测控制

针对有界扰动下异质车辆队列节能与稳定分布式协同控制问题,提出一种新的分布式鲁棒经济模型预测控制(economic model predictive control, EMPC)策略.首先采用不确定误差模型描述有界扰动下异质车辆队列纵向行驶动态特性,再应用tube思想对系统约束进行紧缩设计,补偿有界扰动对系统造成的不确定性.其次,采用局部车辆行驶能耗模型描述车辆队列分布式经济性能优化的有限时域最优控制问题,并利用传统跟踪性能指标设计附加稳定收缩约束函数.进一步,基于系统收缩原理,建立车辆队列闭环系统关于有界扰动的输入-状态稳定性条件.最后,通过与车辆队列传统分布式鲁棒模型预测控制策略的数值仿真对比结果验证了所提出策略的有效性和优越性.     

融合色彩比和梯度不变性的运动阴影检测

为解决运动前景的准确分割受运动阴影影响的问题,提出了一种融合色彩比和梯度不变性的运动阴影检测算法。该算法分析了阴影像素的色彩比和区域纹理梯度的光照不变性,利用亮度变化特性和色彩比不变性初步确定候选运动前景中的阴影像素,然后在候选阴影区域利用纹理梯度不变性进行去错处理,两者的结合弥补了单一特征或单一类型特征的阴影检测性能差的缺陷,提高了阴影检测率和阴影分辨率,能够准确地将阴影和前景区别开来。