最大控制律的多面体不变集鲁棒模型预测控制

为实现线性变参数系统的快速稳定控制,提出一种最大控制律的多面体不变集鲁棒模型预测控制算法。离线时,通过设定一组渐近趋向于稳定点的给定值,按照状态变量到稳定点距离大致相同的原则,构建一系列状态变量值集合,通过优化得到每个集合中较大的控制律,然后采用反推的方式优化得到一系列最大的控制律,并结合系统的输入输出约束得到离线多面体不变集。在线时,根据每个采样周期状态变量在多面体不变集中的位置,通过线性插值优化得到系统的实际控制律。给出离线在线算法的详细步骤和系统的闭环稳定性证明。通过仿真比较验证所提算法的有效性,表明所提算法使系统响应更为快速和稳定。     

语音信号的线性预测分析在DSP上的优化实现

语音信号的线性预测分析是语音压缩中的一个重要环节，占据语音压缩计算中的大部分时间，为提高语音压缩的速度，在C54x系列DSP上用汇编语言实现了语音信号的线性预测分析，并对其进行优化。最终可以使代码的运行时间减少到原来的5％左右。     

滑翔飞行器线性伪谱模型预测控制三维轨迹规划

对高升阻比滑翔飞行器,在线性伪谱模型预测控制基础上提出新的再入制导律,除了满足传统终端约束与路径约束,还能以特定航向角抵达终点。以高维多项式代理技术泛化升阻比,得到关于能量和攻角的表达式,攻角在线调节升阻比以增强规划能力。再入飞行分为下降段和滑翔段,下降段维持最大攻角和零倾侧角以限制热流率。滑翔段应用线性伪谱模型预测控制,用降阶动力学模型预测终端偏差,线性化模型获得误差传播方程。由于积分计算复杂,以高斯伪谱法获取控制量的修正值,修正攻角、倾侧角相关参数和两次倾侧反转的能量时刻消除终端偏差。方法简单易行,精度高,便于在线应用,仿真结果显示该方法能满足提出的规划需求。     

改进的扰动LPV系统输出反馈预测控制

针对一类带有有界状态干扰的多胞描述LPV系统,文中提出了一种鲁棒预测控制改进方法,并设计了保证系统渐近稳定的输出反馈控制器。为抵消有界状态干扰,该控制器考虑无扰动LPV系统,基于离线状态观测器,采用线性矩阵不等式求解预测控制无穷时域最小-最大优化问题。随后利用离线状态观测器获得扰动LPV系统与无扰动LPV系统状态的估计值之差,以确定保性能的反馈增益,从而得到使扰动LPV系统渐近稳定的最优偏移量,并将其与无扰动系统控制律组合作为最优控制律施加于实际系统。实验结果表明,运用改进的鲁棒预测控制方法能获得较好地控制性能,同时提高了系统的稳定性和解决优化问题的效率,仿真试验也验证了该算法的有效性。     

用神经网络实现VBR视频通信量的在线预测

VBR(Varible Bit Rate)视频信号具有时变性、非线性和突发性等特点,实现该信号通信量的高精度预测难度较大.针对以上问题,本文提出了一种用于VBR视频通信量预测的自适应神经网络模型,网络训练采用离线与在线相结合的方式,同时通过删除不重要的权重,以优化网络的拓扑结构,提高网络的推广能力,降低网络在线学习的计算复杂度;对VBR视频通信量预测的模拟结果表明该模型具有高的预测精度,并能满足通信系统对预测实时性的要求.     

基于在线LS-SVM的网络流量预测

为了提高流量预测的准确性,将混沌理论和在线LS-SVM回归技术应用于网络流量预测。采用相空间重构理论计算流量的时延τ、嵌入维数m,据此确定训练样本对并建立在线预测模型,对网络流量数据进行预测。结果表明,该方法能有效地进行流量预测,相对于传统的离线预测方式,该方法具有更好的预测精度。     

酸轧二级系统离线轧制力自适应计算模型

轧制力自适应计算模型分为在线自适应模型和离线自适应模型。在线的自适应模型计算通过条件触发采集数据,将所计算出的自适应系数应用于下一卷的轧制表的计算。离线的自适应模型则是对同一钢种参数的整体调节,适用于新钢种的轧制和同一钢种参数优化,从而使轧制表的设定值更加精确,为提高轧制精度提供依据和方法。     

切削加工参数优化及自适应控制技术综述

阐述离线切削参数优化技术的研究现状,在线自适应切削加工技术的应用,探讨数控加工过程中离线参数优化技术,以及在线自适应加工技术的关键难点。     

基于L_2干扰抑制的压电换能器控制

为了降低压电元件运行中的干扰对超声波发声系统的影响。首先通过类比压电振动模型与压电等效电路模型,得到了可反映压电振动状态的的压电等效电路微分方程,基于线性分式变换(LFT)构建了考虑元件干扰的压电换能器状态模型。然后分析整合状态空间模型,将系统各个干扰整合视为系统扰动,得到含有系统扰动的线性状态空间模型;最后基于L2干扰抑制理论设计系统的反馈控制律。结果表明,仿真系统在存在符合白噪声分布的干扰的情况下,控制律使系统运行状态良好。     

基于场强地图的室内定位技术研究

室内定位技术的发展,要求能提供快速建立、适应性强、成本低的定位系统。基于场强地图的室内定位技术,能大幅减少离线测试工作量。针对当前离线阶段存在预测场强不准的问题,提出了追踪共轭梯度法,能快速建立场强地图。在线阶段提出了加权差分坐标K最近邻法,结果表明该方法与传统方法相比,能使离线阶段的反演模型数据优化,使得在线阶段的定位匹配误差进一步减小,获得更高的定位精度。     

Design of Suboptimal Constrained Nonlinear Quadratic Regulator via Invariant Sets Switching

A design method for a suboptimal constrained nonlinear quadratic regulator (CNLQR) via invariant sets switching is presented. The CNLQR has the merits of both the control invariant set and the gain scheduling, and solves the constrained nonlinear quadratic regulation problem effectively. It first calculates the equilibrium surface of the nonlinear system, and then obtains the off-line local LQR control laws and the corresponding control invariant sets for several equilibrium points. These control invariant sets cover the equilibrium surface such that the closed-loop stability of the nonlinear system can be guaranteed by switching the local LQR laws on-line. The algorithm is computationally efficient, because the state feedback control law and control invariant sets are all solved off-line so that the computational burden of on-line optimization is greatly reduced. A simulation example illustrating the method is presented.     

Robust Model Predictive Control for Piecewise Affine Systems

In this paper, we study a robust model predictive control (MPC) strategy for piecewise affine (PWA) systems with uncertainty that is described as a set of polytopic parameter-varying models in a polytope corresponding to each partition of the PWA systems. First, an infinite horizon MPC technique for guaranteeing robust stability is developed for uncertain PWA systems. According to the condition of the PWA system states, the sequence of piecewise linear feedback controller at each sampling time is derived on-line by solving a convex optimization problem involving linear matrix inequalities. The feasible PWA control law design can robustly stabilize the uncertain PWA systems. However, the on-line optimization problems may lead to a computational burden. Then we further propose an improved robust MPC algorithm. When the current state is outside of the region of PWA systems containing the origin, the proposed on-line robust MPC algorithm is utilized; once the current state enters the region with the origin, sequence attraction domains where the origin is included are constructed off-line one within another, and the explicit control laws corresponding to different attraction domains can drive the state to the origin. The two algorithms are illustrated with a numerical example. The simulation results show that both controller design methods can stabilize the PWA systems with polytopic uncertainty, and the improved algorithm can reduce the on-line computation cost.     

高效的在线/离线代理重签名方案

为了改善代理重签名的性能,该文提出在线/离线代理重签名方案。其基本思想是将重签名算法分成离线阶段和在线阶段。在签名消息到来之前,离线阶段进行重签名的大部分计算,并将这些运算结果保存起来;在签名消息到来时,利用离线阶段保存的数据能在很短的时间内生成消息的在线重签名。文中给出了在线/离线代理重签名方案形式化定义,在此基础上构造了具体实现的方案,并在随机预言模型下给出其安全性证明。该方案可将任意一个代理重签名方案转换为一个高效的在线/离线代理重签名方案。分析结果表明,新方案在效率上优于已有的代理重签名方案,在线重签名算法仅需要1次模减法运算和1次模乘法运算。     

Jitter control in QoS networks

We study jitter control in networks with guaranteed quality of service (QoS) from the competitive analysis point of view: we propose on-line algorithms that control jitter and compare their performance to the best possible (by an off-line algorithm) for any given arrival sequence. For delay jitter, where the goal is to minimize the difference between delay times of different packets, we show that a simple on-line algorithm using a buffer of B slots guarantees the same delay jitter as the best off-line algorithm using buffer space B/2. We prove that the guarantees made by our on-line algorithm hold, even for simple distributed implementations, where the total buffer space is distributed along the path of the connection, provided that the input stream satisfies a certain simple property. For rate jitter, where the goal is to minimize the difference between inter-arrival times, we develop an on-line algorithm using a buffer of size 2B+h for any h⩾1, and compare its jitter to the jitter of an optimal off-line algorithm using buffer size B. We prove that our algorithm guarantees that the difference is bounded by a term proportional to B/h     

耦合电感型Zeta变换器的参数优化方法

针对耦合电感型Zeta变换器的开环频率特性复杂导致的控制器设计困难的问题,文中提出了变换器参数的优化方法。该方法通过调整变换器的电路参数,进而调整变换器幅频特性中的高频谐振峰与谐振谷的位置,使得峰谷之间相互削弱,把相频特性曲线上超过180°部分最大程度减小到180°以内,消除了输出电压响应中的高频振荡成分,降低了变换器从控制变量到输出电压之间的频率特性的复杂程度。测试结果表明,通过该方法进行参数优化后,控制变量到输出电压之间的幅频特性接近二阶系统的幅频特性,相频特性上的相位滞后小于180°。在采用相同控制器的条件下,与优化前相比较,利用文中方法提高了控制器的带宽,改善了系统的输出电压的动态响应,增强了闭环系统的稳定性,验证了所提方法的有效性。     

Special purpose processor for parameter identification of CNC second order servo systems on a low-cost FPGA platform

The parameter identification process has an important role in servo systems tuning on computer numerical control (CNC) machine tools. The parameter identification is mostly done off-line due to the high computational load carried by the identification algorithms. In this work, we present a novel hardware architecture for an application specific processor implementing the recursive least-squares algorithm for the on-line identification. The developed processor is simulated and tested with the necessary elements to perform the CNC machine servo system control. The system was implemented in a low-cost FPGA, getting a maximum sample frequency of 40 kSps.     

结合字典学习技术的ISAR稀疏成像方法

鉴于稀疏ISAR成像方法的成像质量受到待成像场景的稀疏表示不准确的限制,该文将字典学习(DL)技术引入到ISAR稀疏成像中,以提升目标成像质量。该文给出基于离线DL和在线DL两种ISAR稀疏成像方法。前者通过已有同类目标ISAR图像进行学习,获得更优稀疏表示,后者在成像过程中从现有数据中通过优化获得稀疏表示。仿真和实测ISAR数据成像结果表明,结合离线DL和在线DL的成像方法均可获得比现有方法更优的成像结果,离线DL成像优于在线DL成像,而且前者计算效率优于后者。     

无双线性对的基于身份的在线/离线门限签名方案

为了减少公钥密码体制中证书管理带来的开销和提高在线/离线门限签名方案的性能,利用分布式密钥生成协议和可验证秘密共享协议,提出了一种基于身份的在线/离线门限签名方案,并在离散对数假设下证明了新方案满足顽健性和不可伪造性。分析结果表明,新方案避免了传统公钥证书的管理问题和复杂的双线性对运算,大大降低了离线门限签名算法和签名验证算法的计算复杂度,在效率上优于已有的在线/离线门限签名方案。     

Does Physiological Blood Glucose Control Require an Adaptive Control Strategy?

To test the hypothesis that only an adaptive algorithm would guarantee optimal feedback control of glycemia in insulin-dependent diabetes, fasting chronically diabetic dogs at rest were subjected to short-term artificial beta cell treatment. Insulin was applied intravenously and an oral glucose load was given during the experiment. Employing the same dosing algorithm, three different control strategies were employed in a random order on different days: adaptive control (minimum variance controller, Test A), fixed command control using on-line parameter estimates (Test B), and fixed command control using off-line individually optimized dosage constants (Test C). Comparison was made to nondiabetic control animals. The glycemic profiles were entirely normal in Test A and C, but were distinctly elevated in Test B. The peripheral hyperinsulinaemia could, however, not be avoided by adaptive control. It is concluded that the restoration of physiological blood glucose control in insulin-dependent diabetes requires dosage parameters which are either continually adapted to the actual situation (adaptive control) or are optimized to meet the individual's needs. In the latter case, fixed command control may be employed. Peripheral hyperinsulinaemia cannot be avoided as long as insulin is administered by a posthepatic route.