线性离散切换系统的输出调节问题

利用多Lyapunov函数方法，研究线性离散切换系统的输出调节问题．在假定每个子系统都不是输出调节问题可解的条件下，分别给出了在全息反馈控制器和误差反馈控制器作用下，这类系统输出调节问题可解的两个充分条件．同时还分别给出了相应的切换律和控制器的设计方案．最后的仿真例子进一步表明了结论的有效性．     

一类非线性切换系统任意切换采样控制设计

本文针对一类具有非严格反馈形式的非线性切换系统,在输出只在采样点可获得的情况下,提出了一种基于模糊采样观测器的自适应输出反馈控制方法.该方法降低了现有任意切换控制研究结果中因共同控制思想导致的控制器设计的保守性,避免了迭代过程对虚拟控制的反复求导引发的计算爆炸现象及控制器高增益的弊端.切换的自适应律突显了每个子系统的特性,建立的采样控制器节约了信息传输资源.共同Lyapunov函数理论确保了相应闭环切换系统所有变量在任意切换信号下的一致有界性.     

基于驻留时间切换下离散切换系统的异步控制器设计

针对一类切换线性系统,本文提出了一种基于系统状态的驻留时间策略.这种切换策略不仅使异步状态反馈切换系统稳定,而且缩短了系统的运行时间.对于异步切换系统的稳定性和增益问题,本文主要的结论是在子系统运行期间Lyapunov函数允许增加,同时又没有的限制.通过利用基于系统状态的驻留时间策略,推导出了切换线性系统的控制器设计的充分条件.得出的结论也可以推广到非线性切换系统.本文中最后给出的算例用于说明该方法的有效性.     

切换时间受限时离散切换系统的稳定性

切换系统作为一类典型的混杂系统,近年来在国内外受到极大重视。实际工程中,由于切换过于频繁难以使系统保持稳定,针对切换时间间隔受限的情况,研究一类离散线性切换系统的稳定性。利用李亚普诺夫稳定性理论,给出系统满足稳定性的充分条件,并利用此条件设计出相应的切换控制规律和状态反馈子控制器。最后对包含两个离散子系统的切换系统进行了仿真计算,其结果验证了文中所给出定理的有效性。     

切换线性系统的聚合优化

分析了切换线性系统的稳定性和优化问题,提出了一个Armijo步长优化的共轭梯度算法来寻找适当代价函数下的优化切换时间点集.为了确保优化切换路径是可压缩的,提出了代价函数需要满足的受限表达式.设计了几种优化分段状态反馈切换律来搜索聚合系统的最优切换路径,同时这些切换路径就是对应原始切换线性系统的次优化切换路径.最后,一个实例演示了不同切换律下的切换策略和优化代价.     

切换自治系统的动态输出反馈镇定

本文研究离散时间切换线性自治系统的输出反馈镇定问题. 在切换系统可观测的假设下, 设计具有多线性 时变增益的动态观测器, 实现有限时间状态估计. 在此基础上, 设计多路径动态输出反馈切换策略, 实现闭环系统指 数收敛.     

一类开关切换系统的输出反馈镇定

对一类子系统为线性的开关切换系统进行观测器设计，并给出系统动态输出反馈可镇定的充分条件。在所设计的观测器基础上，以系统状态的观测值为依据设计各子控制器和切换方案，使整个闭环系统是指数渐近稳定的。对于切换时间间隔受限制的情况，给出了相应的动态输出反馈可镇定条件和镇定控制方案。实例仿真结果表明，所给出的设计方案是可行的。     

一类线性切换系统的鲁棒状态反馈镇定

考虑一类标称系统存在共同Lyapunov函数的切换系统的鲁棒镇定问题.在不确定性不满足匹配条件下,设计出鲁棒状态反馈控制器,并在给定的切换策略下,确保闭环系统在其平衡点处渐近稳定.仿真结果表明所设计控制器是有效的.     

一类时滞切换系统的鲁棒控制

研究一类状态矩阵和控制输入矩阵同时具有不确定项的线性时滞切换系统的鲁棒控制器的设计问题。,利用多Lyapunov函数方法设计出状态反馈的鲁棒控制器,并设计出切换策略,证明闭环系统在给定的切换策略下在其平衡点处的渐近稳定性。最后通过MATLAB中的LMI工具箱进行仿真,仿真结果验证结论的有效性。     

切换广义系统的H∞输出反馈控制

针对一类切换广义系统,提出了一种更加简单易解的H∞输出反馈控制方法.基于投影引理和Finsler's引理结合线性矩阵不等式技术,给出保证闭环系统在输出反馈控制下是容许的并具有期望的H∞性能水平的严格线性矩阵不等式条件.所提出的充分条件不要求对系统模型进行坐标变换,也不需要对Lyapunov矩阵和其逆矩阵进行分解.给出的结果可经例子进行验证并可以推广到单一的广义系统和正常的切换系统.     

机器人位移和速度反馈的一种方法

本文给出一种机器人控制系统位移和速度反馈的新方法.此方法用传统的差动变压器实现了位移和速度的同时反馈.     

T混沌系统的反馈控制与分析

提出了一种具有三维自治常微分方程组形式的新的T混沌系统,运用非线性系统理论和Routh Hurwitz定理分别对系统平衡点的稳定性作了研究,得到了相关的定理.同时运用线性反馈、非线性反馈、微分反馈、延迟反馈对系统进行了反馈控制,并利用Lyapunov稳定性理论,通过构造V函数对受控系统进行了分析,给出了各反馈参数的范围...     

Effects of timing of formative feedback in computer-assisted learning environments

This study examines the effects of timing of corrective formative feedback on processing text information on question-answering. Undergraduate students read an expository text and answered questions in two attempts. Students were randomly assigned to a no feedback, immediate feedback and delayed feedback conditions. Students in the feedback conditions received feedback on the correctness of their answer after the first attempt and were informed about the right answer after the second attempt. Students were prompted to restudy the text after failing in their first attempt. However, students in the no feedback condition were just prompted to search the text. All students were tested on question-answering, corrective probability and a post-test cued-recall test. Results showed that: (a) feedback reduced the initial time reading the text; (b) feedback increased performance on question answering and cued-recall; (c) delayed feedback produced no advantages over immediate feedback. Theoretical and practical implications of these results are discussed.     

An investigation on the impact of auditory and haptic feedback on rhythmic walking interactions

This paper presents a system capable of rhythmic walking interaction by auditory and haptic display. Likewise, it summarizes the results of the research on the influence of the audio and haptic stimulation on rhythmic walking interaction. The system detects user’s footsteps and either provides interactive real-time feedback or suggests a pace using a synthetic walking sound or vibration. This pace is either a constant tempo or adapts to the walker. Auditory and haptic feedback signals are either ecological physically-based synthetic walking signals or simple sinusoidal beeps. In the experiment, the different auditory and haptic feedback and interaction modes are studied with respect to their effect on the walking tempo. The results show that participants synchronise equally well with the tempo with either audio or haptic cues, but indicate the audio–haptic conditions as the easiest to synchronise with. Moreover, results indicate that multimodal audio–haptic feedback provide the most natural feeling. These results have implications on the design of interactive entertainment or therapeutical applications.     

一种关系数据库关键词检索相关反馈方法

在关系数据库关键词检索(KSORD)中,用户的检索往往不能一次成功,有时需要多次重构查询(找到一组新关键词)来进行检索,但是查询的重构往往要花费用户大量的时间和精力.针对KSORD的结果,提出了一种相关反馈方法来自动重构查询.该方法选用基于向量空间模型的打分机制对KSORD结果打分,根据用户反馈或伪反馈的结果信息,采用基于概率的方法计算扩展用的语词,以查询扩展的方法自动重构查询进行再次检索.实验结果表明,这种方法能够为用户提供更多的相关结果.     

Delaying elaborated feedback within computer-based learning environments: The role of summative and question-based feedback

Elaborative feedback (EF) containing explanations on students' responses benefits learning. Computer-based environments provide learners with EF in different ways, for example, on an immediate question-by-question basis or after answering a set of questions. Recent findings also suggest that delaying EF enhances learning. However, it is unclear to what extent different types of delayed-EF favour students' performance. This study examines whether and how two types of delayed-EF (question-based vs. summative) influence students' question-answering performance and final learning over immediate-EF. One hundred thirty-three secondary-school students read a scientific text and answered 12 multiple-choice questions in a computer-based environment. A day later, students completed a final learning test with 20 open-ended questions. Results showed that neither question-based delayed EF nor summative delayed EF outperformed immediate EF. However, EF moderated the relationship between students' prior knowledge and their performance outcomes, suggesting that students with higher levels of prior knowledge receiving summative delayed EF benefited more.     

一种基于运动状态反馈的机器人接触力控制

针对机器人从自由空间运动控制过渡到约束空间力控制的过程中，存在冲撞振荡，甚至不稳定等问题，提出了利用加速度反馈为力控制提供阻尼，克服单纯依赖速度反馈的局限，进而稳定力控制系统的方法。这种方法不增加系统的复杂性，易于实现。     

A note on asymptotic stabilization of linear systems by periodic, piecewise constant, output feedback

This note studies the asymptotic stabilization problem for controllable and observable, single-input single-output, linear, time-invariant, continuous-time systems by means of memoryless output feedback of the form u(t)=k(t)y(t), with k(t) periodic and piecewise constant. A necessary and sufficient condition, together with a simpler to test sufficient condition, given in terms of a bilinear matrix inequality, is presented. A few illustrative examples complete the paper.     

Global sampled-data output feedback stabilisation for a class of nonlinear systems with unknown output function

This paper discusses the problem of global sampled-data output feedback stabilisation for a class of nonlinear systems whose output function is unknown. A systematic design scheme is developed to construct a linear output feedback control law in sampled-data form. An explicit formula for the maximum allowable sampling period is computed to guarantee global stability of the uncertain nonlinear systems under the proposed controller with appropriate gains. Two examples are given to demonstrate the effectiveness of the proposed design procedure.