用于文本情感分析的特征加权改进算法

文本情感分析领域内的特征加权一般考虑两个影响因子：特征在文档中的重要性（ITD）和特征在表达情感上的重要性（ITS）。结合该领域内两种分类准确率较高的监督特征加权算法,提出了一种新的ITS算法。新算法同时考虑特征在一类文档集里的文档频率（在特定的文档集里,出现某个特征的文档数量）及其占总文档频率的比例,使主要出现且大量出现在同一类文档集里的特征获得更高的ITS权值。实验证明,新算法能提高文本情感分类的准确率。     

Design weighting parameter tuning of multivariable self-tuning controllers

In this paper, we present the method for on-line tuning of a design weighting polynomial parameters of a multivariable self-tuning controller which adapts to changes in the higher-order nonminimum phase system parameters with time delays and noises. The algorithm effect is achieved through the recursive least square algorithm at the parameter estimation stage and also through the Robbins–Monro algorithm at the stage of optimizing the design weighting polynomial parameters of the controller. The proposed method is simple and effective compared with the pole restriction method. The computer simulation results are presented to adapt the higher-order multivariable system with nonminimum phase and with changeable system parameters.     

Design of fuzzy controllers for uncertain nonlinear systems using stability and robustness analyses

This paper analyzes the stability and robustness of uncertain nonlinear systems and shows that the analysis results provide an efficient technique for the design of fuzzy controllers. Based on a fuzzy plant model describing an uncertain nonlinear plant, this design involves the derivation of a stability criterion and a robust area in the uncertain parameter space in terms of some measures of the closed-loop control system matrices. An application example on balancing an inverted pendulum is given to illustrate the simple design methodology, the stability and the robustness of the feedback system incorporated with the proposed fuzzy controller.     

Lyapunov functions for the multivariable Popov criterion with indefinite multipliers

We demonstrate the existence of Lur’e-Postnikov type Lyapunov functions for a reasonably general form of the multivariable Popov criterion. In particular, the multipliers need not be positive semi-definite. We discuss the application to the special cases where the feedback element is either diagonal, unstructured or linear.     

Asymptotic feedback stabilization: A sufficient condition for the existence of control Lyapunov functions

In this paper we study the feedback stabilization problem for a wide class of nonlinear systems that are affine in the control. We offer sufficient conditions for the existence of ‘Control Lyapunov functions’ that according to [3,23] and [28–30] guarantee stabilization at a specified equilibrium by means of a feedback law, which is smooth except possibly at the equilibrium. We note that the results of the paper present a local nature.     

基于权值范围设置的多模型稳定切换控制研究

针对线性加权多模型切换过程中权值难以确定问题,提出了具有Lyapunov函数的多模型稳定切换的充分条件,依据该充分条件可以确定加权多模型的权值范围和快速获取加权因子的取值,实现多模型的平滑切换.所提出的充分条件克服了多模型子系统必须稳定的苛刻条件,通过对自主水下机器人多运动模型切换过程的仿真实验表明,依据权值范围所给定的加权因子能够保证加权多模型切换过程中的渐近稳定性.     

Stabilization for Markovian jump systems with partial information on transition probability based on free-connection weighting matrices

This paper focuses on stability and stabilization for a class of continuous-time Markovian jump systems with partial information on transition probability. The free-connection weighting matrix method is proposed to obtain a less conservative stability criterion of Markovian jump systems with partly unknown transition probability or completely unknown transition probability. As a result, a sufficient condition for the state feedback controller design is derived in terms of linear matrix inequalities. Finally, numerical examples are given to illustrate the effectiveness and the merits of the proposed method.     

采用动态权重和概率扰动策略改进的灰狼优化算法

针对基本灰狼优化（GWO）算法存在易陷入局部最优,进而导致搜索精度偏低的问题,提出了一种改进的GWO （IGWO）算法。一方面,通过引入由GWO算法系数向量构成的权值因子,动态调整算法的位置向量更新方程;另一方面,通过采用概率扰动策略,增强算法迭代后期的种群多样性,从而提升算法跳出局部最优的能力。对多个基准测试函数进行仿真实验,实验结果表明,相对于GWO算法、混合GWO （HGWO）算法、引力搜索算法（GSA）和差分进化（DE）算法,所提IGWO算法有效摆脱了局部收敛,在搜索精度、算法稳定性以及收敛速度上具有明显优势。     

应用无源性分析研究时变非线性系统的稳定性

应用反馈系统的无源性分析研究一类时变非线性系统的稳定性,给出寻找连续衰减的充要条件的方法,并证明对于线性系统这种方法给出的结果和Routh判据完全一致.     

非线性系统有限时间稳定的一个新的充分条件

研究了一类非线性系统的有限时间稳定性．通过函数构造和变量替换的方法,给出一个新的非线性系统有限时间稳定的充分条件．该条件与现有结果相比,具有更少的保守牲．进一步,将所得的结果推广到不确定性非线性系统,通过构造Lyapunov函数方法,给出系统有限时间稳定的充分条件．仿真例子表明了所得结论的有效性．     

Mitigation of symmetry condition in positive realness for adaptive control

Feasibility of nonlinear and adaptive control methodologies in multivariable linear time-invariant systems with state-space realization {A,B,C} is apparently limited by the standard strictly positive realness conditions that imply that the product CB must be positive definite symmetric. This paper expands the applicability of the strictly positive realness conditions used for the proofs of stability of adaptive control or control with uncertainty by showing that the not necessarily symmetric CB is only required to have a diagonal Jordan form and positive eigenvalues. The paper also shows that under the new condition any minimum-phase systems can be made strictly positive real via constant output feedback. The paper illustrates the usefulness of these extended properties with an adaptive control example.     

Conditions for stability of the extended Kalman filter and their application to the frequency tracking problem

The error dynamics of the extended Kalman filter (EKF), employed as an observer for a general nonlinear, stochastic discrete time system, are analyzed. Sufficient conditions for the boundedness of the errors of the EKF are determined. An expression for the bound on the errors is given in terms of the size of the nonlinearities of the system and the error covariance matrices used in the design of the EKF. The results are applied to the design of a stable EKF frequency tracker for a signal with time-varying frequency.This research was supported by the Co-operative Research Centre for Robust and Adaptive Systems ((CR)² ASys). The authors wish to acknowledge the funding of the activities of (CR)² ASys by the Australian Commonwealth Government under the Co-operative Research Centre Program.     

Simple stability criteria for nonlinear time-varying discrete systems

We present two sufficient conditions for asymptotic stability of nonlinear time-varying discrete systems. Our main results generalize Mori's result for linear discrete time-invariant systems to nonlinear time-varying systems.     

Simultaneous interconnection and damping assignment passivity-based control of mechanical systems using dissipative forces

To extend the realm of application of the well known controller design technique of interconnection and damping assignment passivity-based control (IDA-PBC) of mechanical systems two modifications to the standard method are presented in this article. First, similarly to Batlle et al. (2009) and Gómez-Estern and van der Schaft (2004), it is proposed to avoid the splitting of the control action into energy-shaping and damping injection terms, but instead to carry them out simultaneously. Second, motivated by Chang (2014), we propose to consider the inclusion of dissipative forces, going beyond the gyroscopic ones used in standard IDA-PBC. The contribution of our work is the proof that the addition of these two elements provides a non-trivial extension to the basic IDA-PBC methodology. It is also shown that several new controllers for mechanical systems designed invoking other (less systematic procedures) that do not satisfy the conditions of standard IDA-PBC, actually belong to this new class of SIDA-PBC.     

Asymptotic stabilization of passive systems without damping injection: A sampled integral technique

Passivity in physical systems is a restatement of energy balancing, and therefore is a ubiquitous property in engineering applications. Under some weak conditions, the unique equilibrium state of passive systems is stable. However, to ensure asymptotic stability, strict output passivity and a detectability property are required. Although strict output passivity may be enforced via a damping injection that feeds back the passive output, this signal may be noisy or unmeasurable — the paradigmatic example being velocity in mechanical systems. In this paper a sampled integral stabilization (SIS) technique for the asymptotic regulation of passive systems, that requires only the knowledge of the time integral of the passive output — i.e. position in mechanical systems — is proposed. As a generalization of the previous result, it is shown that SIS is applicable to cascade connections of passive systems measuring only the storage function of the second one. Several examples, including a planar elbow manipulator and the rigid body dynamics are shown to satisfy the assumptions for the application of SIS.     

Transverse contraction criteria for existence,stability, and robustness of a limit cycle

This paper derives a differential contraction condition for the existence of an orbitally-stable limit cycle in an autonomous system. This transverse contraction condition can be represented as a pointwise linear matrix inequality (LMI), thus allowing convex optimisation tools such as sum-of-squares programming to be used to search for certificates of the existence of a stable limit cycle. Many desirable properties of contracting dynamics are extended to this context, including the preservation of contraction under a broad class of interconnections. In addition, by introducing the concepts of differential dissipativity and transverse differential dissipativity, contraction and transverse contraction can be established for interconnected systems via LMI conditions on component subsystems.     

Random weighting estimation for fusion of multi-dimensional position data

This paper adopts the concept of random weighting estimation to multi-sensor data fusion. It presents a new random weighting estimation methodology for optimal fusion of multi-dimensional position data. A multi-sensor observation model is constructed for multi-dimensional position. Based on this observation model, a random weighting estimation algorithm is developed for estimation of position data from single sensors. Using the random weighting estimations from each single sensor, an optimization theory is established for optimal fusion of multi-sensor position data. Experimental results demonstrate that the proposed methodology can effectively fuse multi-sensor dimensional position data, and the fusion accuracy is much higher than that of the Kalman fusion method.     

Improved results on stability of continuous-time switched positive linear systems

In this paper, the problems of stability for switched positive linear systems (SPLSs) under arbitrary switching are investigated in a continuous-time context. The so-called “copositive polynomial Lyapunov function” (CPLF) giving a generalization of copositive types of Lyapunov function is first proposed, which is formulated in a higher order form of the positive states of the underlying systems. It is illustrated in this paper that some classical types of Lyapunov functions can be seen as special cases of the proposed CPLF. Then, new stability conditions are developed by the new Lyapunov function approach. It is also proved that the conservativeness of the obtained criteria can be further reduced as the degree of the Lyapunov function increases. A numerical example is given to demonstrate the effectiveness and less conservativeness of the developed techniques.     

Nonisomorphic classes of inhomogeneous bilinear realizations: Realizability and existence

This paper is concerned with the nonisomorphic classes of the inhomogeneos bilinear realizations with unknown initial state.A necessary and sufficient condition is given for the factorizability of the generalized Hankel matrix into the specified form. And then a new realizability condition for inhomogeneous bilinear systems is obtained, which is of practical use.A necessary and sufficient condition for the existence of nonisomorphic (in the sense of linear transformation) spancanonical realizations is given. And the parameters determining the classes of nonisomorphic realizations are obtained in explicit form. As a result, it is shown that if nonisomorphic realizations exist, the cardinality of the family of nonisomorphic classes is equal to that of the real number field.