Stability analysis of nonlinear control systems with characteristics equations having complex coefficients

In this paper, the stability equation method is applied to the analysis of nonlinear systems with characteristics equations having complex coefficients. Three types of systems are studied: those with unstable open-loop poles, unstable characteristics roots or an equal number of open-loop poles and zeros.     

Applications of the stability-equation method to linear systems

This paper presents the applications of the stability-equation method to the analysis and design of linear systems. Control systems with multiple inputs and outputs are considered; the absolute stability and relative stability characteristics are analyzed. Stability conditions for control systems with a transport lag or a distributive lag are presented. Finally, the stability characteristics of a system with a distributive parameter are analyzed.     

Walsh Operational Matrices for Fractional Calculus and Their Application to Distributed Systems

The Walsh operational matrix for performing integration and solving state equations is generalized to fractional calculus for investigating distributed systems. A new set of orthogonal functions is derived from Walsh functions. By using the new functions, the generalized Walsh operational matrices corresponding to √s, √(s²+ 1), e^-s and e^-√s etc. are established. Several distributed parameter problems are solved by the new approach.     

A gradient approach to the determination of stability of limit cycles

This paper presents the applications of the stability equation method to the analysis and design of nonlinear systems. A simplified criterion for finding the limit cycle in a parameter plane is presented, and a simplified method for testing limit cycle stability is introduced. Several examples, considered in the current literature, are used for illustrating the advantages of the method presented.     

Stability-equation method for sampled-data systems

This paper presents a new transformation by which the stability-equation method can be applied for analysis and design of sampled-data systems. New stability criteria applicable to systems with transfer function having both real and complex coefficients are presented. Several kinds of examples are considered with computer results given.     

Journal self-citation study for semiconductor literature: Synchronous and diachronous approach

The present study investigates the self-citations of the most productive semiconductor journals by synchronous (self-citing rate) and diachronous (self-cited rate) approaches. Journal’s productivity of 100 most productive semiconductor journals was gathered from INSPEC database, 1978–1997 through OVID. Data of citation frequency were obtained from the Science Citation Index (SCI), Journal Citation Reports (JCR) 2001 CDROM edition by the title-by-title search. The self-citing and self-cited data were drawn from the Citing Journal Listing and the Cited Journal Listing of the JCR CDROM version 1990–2001. Self-citing and self-cited rates were determined by the method suggested by the JCR. Eighty-seven journals common to INSPEC and JCR in semiconductor were selected as the object of this study and were listed for statistical tests. The results of the present study demonstrate that high self-citing journals are usually older than low self-citing journals. In contrast to the self-citing data, the journal self-cited rate is not closely related to the publication year but reflects the characteristics of various journals. Journals with a short time interval of publication are more possible with high self-citing and self-cited rates. Journals with higher self-citing rate tend to be more productive and receive more citation than journals with lower self-citing rate. The journal self-cited rate has no association with the number of articles that a journal published and the citation it received. A journal with a higher self-citing rate tends to be cited more by itself. The mean self-citing rate is 9.59% and the mean self-cited rate is 15.03%. There is a significant difference between self-citing and self-cited rates within the same set of journals.     

Predicting students' ratings of the importance of strategies to facilitate self‐directed distance learning in Taiwan

Distance students' ratings of the importance of strategies to facilitate self‐directed learning were evaluated. Students from an open university in Taiwan (449 current and 140 inactive) participated in this study. Current students scored significantly higher than inactive students on internal motivation, insight about self, and self‐directed learning readiness. A combination of high internal and external motivation and high self‐directed learning readiness predicted ratings of the importance of five sets of strategies for helping students become self‐directed learners. The study provides information to help distance learning professionals enhance the effectiveness of self‐directed learning and reduce the number of students who become inactive.     

On-line tuning of PI/Lead compensators for decoupling multivariable processes with specifications on phase and bandwidth

In this paper, an on-line identification and auto-tuning method is proposed for multivariable processes. Systematic identifying procedures and on-line tuning rules are developed for computing parameters of proportional plus integration and Lead compensators. The performance of the compensated systems can be evaluated by wanted bandwidth, phase margins and low-interacting characteristics. No iteration for finding parameters of compensator is needed. Parameters of PI/Lead compensator can be retuned if they are needed. Three numerical examples give the proposed method provides better performance, robustness and less interaction effects than those of other mentioned on-line computing methods.     

Analyses and designs of a nonlinear mechanical scanning control system

In this literature, a scanning system with special mechanical structure and electronic control circuit is analyzed and designed. The scanning control system enlarges the field of view (FOV) and saves more 48% power consumption than conversional scanning systems with scanning motor. The considered system is characterized and analyzed by an equivalent nonlinear feedback control system. All analyzed results are verified by digital simulating and real system testing datum.