Tim Hesketh

An application of computerized fuzzy graphics rating scale to the psychological measurement of individual differences

This paper aims to outline and evaluate a new approach to measurement within psychology. A computerized fuzzy graphic rating scale which is an extension of a semantic differential is described. The scale allows respondents to provide an imprecise rating and lends itself to analysis using fuzzy set theory. Respondents rated nine occupational stimuli, carefully chosen to represent three levels of prestige (Daniel, 1983) and three levels of sex-type (Shinar, 1975), eight fuzzy graphic rating scales (5 for prestige and 3 for sex-type). A single expected value was calculated for the fuzzy ratings of the occupations to permit correlations with the a priori values for the nine occupations. Various combinations of scales were obtained by forming the union of individual fuzzy ratings. Expected values based on combined scales were calculated and the results were also correlated with the a priori Daniel and Shinar scale values. Potential applications of the fuzzy graphic rating scale are outlined.

Controller design for hot strip finishing mills

The results to date of a collaborative research project with BHP Steel in Port Kembla, Australia, are described. The project is concerned with control of strip tension and looper angle in BHPs hot strip steel rolling mill (the finishing mill). The new controllers have been successfully implemented on the process and now handle all the production at the mill. The paper describes a model of the process, similar to that reported in the work of others. The development of a full nonlinear controller is traced, based on a recursive nonlinear method (cf., backstepping). Insights are drawn into possible system structures, particularly in the output feedback case when tension measurements may not be available. Alternative controller schemes are examined, including a speculative design which contains filters, similar to those obtained from output feedback designs of linear systems, together with nonlinear operators which invite comparisons with variable structure designs. Simulation results, which provided the justification for the final implementation, together with results from actual production records are presented.

Practical Applications and Psychometric Evaluation of a Computerised Fuzzy Graphic Rating Scale

Publisher Summary This chapter summarizes the need for fuzzy measurement in many fields of psychology. The chapter also describes a fuzzy graphic rating scale, its validation, and ways in which the scale can be used in various fields. Fuzzy logic defines concepts and techniques which provide a mathematical method able to deal with thought processes which are too imprecise to be dealt with by classical mathematical techniques. A perennial issue in psychological assessment has been the extent to which differences in psychological test scores are a function of genuine individual differences rather than differences imposed (or obscured) by the constraints of the measurement procedures. Fuzzy set theory takes account of the reality of imprecision of human thought by allowing ranges of scores to be measured and translated into a single score. Sherif and Sherif discussed the notion of latitudes of acceptance and rejection in attitude measurement. The fuzzy graphic rating scale offers a direct way of addressing these notions of ranges within the domain of attitude measurement.

Piecewise Integral Sliding-Mode Control for T–S Fuzzy Systems

This paper addresses the issue of piecewise integral sliding-mode control (ISMC) for the Takagi-Sugeno (T-S) fuzzy systems. ISMC is chosen to stabilize the T-S fuzzy system because of its superior capability in treating uncertainties. Individual integral sliding surfaces are designed in different operating regions of the T-S fuzzy system. Conditions on the existence of the sliding mode in the associated region are given. The chattering phenomenon around region boundaries is analyzed, and the prevention of such chattering is discussed. An illustrative example is finally given to show the efficiency of the proposed method.

Adaptive mould level control for continuous steel slab casting

Abstract An adaptive controller was applied to mould level control for continuous steel slab casting. The controller is embedded within a PC-based real-time control program, named RTS. The work is the outgrowth of adaptive LQ designs which have been applied since 1981; a multivariable version of the adaptive controller is embedded within Connoisseur, a larger control system. Control of mould level for continuous steel slab casting involves a process whose model contains an integrator and oscillatory terms, noise and non-linearities, while the excitation of the actuation is poor. The combination is potentially devastating for adaptive controllers. The RTS controller incorporates filters, noise models and other techniques to deal with these problems. The on-line experiments offered insights into appropriate methodologies requiring interesting techniques for non-invasive monitoring and changeover from one controller to another so as not to affect normal production.

Piecewise Sliding-Mode Control for T–S Fuzzy Systems

This paper addresses piecewise sliding-mode control for Takagi-Sugeno (T-S) fuzzy models. A novel sliding-mode control (SMC) design approach is developed which is based on individual sliding surface in each local region of the T-S fuzzy systems. Conditions of existence of sliding mode in the associated region are given. The chattering effect around region boundaries is analyzed, and prevention of such chattering is discussed. Two illustrative examples are finally given to illustrate the effectiveness and performance of the proposed controller.

Computerized fuzzy ratings: The concept of a fuzzy class

In this paper, we outline the concept of a fuzzy class used in programs for eliciting computerized fuzzy ratings. Fuzzy ratings allow respondents to provide symmetrical or asymmetrical latitudes of acceptance around a preferred point. These ratings have been used in research testing career theories and person-environment fit models. The variables defining the fuzzy class and the various functions that can be performed by it are described in the paper. The idea of a fuzzy class may be of interest to those involved in expert systems, knowledge engineering, or in fuzzy classification and measurement in general. A program, FUZRATE, written in object-oriented C++ code that uses the concept of a fuzzy class, is available on request. Both source code and a binary (executable) file are available.

Fault accommodation for nonlinear systems using fuzzy adaptive sliding control

An active fault accommodation control law is developed for a class of nonlinear systems to guarantee the closed-loop stability in the presence of a fault, based on a fuzzy logic system representation of the dynamics due to faults. It uses fuzzy logic system to approximate the dynamic caused by the fault. Through the adaptive process of the parameters, the dynamics caused by the fault is counteracted. The fuzzy sliding mode control is introduced to attenuate the fuzzy approximation error. Simultaneity, the closed-loop system is stable in Lyapunov sense and the tracking error converges to a neighbourhood of zero. The example of the proposed design indicates that the fault accommodation control law is effective for a nonlinear system.

Use of fuzzy variables in developing new scales from the Strong Interest Inventory.

In 3 phases of analysis on one Australian sample, the concept of a fuzzy variable was used to develop new sex-type, prestige, and Holland interest scales from the Occupational scales of the Strong Interest Inventory (SII). Theoretically, the scales provide a basis for understanding avoidant reactions and the influence of sex type and prestige on interests. Phases 1 and 2 of the study describe intercorrelations among three measures of Holland themes and measures of sex type and prestige (occupational social space; L. S. Gottfredson, 1981). Phase 3 describes similar relationships but among scales derived from scoring the Occupational scales of the SII separately for distinctive likes and distinctive dislikes. Comments are offered about potential counseling and research uses for the new measures

Fault detection and diagnosis of networked control system

Consider the plant of Multiple-input Networked Control System (NCS) with long reduced delay. The effect of the disturbances to the NCS is discussed and the iterative method is used to compensate the delay when design a reduced-order state observer with a γ-stability margin (0  < γ  < 1) for system. By computing the residual between the output of the practical system and the output of the reduced-order state observer, the fault detection and diagnosis scheme of NCS is given. An illustrative example shows the effectiveness of the method.