On stabilization of nonlinear systems with drift by time-varying feedback laws

This paper deals with the stabilization problem for nonlinear control-affine systems with the use of oscillating feedback controls. We assume that the local controllability around the origin is guaranteed by the rank condition with Lie brackets of length up to 3. This class of systems includes, in particular, mathematical models of rotating rigid bodies. We propose an explicit control design scheme with time-varying trigonometric polynomials whose coefficients depend on the state of the system. The above coefficients are computed in terms of the inversion of the matrix appearing in the controllability condition. It is shown that the proposed controllers can be used to solve the stabilization problem by exploiting the Chen-Fliess expansion of solutions of the closed-loop system. We also present results of numerical simulations for controlled Euler's equations and a mathematical model of underwater vehicle to illustrate the efficiency of the obtained controllers.Comment: This is the author's version of the manuscript accepted for publication in the Proceedings of the 12th International Workshop on Robot Motion Control (RoMoCo'19

Biomechanics of stair descent in older adults

Negotiating stairs is one of the most difficult activities of daily living faced by older adults. Many researchers have studied the cardiovascular and musculoskeletal demands of stair ascent but there is little research on the biomechanics of stair descent. The purpose of this study was to investigate the biomechanics of stair descent in older adults

Obstacle Avoidance Problem for Second Degree Nonholonomic Systems

In this paper, we propose a new control design scheme for solving the obstacle avoidance problem for nonlinear driftless control-affine systems. The class of systems under consideration satisfies controllability conditions with iterated Lie brackets up to the second order. The time-varying control strategy is defined explicitly in terms of the gradient of a potential function. It is shown that the limit behavior of the closed-loop system is characterized by the set of critical points of the potential function. The proposed control design method can be used under rather general assumptions on potential functions, and particular applications with navigation functions are illustrated by numerical examples.Comment: This is the author's accepted version of the paper to appear in: 2018 IEEE Conference on Decision and Control (CDC), (c) IEE

Skills Assessment for Business Services: Final Report

No abstract available

On a class of generating vector fields for the extremum seeking problem: Lie bracket approximation and stability properties

In this paper, we describe a broad class of control functions for extremum seeking problems. We show that it unifies and generalizes existing extremum seeking strategies which are based on Lie bracket approximations, and allows to design new controls with favorable properties in extremum seeking and vibrational stabilization tasks. The second result of this paper is a novel approach for studying the asymptotic behavior of extremum seeking systems. It provides a constructive procedure for defining frequencies of control functions to ensure the practical asymptotic and exponential stability. In contrast to many known results, we also prove asymptotic and exponential stability in the sense of Lyapunov for the proposed class of extremum seeking systems under appropriate assumptions on the vector fields

Review of Regional Skills Assessments: Final Report

No abstract available

Facial recognition and visual processing as we age:Using the Thatcher illusion with famous and non-famous faces

This paper reports a study examining preferred visual processes in recognition of facial features in older vs younger age groups, using Thatcherised images of famous and non-famous people in the one study. The aims were to determine whether decline in visual system processing occurs increasingly as we grow older, and whether there is less decline in recognition of famous (or familiar) faces. Three groups (younger, middle-old and older) made up the sample of 73 people (aged 19-82 years). Visual decline in face recognition across the age groups was assessed based on the Thatcher illusion—using four famous and four non-famous faces either with normal features or with distorted features. The faces were presented one at a time on computer screen, and participants were asked to judge whether the face was distorted (eyes and/or mouth not aligned in relation to the face); in addition, time taken to decision (latency) was also measured. Decline was found in visual processing such that older individuals gave limited attention to facial details (processing faces holistically, with detail errors) and they took longer to decide. Whether the faces were famous or not did not have significant effects on the decisions and there was no interaction with age, though famous faces were given longer attention. Our visual system processes decline as we age in that we give less attention to details and more to holistic processing and so make more errors in recognition. Implications for treatment or amelioration of the effects are discussed.</jats:p

Emotional intelligence and optimistic cognitive style in certainty in career decision making

The current study tested whether Trait Emotional Intelligence variables and Optimistic Cognitive Style together predicted feelings of certainty in career decision making. Few studies have examined the effects of trait emotional intelligence or life style orientation on career choice, and no study has been found that combined both the life orientation (optimism) and the trait emotional intelligence domains and facets: this current study examined the relative weights of these facets and lifestyle orientation in relation to career certainty. Participants were from a convenience sample of 142 university students who completed a paper-and-pencil survey containing the following measures: the Life Orientation Test-Revised (assessing optimism, the Trait Emotional Intelligence Scale (TEIQue), and the Career Decision Scale (CDS).It was found that optimism and the four main domains (of wellbeing, self-control, emotionality, and sociability) and several of the subscales of the TEIQue correlated significantly with career certainty. A unique significant predictor of Career Certainty was found to be Stability-Impulsivity (a facet in the Self-Control domain of the TEIQue) but optimism was not a factor in predicting career certainty when the stability-impulsiveness factor was accounted for. Self-control- stability (low impulsiveness) predicted career certainty. It would seem that stability in thinking and action helps career commitment (certainty). Implications are drawn for career development counselling and suggestions made for future research