Xin X.,Okayama Prefectural University
International Journal of Robust and Nonlinear Control | Year: 2011
Designing and analyzing controllers for mechanical systems with underactuation degree (difference between the number of degrees of freedom and that of inputs) greater than one is a challenging problem. In this paper, for the double pendulum on a cart, which has three degrees of freedom and only one control input, we study an unsolved problem of analyzing the energy-based swing-up control which aims at controlling the total mechanical energy of the cart-double-pendulum system, the velocity and displacement of the cart. Under the energy-based controller, we show that for all initial states of the cart-double-pendulum system, the velocity and displacement of the cart converge to their desired values. Then, by using a property of the mechanical parameters of the double pendulum, we show that if the convergent value of the total mechanical energy is not equal to the potential energy at the up-up equilibrium point, where two links are in the upright position, then the system remains at the up-down, down-up, and down-down equilibrium points, where two links are in the upright-down, down-upright, and down-down positions, respectively. Moreover, we show that each of these three equilibrium points is strictly unstable in the closed-loop system by showing that the Jacobian matrix valued at each equilibrium point has at least one eigenvalue in the open right half plane. This shows that for all initial states with the exception of a set of Lebesgue measure zero, the total mechanical energy converges to the potential energy at the up-up equilibrium point. This paper provides insight into the energy-based control approach to mechanical systems with underactuation degree greater than one. © 2010 John Wiley & Sons, Ltd.
Taniguchi T.,Okayama Prefectural University
Sangyō eiseigaku zasshi = Journal of occupational health | Year: 2012
The purpose of this study was to describe workplace bullying experienced by professional caregivers at welfare facilities for the elderly in Japan and to confirm its effects on stress reactions. A cross-sectional survey was carried out using self-administered questionnaires in 2009 of all the employees working in rural area of facilities for long-term care. Among the 1,233 respondents who filled out all questionnaires concerning stress reactions the Japanese version of the Negative Acts Questionnaire (NAQ) (response rate: 63.9%), we analyzed 897 professional caregivers. We measured stress reactions by using the stress reaction scores of the Brief Job Stress Questionnaire (29 items) and workplace bullying and harassment by using NAQ. We used the unpaired t-test and analysis of covariance (ANCOVA) to compare crude and adjusted average stress reactions with groups classified on the basis of each subscale of the NAQ or all of them. About 40% of both men and women suffered from "malicious gossip" and over 60% of both men and women experienced "someone withholding necessary information so that their work gets complicated". Among women, scores of the lack of vigor and fatigue were significantly higher in caregivers targeted by person-related bullying than those not targeted (p<0.05). Scores of depression were significantly higher in caregivers targeted by work-related bullying than those not targeted (p<0.05). Scores of anxiety were significantly higher among caregivers targeted by sexual harassment than those not targeted (p<0.05). Among men, scores of the lack of vigor were significantly lower in caregivers targeted by work-related bullying than those not targeted (p<0.05). Among women, workplace bullying or harassment could may aggravate effects on psychological stress responses. While among men, work-related bullying was positively associated with vigor.
Xiao J.,Shanghai Normal University |
Xiao J.,University of Wurzburg |
Kai G.,Shanghai Normal University |
Yamamoto K.,Okayama Prefectural University |
Chen X.,Central South University
Critical Reviews in Food Science and Nutrition | Year: 2013
The dietary polyphenols as α-glucosidases inhibitors have attracted great interest among researchers. The aim of this review is to give an overview of the research reports on the structure-activity relationship of dietary polyphenols inhibiting α-glucosidases. The molecular structures that influence the inhibition are the following: (1) The hydroxylation and galloylation of flavonoids including catechins improve the inhibitory activity. (2) The glycosylation of hyroxyl group and hydrogenation of the C2=C3 double bond on flavonoids weaken the inhibition. (3) However, cyaniding glycosides show higher inhibition against than cyanidin. Proanthocyanidins oligomers exhibit a stronger inhibitory activity than their polymers. (4) The hydroxylation on B ring and the glycosylation of stilbenes reduce the inhibitory activity. (5) Caffeoylquinic acids display strong inhibition against α-glucosidases. However, hydroxycinnamic acid, ferulic acid, and gallic acid hardly inhibited α-glucosidases. (6) The coupled galloyl structures attached to C-3 and C-6 of the 4C1 glucose core of ellagitanin gave basic inhibitory activity. (7) The mono-glycosylation of chalcones slightly lowers the inhibition. However, the diglycosylation of chalcones significantly decreased the activity. © 2013 Copyright Taylor and Francis Group, LLC.
Xin X.,Okayama Prefectural University
Advanced Robotics | Year: 2013
The energy-based control approach aiming to control both the total mechanical energy and actuated variables of underactuated mechanical systems has generated renewed interest in recent years. Different from the reports of successful applications of this approach, we investigate whether there exists an underactuated mechanical system for which we fail to control both the total mechanical energy and actuated variable(s) to some given desired values by studying a CWA (Counter-Weighted Acrobot), which is a modified Acrobot with its first link having a counterweight and only its second link being actuated. By analyzing globally the solution of the closed-loop system consisting of the CWA and the controller designed via the energy-based control approach, we show that unless the CWA is linearly controllable at the up-up equilibrium, where links 1 and 2 are in the upright position, the controller fails to achieve the goal of controlling the energy to the potential energy at the equilibrium and controlling the actuated joint variable to zero. We also provide corresponding results for the up-down, down-up, and down-down equilibriums of the CWA, where up and down denote that the link is in the upright and downward positions, respectively. We present numerical simulation results to validate the theoretical results. © 2013 Taylor & Francis Group, LLC.
Xin X.,Okayama Prefectural University |
Liu Y.,Okayama University
Automatica | Year: 2013
This paper concerns reduced-order stable controllers in a unified way for two typical examples of underactuated robots called the Acrobot and the Pendubot, which are two-link planar robots moving in a vertical plane with a single actuator at joints 1 and 2, respectively. The main contributions of this paper are threefold. First, with the aid of properties of the mechanical parameters of two-link planar robots, this paper proves constructively that stable controllers exist for stabilizing the UEP (Upright Equilibrium Point with two links being still in the upright position) of each robot by designing a single output with an adjustable parameter. Second, the paper presents a design method to obtain explicitly a formula of second-order (reduced-order) stable controllers by choosing the adjustable parameter. Third, in terms of strong stabilization, some new features of the Acrobot and the Pendubot are revealed and are compared with those of the cart-pendulum system. Simulation results for the two robots are presented to validate the theoretical results and to demonstrate that the presented stable stabilizing controllers achieve a better control performance than several other controllers. © 2013 Published by Elsevier Ltd.