Iterative learning control for constrained linear systems

This paper considers iterative learning control for linear systems with convex control input constraints. First, the constrained ILC problem is formulated in a novel successive projection framework. Then, based on this projection method, two algorithms are proposed to solve this constrained ILC problem. The results show that, when perfect tracking is possible, both algorithms can achieve perfect tracking. The two algorithms differ however in that one algorithm needs much less computation than the other. When perfect tracking is not possible, both algorithms can exhibit a form of practical convergence to a "best approximation". The effect of weighting matrices on the performance of the algorithms is also discussed and finally, numerical simulations are given to demonstrate the e®ectiveness of the proposed methods

Modelling the influence of non-minimum phase zeros on gradient based linear iterative learning control

The subject of this paper is modeling of the influence of non-minimum phase plant dynamics on the performance possible from gradient based norm optimal iterative learning control algorithms. It is established that performance in the presence of right-half plane plant zeros typically has two phases. These consist of an initial fast monotonic reduction of the L2 error norm followed by a very slow asymptotic convergence. Although the norm of the tracking error does eventually converge to zero, the practical implications over finite trials is apparent convergence to a non-zero error. The source of this slow convergence is identified and a model of this behavior as a (set of) linear constraint(s) is developed. This is shown to provide a good prediction of the magnitude of error norm where slow convergence begins. Formulae for this norm are obtained for single-input single-output systems with several right half plane zeroes using Lagrangian techniques and experimental results are given that confirm the practical validity of the analysis

Multivariable norm optimal iterative learning control with auxiliary optimization

The paper describes a substantial extension of Norm Optimal Iterative Learning Control (NOILC) that permits tracking of a class of finite dimensional reference signals whilst simultaneously converging to the solution of a constrained quadratic optimization problem. The theory is presented in a general functional analytical framework using operators between chosen real Hilbert spaces. This is applied to solve problems in continuous time where tracking is only required at selected intermediate points of the time interval but, simultaneously, the solution is required to minimize a specified quadratic objective function of the input signals and chosen auxiliary (state) variables. Applications to the discrete time case, including the case of multi-rate sampling, are also summarized. The algorithms are motivated by practical need and provide a methodology for reducing undesirable effects such as payload spillage, vibration tendencies and actuator wear whilst maintaining the desired tracking accuracy necessary for task completion. Solutions in terms of NOILC methodologies involving both feedforward and feedback components offer the possibilities of greater robustness than purely feedforward actions. Robustness of the feedforward implementation is discussed and the work is illustrated by experimental results from a robotic manipulator

On subsets of S^n whose (n + 1)-point subsets are contained in open hemispheres

We investigate the nature of subsets of spheres which satisfy a tameness condition associated with the Bieri–Groves FPm-conjecture. We find that there is a natural polyhedrality in the case of n-tame subsets of an (n − 1)-sphere. In the case n = 3 we establish a strong polyhedrality condition for certain maximal open 3-tame sets. Many examples are included

The Price Premium for Organic Babyfood: A Hedonic Analysis

The price premium associated with organic babyfood is estimated by applying a hedonic model to price and characteristic data for babyfood products collected in two cities: Raleigh, North Carolina, and San Jose, California. The price per ounce of babyfood is modeled as a function of a number of babyfood and store characteristics. The estimated organic price premium is generally equal to 3 cents to 4 cents per ounce. To the extent this premium reflects consumer willingness to pay to reduce pesticide exposures, it could be used to infer values for reduced dietary exposures to pesticide residues for babies.babyfood, hedonic analysis, organic foods, Demand and Price Analysis,

Graduate Education in Geographically - Integrated History: A Personal Account

This article discusses graduate education in geographically-integrated history as developed by the History Department of Idaho State University for its M.A. in Historical Resources Management. This Master's program is based the use of geographic information systems (GIS) and related information technologies. In addition to discussing the rationale and design of the program, the article illustrates what is involved in graduate education of this type through a description of the author's introductory graduate course "Geographic Information Systems in Historical Studies.

Prosthesis coupling

A coupling for use in an apparatus for connecting a prosthesis to the bone of a stump of an amputated limb is described which permits a bio-compatible carbon sleeve forming a part of the prosthesis connector to float so as to prevent disturbing the skin seal around the carbon sleeve. The coupling includes a flexible member interposed between a socket that is inserted within an intermedullary cavity of the bone and the sleeve. A lock pin is carried by the prosthesis and has a stem portion which is adapted to be coaxially disposed and slideably within the tubular female socket for securing the prosthesis to the stump. The skin around the percutaneous carbon sleeve is able to move as a result of the flexing coupling so as to reduce stresses caused by changes in the stump shape and/or movement between the bone and the flesh portion of the stump

Fourth Amendment Remedial Equilibration: A Comment on \u3ci\u3eHerring v. United States\u3c/i\u3e and \u3ci\u3ePearson v. Callahan\u3c/i\u3e

In two recent decisions, the Supreme Court addressed remedies under the Fourth Amendment by assuming that this remedial construction did not alter the value of the underlying right meant to be protected by the Constitution. First, in Herring v. United States, the court broadened exceptions to the exclusionary rule and implied that suppression may not be required for negligent errors generally. Then, in Pearson v. Callahan, the Court abandoned it\u27s battle-of-order rule - which required courts to consider the right before inquiring whether that right was clearly established at the time of the violation - when considering qualified immunity defenses in Section 1983 civil rights actions. Both cases, I argue, adhere to a from of rights essentialism that presumes rights construction and remedial enforcement decisions are separate and, thereby, do not affect each other. By contrast, I advance the remedial equilibration thesis that sees the value of rights through their remedies and finds rights essentialism dangerously inattentive to the consequences of constricting remedies for the underlying right. Herring and Pearson, then, take on new significance from this perspective because of what they mean for the underlying Fourth Amendment right because it is not just Fourth Amendment remedies that have been constricted by these decisions, but the value of the right itself may be altered and potentially devalued