Search

Editorial. Discusses issues pertaining to the use of iterative learning control (ILC) in dealing with difficulties associated with performance design of control systems. Background on the ILC concept; Formulation of the ILC problem.

In this paper we use the formalism of iterative learning control (ILC) to solve the repetitive control problem of forcing a system to track a prescribed periodic reference signal. Although the systems we consider operate continuously in time, rather than with trials that have distinct starting and ending times, we use the ILC approach by defining a 'trial' in terms of completion of a single 'period' of the output trajectory, where a period is an interval from the start of the trial until the system returns to its initial state. The ILC scheme we develop does not use the standard assumption of uniform trial length. In the final result the periodic motion is achieved by 'repetition' of the learned ILC input signal for a single period. Analysis of the convergence of the algorithm uses an intermediate convergence result for the typical ILC problem. This intermediate result is based on a multi-loop control interpretation of the signal flow in ILC. The idea is demonstrated on an example and it is noted that it may be possible to generalize the ideas to broader classes of systems and ILC algorithms. [ABSTRACT FROM AUTHOR]

Discusses the structure and function of P-selectin glycoprotein ligand-1. Expression of the selectin family of adhesion molecules on activated endothelial cells, activated platelets and peripheral blood leukocytes; Interaction with P-, L- and E-selectin; Mediation function in cell adhesion.