Weak exponential stability for time-periodic differential inclusions via first approximation averaging

Published online: 20 June 2012In this work we propose a method to study a weak exponential stability for time-varying differential inclusions applying an averaging procedure to a first approximation. Namely, we show that a weak exponential stability of the averaged first approximation to the differential inclusion implies the weak exponential stability of the original time-varying inclusion. The result is illustrated by an example.FC

Nonlinear feedback control with global stabilization

Hamilton-Jacobi-Bellman theory is shown to provide a unified framework for nonlinear feedback control laws for special classes of nonlinear systems. These classes include Jurdjevic-Quinn type systems, as well as minimum phase systems with relative degree {1, 1, ..., 1}. Several examples are given to illustrate these results. For the controlled Lorenz equation, results obtained by Vincent and Yu are extended. Next, for spacecraft angular velocity stabilization with two torque inputs, a family of nonlinear feedback control laws that globally asymptotically stabilize angular velocity is established. Special cases of this family of control laws include generalizations of the locally stabilizing control laws of Brockett and Aeyels to global stabilization as well as the globally stabilizing control laws of Irving and Crouch and Byrnes and Isidori. Finally, the results are applied to spacecraft angular velocity stabilization with only one torque input. These last results extend control laws given by Outbib and Sallet.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42625/1/10638_2005_Article_BF01968501.pd

An iterative approach to eigenvalue assignment for nonlinear systems

In this paper, the authors present a method for controlling a nonlinear system by using the ideas of eigenvalues assignment. A time-varying approach to nonlinear exponential stability via eigenvalue placement is studied based on an iteration technique that approaches a nonlinear system by a sequence of linear time varying equations. The convergent behaviour of this method is shown and applied to a practical nonlinear example in order to illustrate these ideas

Homogeneous Lyapunov Functions and Necessary Conditions for Stabilization

peer reviewedWe provide necessary conditions for the stabilization of nonlinear control systems with the additional requirement that a time-invariant homogeneous Lyapunov function exists for the closed-loop system

De impact van ziekenhuiscontext op kwaliteitsverbetering voor patiënten met een STEMI.

The success of quality improvement interventions is mixed, resulting in persistent performance variation and suboptimal patient care. To increase the impact of quality improvement interventions, complex multifaceted and multicomponent interventions like care pathways are used. On average, care pathways have moderate positive effects on quality of care, teamwork and organization of care. Context is a possible explanation for the variability in care pathway effects. To increase understanding on the impact of context on quality improvement, a care pathway for patients with ST-elevation myocardial infarction (STEMI) is a both clinically and socially relevant case. A model care pathway for in-hospital STEMI care included key interventions and quality indicators and clarified the care process and roles between the teams and professional groups involved. The key interventions and quality indicators were selected and validated by a multidisciplinary expert panel. After a first retrospective measurement in 15 hospitals, an importance-performance analysis set improvement priorities by depicting the importance of key intervention to their performance. The improvement priorities focused on timely percutaneous coronary intervention (PCI) and secondary prevention. Subsequently, the incremental, two-phased implementation of the care pathway focused on the selected improvement priorities. The care pathway was implemented as a quality improvement collaborative using the model care pathway, audit and feedback and strategies for change as mechanisms. The care pathway improved the delivery of in-hospital care for myocardial infarction through coordination of evidence-based key interventions. Incremental efforts were needed to achieve a significant increase in the percentage of patients receiving timely PCI. Likewise, the significant increase of guideline-recommended secondary prevention was achieved after the second implementation phase only. Apart from the effect on STEMI care, the care pathway helped to bridge professional boundaries and organizational division. After care pathway implementation, a significant improvement of teamwork and a significant improvement of the organization of STEMI care were shown. Importantly, the care pathway effect on teamwork and organization of STEMI care was higher in hospitals with higher support and capacity on quality improvement. A theory-based evaluation of the implementation process provided understanding on the impact of the hospital context on the care pathway effect. The implementation process evaluation explained how and why the hospital, its clinicians, and its management responded to the care pathway mechanisms, and how intervention fidelity effected in-hospital care and teamwork for myocardial infarction. None of the hospitals showed complete fidelity to the planned intervention. Hospitals chose specific improvement priorities based on care pathway mechanisms, clinical judgement and the hospital's openness to change. The path from entering the improvement intervention to implementation was not straightforward. The interplay between hospital context, care pathway mechanisms and implementation fidelity evolved over the course of the implementation and included setbacks and unanticipated events. Our findings are important for healthcare managers and policy makers aiming to increase the effect of quality improvement interventions in hospitals. The hospital context, care pathway mechanisms and implementation fidelity have a direct impact on the care pathway implementation. Furthermore, the care pathway effect is achieved by the interplay between hospital context, intervention mechanisms and implementation fidelity. This interplay is dynamic and evolves throughout the implementation. A hospital, both as an organization as well as through its employees, has an impact on in the implementation of a quality improvement intervention. A contextual openness to the intervention mechanisms increases implementation fidelity and the subsequent effect on patient care. Understanding ex ante this openness to the proposed intervention mechanisms, may help to increase the care pathway effect.status: publishe

Stability for Dynamic-systems With 1st Integrals - a Topological Criterion

This paper provides a new criterion for stability of equilibrium points of topological flows in the presence of first integrals. The result generalizes a well known criterion for stability of such systems obtained by means of Liapunov theory