48 research outputs found
Decay rate estimations for linear quadratic optimal regulators
Let be the optimal control of the open-loop system
in a linear quadratic optimization problem. By using
different complex variable arguments, we give several lower and upper estimates
of the exponential decay rate of the closed-loop system .
Main attention is given to the case of a skew-Hermitian matrix .
Given an operator , for a class of cases, we find a matrix that
provides an almost optimal decay rate.
We show how our results can be applied to the problem of optimizing the decay
rate for a large finite collection of control systems , , and illustrate this on an example of a concrete mechanical system. At the
end of the article, we pose several questions concerning the decay rates in the
context of linear quadratic optimization and in a more general context of the
pole placement problem.Comment: 25 pages, 1 figur
Instability in clinical risk stratification models using deep learning
While it has been well known in the ML community that deep learning models
suffer from instability, the consequences for healthcare deployments are under
characterised. We study the stability of different model architectures trained
on electronic health records, using a set of outpatient prediction tasks as a
case study. We show that repeated training runs of the same deep learning model
on the same training data can result in significantly different outcomes at a
patient level even though global performance metrics remain stable. We propose
two stability metrics for measuring the effect of randomness of model training,
as well as mitigation strategies for improving model stability.Comment: Accepted for publication in Machine Learning for Health (ML4H) 202