Search

We study the problem of synthesizing controllers that enforce hard state-constraints under occasionally missing state measurements. Although the problem can be solved as a partial information game via power set construction, it is undesired to do so because power set construction is computationally expensive. In this paper, we consider the instances where the missing data pattern can be specified by an automaton, and show that, for such cases, the synthesis problem admits a simpler solution. We introduce string automata and exploit the causality requirement to define the structure of the controller, and further use this structure to derive a product system. The synthesis problem then reduces to a full-information game on this product system. Two examples illustrate the efficacy of the proposed approach.

Background More and more studies began to explore the hazardous health effects of PM2.5, but few reported its impacts on stillbirth. The sparse results were inconsistent and remained to be integrated. Therefore, we aimed to reveal the association between maternal exposure to PM2.5 and stillbirth. Methods In this meta-analysis, we searched PubMed, Web of Science, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases for related articles written in English and published before October 18, 2020. Study selection was conducted according to the predetermined criteria and data attraction was done with predesigned form. A new instrument was applied to conduct the risk of bias assessment. And random-effect models were used to pool the estimates. Results A total of 3655 records were identified from the databases, but only 7 studies were ultimately included in this study. Positive association was found between the maternal exposure to PM2.5 (per 10 μg/m3 increased) in the entire pregnancy (OR: 1.15, 95% CI: 1.07–1.25) and third trimester (OR: 1.09, 95% CI: 1.01–1.18) and stillbirth, but the association between the maternal exposure to PM2.5 (per 10 μg/m3 increased) in the first trimester (OR: 1.01, 95% CI: 0.90–1.13) and second trimester (OR: 1.06, 95% CI: 0.98–1.14) and stillbirth was not statistically significant. Besides, there was no publication bias. Conclusions Maternal exposure to PM2.5 in the entire pregnancy and third trimester was associated with elevated risk of stillbirth. However, due to the high heterogeneity, further pathophysiological researches and high quality population studies were still warranted.

In this paper, we consider the robustification and parametrization of an invariance switching controller with respect to a scalar variable (parameter) that affects the system dynamics. By robustification, we mean searching for a switching controller that guarantees invariance of a set, under a large enough range of the parameter values. In case such a robust controller does not exist, we do parametrization, i.e., searching for a collection of controllers, each one robust to a smaller range of parameter values. A parametrized controller can be applied in real-time by picking the appropriate switching surfaces based on the measurement of the parameter. To be more specific, assuming (i) the system dynamics is affine, and is monotone in the considered parameter, (ii) the invariance switching controller is defined on a rectangle in the state space, we show that the robustification and parametrization problems can be reduced to solving a sequence of linear programming problems. The proposed approach is illustrated by several numerical examples.