Active vibration control of flexible bodied railway vehicles via smart structures

Future railway vehicles are going to be designed lighter in order to achieve higher speed. Suppressing the flexible modes becomes a crucial issue for improving the ride quality of the light-weight high speed railway vehicles. The concept of smart structure brings structural damping to flexible structures by integrating smart actuators and sensors onto the structure. Smart structure eliminates the need for extensive heavy mechanical actuation systems and achieves higher performance levels through their functionality for suppressing the flexible modes. Active secondary suspension is the effective conventional approach for vibration control of the railway vehicle to improve the ride quality. But its ability in suppressing the flexible modes is limited. So it is motivated to combine active structural damping for suppressing the flexible modes and the vibration control through active secondary suspension which has an effect on both rigid and flexible modes. The side-view model of the flexible-bodied railway vehicle integrated with piezoelectric actuators and sensors is derived. The procedure for selection of placement configurations of the piezoelectric actuators and sensors using structural norms is presented. Initial control studies show that the flexibility of the vehicle body will cause a considerable degradation in ride quality if it is neglected in the design model. Centralized and decentralized control strategies with various control approaches (e.g. modal control with skyhook damping, LQG/H2 control, H_infinity control and model predictive control (MPC))are applied for the combined control of active structural damping and active suspension control. The active structural damping effectively suppresses the flexible modes as a complement to the work of the active suspension control

Model predictive control based on mixed H2/H∞ control approach for active vibration control of railway vehicles

This paper investigates the application of Model Predictive Control (MPC) technology based on mixed H2/H1 control approach for active suspension control of a railway vehicle, the aim being to improve the ride quality of the railway vehicle. Comparisons are made with more conventional control approaches, and the applicability of the linear matrix inequality approach is illustrated via the railway vehicle example

Investigation of a Measles Outbreak in China to Identify Gaps in Vaccination Coverage, Routes of Transmission, and Interventions

<div><p>Background</p><p>A measles outbreak occurred in a western county of China in 2013, the year after China’s historic nadir of measles. We conducted a field investigation to identify gaps in measles vaccination coverage and immunization program weaknesses, and to provide recommendations for measles outbreak response and immunization program improvement.</p><p>Methods</p><p>We analyzed surveillance data from 2008 to 2013 to describe the measles epidemiology of the county. Measles-containing vaccine coverage was estimated using two methods: previously-reported administrative coverage and an estimation of coverage by clinic-kept vaccination records (n = 542). We conducted a rapid field coverage assessment in a migrant population village to evaluate coverage after emergency vaccination. We conducted a review of hospital records of measles cases to address the role hospital transmission played during the early stage of this outbreak.</p><p>Results</p><p>There were 153 cases in the outbreak, primarily among children too young to vaccinate, unvaccinated children less than 3 years old, and adults. Measles-containing vaccine coverage by the field assessment showed that 20% of children aged 8–17 months had zero doses, and 9% of ≥2 years old children had fewer than two doses. The vaccination statuses of all adult cases were either zero doses or unknown. At least 61% of cases had been hospitalized. The proportion of cases who had been hospital-exposed 7 to 21 days prior to rash onset decreased from 52% to 22% after hospitals strengthen their isolation measures.</p><p>Conclusions</p><p>This outbreak was a result of measles vaccination coverage gaps among young children and adults, and insufficient hospital isolation of cases. The lower coverage seen in the field estimation compared with reported coverage showed that reported coverage could have been overestimated. Hospitals were sites of transmission in the early stage of the outbreak. A strict hospital isolation policy could decrease spread of measles. Emergency vaccination was associated with stopping measles transmission in low coverage areas.</p></div

Time distribution of measles cases by illness onset date, categorized by hospital exposure history.

<p>Time distribution of measles cases by illness onset date, categorized by hospital exposure history.</p

MCV coverage assessment of different age groups^*.

<p>MCV coverage assessment of different age groups^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133983#t002fn001" target="_blank">*</a>}.</p

Distribution of MCV2 vaccination month.

<p>Distribution of MCV2 vaccination month.</p

Supplementary immunization activities (SIAs) and screening-and-vaccination activities (SVA) conducted during 2008–2013, W county, China.

<p>Supplementary immunization activities (SIAs) and screening-and-vaccination activities (SVA) conducted during 2008–2013, W county, China.</p

Hospital exposure histories prior to rash onset for 13 cases.

<p>Hospital exposure histories prior to rash onset for 13 cases.</p

Distribution of MCV1 vaccination month

<p>Distribution of MCV1 vaccination month</p

Distribution of MCV vaccination status among different age groups.

<p>Distribution of MCV vaccination status among different age groups.</p