Adaptive Fuzzy Backstepping Output Feedback Control of Nonlinear Time-delay Systems with Unknown High-frequency Gain Sign

In this paper, an adaptive fuzzy robust feedback control approach is proposed for a class of single-input and singleoutput （SISO） strict-feedback nonlinear systems with unknown nonlinear functions, time delays, unknown high-frequency gain sign, and without the measurements of the states. In the backstepping recursive design, fuzzy logic systems are employed to approximate the unknown smooth nonlinear functions, K-filters is designed to estimate the unmeasured states, and Nussbaum gain functions are introduced to solve the problem of unknown sign of high-frequency gain. By combining adaptive fuzzy control theory and adaptive backstepping design, a stable adaptive fuzzy output feedback control scheme is developed. It has been proven that the proposed adaptive fuzzy robust control approach can guarantee that all the signals of the closed-loop system are uniformly ultimately bounded and the tracking error can converge to a small neighborhood of the origin by appropriately choosing design parameters. Simulation results have shown the effectiveness of the proposed method.

Recent Progress in Networked Control Systems——A Survey

For the past decades,networked control systems(NCSs),as an interdisciplinary subject,have been one of the main research highlights and many fruitful results from different aspects have been achieved.With these growing research trends,it is significant to consolidate the latest knowledge and information to keep up with the research needs.In this paper,the results of different aspects of NCSs,such as quantization,estimation,fault detection and networked predictive control,are summarized.In addition,with the development of cloud technique,cloud control systems are proposed for the further development of NCSs.

Development of fetal growth charts in twins stratified by chorionicity and mode of conception:a retrospective cohort study in China

Background:Twin pregnancies continue to increase worldwide;however,the current clinical prenatal evaluation for the intrauterine growth of twins still relies on the growth standards of singletons.We attempted to establish a set of fetal biometric references for Chinese twin pregnancies,stratified by chorionicity and conception mode as spontaneously conceived monochorionic diamniotic(SC-MCDA),spontaneously conceived dichorionic diamniotic(SC-DCDA),and assisted reproductive technology dichorionic diamniotic(ART-DCDA)twins.Methods:From 2016 to 2019,the ultrasonographic fetal biometric measurements were longitudinally collected in pregnant women,including fetal weight,biparietal diameter,head circumference,abdominal circumference,femur length,and humerus length.The linear mixed models were used to test the difference of growth patterns between groups,and the growth curve of each biometric parameter was modeled by a generalized additive model for location scale and shape.Results:A total of 929 twin pregnant women and 2019 singleton pregnant women,met the inclusion criteria.Among twin pregnancies,148 were SC-MCDA,215 were SC-DCDA,and 566 were ART-DCDA twins.Overall,SC-DCDA twins grew faster than SC-MCDA twins,while slower than ART-DCDA twins(all P<0.05),and all of the three groups showed significant differences comparing with singletons,especially during the third trimester.Hence,the customized fetal growth charts of each fetal biometric parameter were,respectively,constructed for SC-MCDA,SC-DCDA,and ART-DCDA twins.Conclusions:The fetal biometric trajectories demonstrated characteristic patterns according to chorionicity and conception mode.To fill the gap,we modeled fetal biometric parameters for Chinese SC-MCDA,SC-DCDA,and ART-DCDA twin pregnancies,hoping to provide a reference for the further establishment of fetal growth reference values for Chinese twin fetuses.