Fuzzy-Model-Based Finite Frequency Fault Detection Filtering Design for Two-Dimensional Nonlinear Systems

This article studies the fault detection filtering design problem for Roesser type two-dimensional(2-D)nonlinear systems described by uncertain 2-D Takagi-Sugeno(T-S)fuzzy models.Firstly,fuzzy Lyapunov functions are constructed and the 2-D Fourier transform is exploited,based on which a finite frequency fault detection filtering design method is proposed such that a residual signal is generated with robustness to external disturbances and sensitivity to faults.It has been shown that the utilization of available frequency spectrum information of faults and disturbances makes the proposed filtering design method more general and less conservative compared with a conventional nonfrequency based filtering design approach.Then,with the proposed evaluation function and its threshold,a novel mixed finite frequency H_(∞)/H_(-)fault detection algorithm is developed,based on which the fault can be immediately detected once the evaluation function exceeds the threshold.Finally,it is verified with simulation studies that the proposed method is effective and less conservative than conventional non-frequency and/or common Lyapunov function based filtering design methods.

Structure of the Upper Mantle and Transition Zone Beneath the South China Block Imaged by Finite Frequency Tomography

We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block（SCB） and its surroundings from earthquakes occurring between July 2007 and July 2010,to better understand upper mantle deformation.Differential travel-times in the pair of stations with appropriate weighting for each station are used in the inversion.Our results are consistent with previous tomography that show a high velocity anomaly beneath the Sichuan basin and a high velocity anomaly in the transition zone beneath the Yangtze Craton.However,the resolution of mantle heterogeneity provides new insight into the tectonic framework of subduction of Burmese lithosphere in the west part of the study region and subduction of oceanic lithosphere in the east.In the subduction realm,west of 107°E,a significant fast S-wave anomaly is located on the southeast of Sichuan Basin.East of 107°E,and two narrow and discontinuous fast S-wave anomalies occur at a depth of 400-600 km beneath the middle of the South China block overlain by the pronounced low S-wave anomalies at a depth of 100 and 400 km.If the fast anomalies located in the mantle transition zone represent stagnant slabs,their fragmented nature may suggest that they could be produced by different episodes of subduction beneath western Pacific island and the above slow velocity anomaly may associated with the back-arc regions of ongoing subduction.In addition,tomography also reveals an anomalously high S-wave velocity continental root extends eastward to a depth 400 km beneath the eastern Sichuan Basin.This anomaly may be related to eastern extrusion of Indian lithosphere associated with the collision of India and Eurasia.Moreover,our results also show large slow anomalies beneath the Red River fault region connected to deeper anomalies beneath the South China Fold Belt and South China Sea.AH these observations are consistent with the scenario that the South China block has been built by both of subduction of Paleopacific plate and eastward subduction of Burma microplate.

Finite Frequency Fuzzy H∞Control for Uncertain Active Suspension Systems With Sensor Failure

This paper investigates the problem of finite frequency fuzzy H_∞ control for uncertain active vehicle suspension systems, in which sensor failure is taken into account. TakagiSugeno(T-S) fuzzy model is established for considered suspension systems. In order to describe the sensor fault effectively, a corresponding model is introduced. A vital performance index,H_∞ performance, is utilized to measure the drive comfort. In the framework of Kalman-Yakubovich-Popov theory, the H_∞ norm from external perturbation to controlled output is optimized effectively in the frequency domain of 4 Hz-8 Hz to enhance ride comfort level. Meanwhile, three suspension constrained requirements, i.e., ride comfort level, manipulation stability,suspension deflection are also guaranteed. Furthermore, sufficient conditions are developed to design a fuzzy controller to guarantee the desired performance of active suspension systems. Finally, the proposed control scheme is applied to a quarter-vehicle active suspension, and simulation results are given to illustrate the effectiveness of the proposed approach.

Static-Output-Feedback Based Robust Fuzzy Wheelbase Preview Control for Uncertain Active Suspensions With Time Delay and Finite Frequency Constraint

This paper proposes a static-output-feedback based robust fuzzy wheelbase preview control algorithm for uncertain active suspensions with time delay and finite frequency constraint.Firstly,a Takagi-Sugeno(T-S)fuzzy augmented model is established to formulate the half-car active suspension system with consideration of time delay,sprung mass variation and wheelbase preview information.Secondly,in view of the resonation between human’s organs and vertical vibrations in the frequency range of 4–8 Hz,a finite frequency control criterion in terms of H∞norm is developed to improve ride comfort.Meanwhile,other mechanical constraints are also considered and satisfied via generalized H2 norm.Thirdly,in order to maintain the feasibility of the controller despite of some state variables are not online-measured,a two stage approach is adopted to derive a static output feedback controller.Finally,numerical simulation results illustrate the excellent performance of the proposed controller.

H_∞ fault estimation for a class of linear time-delay systems in finite frequency domain

This paper deals with the problem of H∞ fault estimation for linear time-delay systems in finite frequency domain.First a generalized coordinate change is applied to the original system such that in the new coordinates all the time-delay terms are injected by the system＇s input and output.Then an observer-based H∞ fault estimator with input and output injections is proposed for fault estimation with known frequency range.With the aid of Generalized Kalman-Yakubovich-Popov lemma,sufficient conditions on the existence of the H∞ fault estimator are derived and a solution to the observer gain matrices is obtained by solving a set of linear matrix inequalities.Finally,a numerical example is given to illustrate the effectiveness of the proposed method.

Analysis of Frequency Characteristics and Sensitivity of Compliant Mechanisms

Based on a modified pseudo-rigid-body model,the frequency characteristics and sensitivity of the large-deformation compliant mechanism are studied.Firstly,the pseudo-rigid-body model under the static and kinetic conditions is modified to enable the modified pseudo-rigid-body model to be more suitable for the dynamic analysis of the compliant mechanism.Subsequently,based on the modified pseudo-rigid-body model,the dynamic equations of the ordinary compliant four-bar mechanism are established using the analytical mechanics.Finally,in combination with the finite element analysis software ANSYS,the frequency characteristics and sensitivity of the compliant mechanism are analyzed by taking the compliant parallel-guiding mechanism and the compliant bistable mechanism as examples.From the simulation results,the dynamic characteristics of compliant mechanism are relatively sensitive to the structure size,section parameter,and characteristic parameter of material on mechanisms.The results could provide great theoretical significance and application values for the structural optimization of compliant mechanisms,the improvement of their dynamic properties and the expansion of their application range.

Indication from finite-frequency tomography beneath the North China Craton： The heterogeneity of craton destruction

We picked new traveltime residual datasets in three frequency bands （0.02%）. 1,0.1-0.8, and 0.8-2.0 Hz） for P-waves from 793 teleseismic events and two frequency bands （0.02-0.1 and 0.1-0.8 Hz） for S-waves from 310 teleseismic events, recorded by 389 permanent stations of the China National Seismic Network and 832 broadband stations of 10 temporary arrays deployed in the North China Craton （NCC） region. The final datasets are composed of 65628 P-arrivals and 47050 S-arrivals. Based on previous research and our team＇s 2012 tomographic work, we constructed new three-dimensional P-velocity and S- velocity models of the NCC through some improvements, such as augmenting a much denser station coverage in the western NCC, considering the incident angle effect in crustal correction and using a multi-frequency joint inversion tomographic technique. The new velocity models provide several salient features, from which we draw possible inferences on regional dynamic processes. We observed high-velocity anomalies in the mantle transition zone （MTZ）. Obvious morphological het- erogeneities suggest buckling and/or fragmentation of the subducted Pacific slab, and some of the slab materials are visible below 660-kin discontinuities. The velocity structure of the eastern NCC is dominated by small-scale lateral heterogeneities. At shallow depths, high-velocity anomalies beneath the southern part of the eastern NCC and the Yanshan region likely represent a remnant of cratonic lithosphere, which may suggest that the NCC destruction is spatially non-uniform. We also detected a high-velocity anomaly in the Sulu Orogen extending downward to -300 kin, which is seemingly controlled by the Tan-Lu Fault. The northern boundary of this anomaly spatially coincides with the Yantai-Qingdao-Wulian Fault, and is likely a remnant of the Yangtze cratonic lithosphere subducting northwestward. Significant low-velocity anomalies imaged beneath the central NCC show a spatial discordance between their northern and southern parts. The northern low-velocity anomaly extends downward to the top of MTZ with a lateral NW-SE strike, whereas the southern one tapers off at -200-300 kin. Low-velocity anomalies are present beneath the Phanerozoic orogenic belts surrounding the NCC, the Paleoproterozoic Trans-North China Orogen, and the Tan-Lu Fault. This feature not only shows excellent spatial correlation with the orogens at the surface, it also exhibits a consistent vertical continuity in a depth range of 60-250 km. This intriguing feature suggests that the collisional orogenic belts and Tan-Lu Fault are inherited weak zones, which may play a key role in craton destruction. By combining multidisciplinary results in this area, we suggest that the spatial heterogeneities associated with the NCC destruction most likely result from the combined effects of a spatially non-uniform distribution of wet upwellings triggered by the subducted Pacific slab and pre-existing weak zones in the eratonic lithosphere.

Efficient numerical analysis of guided wave structures by compact FDFD with PVL method

An efficient numerical simulation technique is introduced to extract the propagation characteristics of a millimeter guided wave structure. The method is based on the application of the Krylov subspace model order reduction technique (Padé via Lanczos) to the compact finite difference frequency domain (FDFD) method. This new technique speeds up the solution by decreasing the originally larger system matrix into one lower order system matrix. Numerical experiments from several millimeter guided wave structures demonstrate the efficiency and accuracy of this algorithm.