A point stabilization scheme of a wheeled mobile robot （WMR） which moves on uneven surface is presented by using tuzzy control. Taking the kinematics and dynamics of the vehicle into account, the fuzzy controller is...A point stabilization scheme of a wheeled mobile robot （WMR） which moves on uneven surface is presented by using tuzzy control. Taking the kinematics and dynamics of the vehicle into account, the fuzzy controller is employed to regulate the robot based on a kinematic nonlinear state feedback control law. Herein, the fuzzy strategy is composed of two velocity control laws which are used to adjust the speed and angular velocity, respectively. Subsequently, genetic algorithm （GA） is applied to optimize the controller parameters. Through the self-optimization, a group of optimum parameters is gotten. Simulation results are presented to show the effectiveness of the control strategy.展开更多
Multi-component and multi-point trace gas sensing in the wavelength modulation spectroscopy is demonstrated based on the frequency-division multiplexing and time-division multiplexing technology.A reference photodetec...Multi-component and multi-point trace gas sensing in the wavelength modulation spectroscopy is demonstrated based on the frequency-division multiplexing and time-division multiplexing technology.A reference photodetector is connected in series with a reference gas cell with the constant concentration to measure the second-harmonics peak of the components for wavelength stabilization in real time.The central wavelengths of the distributed feedback lasers are locked to the target gas absorption centers by the reference second-harmonics signal using a digital proportional-integral-derivative controller.The distributed feedback lasers with different wavelengths and modulation frequencies are injected into the gas cell to achieve multi-components gas measurement by the frequency-division multiplexing technology.In addition,multi-point trace gas sensing is achieved by the time-division multiplexing technology using a photoswitch and a relay unit.We use this scheme to detect methane(CH4)at 1650.9 nm and water vapor(H2O)at 1368.597 nm as a proof of principle with the gas cell path length of 10 cm.The minimum detection limits achieved for H2O and CH4 are 1.13 ppm and 11.85 ppm respectively,with three-point gas cell measurement;thus 10.5-fold and 10.1-fold improvements are achieved in comparison with the traditional wavelength modulation spectroscopy.Meanwhile,their excellent R-square values reach 0.9983 and 0.99564 for the concentration ranges of 500 ppm to 2000 ppm and 800 ppm to 2700 ppm,respectively.展开更多
A variety of problems in operations research, performance analysis, manufacturing, and communication networks, etc., can be modelled as discrete event systems with minimum and maximum constraints. When such systems re...A variety of problems in operations research, performance analysis, manufacturing, and communication networks, etc., can be modelled as discrete event systems with minimum and maximum constraints. When such systems require only maximum constraints （or dually, only minimum constraints）, they can be studied using linear methods based on max-plus algebra. Systems with mixed constraints are called min-max systems in which rain, max and addition operations appear simultaneously. A significant amount of work on such systems can be seen in literature. In this paper we provide some new results with regard to the balance problem of min-max functions; these are the structure properties of min-max systems. We use these results in the structural stabilization. Our main results are two sufficient conditions for the balance and one sufficient condition for the structural stabilization. The block technique is used to analyse the structure of the systems. The proposed methods, based on directed graph and max-plus algebra are constructive in nature. We provide several examples to demonstrate how the methods work in practice.展开更多
The optimal decay rate problem is considered for boundary control system modeling by a flexible structure consisting of a Eular-Bernoulli beam. Controls are a bending moment in proportion to angular velocity and a she...The optimal decay rate problem is considered for boundary control system modeling by a flexible structure consisting of a Eular-Bernoulli beam. Controls are a bending moment in proportion to angular velocity and a shear force in proportion to velocity. A sensitivity asymptotic analysis of the system's eigenvalues and eigenfunctions is set up. It is proved that, for every 0<K 2<+∞ and 0<-K 1<+∞, all the generalized eigenfunctions of form a Riesz basis ofV×H, and the optimal exponential decay rate can be obtained from the spectrum of the system.展开更多
Noise,vibration and harshness(NVH)problems in vehicle engineering are always challenging in both traditional vehicles and intelligent vehicles.Although high accuracy manufacturing,modern structural roads and advanced ...Noise,vibration and harshness(NVH)problems in vehicle engineering are always challenging in both traditional vehicles and intelligent vehicles.Although high accuracy manufacturing,modern structural roads and advanced suspension technology have already significantly reduced NVH problems and their impacts;off-road condition,obstacles and extreme operating condition could still trigger NVH problems unexpectedly.This paper proposes a vehicular electronic image stabilization(EIS)system to solve the vibration problem of the camera and ensure the environment perceptive function of vehicles.Firstly,feature point detection and matching based on an oriented FAST and rotated BRIEF(ORB)algorithm are implemented to match images in the process of EIS.Furthermore,a novel improved random sampling consensus algorithm(i-RANSAC)is proposed to eliminate mismatched feature points and increase the matching accuracy significantly.And an adaptive Kalman filter(AKF)is applied to improve the adaptability of the vehicular EIS.Finally,an experimental platform based on a gasoline model car was established to validate its performance.The experimental results show that the proposed EIS system can satisfy vehicular performance requirements even under off-road condition with obvious obstacles.展开更多
An element decomposition method with variance strain stabilization(EDM-VSS) is proposed. In the present EDM-VSS, the quadrilateral element is first divided into four sub-triangular cells, and the local strains in sub-...An element decomposition method with variance strain stabilization(EDM-VSS) is proposed. In the present EDM-VSS, the quadrilateral element is first divided into four sub-triangular cells, and the local strains in sub-triangular cells are obtained using linear interpolation function. For each quadrilateral element, the strain of the whole quadrilateral is the weighted average value of the local strains, which means only one integration point is adopted to construct the stiffness matrix. The stabilization item of the stiffness matrix is constructed by variance of the local strains, which can eliminate the instability of the one-point integration formulation and largely increase the accuracy of the element. Compared with conventional full integration quadrilateral element, the EDM-VSS achieves more accurate results and expends much lower computational cost. More importantly, as no mapping or coordinate transformation is involved in the present EDM-VSS, the restriction on the conventional quadrilateral elements can be removed and problem domain can be discretized in more flexible ways. To verify the accuracy and stability of the present formulation, a number of numerical examples are studied to demonstrate the efficiency of the present EDM-VSS.展开更多
Zeta potential is one of the most relevant parameters controlling the rheological behavior of ceramic suspensions. In this work, it was observed that for pH values below the isoelectric point (IEP), the positive value...Zeta potential is one of the most relevant parameters controlling the rheological behavior of ceramic suspensions. In this work, it was observed that for pH values below the isoelectric point (IEP), the positive value of zeta potential of water suspensions of α-quartz and α-cristobalite, experiences a sudden steep increase with the increase in specific surface area of the powders. For pH values above the IEP, the zeta potential values of crystalline forms of silica (α-quartz and α-cristobalite), get gradually more negative with the increase in pH. Conversely in the case of vitreous silica, for pH values above 6, there occurs a steep change towards more negative values of zeta potential than those presented by quartz and cristobalite. These findings have not yet been accounted for in the DLVO theory but may provide subsidies for better understanding of how to stabilize and destabilize crystalline and vitreous silica water suspensions.展开更多
In this papery we are concerned with the problem of stabilization for autonomous dynamical systems. We use theories in Liapunov stability and Lasalle stability theory and show that system （H） is stabilizable.
基金supported by the State Key Laboratory of Robotics and System (SKLR-2010-MS-14)the State Key Laboratory of Embedded System and Service Computing (2010-11)
文摘A point stabilization scheme of a wheeled mobile robot （WMR） which moves on uneven surface is presented by using tuzzy control. Taking the kinematics and dynamics of the vehicle into account, the fuzzy controller is employed to regulate the robot based on a kinematic nonlinear state feedback control law. Herein, the fuzzy strategy is composed of two velocity control laws which are used to adjust the speed and angular velocity, respectively. Subsequently, genetic algorithm （GA） is applied to optimize the controller parameters. Through the self-optimization, a group of optimum parameters is gotten. Simulation results are presented to show the effectiveness of the control strategy.
基金This work was supported by the Research Fund for the Doctoral Program of Liao Cheng University(Grant No.318051543)and the National Natural Science Foundation of China(Grant No.61475085).
文摘Multi-component and multi-point trace gas sensing in the wavelength modulation spectroscopy is demonstrated based on the frequency-division multiplexing and time-division multiplexing technology.A reference photodetector is connected in series with a reference gas cell with the constant concentration to measure the second-harmonics peak of the components for wavelength stabilization in real time.The central wavelengths of the distributed feedback lasers are locked to the target gas absorption centers by the reference second-harmonics signal using a digital proportional-integral-derivative controller.The distributed feedback lasers with different wavelengths and modulation frequencies are injected into the gas cell to achieve multi-components gas measurement by the frequency-division multiplexing technology.In addition,multi-point trace gas sensing is achieved by the time-division multiplexing technology using a photoswitch and a relay unit.We use this scheme to detect methane(CH4)at 1650.9 nm and water vapor(H2O)at 1368.597 nm as a proof of principle with the gas cell path length of 10 cm.The minimum detection limits achieved for H2O and CH4 are 1.13 ppm and 11.85 ppm respectively,with three-point gas cell measurement;thus 10.5-fold and 10.1-fold improvements are achieved in comparison with the traditional wavelength modulation spectroscopy.Meanwhile,their excellent R-square values reach 0.9983 and 0.99564 for the concentration ranges of 500 ppm to 2000 ppm and 800 ppm to 2700 ppm,respectively.
基金This work was supported by National Natural Science of China (No.69874040) the National Key Project of China, and the Hundred Talents Program of the Chinese Academy of Sciences.
文摘A variety of problems in operations research, performance analysis, manufacturing, and communication networks, etc., can be modelled as discrete event systems with minimum and maximum constraints. When such systems require only maximum constraints （or dually, only minimum constraints）, they can be studied using linear methods based on max-plus algebra. Systems with mixed constraints are called min-max systems in which rain, max and addition operations appear simultaneously. A significant amount of work on such systems can be seen in literature. In this paper we provide some new results with regard to the balance problem of min-max functions; these are the structure properties of min-max systems. We use these results in the structural stabilization. Our main results are two sufficient conditions for the balance and one sufficient condition for the structural stabilization. The block technique is used to analyse the structure of the systems. The proposed methods, based on directed graph and max-plus algebra are constructive in nature. We provide several examples to demonstrate how the methods work in practice.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 69674011, 19671054)Science Foundation of Shanxi University.
文摘The optimal decay rate problem is considered for boundary control system modeling by a flexible structure consisting of a Eular-Bernoulli beam. Controls are a bending moment in proportion to angular velocity and a shear force in proportion to velocity. A sensitivity asymptotic analysis of the system's eigenvalues and eigenfunctions is set up. It is proved that, for every 0<K 2<+∞ and 0<-K 1<+∞, all the generalized eigenfunctions of form a Riesz basis ofV×H, and the optimal exponential decay rate can be obtained from the spectrum of the system.
基金National Natural Science Foundation of China(Grant Nos.52072072,52025121 and 51605087).
文摘Noise,vibration and harshness(NVH)problems in vehicle engineering are always challenging in both traditional vehicles and intelligent vehicles.Although high accuracy manufacturing,modern structural roads and advanced suspension technology have already significantly reduced NVH problems and their impacts;off-road condition,obstacles and extreme operating condition could still trigger NVH problems unexpectedly.This paper proposes a vehicular electronic image stabilization(EIS)system to solve the vibration problem of the camera and ensure the environment perceptive function of vehicles.Firstly,feature point detection and matching based on an oriented FAST and rotated BRIEF(ORB)algorithm are implemented to match images in the process of EIS.Furthermore,a novel improved random sampling consensus algorithm(i-RANSAC)is proposed to eliminate mismatched feature points and increase the matching accuracy significantly.And an adaptive Kalman filter(AKF)is applied to improve the adaptability of the vehicular EIS.Finally,an experimental platform based on a gasoline model car was established to validate its performance.The experimental results show that the proposed EIS system can satisfy vehicular performance requirements even under off-road condition with obvious obstacles.
基金supported by the National Natural Science Foundation of China(Grant Nos.11472101 and 61232014)Postdoctoral Science Foundation of China(Grant No.2013M531780)the National Laboratory for Electric Vehicles Foundations
文摘An element decomposition method with variance strain stabilization(EDM-VSS) is proposed. In the present EDM-VSS, the quadrilateral element is first divided into four sub-triangular cells, and the local strains in sub-triangular cells are obtained using linear interpolation function. For each quadrilateral element, the strain of the whole quadrilateral is the weighted average value of the local strains, which means only one integration point is adopted to construct the stiffness matrix. The stabilization item of the stiffness matrix is constructed by variance of the local strains, which can eliminate the instability of the one-point integration formulation and largely increase the accuracy of the element. Compared with conventional full integration quadrilateral element, the EDM-VSS achieves more accurate results and expends much lower computational cost. More importantly, as no mapping or coordinate transformation is involved in the present EDM-VSS, the restriction on the conventional quadrilateral elements can be removed and problem domain can be discretized in more flexible ways. To verify the accuracy and stability of the present formulation, a number of numerical examples are studied to demonstrate the efficiency of the present EDM-VSS.
基金FAPESP process number 98/14324-0 Capes Agency,process number 33001014004P9.
文摘Zeta potential is one of the most relevant parameters controlling the rheological behavior of ceramic suspensions. In this work, it was observed that for pH values below the isoelectric point (IEP), the positive value of zeta potential of water suspensions of α-quartz and α-cristobalite, experiences a sudden steep increase with the increase in specific surface area of the powders. For pH values above the IEP, the zeta potential values of crystalline forms of silica (α-quartz and α-cristobalite), get gradually more negative with the increase in pH. Conversely in the case of vitreous silica, for pH values above 6, there occurs a steep change towards more negative values of zeta potential than those presented by quartz and cristobalite. These findings have not yet been accounted for in the DLVO theory but may provide subsidies for better understanding of how to stabilize and destabilize crystalline and vitreous silica water suspensions.
文摘In this papery we are concerned with the problem of stabilization for autonomous dynamical systems. We use theories in Liapunov stability and Lasalle stability theory and show that system （H） is stabilizable.
