The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
Kevin Zumbrun - One of the best experts on this subject based on the ideXlab platform.
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Periodic Coefficient damping estimates and stability of large amplitude roll waves in inclined thin film flow
Siam Journal on Mathematical Analysis, 2016Co-Authors: Miguel L Rodrigues, Kevin ZumbrunAbstract:A technical obstruction preventing the conclusion of nonlinear stability of large-Froude number roll waves of the St. Venant equations for inclined thin film flow is the “slope condition” of Johnson, Noble, and Zumbrun, used to obtain pointwise symmetrizability of the linearized equations and thereby high-frequency resolvent bounds and a crucial $H^s$ nonlinear damping estimate. Numerically, this condition is seen to hold for Froude numbers $2
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Periodic-Coefficient damping estimates, and stability of large-amplitude roll waves in inclined thin film flow
SIAM Journal on Mathematical Analysis, 2016Co-Authors: Luis Miguel Rodrigues, Kevin ZumbrunAbstract:A technical obstruction preventing the conclusion of nonlinear stability of large-Froude number roll waves of the St. Venant equations for inclined thin film flow is the " slope condition " of Johnson-Noble-Zumbrun, used to obtain pointwise symmetrizability of the linearized equations and thereby high-frequency resolvent bounds and a crucial H s nonlinear damping estimate. Numerically, this condition is seen to hold for Froude numbers 2 < F 3.5, but to fail for 3.5 F. As hydraulic engineering applications typically involve Froude number 3 F 5, this issue is indeed relevant to practical considerations. Here, we show that the pointwise slope condition can be replaced by an averaged version which holds always, thereby completing the nonlinear theory in the large-F case. The analysis has potentially larger interest as an extension to the Periodic case of a type of weighted " Kawashima-type " damping estimate introduced in the asymptotically-constant Coefficient case for the study of stability of large-amplitude viscous shock waves.
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Periodic Coefficient damping estimates and stability of large amplitude roll waves in inclined thin film flow
arXiv: Analysis of PDEs, 2015Co-Authors: Luis Miguel Rodrigues, Kevin ZumbrunAbstract:A technical obstruction preventing the conclusion of nonlinear stability of large-Froude number roll waves of the St. Venant equations for inclined thin film flow is the "slope condition" of Johnson-Noble-Zumbrun, used to obtain pointwise symmetrizability of the linearized equations and thereby high-frequency resolvent bounds and a crucial H s nonlinear damping estimate. Numerically, this condition is seen to hold for Froude numbers 2 \textless{} F 3.5, but to fail for 3.5 F. As hydraulic engineering applications typically involve Froude number 3 F 5, this issue is indeed relevant to practical considerations. Here, we show that the pointwise slope condition can be replaced by an averaged version which holds always, thereby completing the nonlinear theory in the large-F case. The analysis has potentially larger interest as an extension to the Periodic case of a type of weighted "Kawashima-type" damping estimate introduced in the asymptotically-constant Coefficient case for the study of stability of large-amplitude viscous shock waves.
Yongjian Ji - One of the best experts on this subject based on the ideXlab platform.
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an updated full discretization milling stability prediction method based on the higher order hermite newton interpolation polynomial
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Yongjian Ji, Xibin Wang, Hongjun WangAbstract:Chatter is undesirable self-excited vibrations, which always lead to adverse effects during milling process. Selecting a reasonable combination of cutting parameters is an effective way to avoid chatter. Based on the mathematical model of milling process and the Floquet theory, the stable cutting area can be determined. The stability lobe diagrams (SLD) could be obtained by different interpolation methods. To study the effect of higher order interpolation methods on the accuracy and efficiency of milling stability prediction, the state item, the time-delayed item, and the Periodic-Coefficient item of the state-space equation are approximated by different higher order interpolation methods, respectively. The calculations show that when the state item is approximated by the third-order Hermite interpolation polynomial, third-order Newton interpolation of the time-delayed item can improve the accuracy of SLD, while higher order interpolation of Periodic-Coefficient item has negative effect on improving effectiveness and efficiency compared to high-order interpolation of the state item and the time-delayed item. In order to obtain the SLD of milling process more accurately, an updated full-discretization milling stability prediction method which based on the third-order Hermite-Newton interpolation polynomial approximation is proposed in this paper. By dividing the tooth passing period equally into a finite set of time intervals, the third-order Hermite interpolation polynomial and the third-order Newton interpolation polynomial are utilized in each time interval to estimate the state item and the time-delayed item, respectively. The comparison of convergence rate of the critical eigenvalues and the SLD of the proposed method between the existing methods is carried out. The results indicate that the proposed method show a faster convergence rate than that of other methods, and its SLD is more close to the ideal ones with small number of time intervals.
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third order updated full discretization method for milling stability prediction
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Xibin Wang, Dongqian Wang, Li Jiao, Yongjian JiAbstract:Based on third-order Newton interpolation polynomial and direct integration scheme (DIS), this paper proposes a method to generate stability lobe diagram in milling process. The dynamic model of milling process with consideration of regeneration effect is described by time Periodic delay-differential equation (DDE). Then, the DDE is rewritten as state space equation by a transformation. After equally discretizing the time delay into a series of small time intervals, the state space equation of milling system is integrated on the small time interval. Both the state term and delayed term are interpolated by third-order Newton interpolation polynomial, and the Periodic-Coefficient matrix is interpolated by first-order Newton interpolation polynomial. The state transition matrix which reflects the discrete mapping relation of dynamic responses for current tooth pass period and immediate previous tooth pass period is obtained directly. The accuracy of the proposed method is evaluated by comparing with benchmark methods in terms of the rate of convergence. The efficiency of the proposed method is verified through the comparison of computational time with existing methods. The proposed method is proved to be an accurate and efficient method by the comparison results. The distinction between up-milling and down-milling operations is also analyzed by comparing the stability lobe diagrams for these two operations. Besides, according to the analysis of rate of convergence, the number of substitutions, which are used to convert the variables located out of the required range into the required range, may affect the results of stability lobe diagrams. Moreover, the stability lobe diagram cannot be generated by using fourth-order updated full-discretization method.
T Aboulnasr - One of the best experts on this subject based on the ideXlab platform.
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kalman based Periodic Coefficient update for fir adaptive filters
International Conference on Multimedia and Expo, 2007Co-Authors: N Avesta, T AboulnasrAbstract:This paper presents a novel partial update algorithm for FIR adaptive filters based on a Kalman background engine. In the proposed system, a Kalman filter is setup with the Coefficients of the full adaptive filter as the states to be estimated. The observation of the Kalman filter is the subset of the Coefficients of the adaptive FIR filter being updated. It is shown that this setup allows for an improved estimation of the full set of filter Coefficients despite the partial update. We propose two methods for postmortem improvements on an ordinary M-Tap Periodic update LMS. We also propose a Kalman feedback method, in conjunction with a 1-Tap Periodic update TMS, which has a similar performance to a full length LMS, for non-stationary system identification.
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ICME - Kalman-Based Periodic Coefficient Update for FIR Adaptive Filters
Multimedia and Expo 2007 IEEE International Conference on, 2007Co-Authors: N Avesta, T AboulnasrAbstract:This paper presents a novel partial update algorithm for FIR adaptive filters based on a Kalman background engine. In the proposed system, a Kalman filter is setup with the Coefficients of the full adaptive filter as the states to be estimated. The observation of the Kalman filter is the subset of the Coefficients of the adaptive FIR filter being updated. It is shown that this setup allows for an improved estimation of the full set of filter Coefficients despite the partial update. We propose two methods for postmortem improvements on an ordinary M-Tap Periodic update LMS. We also propose a Kalman feedback method, in conjunction with a 1-Tap Periodic update TMS, which has a similar performance to a full length LMS, for non-stationary system identification.
Han Ding - One of the best experts on this subject based on the ideXlab platform.
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mechanics and multi regenerative stability of variable pitch and variable helix milling tools considering runout
International Journal of Machine Tools & Manufacture, 2017Co-Authors: Jinbo Niu, Ye Ding, Li-min Zhu, Han DingAbstract:Abstract Variable pitch and variable helix (VPVH) milling tools are usually utilized to mitigate regenerative chatter vibrations by destroying the vibration phases between adjacent teeth. But this chatter suppression mechanism may considerably be disturbed by the inevitable tool runout, which could also change the phases, even to a larger extent. Thus the cutting performance of VPVH tools in terms of mechanics and dynamics should be re-evaluated by taking runout into consideration. This paper firstly sets up the mechanistic model for VPVH tools and then presents a combined nonlinear optimization procedure to identify the cutting Coefficients and runout parameters. Secondly, the dynamic system of VPVH tools considering runout is modeled by a Periodic-Coefficient delay differential equation with multiple underdetermined delays. Afterwards, the generalized Runge-Kutta (GRK) method is extended to tackle the runout-induced multi-regenerative effects and thus to analyze the milling process stability. The accuracy and efficiency of the GRK method is validated using published numerical examples. A series of cutting experiments with a commercially available VPVH tool are performed to verify the presented mechanistic and dynamic models. It confirms that runout cannot be neglected when evaluating the cutting performance of VPVH tools. Finally, the joint influences of runout and pitch/helix angles on cutting forces and chatter stability of VPVH tools are discussed in detail based on the proposed approach.
Xibin Wang - One of the best experts on this subject based on the ideXlab platform.
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an updated full discretization milling stability prediction method based on the higher order hermite newton interpolation polynomial
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Yongjian Ji, Xibin Wang, Hongjun WangAbstract:Chatter is undesirable self-excited vibrations, which always lead to adverse effects during milling process. Selecting a reasonable combination of cutting parameters is an effective way to avoid chatter. Based on the mathematical model of milling process and the Floquet theory, the stable cutting area can be determined. The stability lobe diagrams (SLD) could be obtained by different interpolation methods. To study the effect of higher order interpolation methods on the accuracy and efficiency of milling stability prediction, the state item, the time-delayed item, and the Periodic-Coefficient item of the state-space equation are approximated by different higher order interpolation methods, respectively. The calculations show that when the state item is approximated by the third-order Hermite interpolation polynomial, third-order Newton interpolation of the time-delayed item can improve the accuracy of SLD, while higher order interpolation of Periodic-Coefficient item has negative effect on improving effectiveness and efficiency compared to high-order interpolation of the state item and the time-delayed item. In order to obtain the SLD of milling process more accurately, an updated full-discretization milling stability prediction method which based on the third-order Hermite-Newton interpolation polynomial approximation is proposed in this paper. By dividing the tooth passing period equally into a finite set of time intervals, the third-order Hermite interpolation polynomial and the third-order Newton interpolation polynomial are utilized in each time interval to estimate the state item and the time-delayed item, respectively. The comparison of convergence rate of the critical eigenvalues and the SLD of the proposed method between the existing methods is carried out. The results indicate that the proposed method show a faster convergence rate than that of other methods, and its SLD is more close to the ideal ones with small number of time intervals.
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third order updated full discretization method for milling stability prediction
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Xibin Wang, Dongqian Wang, Li Jiao, Yongjian JiAbstract:Based on third-order Newton interpolation polynomial and direct integration scheme (DIS), this paper proposes a method to generate stability lobe diagram in milling process. The dynamic model of milling process with consideration of regeneration effect is described by time Periodic delay-differential equation (DDE). Then, the DDE is rewritten as state space equation by a transformation. After equally discretizing the time delay into a series of small time intervals, the state space equation of milling system is integrated on the small time interval. Both the state term and delayed term are interpolated by third-order Newton interpolation polynomial, and the Periodic-Coefficient matrix is interpolated by first-order Newton interpolation polynomial. The state transition matrix which reflects the discrete mapping relation of dynamic responses for current tooth pass period and immediate previous tooth pass period is obtained directly. The accuracy of the proposed method is evaluated by comparing with benchmark methods in terms of the rate of convergence. The efficiency of the proposed method is verified through the comparison of computational time with existing methods. The proposed method is proved to be an accurate and efficient method by the comparison results. The distinction between up-milling and down-milling operations is also analyzed by comparing the stability lobe diagrams for these two operations. Besides, according to the analysis of rate of convergence, the number of substitutions, which are used to convert the variables located out of the required range into the required range, may affect the results of stability lobe diagrams. Moreover, the stability lobe diagram cannot be generated by using fourth-order updated full-discretization method.