Papers by Author: Yi Lun Liu

Abstract: To meet the demand of the signal stable at high speed, the key is control precision for the characteristic impedance of FPC. This article is intended to study the strip-line structure for reducing cross-talk (noise) and their theoretical analysis and calculation. By varying effect factor and countermeasure in the production process of FPC, and the optimal process parameter have been obtained. By using the some testing technology, the impedance of strip-line in FPC have been tested.

Abstract: The five-octave mill stochastic dynamics model was established, and then constructed the virtual rolling force excitation, converted random excitation into the rolling force deterministic harmonic excitation by taking advantage of pseudo-excitation method, finally the variance and power spectral density dynamic random changes in the roll gap was Obtained . The results show that the emergence degree of rolled-strip oscillation marks is proportional to random rolling force power spectral density, and in over the five-octave frequency, the roll gap’s dynamic variance no longer change.

Abstract: In the rolling process, deviation is the phenomenon that the strap width direction's centerline deviates from rolling system setting centerline,serious deviation will cause product quality drop and rolling equipment fault. This paper has established the finite element model to the hot tandem rolling aluminum strap, analyzed the strap’s deviation rule under four kinds of incentives,obtained the neural network predictive model and the control policy of the tail deviation.The result to analyze a set of fact deviation data shows this method may control tail deviation in preconcerted permission range.

Abstract: Ideally rolling parameter is symmetrical relative to rolling Hcenter lineH in the rolling process. When there is transverse asymmetry incentives disturbance, Hsymmetrical stateH will be destroyed. Some Hquality problemsH will happen. The paper study transverse asymmetry characteristic of force and deformation of rolling mill and mill bar, establish parameter relationship equation of transverse asymmetry characteristic of force and deformation, establish parameter relationship figure of transverse asymmetry characteristic of force and deformation. Using this figure, we get balance control model with a view to removing strip delivery wedge.

Abstract: Based on wavelet transform and artificial neural network, a novel method which takes advantage of both the multi-resolution decomposition of wavelet transform and the classification characteristics of artificial neural network is proposed for fault detection of permanent magnet linear synchronous motor (PMLSM). According to the characteristic of unhealthy PMLSM, the wavelet transform is carried out to decompose and reconstruct winding current signal. Then the energy of each frequency band as faulty features can be detected through spectrum analysis of wavelet coefficients about each frequency band. With normalization method, the feature vectors are constructed from relative energy for energy of each frequency band. The proposed method is applied to the fault detection of PMLSM, and the result of simulation proved that the wavelet neural network can effectively detect different conditions of PMLSM.

Abstract: A two dimensional stochastic nonlinear dynamical model of rolls is presented considering the stochastic factor of the rolling force. The Hamilton function is also described as one dimension diffusion process by using stochastic average method, the singular boundary theory was taken for analyzing the global stochastic stability of the system, and the system’s stochastic stability is researched by solving the Fokker-Planck-Kolmogorov (FPK) equation. The results show that the generalized energy H in the range of 0.02 to 0.4, the system’s response has the minimum transition probability density, and the system state is not easy to change, therefore the system generalized energy H should be to limit in this range in the design and operation of the rolling mill.

Abstract: The stochastic excitation power spectral density (PSD) model and ARMA time series model are established based on the stochastic rolling force acquisition data, which is processed into stationary, normal and zero mean from a aluminum hot strip tandem mill. Characteristics of rolling force ARMA time series models are discussed by means of random process theory. The rolling forces PSD function of facilitating engineering application is obtained by utilizing Levenberg-Marquardt combined with generalized global planning algorithm, and the stochastic excitation model is established. It provides the basis for the prediction of rolling force.

Abstract: With the increasing of printing machine’s working speed, the minor changes of design variables will decrease mechanical precision and stability in working state. So, high-speed and high stability are the tow mutual restraint aspects in modern printing machine design. The web press is the highest printing speed and large-scale with, but the stability of fold mechanism is the most significant constraints to speed. In order to increase the mechanism speed and stability, the two robust criterions, kinematics and dynamics precision, has been proposed. Through the kinetic analysis to the fold mechanism of web press, the dynamic model of the mechanism response to design variables has been established. By the model, the optimization model has been established based on robust analysis. Through the robust model, seeking the design variables with the best robustness，the goal of increasing the mechanical long-term stability in high speed can be attached in the condition of ensuring the fold precision. The design example shows that in the case of the stable design variables, the kinematics performances of robust design and trace optimization design are slightly different , but the dynamic performances of robust design are much better than that of trace optimization, and in the case of the design variables’ slight changes, robust design can make the mechanism’s dynamic performances still maintain, but the trace optimization doesn’t. In short, robust design is a good way to increase the stability of machine.

Abstract: During the hot rolling process, the perturbation of transverse asymmetry factor will generate strip steering, strip delivery wedge and other failure state. During the steady rolling stage, the constraint action of tension and so on can restrain strip steering. Transverse asymmetry characteristic mainly passes in the form of strip delivery wedge between the standers. Firstly this paper researches correlation of transverse asymmetry characteristic parameter toward single stander, establishes a function model to reflect transverse asymmetry result status, for instance strip delivery wedge, strip entry wedge, strip eccentric, gap wedge and other transverse asymmetry disturbance factor. Then the paper establishes transfer model of transverse asymmetry characteristic between standers, gets result status of strip delivery wedge between each ensuing standers under strip entry wedge, strip eccentric, gap wedge and other combination of disturbance. At last the paper takes working condition of actual aluminum hot rolling production line as an example, computes transfer coefficient of strip delivery wedge under several perturbation and discuss transfer discipline of transverse asymmetry characteristic between standers.

Abstract: Performing bispectrum analysis on the actual measured vibration signals of the roller bearing with different failure modes, it developed that the spectrum distribution regions are similar among the same failure modes, and distinguishable among the different failure modes, thus this character can be used to classify fault types. The binary images extracted from the bispectra are taken as the feature vectors. The fuzzy clustering analysis based on objective function is applied for pattern recognition, which makes use of the binary image to construct a core and a domain representing the common and scope of bispectrum distribution, respectively, then constructs the objective function as the classify to achieve pattern recognition and diagnosis. The roller bearing fault diagnosis is performed as an example to verify the feasibility of the proposed method.