Aiming at the problems of low accuracy and poor robustness that existed in the current hot rolling strip width spread model,an improved strip spread prediction model based on a material forming mechanism and Bayesian ...Aiming at the problems of low accuracy and poor robustness that existed in the current hot rolling strip width spread model,an improved strip spread prediction model based on a material forming mechanism and Bayesian optimized adaptive differential evolution algorithm(BADE)was proposed.At first,we improved the original spread mechanism model by adding the weight and bias term to enhance the model robustness based on rolling temperature.Then,the BADE algorithm was proposed to optimize the improved spread mechanism model.The optimization algorithm is based on a novel adaptive differential evolution algorithm,which can effectively achieve the global optimal solution.Finally,the prediction performances of five machine learning algorithms were compared in experiments.The results show that the prediction accuracy of the improved spread model is obviously better than that of the machine learning algorithms,which proves the effectiveness of the proposed method.展开更多
Width spread is usually considered in hot rolling, nevertheless, it can be ignore in cold rolling. In order to control the crown and flatness better simultaneously and realize the decoupling of crown and flatness, the...Width spread is usually considered in hot rolling, nevertheless, it can be ignore in cold rolling. In order to control the crown and flatness better simultaneously and realize the decoupling of crown and flatness, the transverse displacement function of strip is defined and deduced. The factors that affects the width spread are analyzing with the function. According to the unchanged principle of volume before and after rolling, the flatness model which considers the width spread is deduced. Through the model, the transverse metal flowing of different stands and different thickness is analyzing, it is found that the width spread is biggest in cold rolling at the No. 1 stand because of the maximum thickness and reduction and the minimum deformation resistance. It gives a good foundation for the decoupling of crown and flatness.展开更多
Research works on width compensation and correction were carried out in order to eliminate the effects of the PVPC （ plan view pattern control） on width accuracy of plate mill. The thickness correction calculation f...Research works on width compensation and correction were carried out in order to eliminate the effects of the PVPC （ plan view pattern control） on width accuracy of plate mill. The thickness correction calculation formula was derived for compensation the width deviation caused by PVPC function, and the formula is unified under the thinning and thickening conditions. In order to improve the width calculation accuracy, width spread calculation process was modified with dividing one large reduction pass to several small reduction calculation steps. The thickness wedge was simplified to rectangle based on the volume constant principle, and the width spread model for PVPC was constructed. The width compensation and correction for the PVPC functions are used for the online control process, and the Product dimension accuracy is improved. With the decrease of Crop losses, the Droduct yield was increased with 0. 2%.展开更多
Based on the practical data of a strip hot rolling line and the flow patterns of the rolling process, the principle of the effect of the tension between mill stands on the strip width was analyzed. The results show th...Based on the practical data of a strip hot rolling line and the flow patterns of the rolling process, the principle of the effect of the tension between mill stands on the strip width was analyzed. The results show that the tension between the upstream mill stands has a significant effect on strip width. The width change takes place in the deforming region between two mill stands, the effect of back tension is more than that of forward tension, and the width narrowing takes place in the biting position of the back slip region. Reasonable tension and its gradient setup are therefore significant factors in the accuracy of the strip width control.展开更多
随机开关频率调制策略通过将开关频率在扩频范围内随机变化抑制高频谐波。虽然过宽的扩频范围能更有效地抑制高频谐波,但同时会带来严重的电流畸变和较大的转矩脉动。为此,该文提出在窄扩频范围下考虑随机数变化的随机开关频率空间矢量...随机开关频率调制策略通过将开关频率在扩频范围内随机变化抑制高频谐波。虽然过宽的扩频范围能更有效地抑制高频谐波,但同时会带来严重的电流畸变和较大的转矩脉动。为此,该文提出在窄扩频范围下考虑随机数变化的随机开关频率空间矢量脉宽调制(random switching frequency space vector pulse width modulation,RSF-SVPWM)。与传统的RSF-SVPWM相比,提出的方法通过限制相邻随机数变化的最大值,减小了相邻随机数的相对变化,使高频谐波由三角形分布变为梯形分布,从而降低了高频谐波幅值,实现窄扩频范围内对高频谐波的有效抑制。实验结果表明,在相同的扩频范围内,该方法更有效地降低了开关频率及其整数倍处谐波的峰值。展开更多
It is found that in free space, the curves of the mean-squared beam width may each have a cross point at a certain propagation distance Zc. For Gaussian array beams, the analytical expressions of zc are derived. For t...It is found that in free space, the curves of the mean-squared beam width may each have a cross point at a certain propagation distance Zc. For Gaussian array beams, the analytical expressions of zc are derived. For the coherent com- bination, Zc is larger than that for the incoherent combination. However, in non-Kolmogorov turbulence, the cross point disappears, and the Gaussian array beams will have the same directionality in terms of the angular spread. Furthermore, a short propagation distance is needed to reach the same directionality when the generalized exponent is equal to 3.108. In particular, it is shown that the condition obtained in previous studies is not necessary for laser beams to have the same directionality in turbulence, which is explained physically. On the other hand, the relative average intensity distributions at the position where the Gaussian array beams have the same mean-squared beam width are also examined.展开更多
In order to study the penetration depth and the spread width in a transverse jet, a flow-visualization based experimental setup was built.A phase tunable laser and CCD system was employed, and several jet to crossflow...In order to study the penetration depth and the spread width in a transverse jet, a flow-visualization based experimental setup was built.A phase tunable laser and CCD system was employed, and several jet to crossflow velocity ratio (r=2, 4, 8, 12, 16) were investigated.Experimental results showed that the jet to crossflow velocity ratio is the key parameter to control the penetration depth and the blending law of the jet, and that larger jet to crossflow velocity ratio resulted in much deeper penetration depth.The experimental data agreed well with the previous reports, and predicting formula was derived as the fitting equation y/rd=1.3615(x/rd)0.5608 with the correlation coefficient R=0.9996.On the other hand, the larger jet to crossflow velocity ratio is not the greater access to the spread width, and in this work, the case of r=8 obtained the largest spread width, and the spread width remains relatively large in a large penetration zone.展开更多
基金support from National Natural Science Foundation of China(Grant Nos.61633019,61533013 and 62273234).
文摘Aiming at the problems of low accuracy and poor robustness that existed in the current hot rolling strip width spread model,an improved strip spread prediction model based on a material forming mechanism and Bayesian optimized adaptive differential evolution algorithm(BADE)was proposed.At first,we improved the original spread mechanism model by adding the weight and bias term to enhance the model robustness based on rolling temperature.Then,the BADE algorithm was proposed to optimize the improved spread mechanism model.The optimization algorithm is based on a novel adaptive differential evolution algorithm,which can effectively achieve the global optimal solution.Finally,the prediction performances of five machine learning algorithms were compared in experiments.The results show that the prediction accuracy of the improved spread model is obviously better than that of the machine learning algorithms,which proves the effectiveness of the proposed method.
基金Supported by Beijing Higher Education Young Elite Teacher Project(No.YETP0369)
文摘Width spread is usually considered in hot rolling, nevertheless, it can be ignore in cold rolling. In order to control the crown and flatness better simultaneously and realize the decoupling of crown and flatness, the transverse displacement function of strip is defined and deduced. The factors that affects the width spread are analyzing with the function. According to the unchanged principle of volume before and after rolling, the flatness model which considers the width spread is deduced. Through the model, the transverse metal flowing of different stands and different thickness is analyzing, it is found that the width spread is biggest in cold rolling at the No. 1 stand because of the maximum thickness and reduction and the minimum deformation resistance. It gives a good foundation for the decoupling of crown and flatness.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No.N120407007)
文摘Research works on width compensation and correction were carried out in order to eliminate the effects of the PVPC （ plan view pattern control） on width accuracy of plate mill. The thickness correction calculation formula was derived for compensation the width deviation caused by PVPC function, and the formula is unified under the thinning and thickening conditions. In order to improve the width calculation accuracy, width spread calculation process was modified with dividing one large reduction pass to several small reduction calculation steps. The thickness wedge was simplified to rectangle based on the volume constant principle, and the width spread model for PVPC was constructed. The width compensation and correction for the PVPC functions are used for the online control process, and the Product dimension accuracy is improved. With the decrease of Crop losses, the Droduct yield was increased with 0. 2%.
文摘Based on the practical data of a strip hot rolling line and the flow patterns of the rolling process, the principle of the effect of the tension between mill stands on the strip width was analyzed. The results show that the tension between the upstream mill stands has a significant effect on strip width. The width change takes place in the deforming region between two mill stands, the effect of back tension is more than that of forward tension, and the width narrowing takes place in the biting position of the back slip region. Reasonable tension and its gradient setup are therefore significant factors in the accuracy of the strip width control.
文摘随机开关频率调制策略通过将开关频率在扩频范围内随机变化抑制高频谐波。虽然过宽的扩频范围能更有效地抑制高频谐波,但同时会带来严重的电流畸变和较大的转矩脉动。为此,该文提出在窄扩频范围下考虑随机数变化的随机开关频率空间矢量脉宽调制(random switching frequency space vector pulse width modulation,RSF-SVPWM)。与传统的RSF-SVPWM相比,提出的方法通过限制相邻随机数变化的最大值,减小了相邻随机数的相对变化,使高频谐波由三角形分布变为梯形分布,从而降低了高频谐波幅值,实现窄扩频范围内对高频谐波的有效抑制。实验结果表明,在相同的扩频范围内,该方法更有效地降低了开关频率及其整数倍处谐波的峰值。
基金supported by the National Natural Science Foundation of China(Grant No.61178070)the Construction Plan for Scientific Research Innovation Teams of Universities in Sichuan Province,China(Grant No.12TD008)
文摘It is found that in free space, the curves of the mean-squared beam width may each have a cross point at a certain propagation distance Zc. For Gaussian array beams, the analytical expressions of zc are derived. For the coherent com- bination, Zc is larger than that for the incoherent combination. However, in non-Kolmogorov turbulence, the cross point disappears, and the Gaussian array beams will have the same directionality in terms of the angular spread. Furthermore, a short propagation distance is needed to reach the same directionality when the generalized exponent is equal to 3.108. In particular, it is shown that the condition obtained in previous studies is not necessary for laser beams to have the same directionality in turbulence, which is explained physically. On the other hand, the relative average intensity distributions at the position where the Gaussian array beams have the same mean-squared beam width are also examined.
文摘In order to study the penetration depth and the spread width in a transverse jet, a flow-visualization based experimental setup was built.A phase tunable laser and CCD system was employed, and several jet to crossflow velocity ratio (r=2, 4, 8, 12, 16) were investigated.Experimental results showed that the jet to crossflow velocity ratio is the key parameter to control the penetration depth and the blending law of the jet, and that larger jet to crossflow velocity ratio resulted in much deeper penetration depth.The experimental data agreed well with the previous reports, and predicting formula was derived as the fitting equation y/rd=1.3615(x/rd)0.5608 with the correlation coefficient R=0.9996.On the other hand, the larger jet to crossflow velocity ratio is not the greater access to the spread width, and in this work, the case of r=8 obtained the largest spread width, and the spread width remains relatively large in a large penetration zone.
