The iterative learning control （ILC） has been demon-strated to be capable of considerably improving the tracking perfor-mance of systems which are affected by the iteration-independent disturbance. However, the achi...The iterative learning control （ILC） has been demon-strated to be capable of considerably improving the tracking perfor-mance of systems which are affected by the iteration-independent disturbance. However, the achievable performance is greatly degraded when iteration-dependent, stochastic disturbances are pre-sented. This paper considers the robustness of the ILC algorithm for the nonlinear system in presence of stochastic measurement disturbances. The robust convergence of the P-type ILC algorithm is firstly addressed, and then an improved ILC algorithm with a decreasing gain is proposed. Theoretical analyses show that the proposed algorithm can guarantee that the tracking error of the nonlinear system tends to zero in presence of measurement dis-turbances. The analysis is also supported by a numerical example.展开更多
The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema®HB50 and Tensylon®HSBD 30A through structural hybridization method.Laminates having 20 mm thickness...The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema®HB50 and Tensylon®HSBD 30A through structural hybridization method.Laminates having 20 mm thickness were fabricated and subjected to 7.6239 mm mild steel core projectile with an impact velocity of 730±10 ms1.Parameters such as energy absorption,back face deformation and rate of back face deformation were measured as a function of hybridization ratio.It was observed that hybrid laminate with 50:50 ratio(w/w)of Tensylon®and Dyneema®with Tensylon®as front face showed 200%more energy absorption when compared to 100%Tensylon®laminate and showed equal energy absorption as that of expensive 100%Dyneema®laminate.Moreover,hybrid laminate with TD50:50 ratio showed 40%lower in terms of final back face deformation than Dyneema®laminate.Rate of back face deformation was also found to be slow for hybrid laminate as compared to Dyneema®laminate.Dynamic mechanical analysis showed that,Tensylon®laminate has got higher stiffness and lower damping factor than Dyneema®and hybrid laminates.The interface between Tensylon®and Dyneema®layers was found to be separating during the penetration process due to the poor interfacial bonding.Failure behaviour of laminates for different hybridization ratios were studied by sectioning the impacted laminates.It was observed that,the Tensylon®laminate has undergone shear cutting of fibers as major failure mode whereas the hybrid laminate showed shear cutting followed by tensile stretching,fiber pull out and delamination.These inputs are highly useful for body armour applications to design cost effective armour with enhanced performance.展开更多
The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally....The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally.Ball milling was used to disperse different weight(wt)percentages(0,1,2,4,6 wt.%)of nanoclay into phenolic resin.Viscosity changes to resin due to nanoclay was studied.On the other hand,nanoclay added phenolic matrix composites(Type-II)were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser(TGA).This data was used to understand the mechanical,thermal and ablation properties of Type-I composites.Inter laminar shear strength(ILSS),flexural strength and flexural modulus of Type I composites increased by about 29%,12%and 7%respectively at2 wt.%addition of nanoclay beyond which these properties decreased.This was attributed to reduced fiber volume fraction(%Vf)of Type-I composites due to nanoclay addition at such high loadings.Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux(125 W/cm^(2))and high heat flux levels(500 W/cm^(2)).Mass ablation rates have increased at both flux levels marginally up to 2 wt.%addition of nanoclay beyond which it has increased significantly.This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.%addition of nanoclay.Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay,which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.展开更多
Due to editing errors,the ordinate and unit of Fig.5(a)in the article were incorrect.The correct ordinate of Fig.5(a)should be Flexural strength(MPa).In the published article<Effect of organo-modified montmorilloni...Due to editing errors,the ordinate and unit of Fig.5(a)in the article were incorrect.The correct ordinate of Fig.5(a)should be Flexural strength(MPa).In the published article<Effect of organo-modified montmorillonite nanoclay on mechanical,thermal and ablation behavior of carbon fiber/phenolic resin composites>.展开更多
基金supported by the National Natural Science Foundation of China (61203065 60834001)the Program of Open Laboratory Foundation of Control Engineering Key Discipline of Henan Provincial High Education (KG 2011-10)
文摘The iterative learning control （ILC） has been demon-strated to be capable of considerably improving the tracking perfor-mance of systems which are affected by the iteration-independent disturbance. However, the achievable performance is greatly degraded when iteration-dependent, stochastic disturbances are pre-sented. This paper considers the robustness of the ILC algorithm for the nonlinear system in presence of stochastic measurement disturbances. The robust convergence of the P-type ILC algorithm is firstly addressed, and then an improved ILC algorithm with a decreasing gain is proposed. Theoretical analyses show that the proposed algorithm can guarantee that the tracking error of the nonlinear system tends to zero in presence of measurement dis-turbances. The analysis is also supported by a numerical example.
基金Supported by State Key Program of National Natural Science Foundation of China （60834001） and National Natural Science Foundation of China （60774022）.Acknowledgement Authors would like to thank NSFC organizers and participants who shared their ideas and works with us during the NSFC workshop on data-based control, decision making, scheduling, and fault diagnosis. In particular, authors would like to thank Chai Tian-You, Sun You-Xian, Wang Hong, Yan Hong-Sheng, and Gao Fu-Rong for discussing the concept on design model shown in Fig. 12, the concept on temporal multi-scale shown in Fig. 8, the concept on fault diagnosis shown in Fig. 14, the concept on dynamic scheduling shown in Fig. 15, and the concept on interval model shown in Fig. 16, respectively.
基金the support rendered by the staff of Armour Design and Development Division(ADDD).
文摘The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema®HB50 and Tensylon®HSBD 30A through structural hybridization method.Laminates having 20 mm thickness were fabricated and subjected to 7.6239 mm mild steel core projectile with an impact velocity of 730±10 ms1.Parameters such as energy absorption,back face deformation and rate of back face deformation were measured as a function of hybridization ratio.It was observed that hybrid laminate with 50:50 ratio(w/w)of Tensylon®and Dyneema®with Tensylon®as front face showed 200%more energy absorption when compared to 100%Tensylon®laminate and showed equal energy absorption as that of expensive 100%Dyneema®laminate.Moreover,hybrid laminate with TD50:50 ratio showed 40%lower in terms of final back face deformation than Dyneema®laminate.Rate of back face deformation was also found to be slow for hybrid laminate as compared to Dyneema®laminate.Dynamic mechanical analysis showed that,Tensylon®laminate has got higher stiffness and lower damping factor than Dyneema®and hybrid laminates.The interface between Tensylon®and Dyneema®layers was found to be separating during the penetration process due to the poor interfacial bonding.Failure behaviour of laminates for different hybridization ratios were studied by sectioning the impacted laminates.It was observed that,the Tensylon®laminate has undergone shear cutting of fibers as major failure mode whereas the hybrid laminate showed shear cutting followed by tensile stretching,fiber pull out and delamination.These inputs are highly useful for body armour applications to design cost effective armour with enhanced performance.
文摘The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally.Ball milling was used to disperse different weight(wt)percentages(0,1,2,4,6 wt.%)of nanoclay into phenolic resin.Viscosity changes to resin due to nanoclay was studied.On the other hand,nanoclay added phenolic matrix composites(Type-II)were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser(TGA).This data was used to understand the mechanical,thermal and ablation properties of Type-I composites.Inter laminar shear strength(ILSS),flexural strength and flexural modulus of Type I composites increased by about 29%,12%and 7%respectively at2 wt.%addition of nanoclay beyond which these properties decreased.This was attributed to reduced fiber volume fraction(%Vf)of Type-I composites due to nanoclay addition at such high loadings.Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux(125 W/cm^(2))and high heat flux levels(500 W/cm^(2)).Mass ablation rates have increased at both flux levels marginally up to 2 wt.%addition of nanoclay beyond which it has increased significantly.This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.%addition of nanoclay.Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay,which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.
文摘Due to editing errors,the ordinate and unit of Fig.5(a)in the article were incorrect.The correct ordinate of Fig.5(a)should be Flexural strength(MPa).In the published article<Effect of organo-modified montmorillonite nanoclay on mechanical,thermal and ablation behavior of carbon fiber/phenolic resin composites>.
