Damage on surfaces often compromises the efficiency of some types of energy production, the safety and reliability of components, and ultimately increases costs. The environment can degrade the structural integrity of...Damage on surfaces often compromises the efficiency of some types of energy production, the safety and reliability of components, and ultimately increases costs. The environment can degrade the structural integrity of surfaces in service by the accumulation of large numbers of small destructive events, which based on the Central Limit Theorem leads to a Gaussian distribution of pit depth. In order to develop safety envelopes relating fracture loci with topological parameters of a brittle material, scatter plots were obtained and analyzed. Starting with an engineering surface, after 6 to 9 micrometers of average degradation depth, safety envelopes could be developed using average roughness and two other proposed parameters. Interestingly, maximum pit depth showed very low correlation with the location of fracture, at the early stage of degradation studied. This is attributed to relaxation of stress concentration at a given pit location due to the assuaging effect caused by neighboring pits. Additionally, energy at fracture was obtained, and a maximum relaxation region was observed. Analytical and experimental study of this region, as well as ductility effects are currently under research.展开更多
In recent years improper allocation of safety input has prevailed in coal mines in China, which resulted in the frequent accidents in coal mining operation. A comprehensive assessment of the input efficiency of coal m...In recent years improper allocation of safety input has prevailed in coal mines in China, which resulted in the frequent accidents in coal mining operation. A comprehensive assessment of the input efficiency of coal mine safety should lead to improved efficiency in the use of funds and management resources. This helps government and enterprise managers better understand how safety inputs are used and to optimize allocation of resources. Study on coal mine＇s efficiency assessment of safety input was con- ducted in this paper. A C^2R model with non-Archimedean infinitesimal vector based on output is established after consideration of the input characteristics and the model properties. An assessment of an operating mine was done using a specific set of input and output criteria. It is found that the safety input was efficient in 2002 and 2005 and was weakly efficient in 2003. However, the efficiency was relatively low in both 2001 and 2004. The safety input resources can be optimized and adjusted by means of projection theory. Such analysis shows that, on average in 2001 and 2004, 45% of the expended funds could have been saved. Likewise, 10% of the safety management and technical staff could have been eliminated and working hours devoted to safety could have been reduced by 12%. These conditions could have Riven the same results.展开更多
Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as...Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as a result the conventional envelope protection system cannot successfully do with the condition. So dynamic envelope based on differential manifold theory, which can take more coupling factors into account, is proposed as a basis to design a novel envelope protection system. Then the relationship between the dynamic envelope and the control coefficient or pilot command is obtained, and the result shows that the dynamic envelope can be enlarged with the change of control coefficient. Furthermore, quantification of flight security is realized via defining relative distance between flight state and dynamic envelope, which can detect whether there is a risk for an aircraft in flight. Finally, an envelope protection system based on dynamic envelope enlargement is proposed on the basis. NASA＇s Generic Transport Model encountering hazard gust wind in climbing phase is taken as an example to verify the system＇s feasibility. The result shows that the system can give a better operation encountering upset condition and to a certain extent reduce the number of accidents or incidents.展开更多
In this paper,as for the unmanned air vehicle(UAV)under external disturbance,an attainable-equilibrium-set-based safety fight envelope(SFE)calculation method is proposed,based on which a prescribed performance protect...In this paper,as for the unmanned air vehicle(UAV)under external disturbance,an attainable-equilibrium-set-based safety fight envelope(SFE)calculation method is proposed,based on which a prescribed performance protection control scheme is presented.Firstly,the existing definition of the SFE based on attainable equilibrium set(AES)is extended to make it consistent and suitable for the UAV system under disturbance.Secondly,a higher-order disturbance observer(HODO)is developed to estimate the disturbances and the disturbance estimation is applied in the computation of the SFE.Thirdly,by using the calculated SFE,a desired safety trajectory based on the time-varying safety margin function and first-order filter is developed to prevent the states of the UAV system from exceeding the SFE.Moreover,an SFE protection controller is proposed by combining the desired safety trajectory,backstepping method,HODO design,and prescribed performance(PP)control technique.In particular,the closed-loop system is established on the basis of disturbance estimation error,filter error,and tracking error.Finally,the stability of the closed-loop system is verified by the Lyapunov stability theory,and the simulations are presented to illustrate the effectiveness of the proposed control scheme.展开更多
Two independent barrier envelopes are the usual requirement used in most well operations to avoid catastrophic accidents.These are classified as primary-concerning preventing the occurrence of a kick,and secondary-con...Two independent barrier envelopes are the usual requirement used in most well operations to avoid catastrophic accidents.These are classified as primary-concerning preventing the occurrence of a kick,and secondary-concerning controlling the kick to avoid a blowout.Barrier envelopes consist of barrier elements,thus verifying the quality of these elements is fundamental.Barrier elements may be either redundant or mandatory,and these relationships are what constitute the barrier envelopes.In this work,we present a methodology to evaluate well safety by identifying existing barrier elements and barrier envelopes and mapping their relationships through the usage of graphs technique.This technique explicitly states the relationship between barriers and between them and envelopes.It enables a simpler visualization for well designers and allows the development of computer programs to control the safety and integrity of wells,both in the design phase and during drilling.12 graphs are provided for a 4-phase well(conductor,surface,production,and drill-in),considering both the primary and secondary enve-lopes.Reasoning for constructing each graph is thoroughly provided.If these graphs are used,reliability values can then be assigned to each barrier element,which results in the reliability of entire barrier envelopes.This can be further extended to analyze the safety of each operation by applying the system to operational sequences and even comparing well designs.展开更多
文摘Damage on surfaces often compromises the efficiency of some types of energy production, the safety and reliability of components, and ultimately increases costs. The environment can degrade the structural integrity of surfaces in service by the accumulation of large numbers of small destructive events, which based on the Central Limit Theorem leads to a Gaussian distribution of pit depth. In order to develop safety envelopes relating fracture loci with topological parameters of a brittle material, scatter plots were obtained and analyzed. Starting with an engineering surface, after 6 to 9 micrometers of average degradation depth, safety envelopes could be developed using average roughness and two other proposed parameters. Interestingly, maximum pit depth showed very low correlation with the location of fracture, at the early stage of degradation studied. This is attributed to relaxation of stress concentration at a given pit location due to the assuaging effect caused by neighboring pits. Additionally, energy at fracture was obtained, and a maximum relaxation region was observed. Analytical and experimental study of this region, as well as ductility effects are currently under research.
基金Project 70771105 supported by the National Natural Science Foundation of China
文摘In recent years improper allocation of safety input has prevailed in coal mines in China, which resulted in the frequent accidents in coal mining operation. A comprehensive assessment of the input efficiency of coal mine safety should lead to improved efficiency in the use of funds and management resources. This helps government and enterprise managers better understand how safety inputs are used and to optimize allocation of resources. Study on coal mine＇s efficiency assessment of safety input was con- ducted in this paper. A C^2R model with non-Archimedean infinitesimal vector based on output is established after consideration of the input characteristics and the model properties. An assessment of an operating mine was done using a specific set of input and output criteria. It is found that the safety input was efficient in 2002 and 2005 and was weakly efficient in 2003. However, the efficiency was relatively low in both 2001 and 2004. The safety input resources can be optimized and adjusted by means of projection theory. Such analysis shows that, on average in 2001 and 2004, 45% of the expended funds could have been saved. Likewise, 10% of the safety management and technical staff could have been eliminated and working hours devoted to safety could have been reduced by 12%. These conditions could have Riven the same results.
基金supported by the National Key Basic Research Program of China (No.2015CB755805)
文摘Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as a result the conventional envelope protection system cannot successfully do with the condition. So dynamic envelope based on differential manifold theory, which can take more coupling factors into account, is proposed as a basis to design a novel envelope protection system. Then the relationship between the dynamic envelope and the control coefficient or pilot command is obtained, and the result shows that the dynamic envelope can be enlarged with the change of control coefficient. Furthermore, quantification of flight security is realized via defining relative distance between flight state and dynamic envelope, which can detect whether there is a risk for an aircraft in flight. Finally, an envelope protection system based on dynamic envelope enlargement is proposed on the basis. NASA＇s Generic Transport Model encountering hazard gust wind in climbing phase is taken as an example to verify the system＇s feasibility. The result shows that the system can give a better operation encountering upset condition and to a certain extent reduce the number of accidents or incidents.
基金supported in part by the National Science Fund for Distinguished Young Scholars 61825302in part by the National Natural Science Foundation of China under Grant U2013201in part by the Key R&D projects(Social Development)in Jiangsu Province of China under Grant BE2020704.
文摘In this paper,as for the unmanned air vehicle(UAV)under external disturbance,an attainable-equilibrium-set-based safety fight envelope(SFE)calculation method is proposed,based on which a prescribed performance protection control scheme is presented.Firstly,the existing definition of the SFE based on attainable equilibrium set(AES)is extended to make it consistent and suitable for the UAV system under disturbance.Secondly,a higher-order disturbance observer(HODO)is developed to estimate the disturbances and the disturbance estimation is applied in the computation of the SFE.Thirdly,by using the calculated SFE,a desired safety trajectory based on the time-varying safety margin function and first-order filter is developed to prevent the states of the UAV system from exceeding the SFE.Moreover,an SFE protection controller is proposed by combining the desired safety trajectory,backstepping method,HODO design,and prescribed performance(PP)control technique.In particular,the closed-loop system is established on the basis of disturbance estimation error,filter error,and tracking error.Finally,the stability of the closed-loop system is verified by the Lyapunov stability theory,and the simulations are presented to illustrate the effectiveness of the proposed control scheme.
文摘Two independent barrier envelopes are the usual requirement used in most well operations to avoid catastrophic accidents.These are classified as primary-concerning preventing the occurrence of a kick,and secondary-concerning controlling the kick to avoid a blowout.Barrier envelopes consist of barrier elements,thus verifying the quality of these elements is fundamental.Barrier elements may be either redundant or mandatory,and these relationships are what constitute the barrier envelopes.In this work,we present a methodology to evaluate well safety by identifying existing barrier elements and barrier envelopes and mapping their relationships through the usage of graphs technique.This technique explicitly states the relationship between barriers and between them and envelopes.It enables a simpler visualization for well designers and allows the development of computer programs to control the safety and integrity of wells,both in the design phase and during drilling.12 graphs are provided for a 4-phase well(conductor,surface,production,and drill-in),considering both the primary and secondary enve-lopes.Reasoning for constructing each graph is thoroughly provided.If these graphs are used,reliability values can then be assigned to each barrier element,which results in the reliability of entire barrier envelopes.This can be further extended to analyze the safety of each operation by applying the system to operational sequences and even comparing well designs.
