Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation....Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation.The results show that,under a coal pillar,vertical stress in a floor stratum increases while horizontal stress decreases.We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars.Based on this,we propose control technologies of the surrounding rock of a roadway under a coal pillar,such as high strength and high pre-stressed bolt support,cable reinforcement support single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock,which have been successfully applied in a stability control project of a roadway under a coal pillar.展开更多
To solve the problem of supporting three downhill coal structures in the Yongan Coal Mine of Shanxi Jincheng, we studied the regular development of stress and plastic zones and characteristics of deformation of rock s...To solve the problem of supporting three downhill coal structures in the Yongan Coal Mine of Shanxi Jincheng, we studied the regular development of stress and plastic zones and characteristics of deformation of rock surrounding roadway groups after a period of roadway driving, mining one side as well as mining both sides, we used FLAC 3D for our numerical and theoretical analyses. Field test were carried out, where we revealed the deformation mechanism of roadways and its coal pillars in complex stress conditions. We proposed a roadway stability control technology using backwall grouting with high-water rapid hardening material and combined support with bolt and cable anchoring after mining both sides. Our field practices showed that deformation of rock surrounding roadways can be controlled with this technology.展开更多
The principle of a new type of no-pulsation continuous rotary electro-hydraulic servomotor applied to simulators is introduced. LuGre friction model was analyzed. The identification method of LuGre parameters was prop...The principle of a new type of no-pulsation continuous rotary electro-hydraulic servomotor applied to simulators is introduced. LuGre friction model was analyzed. The identification method of LuGre parameters was proposed, and the measures to compensate the effect of friction forces were given. A friction torque model for the new rotary motor was proposed. The low-speed response and step response of the motor were studied experimentally. Experimental results proved that using friction compensation could eliminate stick-slip motion at the low speed, which makes the servomotor applicable to simulators.展开更多
An auxiliary gas control technology is described that can reduce coal and gas outburst accidents when there is no existing protective coal seam and gas pre-draining is not effective.Numerical simulation methods were u...An auxiliary gas control technology is described that can reduce coal and gas outburst accidents when there is no existing protective coal seam and gas pre-draining is not effective.Numerical simulation methods were used to study the stress distribution ahead of the roadway face for different in situ stresses.The results from the simulation can then provide a new gas control technology.The results show that a high stress concentration,high stresses,and high displacement gradients appear ahead of the roadway face when the maximum in situ stress is aligned perpendicular to the roadway axis.The risk of gas outburst is higher when the stresses decrease rapidly over distance and when the release of more energy occurs immediately after driving the roadway.The gas outburst risk is much smaller when the in situ stress is aligned parallel to the roadway axis.During design of the coal mine most of the coal roadways should be arranged to parallel the maximum in situ stress.This will decrease the outburst risk in general and may be considered a new gas outburst prevention method.展开更多
This paper develops a unified methodology for a real-time speed control of brushless direct-current motor drive systems in the presence of measurement noise and load torque disturbance. First, the mathematical model a...This paper develops a unified methodology for a real-time speed control of brushless direct-current motor drive systems in the presence of measurement noise and load torque disturbance. First, the mathematical model and hardware structure of system is established. Next, an optimal state feed back controller using the Kalman filter state estimation technique is derived. This is followed by an adaptive control algorithm to compensate for the effects of noise and disturbance. Those two algorithms working together can provide a very-high-speed regulation and dynamic response over a wide range of operating conditions. Simulated responses are presented to highlight the effectiveness of the proposed control strategy.展开更多
The application of actuator made of piezoelectric material,particularly the advanced piezoelectric fiber composite due to the rapid development of smart materials and structures and active control technology in aviati...The application of actuator made of piezoelectric material,particularly the advanced piezoelectric fiber composite due to the rapid development of smart materials and structures and active control technology in aviation and aerospace industry,to aircraft for performance enhancements such as flight control,aerodynamic force optimization,structure weight reduction,and overall aircraft design represents a new challenge to researches.It is considered as one of the key technologies for developing future flight vehicle.An approach with virtual control surface instead of conventional control surface to control aerodynamic force distribution and flight performance by use of piezoelectric fiber composite actuators distributed on wing surface is presented here.Particularly,the design and implementation of increasing lift force,providing roll maneuver,decreasing induced drag and wing root moment in different flight environments by the same structure control platform are studied.The control effect and sensitivity are examined quantitatively.Generally speaking,better control effect can be obtained by making better use of aeroelastic character to enlarge the actuation strain produced by piezoelectric material.展开更多
基金the National Natural Science Foundation of China(No.50774077)the State Key Laboratory of Coal Resources and Safe Mining Autonomous Study Subject Foundation of China(No.SKLCRSM08X04)+2 种基金the National Basic Research Program of China,the National Excellence Doctor Degree Dissertation Special Foundation of China(No.200760)the New Century Talent Support Program of the Ministry of Education of China(No.NCET-06-0475)the Youth Scientific Research Foundation of China University of Mining & Technology(No. 2008A002)
文摘Given the difficulties encountered in roadway support under coal pillars,we studied the characteristics of stress distribution and their effect on roadway stability,using theoretical analysis and numerical simulation.The results show that,under a coal pillar,vertical stress in a floor stratum increases while horizontal stress decreases.We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars.Based on this,we propose control technologies of the surrounding rock of a roadway under a coal pillar,such as high strength and high pre-stressed bolt support,cable reinforcement support single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock,which have been successfully applied in a stability control project of a roadway under a coal pillar.
基金Financial support for this work,provided by the National Natural Science Foundation of China (No.50774077)the Research Foundation of the State Key Laboratory of Coal Resources and Mine Safety (No.SKLCRSM08X04)+3 种基金the National Basic Research Program of China (No.2007CB209401)the Foundation for the Author of National Excellent Doctoral Dissertation of China (No.200760)the Program for New Century Excellent Talents in University (No.NCET-06-0475)the Science Foundation for Youth of China University of Mining and Technology (No.2008A002)
文摘To solve the problem of supporting three downhill coal structures in the Yongan Coal Mine of Shanxi Jincheng, we studied the regular development of stress and plastic zones and characteristics of deformation of rock surrounding roadway groups after a period of roadway driving, mining one side as well as mining both sides, we used FLAC 3D for our numerical and theoretical analyses. Field test were carried out, where we revealed the deformation mechanism of roadways and its coal pillars in complex stress conditions. We proposed a roadway stability control technology using backwall grouting with high-water rapid hardening material and combined support with bolt and cable anchoring after mining both sides. Our field practices showed that deformation of rock surrounding roadways can be controlled with this technology.
文摘The principle of a new type of no-pulsation continuous rotary electro-hydraulic servomotor applied to simulators is introduced. LuGre friction model was analyzed. The identification method of LuGre parameters was proposed, and the measures to compensate the effect of friction forces were given. A friction torque model for the new rotary motor was proposed. The low-speed response and step response of the motor were studied experimentally. Experimental results proved that using friction compensation could eliminate stick-slip motion at the low speed, which makes the servomotor applicable to simulators.
基金Financial support provided by the National Basic Research Program of China(No. 2011CB201205)the National Natural Science Foundation of China (No. 51074161)+2 种基金the Independent Research Fund of the State Key Laboratory of Coal Resources and Mine Safety(No. SKLCRSM08X03)the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety, CUMT (No. 09KF09)the National Natural Science Foundation of Youth Science Foundationof China (No. 50804048)
文摘An auxiliary gas control technology is described that can reduce coal and gas outburst accidents when there is no existing protective coal seam and gas pre-draining is not effective.Numerical simulation methods were used to study the stress distribution ahead of the roadway face for different in situ stresses.The results from the simulation can then provide a new gas control technology.The results show that a high stress concentration,high stresses,and high displacement gradients appear ahead of the roadway face when the maximum in situ stress is aligned perpendicular to the roadway axis.The risk of gas outburst is higher when the stresses decrease rapidly over distance and when the release of more energy occurs immediately after driving the roadway.The gas outburst risk is much smaller when the in situ stress is aligned parallel to the roadway axis.During design of the coal mine most of the coal roadways should be arranged to parallel the maximum in situ stress.This will decrease the outburst risk in general and may be considered a new gas outburst prevention method.
文摘This paper develops a unified methodology for a real-time speed control of brushless direct-current motor drive systems in the presence of measurement noise and load torque disturbance. First, the mathematical model and hardware structure of system is established. Next, an optimal state feed back controller using the Kalman filter state estimation technique is derived. This is followed by an adaptive control algorithm to compensate for the effects of noise and disturbance. Those two algorithms working together can provide a very-high-speed regulation and dynamic response over a wide range of operating conditions. Simulated responses are presented to highlight the effectiveness of the proposed control strategy.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.YWF-10-01-B05)the National Natural Science Foundation of China(Grant No.10772183)the Intellectual Innovation Project of the Chinese Academy of Sciences(Grant No.KJCX2-YW-L07)
文摘The application of actuator made of piezoelectric material,particularly the advanced piezoelectric fiber composite due to the rapid development of smart materials and structures and active control technology in aviation and aerospace industry,to aircraft for performance enhancements such as flight control,aerodynamic force optimization,structure weight reduction,and overall aircraft design represents a new challenge to researches.It is considered as one of the key technologies for developing future flight vehicle.An approach with virtual control surface instead of conventional control surface to control aerodynamic force distribution and flight performance by use of piezoelectric fiber composite actuators distributed on wing surface is presented here.Particularly,the design and implementation of increasing lift force,providing roll maneuver,decreasing induced drag and wing root moment in different flight environments by the same structure control platform are studied.The control effect and sensitivity are examined quantitatively.Generally speaking,better control effect can be obtained by making better use of aeroelastic character to enlarge the actuation strain produced by piezoelectric material.
