In the field of heavy forging, there are numerous researches on deformation rule in forging process by FEM simulation, however, not many scholars take the equipment constraint and the mutual reaction load between the ...In the field of heavy forging, there are numerous researches on deformation rule in forging process by FEM simulation, however, not many scholars take the equipment constraint and the mutual reaction load between the forging manipulator clamp and the forging blank into account, which will impact on safety of manipulator body and quality of forging blank. This paper presents an impedance model to describe the load and formulates compliance strategies correspondingly to reduce the mutual reaction load for forging manipulator. Firstly, an FEM model of forging process is built. Meanwhile, the clamp of forging manipulator is added to the model as movement constraint and interaction part between the manipulator and the forming process. Secondly, a typical forging process is simulated by changing the movement constraint, and then an impedance model is established to describe the relationship between the load and movement constraint. Finally, two kinds of compliance strategies are formulated according to the impedance model, one is called free compliance, and the other is initiative/passive compliance. The simulation results show that compliance strategies reduce the load amounting to 5 000 kN in z direction between the manipulator clamp and the forging blank obviously, which may lead to serious accidents, such as the capsizing of forging manipulator, the fracture of manipulator clamp, and so on. The proposed research simulates the more real forging process, gets the initiative/passive compliance strategy which is more simple and suitable to the real producing and better for forming a forging process planning and control system in the modern production, and improves the quality and efficiency of heavy forging.展开更多
Recent research on the grinding force involved in cylindrical plunge grinding has focused mainly on steady-state conditions.Unlike in conventional external cylindrical plunge grinding,the conditions between the grindi...Recent research on the grinding force involved in cylindrical plunge grinding has focused mainly on steady-state conditions.Unlike in conventional external cylindrical plunge grinding,the conditions between the grinding wheel and the crankpin change periodically in path controlled grinding because of the eccentricity of the crankpin and the constant rotational speed of the crankshaft.The objective of this study is to investigate the effects of various grinding conditions on the characteristics of the grinding force during continuous path controlled grinding.Path controlled plunge grinding is conducted at a constant rotational speed using a cubic boron nitride（CBN）wheel.The grinding force is determined by measuring the torque.The experimental results show that the force and torque vary sinusoidally during dry grinding and load grinding.The variations in the results reveal that the resultant grinding force and torque decrease with higher grinding speeds and increase with higher peripheral speeds of the pin and higher grinding depths.In path controlled grinding,unlike in conventional external cylindrical plunge grinding,the axial grinding force cannot be disregarded.The speeds and speed ratios of the workpiece and wheel are also analyzed,and the analysis results show that up-grinding and down-grinding occur during the grinding process.This paper proposes a method for describing the force behavior under varied process conditions during continuous path controlled grinding,which provides a beneficial reference for describing the material removal mechanism and for optimizing continuous controlled crankpin grinding.展开更多
Oscillatory failure cases(OFC)detection in the fly-by-wire(FBW)flight control system for civil aircraft is addressed in this paper.First,OFC is ranked four levels:Handling quality,static load,global structure fatigue ...Oscillatory failure cases(OFC)detection in the fly-by-wire(FBW)flight control system for civil aircraft is addressed in this paper.First,OFC is ranked four levels:Handling quality,static load,global structure fatigue and local fatigue,according to their respect impact on aircraft.Second,we present voting and comparing monitors based on un-similarity redundancy commands to detect OFC.Third,the associated performances,the thresholds and the counters of the monitors are calculated by the high fidelity nonlinear aircraft models.Finally,the monitors of OFC are verified by the Iron Bird Platform with real parameters of the flight control system.The results show that our approach can detect OFC rapidly.展开更多
基金supported by National Basic Research Program of China(973 Program, Grant No. 2006CB705400)
文摘In the field of heavy forging, there are numerous researches on deformation rule in forging process by FEM simulation, however, not many scholars take the equipment constraint and the mutual reaction load between the forging manipulator clamp and the forging blank into account, which will impact on safety of manipulator body and quality of forging blank. This paper presents an impedance model to describe the load and formulates compliance strategies correspondingly to reduce the mutual reaction load for forging manipulator. Firstly, an FEM model of forging process is built. Meanwhile, the clamp of forging manipulator is added to the model as movement constraint and interaction part between the manipulator and the forming process. Secondly, a typical forging process is simulated by changing the movement constraint, and then an impedance model is established to describe the relationship between the load and movement constraint. Finally, two kinds of compliance strategies are formulated according to the impedance model, one is called free compliance, and the other is initiative/passive compliance. The simulation results show that compliance strategies reduce the load amounting to 5 000 kN in z direction between the manipulator clamp and the forging blank obviously, which may lead to serious accidents, such as the capsizing of forging manipulator, the fracture of manipulator clamp, and so on. The proposed research simulates the more real forging process, gets the initiative/passive compliance strategy which is more simple and suitable to the real producing and better for forming a forging process planning and control system in the modern production, and improves the quality and efficiency of heavy forging.
基金Supported by National Science and Technology Major Project of China(Grant No.20133ZX04002-031)Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.551121063)State Key Laboratory of Mechanical System and Vibration of China(Grant No.MSV2D2014112)
文摘Recent research on the grinding force involved in cylindrical plunge grinding has focused mainly on steady-state conditions.Unlike in conventional external cylindrical plunge grinding,the conditions between the grinding wheel and the crankpin change periodically in path controlled grinding because of the eccentricity of the crankpin and the constant rotational speed of the crankshaft.The objective of this study is to investigate the effects of various grinding conditions on the characteristics of the grinding force during continuous path controlled grinding.Path controlled plunge grinding is conducted at a constant rotational speed using a cubic boron nitride（CBN）wheel.The grinding force is determined by measuring the torque.The experimental results show that the force and torque vary sinusoidally during dry grinding and load grinding.The variations in the results reveal that the resultant grinding force and torque decrease with higher grinding speeds and increase with higher peripheral speeds of the pin and higher grinding depths.In path controlled grinding,unlike in conventional external cylindrical plunge grinding,the axial grinding force cannot be disregarded.The speeds and speed ratios of the workpiece and wheel are also analyzed,and the analysis results show that up-grinding and down-grinding occur during the grinding process.This paper proposes a method for describing the force behavior under varied process conditions during continuous path controlled grinding,which provides a beneficial reference for describing the material removal mechanism and for optimizing continuous controlled crankpin grinding.
文摘Oscillatory failure cases(OFC)detection in the fly-by-wire(FBW)flight control system for civil aircraft is addressed in this paper.First,OFC is ranked four levels:Handling quality,static load,global structure fatigue and local fatigue,according to their respect impact on aircraft.Second,we present voting and comparing monitors based on un-similarity redundancy commands to detect OFC.Third,the associated performances,the thresholds and the counters of the monitors are calculated by the high fidelity nonlinear aircraft models.Finally,the monitors of OFC are verified by the Iron Bird Platform with real parameters of the flight control system.The results show that our approach can detect OFC rapidly.
