On fully-mechanized faces in nearly horizontal thin coal seams （NHTCS）, the selection of the auxiliary transportation mode is difficult. Generally, auxiliary transportation mainly includes trackless or rail transpor...On fully-mechanized faces in nearly horizontal thin coal seams （NHTCS）, the selection of the auxiliary transportation mode is difficult. Generally, auxiliary transportation mainly includes trackless or rail transportation. Combined with a familiar NHTCS fully-mechanized face, a multi-attribute decision- making model was set up for the decision. The index weight was objectively determined with the fuzzy number and entropy method. The priority order of auxiliary transportation modes was obtained from the Preference Ranking Organization Method for Enrichment Evaluation （PROMETHEE）. The results show that： the net flow of the mode can be expressed by the function of the surrounding rock deformation of the roadway, the dimension of equipment and the thickness of the coal seam; Based on the cost type index, there is a positive correlation between the net flow with the height and width of the trackless auxiliary transportation equipment, respectively. The trackless auxiliary transportation equipment selection principle should be ＂height first then width＂. Combined with the field application of the trackless auxil- iary transportation in Liangshuijing coal mine, the proper method to achieve the safe and high-efficient exploitation of a NHTCS fully-mechanized face is trackless tvred vehicle auxiliary transportation.展开更多
G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuo...G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining： （1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is required.Based on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.展开更多
基金the National High Technology Plan of China (No. 2012AA062101)the National Natural Science Foundation of China (No. 51374200)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘On fully-mechanized faces in nearly horizontal thin coal seams （NHTCS）, the selection of the auxiliary transportation mode is difficult. Generally, auxiliary transportation mainly includes trackless or rail transportation. Combined with a familiar NHTCS fully-mechanized face, a multi-attribute decision- making model was set up for the decision. The index weight was objectively determined with the fuzzy number and entropy method. The priority order of auxiliary transportation modes was obtained from the Preference Ranking Organization Method for Enrichment Evaluation （PROMETHEE）. The results show that： the net flow of the mode can be expressed by the function of the surrounding rock deformation of the roadway, the dimension of equipment and the thickness of the coal seam; Based on the cost type index, there is a positive correlation between the net flow with the height and width of the trackless auxiliary transportation equipment, respectively. The trackless auxiliary transportation equipment selection principle should be ＂height first then width＂. Combined with the field application of the trackless auxil- iary transportation in Liangshuijing coal mine, the proper method to achieve the safe and high-efficient exploitation of a NHTCS fully-mechanized face is trackless tvred vehicle auxiliary transportation.
基金supported by the National Science and Technology Major Projects(Grant Nos.2013ZX04007041 and 2012ZX04001012)General Financial Grant from the China Postdoctoral Science Foundation(Grant No.2014M552032)
文摘G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining： （1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is required.Based on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.
