Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation...Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation of equipment. Existing methods for damage perception of planetary gear trains mainly rely on linear vibration analysis. However, these methods based on linear vibration signal analysis face challenges such as rich vibration sources, complex signal coupling and modulation mechanisms, significant influence of transmission paths, and difficulties in separating damage information. This paper proposes a method for separating instantaneous angular speed (IAS) signals for planetary gear fault diagnosis. Firstly, this method obtains encoder pulse signals through a built-in encoder. Based on this, it calculates the IAS signals using the Hilbert transform, and obtains the time-domain synchronous average signal of the IAS of the planetary gear through time-domain synchronous averaging technology, thus realizing the fault diagnosis of the planetary gear train. Experimental results validate the effectiveness of the calculated IAS signals, demonstrating that the time-domain synchronous averaging technology can highlight impact characteristics, effectively separate and extract fault impacts, greatly reduce the testing cost of experiments, and provide an effective tool for the fault diagnosis of planetary gear trains.展开更多
因为轨道交通车辆制动冲击暂时没有统一的评价方法,分析标准中平均冲击和瞬时冲击的定义以及制动过程中制动冲击产生的情况,确认采用瞬时冲击作为制动冲击评价对象更能反映制动冲击的变化情况,同时对于《铁路应用-乘客乘坐舒适度-测量...因为轨道交通车辆制动冲击暂时没有统一的评价方法,分析标准中平均冲击和瞬时冲击的定义以及制动过程中制动冲击产生的情况,确认采用瞬时冲击作为制动冲击评价对象更能反映制动冲击的变化情况,同时对于《铁路应用-乘客乘坐舒适度-测量与评价》BS EN 12299—2009中提出的横向瞬时减速度一阶导数数据分析方法进行分析和提炼,提出制动冲击的数据分析方法。展开更多
In the description of the characteristic volume of fire behavior,fire intensity I<sub>r</sub>ate of spread R,and flame length L,etc.all have their scientific definitions,while the bound be-tween the fireli...In the description of the characteristic volume of fire behavior,fire intensity I<sub>r</sub>ate of spread R,and flame length L,etc.all have their scientific definitions,while the bound be-tween the fireline and the residual region of a fire scene is not yet scientifically defined.This pa-per tries to find out theoretically the basis for dividing the bound,to give the fireline thickness D a scientific definition,and to propose a method of quantitative calculation.According to the generality of fuels,the time-dependent curves of fuels combustion rate are utilized to work out a formula by experience.On the basis of defining scientifically the fireline thickness,the Byram’s formula is corrected,and a new one for calculating the fire intensity of slurface fire,i.e.I=0.788HWr,is presented.In this formula,H is the fuel low heat of combustion,the calculating method of the thermal cuyrrent intensity j is given,and J<sub>max</sub>=1.25HWR/D,the calculating formula of flame length is revised,and L=0.0775I<sup>0.46</sup>. In the展开更多
We calculate the average speed of a projectile in the absence of air resistance, a quantity that is missing from the treatment of the problem in the literature. We then show that this quantity is equal to the time-ave...We calculate the average speed of a projectile in the absence of air resistance, a quantity that is missing from the treatment of the problem in the literature. We then show that this quantity is equal to the time-average instantaneous speed of the projectile, but different from its space-average instantaneous speed. It is then shown that this behavior is shared by general motion of all particles regardless of the dimensionality of motion and the nature of the forces involved. The equality of average speed and time-average instantaneous speed can be useful in situations where the calculation of one is more difficult than the other. Thus, making it more efficient to calculate one by calculating the other.展开更多
文摘Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation of equipment. Existing methods for damage perception of planetary gear trains mainly rely on linear vibration analysis. However, these methods based on linear vibration signal analysis face challenges such as rich vibration sources, complex signal coupling and modulation mechanisms, significant influence of transmission paths, and difficulties in separating damage information. This paper proposes a method for separating instantaneous angular speed (IAS) signals for planetary gear fault diagnosis. Firstly, this method obtains encoder pulse signals through a built-in encoder. Based on this, it calculates the IAS signals using the Hilbert transform, and obtains the time-domain synchronous average signal of the IAS of the planetary gear through time-domain synchronous averaging technology, thus realizing the fault diagnosis of the planetary gear train. Experimental results validate the effectiveness of the calculated IAS signals, demonstrating that the time-domain synchronous averaging technology can highlight impact characteristics, effectively separate and extract fault impacts, greatly reduce the testing cost of experiments, and provide an effective tool for the fault diagnosis of planetary gear trains.
文摘因为轨道交通车辆制动冲击暂时没有统一的评价方法,分析标准中平均冲击和瞬时冲击的定义以及制动过程中制动冲击产生的情况,确认采用瞬时冲击作为制动冲击评价对象更能反映制动冲击的变化情况,同时对于《铁路应用-乘客乘坐舒适度-测量与评价》BS EN 12299—2009中提出的横向瞬时减速度一阶导数数据分析方法进行分析和提炼,提出制动冲击的数据分析方法。
文摘In the description of the characteristic volume of fire behavior,fire intensity I<sub>r</sub>ate of spread R,and flame length L,etc.all have their scientific definitions,while the bound be-tween the fireline and the residual region of a fire scene is not yet scientifically defined.This pa-per tries to find out theoretically the basis for dividing the bound,to give the fireline thickness D a scientific definition,and to propose a method of quantitative calculation.According to the generality of fuels,the time-dependent curves of fuels combustion rate are utilized to work out a formula by experience.On the basis of defining scientifically the fireline thickness,the Byram’s formula is corrected,and a new one for calculating the fire intensity of slurface fire,i.e.I=0.788HWr,is presented.In this formula,H is the fuel low heat of combustion,the calculating method of the thermal cuyrrent intensity j is given,and J<sub>max</sub>=1.25HWR/D,the calculating formula of flame length is revised,and L=0.0775I<sup>0.46</sup>. In the
文摘We calculate the average speed of a projectile in the absence of air resistance, a quantity that is missing from the treatment of the problem in the literature. We then show that this quantity is equal to the time-average instantaneous speed of the projectile, but different from its space-average instantaneous speed. It is then shown that this behavior is shared by general motion of all particles regardless of the dimensionality of motion and the nature of the forces involved. The equality of average speed and time-average instantaneous speed can be useful in situations where the calculation of one is more difficult than the other. Thus, making it more efficient to calculate one by calculating the other.
