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
A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target intercep...A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.展开更多
To investigate the cage stability of high-speed oil-lubricated angular contact ball bearings, a dynamic model of cages is developed on the basis of Gupta’s and Meeks’ work. The model can simulate the cage motion und...To investigate the cage stability of high-speed oil-lubricated angular contact ball bearings, a dynamic model of cages is developed on the basis of Gupta’s and Meeks’ work. The model can simulate the cage motion under oil lubrication with all six degrees of freedom. Particularly, the model introduces oil-film damping and hysteresis damping, and deals with the collision contact as imperfect elastic contact. In addition, the effects of inner ring rotational speed, the ratio of pocket clearance to guiding clearance and applied load on the cage stability are investigated by simulating the cage motion with the model. The results can provide a theoretical basis for the design of ball bearing parameters.展开更多
The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further cause...The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.展开更多
Synergic movement of finger's joints provides human hand tremendous dexterities,and the detection of kinematics parameters is critical to describe and evaluate the kinesiology functions of the fingers.The present ...Synergic movement of finger's joints provides human hand tremendous dexterities,and the detection of kinematics parameters is critical to describe and evaluate the kinesiology functions of the fingers.The present work is the attempt to investigate how the angular velocity and angular acceleration of the joints of index finger vary with respect to time during conducting a motor task.A high-speed video camera has been employed to visually record the movement of index finger,and miniaturized(5-mm diameter) reflective markers have affixed to the subject's index finger on the side close to thumb and dorsum of thumb at different joint landmarks.Captured images have been reviewed frame by frame to get the coordinate values of each joint,and the angular displacements,angular velocities and angular acceleration can be obtained with triangle function.The experiment results show that the methods here can detect the kinematics parameters of index finger joints during moving,and can be a valid route to study the motor function of index finger.展开更多
In order to satisfy the requirement of high precision measurement in a high dynamic environment,a kind of gyro aided multi-accelerometer inertial measurement unit(GAMA-IMU)with six accelerometers and two gyros(6A2G)wa...In order to satisfy the requirement of high precision measurement in a high dynamic environment,a kind of gyro aided multi-accelerometer inertial measurement unit(GAMA-IMU)with six accelerometers and two gyros(6A2G)was proposed in this paper.The available configurations have the problem of low measurement precision in a high dynamic environment due to channel coupling.The three channels were decoupled when calculating the angular velocity in the proposed configuration.The yawing and pitching angular velocity were directly measured by gyros,while only the rolling angular velocity was obtained by the GAMA-IMU indirectly from the rolling angular acceleration and quadratic component of rolling angular velocity.Then a single channel rolling angular velocity calculation model was established and the extended Kalman filter(EKF)was used to do state estimation.Simulations were carried out and results indicated that the calculation precision of the proposed 6A2 Gconfiguration could meet the demand of high precision measurement for a high-speed rotating carrier.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A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.
基金Supported by National Key Technology Research and Development Program of China during the 11th Five-Year Plan Period (No. JPPT-115-189)National Natural Science Foundation of China (No. 50975033)
文摘To investigate the cage stability of high-speed oil-lubricated angular contact ball bearings, a dynamic model of cages is developed on the basis of Gupta’s and Meeks’ work. The model can simulate the cage motion under oil lubrication with all six degrees of freedom. Particularly, the model introduces oil-film damping and hysteresis damping, and deals with the collision contact as imperfect elastic contact. In addition, the effects of inner ring rotational speed, the ratio of pocket clearance to guiding clearance and applied load on the cage stability are investigated by simulating the cage motion with the model. The results can provide a theoretical basis for the design of ball bearing parameters.
基金Project(2011CB706606) supported by the National Basic Research of ChinaProject(51405375) supported by the National Natural Science Foundation of China
文摘The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.
基金Supported by the National Natural Science Foundation of China (30770546 )Natural Science Foundation of Chongqing(2006BB2043,2007BB5148)
文摘Synergic movement of finger's joints provides human hand tremendous dexterities,and the detection of kinematics parameters is critical to describe and evaluate the kinesiology functions of the fingers.The present work is the attempt to investigate how the angular velocity and angular acceleration of the joints of index finger vary with respect to time during conducting a motor task.A high-speed video camera has been employed to visually record the movement of index finger,and miniaturized(5-mm diameter) reflective markers have affixed to the subject's index finger on the side close to thumb and dorsum of thumb at different joint landmarks.Captured images have been reviewed frame by frame to get the coordinate values of each joint,and the angular displacements,angular velocities and angular acceleration can be obtained with triangle function.The experiment results show that the methods here can detect the kinematics parameters of index finger joints during moving,and can be a valid route to study the motor function of index finger.
文摘In order to satisfy the requirement of high precision measurement in a high dynamic environment,a kind of gyro aided multi-accelerometer inertial measurement unit(GAMA-IMU)with six accelerometers and two gyros(6A2G)was proposed in this paper.The available configurations have the problem of low measurement precision in a high dynamic environment due to channel coupling.The three channels were decoupled when calculating the angular velocity in the proposed configuration.The yawing and pitching angular velocity were directly measured by gyros,while only the rolling angular velocity was obtained by the GAMA-IMU indirectly from the rolling angular acceleration and quadratic component of rolling angular velocity.Then a single channel rolling angular velocity calculation model was established and the extended Kalman filter(EKF)was used to do state estimation.Simulations were carried out and results indicated that the calculation precision of the proposed 6A2 Gconfiguration could meet the demand of high precision measurement for a high-speed rotating carrier.
