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RSS2017 Vol. 36, No. 11
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2017, 36(11): 1641-1645.
doi: 10.13433/j.cnki.1003-8728.2017.1101
PDF 1036KB
Abstract:
Titanium alloy and carbon fiber reinforced plastic（CFRP) are both wildly used in aerospace industries. The hole-making process for titanium alloy/composite materials laminated structure has higher requirements for the drilling tools. In this paper, two different “changed point angle” drill bits were used to investigate the effect of the point angle on the cutting force and quality of holes. The results show that S-L type drill（the point angle change from small to large) presents the higher axial cutting force and poor quality in hole exit, but lower torque and higher dimensional accuracy. For the L-S type drill（the point angle change from large to small), it presents the higher drilling torque and bad machining quality of hole surface, but lower axial cutting force and burrs/tears in hole exit. Meanwhile, the L-S type drill can also provide better cylindrical form tolerance in CFRP layer. Therefore, L-S type drill has more advantages in drilling process of titanium alloy/CFRP laminated structure when CFRP layer is in the bottom of the stack.
Titanium alloy and carbon fiber reinforced plastic（CFRP) are both wildly used in aerospace industries. The hole-making process for titanium alloy/composite materials laminated structure has higher requirements for the drilling tools. In this paper, two different “changed point angle” drill bits were used to investigate the effect of the point angle on the cutting force and quality of holes. The results show that S-L type drill（the point angle change from small to large) presents the higher axial cutting force and poor quality in hole exit, but lower torque and higher dimensional accuracy. For the L-S type drill（the point angle change from large to small), it presents the higher drilling torque and bad machining quality of hole surface, but lower axial cutting force and burrs/tears in hole exit. Meanwhile, the L-S type drill can also provide better cylindrical form tolerance in CFRP layer. Therefore, L-S type drill has more advantages in drilling process of titanium alloy/CFRP laminated structure when CFRP layer is in the bottom of the stack.
2017, 36(11): 1646-1652.
doi: 10.13433/j.cnki.1003-8728.2017.1102
Abstract:
In order to solve the problem that the contact region of spiral bevel and hypoid gear which generated by duplex helical method was difficult to adjust, a pinion conjugate tooth surface was obtained by generating model for spiral bevel and hypoid gear, and then modified the pinion conjugate tooth surface according to the preset meshing performance of tooth surface to obtain a pinion target tooth surface. Considering the constraint condition, the optimal model was built by setting the least sum of square errors between the pinion resultant tooth surface and the pinion target on both sides as object and setting the adjustment amount of pinion machining parameters as variables. The model was solved by the method of nonlinearly constrained optimization. Taking a hypoid gear drive 8×43 that manufactured by duplex helical method, the proposed menthod were proven by numerical computation and rolling test.
In order to solve the problem that the contact region of spiral bevel and hypoid gear which generated by duplex helical method was difficult to adjust, a pinion conjugate tooth surface was obtained by generating model for spiral bevel and hypoid gear, and then modified the pinion conjugate tooth surface according to the preset meshing performance of tooth surface to obtain a pinion target tooth surface. Considering the constraint condition, the optimal model was built by setting the least sum of square errors between the pinion resultant tooth surface and the pinion target on both sides as object and setting the adjustment amount of pinion machining parameters as variables. The model was solved by the method of nonlinearly constrained optimization. Taking a hypoid gear drive 8×43 that manufactured by duplex helical method, the proposed menthod were proven by numerical computation and rolling test.
2017, 36(11): 1653-1657.
doi: 10.13433/j.cnki.1003-8728.2017.1103
Abstract:
The constrained path following problem for an underactuated autonomous underwater vehicle（AUV) is investigated with nonlinear model predictive control（MPC) in this paper. The second order derivative of the path parameter is used as a virtual input to control the evolution of the desired path, and the dynamics of the path is utilized for prediction. Then a constrained path following controller is derived by using the nonlinear MPC technique. By solving the constrained optimization problems in a receding horizon fashion, the control input satisfying the constraints is obtained. Finally, simulation studies with circle path following using the REMUS AUV model are performed and the results demonstrate that the proposed controller is effective and can handle constraints explicitly.
The constrained path following problem for an underactuated autonomous underwater vehicle（AUV) is investigated with nonlinear model predictive control（MPC) in this paper. The second order derivative of the path parameter is used as a virtual input to control the evolution of the desired path, and the dynamics of the path is utilized for prediction. Then a constrained path following controller is derived by using the nonlinear MPC technique. By solving the constrained optimization problems in a receding horizon fashion, the control input satisfying the constraints is obtained. Finally, simulation studies with circle path following using the REMUS AUV model are performed and the results demonstrate that the proposed controller is effective and can handle constraints explicitly.
2017, 36(11): 1658-1665.
doi: 10.13433/j.cnki.1003-8728.2017.1104
Abstract:
This paper presents a novel CT-guided puncture robotic system with 7 degrees of freedom（DOF), which can improve the accuracy of the brachytherapy for thoracoabdominal cancer. According to the design requirements, the space constraints and CT compatibility of the drive mode was solved with remote tendon-sheath transmission, and a new structure of the robot was developed. Using kinematical analysis, the structure parameters of the robot were optimized according to the space dimension. Dynamics model for robot was established to acquire the relationship between the joint force/torque and the motion parameters of the joint based on the Lagrangian equation. Finally, the experiment of positioning error correction was made to improve the positioning accuracy of the robot. And the measurement experiment of robot puncture accuracy was completed, in which the error is 1.09 mm. It proved the robot system can meet the requirements of surgical accuracy.
This paper presents a novel CT-guided puncture robotic system with 7 degrees of freedom（DOF), which can improve the accuracy of the brachytherapy for thoracoabdominal cancer. According to the design requirements, the space constraints and CT compatibility of the drive mode was solved with remote tendon-sheath transmission, and a new structure of the robot was developed. Using kinematical analysis, the structure parameters of the robot were optimized according to the space dimension. Dynamics model for robot was established to acquire the relationship between the joint force/torque and the motion parameters of the joint based on the Lagrangian equation. Finally, the experiment of positioning error correction was made to improve the positioning accuracy of the robot. And the measurement experiment of robot puncture accuracy was completed, in which the error is 1.09 mm. It proved the robot system can meet the requirements of surgical accuracy.
2017, 36(11): 1666-1673.
doi: 10.13433/j.cnki.1003-8728.2017.1105
Abstract:
In view of the current throttle valve can't be automatically changed according to the need to change the size of the nozzle and other issues, a new type of natural gas well down-hole constant pressure throttle valve is simulated using ANSYS, the down-hole throttle valve can control the throttle opening size automatically according to the change of inlet pressure, which makes sure that the outlet pressure of throttle valve is basically in the designed area. The pressure, velocity and temperature of the throttle valve of the throttle valve are analyzed under the normal operating pressure range and different opening size, the simulation results are consistent with the theoretical calculation ones. Through analyzing the erosion of valve core and valve seat in two phase flow gas-solid, the results show that throttle valve core cone erosion wear is the most serious, the maximum erosion rate was 4.413×10-7 kg/(m2·s). Finally, based on the numerical simulation results, the throttle valve core and valve seat structure are optimized, the optimization results demonstrate that when the throttle valve seat angle is set to β=10°, the valve core erosion rate is the minimal.
In view of the current throttle valve can't be automatically changed according to the need to change the size of the nozzle and other issues, a new type of natural gas well down-hole constant pressure throttle valve is simulated using ANSYS, the down-hole throttle valve can control the throttle opening size automatically according to the change of inlet pressure, which makes sure that the outlet pressure of throttle valve is basically in the designed area. The pressure, velocity and temperature of the throttle valve of the throttle valve are analyzed under the normal operating pressure range and different opening size, the simulation results are consistent with the theoretical calculation ones. Through analyzing the erosion of valve core and valve seat in two phase flow gas-solid, the results show that throttle valve core cone erosion wear is the most serious, the maximum erosion rate was 4.413×10-7 kg/(m2·s). Finally, based on the numerical simulation results, the throttle valve core and valve seat structure are optimized, the optimization results demonstrate that when the throttle valve seat angle is set to β=10°, the valve core erosion rate is the minimal.
2017, 36(11): 1674-1677.
doi: 10.13433/j.cnki.1003-8728.2017.1106
Abstract:
Contact ratio is a main factor to influence meshing performance of gear transmission, and it is also a key index to judge continuity and load distribution of gear transmission. Gear with S-shaped tooth profile is developed as a new tooth profile of gear so as to enhance contact strength of gear. In order to further study on it, the formula is deduced to calculate the contact ratio of gear transmission with S-shaped tooth profile, and the change law in contact ratio is discussed varying with the number of teeth, modulus, pressure angle, and derivative coefficient, which is comparing with the involute gear with small number of teeth under the same design parameters. And the results show that the gear with S-shaped tooth profile has a large advantage in contact ratio comparing with the involute gear under the same parameters.
Contact ratio is a main factor to influence meshing performance of gear transmission, and it is also a key index to judge continuity and load distribution of gear transmission. Gear with S-shaped tooth profile is developed as a new tooth profile of gear so as to enhance contact strength of gear. In order to further study on it, the formula is deduced to calculate the contact ratio of gear transmission with S-shaped tooth profile, and the change law in contact ratio is discussed varying with the number of teeth, modulus, pressure angle, and derivative coefficient, which is comparing with the involute gear with small number of teeth under the same design parameters. And the results show that the gear with S-shaped tooth profile has a large advantage in contact ratio comparing with the involute gear under the same parameters.
2017, 36(11): 1678-1683.
doi: 10.13433/j.cnki.1003-8728.2017.1107
Abstract:
Because of the high incidence of prostate cancer, low operating stability and seed radiation, an ultrasound-guided robotic minimally invasive surgical system which consists of ultrasonic image navigation, surgical robot and prostate cancer spatial positioning device is developed. First, the degree of freedom distribution and the working range of the joints of the surgical robot are determined, and its working space is reduced. Then the static analysis of its key components is conducted under the different positions and orientations of the robot. Finally, the accuracy tests are carried out with a laser tracker. The electromagnetic positioning instrument and the robotic mechanical precision are verified and the error compensation is realized. The experimental results show that the error of the minimally invasive surgical system is less than 1 mm, which meets the needs of brachytherapy for prostate cancer.
Because of the high incidence of prostate cancer, low operating stability and seed radiation, an ultrasound-guided robotic minimally invasive surgical system which consists of ultrasonic image navigation, surgical robot and prostate cancer spatial positioning device is developed. First, the degree of freedom distribution and the working range of the joints of the surgical robot are determined, and its working space is reduced. Then the static analysis of its key components is conducted under the different positions and orientations of the robot. Finally, the accuracy tests are carried out with a laser tracker. The electromagnetic positioning instrument and the robotic mechanical precision are verified and the error compensation is realized. The experimental results show that the error of the minimally invasive surgical system is less than 1 mm, which meets the needs of brachytherapy for prostate cancer.
2017, 36(11): 1684-1688.
doi: 10.13433/j.cnki.1003-8728.2017.1108
Abstract:
Most existing studies did not consider the elasticity of propeller. A simplified model of propeller composed of beam and spring oscillator is constructed. The impact of different simplified modes of propeller on the longitudinal vibration of propulsion shafting is analyzed and the impact of the relationship between umbrella modes frequency of propeller and longitudinal vibration modal frequency of shafting is studied. The results show that the umbrella modes of propeller have distinct embodiment in longitudinal vibration of shafting. The first umbrella modal frequency of propeller has an important impact on the shafting vibration of the first two longitudinal modal frequencies. The second umbrella modal frequency of propeller can obviously affect the shafting vibration of the second longitudinal modal frequency. The vibration power flow of thrust bearing base will be reduced when the second umbrella modal frequency of propeller is close to the anti-resonance frequency of shafting.
Most existing studies did not consider the elasticity of propeller. A simplified model of propeller composed of beam and spring oscillator is constructed. The impact of different simplified modes of propeller on the longitudinal vibration of propulsion shafting is analyzed and the impact of the relationship between umbrella modes frequency of propeller and longitudinal vibration modal frequency of shafting is studied. The results show that the umbrella modes of propeller have distinct embodiment in longitudinal vibration of shafting. The first umbrella modal frequency of propeller has an important impact on the shafting vibration of the first two longitudinal modal frequencies. The second umbrella modal frequency of propeller can obviously affect the shafting vibration of the second longitudinal modal frequency. The vibration power flow of thrust bearing base will be reduced when the second umbrella modal frequency of propeller is close to the anti-resonance frequency of shafting.
2017, 36(11): 1689-1694.
doi: 10.13433/j.cnki.1003-8728.2017.1109
Abstract:
High voltage circuit breaker is not benefit for reliability experimental study due to large loading force and area, with similarity theory the similar model design method of the main contact of transmission mechanism is proposed, and the dynamic stress similarity of link is studied. The closed-loop vector and dynamic static method are used to analyze the kinematics and dynamics of the main contact mechanism. In order to obtain the similar relationship of kinematics and dynamics between the main contact mechanism and its own similar model, the equation analysis method and the dimensional analysis method are used and the correctness of the theoretical analysis is verified by ADAMS. With the finite element software ANSYS, the dynamic stress relationship of link between the prototype mechanism and the similar model is acquired.
High voltage circuit breaker is not benefit for reliability experimental study due to large loading force and area, with similarity theory the similar model design method of the main contact of transmission mechanism is proposed, and the dynamic stress similarity of link is studied. The closed-loop vector and dynamic static method are used to analyze the kinematics and dynamics of the main contact mechanism. In order to obtain the similar relationship of kinematics and dynamics between the main contact mechanism and its own similar model, the equation analysis method and the dimensional analysis method are used and the correctness of the theoretical analysis is verified by ADAMS. With the finite element software ANSYS, the dynamic stress relationship of link between the prototype mechanism and the similar model is acquired.
2017, 36(11): 1695-1700.
doi: 10.13433/j.cnki.1003-8728.2017.1110
Abstract:
Aiming at the extraction of useful fault feature information from bearing vibration signal affected by the noise, the variational mode decomposition（VMD) and wavelet threshold denoising method based on genetic algorithm is proposed. The method firstly utilizes genetic algorithm selecting appropriate parameters of the VMD, then the noise signal is decomposed adaptively by VMD method, finally processing the modes of decomposition respectively by wavelet threshold method, restructuring the signal to get denoised signal. Experimental results on actual bearing signals show that the proposed method can obtain higher signal-to-noise ratio and lower mean square deviation compared with several common denoising methods.
Aiming at the extraction of useful fault feature information from bearing vibration signal affected by the noise, the variational mode decomposition（VMD) and wavelet threshold denoising method based on genetic algorithm is proposed. The method firstly utilizes genetic algorithm selecting appropriate parameters of the VMD, then the noise signal is decomposed adaptively by VMD method, finally processing the modes of decomposition respectively by wavelet threshold method, restructuring the signal to get denoised signal. Experimental results on actual bearing signals show that the proposed method can obtain higher signal-to-noise ratio and lower mean square deviation compared with several common denoising methods.
2017, 36(11): 1701-1707.
doi: 10.13433/j.cnki.1003-8728.2017.1111
Abstract:
In the thin coal seam, the shearer's loading rate is always a question that received much more concerns. In order to improve the loading rate and ensure the minimum energy consumption, the biggest cutting area, in the range of cutting power, and then achieve the optimal cutting performance, the shearer's kinematics parameter matching is studied. The discrete element simulation model of shearer's cutting unit is established by EDEM software, based on the relationship of drum rotating speed, haulage speed and loading rate, actual coal capacity. The cutting specific energy consumption and cutting area mathematical model is established by MATLAB software. Take the loading rate, actual coal capacity, cutting area and specific energy consumption as objective function, the multiobjective optimization equation of the kinematic parameters of shearer drum is established. The optimum matching value of the haulage speed and drum rotating speed is obtained by optimization. The research results show that when the drum rotating speed is 53.4 r/min and haulage speed is 8.9 m/min, drum performance achieves to the best; and then the loading rate is 59.025 7%, the actual coal capacity is 200.541 1 t/h, cutting area is 56.667 cm2, cutting specific energy consumption is 0.874 kW·h/m3.
In the thin coal seam, the shearer's loading rate is always a question that received much more concerns. In order to improve the loading rate and ensure the minimum energy consumption, the biggest cutting area, in the range of cutting power, and then achieve the optimal cutting performance, the shearer's kinematics parameter matching is studied. The discrete element simulation model of shearer's cutting unit is established by EDEM software, based on the relationship of drum rotating speed, haulage speed and loading rate, actual coal capacity. The cutting specific energy consumption and cutting area mathematical model is established by MATLAB software. Take the loading rate, actual coal capacity, cutting area and specific energy consumption as objective function, the multiobjective optimization equation of the kinematic parameters of shearer drum is established. The optimum matching value of the haulage speed and drum rotating speed is obtained by optimization. The research results show that when the drum rotating speed is 53.4 r/min and haulage speed is 8.9 m/min, drum performance achieves to the best; and then the loading rate is 59.025 7%, the actual coal capacity is 200.541 1 t/h, cutting area is 56.667 cm2, cutting specific energy consumption is 0.874 kW·h/m3.
2017, 36(11): 1708-1714.
doi: 10.13433/j.cnki.1003-8728.2017.1112
Abstract:
In view of the fact that a centrifugal pump for land use can not meet the requirements of 1 000 m deep-sea mining, a high-performance two-stage type slurry pump was designed. The impeller and the space guidance vane were selected. The inner turbulent flow of the two-stage pump was simulated with the three-dimensional Reynolds-average N-S equations and the RNG κ-ε turbulence model. The distribution law of solid-liquid two-phase flow was analyzed and the performance of the slurry pump was predicted with the SIMPLEC algorithm. The simulation results show that under different flow conditions, the pressure on the pressure surface of the impeller blade on the same cylinder radius is greater than that on the suction surface. When the flow is greater, the impeller entrance velocity is smaller, and the influence of the impeller on solid and fluid acceleration is weaker; the outlet velocity in the impeller is small. Then the outlet and inlet fluid velocity differences are smaller in the space guidance vane, producing a worse rotational effect and a smaller head, and the performance of the equipment is reduced. Efficiency increases with the increase of flow rate, so the work flow should be selected 500 m3/h~600 m3/h.
In view of the fact that a centrifugal pump for land use can not meet the requirements of 1 000 m deep-sea mining, a high-performance two-stage type slurry pump was designed. The impeller and the space guidance vane were selected. The inner turbulent flow of the two-stage pump was simulated with the three-dimensional Reynolds-average N-S equations and the RNG κ-ε turbulence model. The distribution law of solid-liquid two-phase flow was analyzed and the performance of the slurry pump was predicted with the SIMPLEC algorithm. The simulation results show that under different flow conditions, the pressure on the pressure surface of the impeller blade on the same cylinder radius is greater than that on the suction surface. When the flow is greater, the impeller entrance velocity is smaller, and the influence of the impeller on solid and fluid acceleration is weaker; the outlet velocity in the impeller is small. Then the outlet and inlet fluid velocity differences are smaller in the space guidance vane, producing a worse rotational effect and a smaller head, and the performance of the equipment is reduced. Efficiency increases with the increase of flow rate, so the work flow should be selected 500 m3/h~600 m3/h.
2017, 36(11): 1715-1721.
doi: 10.13433/j.cnki.1003-8728.2017.1113
Abstract:
The extrusion velocity(A), filling velocity(B), layer thickness(C) and filling pattern(D) are selected as the controlling factors in fused deposition modeling（FDM). Firstly, the influencing degree of the process parameters on the single index such as length deviation rate, width deviation rate and porosity is determined by orthogonal experiment, considering the interaction between the controlling factors. Then the experimental results are comprehensive evaluated based on the entropy-weight technique for order preference by similarity to an ideal solution（TOPSIS) model and the relative closeness is used as the comprehensive index. Combining the range analysis and variance analysis, the influencing degree of the process parameters on the comprehensive index and the optimal combination of processing parameters is determined. The experiment results show that the filling pattern, filling velocity, the interaction between extrusion velocity and filling velocity, has a strong influence on comprehensive index, and the optimal combination of the processing parameters is A1B3C1D1. Besides, a verification test is carried out and shows that the optimization scheme of the comprehensive index is improved by 2.25%.
The extrusion velocity(A), filling velocity(B), layer thickness(C) and filling pattern(D) are selected as the controlling factors in fused deposition modeling（FDM). Firstly, the influencing degree of the process parameters on the single index such as length deviation rate, width deviation rate and porosity is determined by orthogonal experiment, considering the interaction between the controlling factors. Then the experimental results are comprehensive evaluated based on the entropy-weight technique for order preference by similarity to an ideal solution（TOPSIS) model and the relative closeness is used as the comprehensive index. Combining the range analysis and variance analysis, the influencing degree of the process parameters on the comprehensive index and the optimal combination of processing parameters is determined. The experiment results show that the filling pattern, filling velocity, the interaction between extrusion velocity and filling velocity, has a strong influence on comprehensive index, and the optimal combination of the processing parameters is A1B3C1D1. Besides, a verification test is carried out and shows that the optimization scheme of the comprehensive index is improved by 2.25%.
2017, 36(11): 1722-1728.
doi: 10.13433/j.cnki.1003-8728.2017.1114
Abstract:
Aiming to the surface finishing of common-rail tube micro-holes manufactured by electrical discharge machining, abrasive flow polishing was adopted. The effects of the processing parameters and their interaction on the surface roughness have been studied via orthogonal experiments. The prediction model for surface roughness via multiple nonlinear regression equation was established based on the second order response surface model or power function model. The results showed that the processing parameters had a significant influence on the polishing effect, but the interaction had less impact on it. The surface roughness of the tunnels has a negative correlation with the pressure, concentration and processing time, but the positive correlation with the grain size when it exceeds a critical value of 148 μm. At grain size below critical value, it shows a positive correlation with polishing efficiency. The combinatorial optimization is obtained, and under this condition, the surface roughness value decreased from 1.31 μm to 0.2 μm. The prediction accuracy via second-order polynomial regression equation was higher than that via power function regression equation. The correlation coefficient was up to 0.990, and the prediction errors was less than 9.54%.
Aiming to the surface finishing of common-rail tube micro-holes manufactured by electrical discharge machining, abrasive flow polishing was adopted. The effects of the processing parameters and their interaction on the surface roughness have been studied via orthogonal experiments. The prediction model for surface roughness via multiple nonlinear regression equation was established based on the second order response surface model or power function model. The results showed that the processing parameters had a significant influence on the polishing effect, but the interaction had less impact on it. The surface roughness of the tunnels has a negative correlation with the pressure, concentration and processing time, but the positive correlation with the grain size when it exceeds a critical value of 148 μm. At grain size below critical value, it shows a positive correlation with polishing efficiency. The combinatorial optimization is obtained, and under this condition, the surface roughness value decreased from 1.31 μm to 0.2 μm. The prediction accuracy via second-order polynomial regression equation was higher than that via power function regression equation. The correlation coefficient was up to 0.990, and the prediction errors was less than 9.54%.
2017, 36(11): 1729-1733.
doi: 10.13433/j.cnki.1003-8728.2017.1115
Abstract:
Firstly, the bearing condition of the fibers around hole-exit in drilling of carbon fiber-reinforced polymer（CFRP) was analyzed. Based on the present analysis, the burr formation mechanism is presented and the quantification method for hole-exit burr was given. Secondly, the conception of “forward” and “reverse” cutting was defined. Then the minor cutting edge was modified according to the “reverse” cutting. Thirdly, the angles of the modification cutting edge were determined with respect to the dynamic drilling angle and the burr thickness. The grinding method was also presented. Lastly, the experiments were conducted to verify the validation of the modification drill bit in minimizing hole-exit burr.
Firstly, the bearing condition of the fibers around hole-exit in drilling of carbon fiber-reinforced polymer（CFRP) was analyzed. Based on the present analysis, the burr formation mechanism is presented and the quantification method for hole-exit burr was given. Secondly, the conception of “forward” and “reverse” cutting was defined. Then the minor cutting edge was modified according to the “reverse” cutting. Thirdly, the angles of the modification cutting edge were determined with respect to the dynamic drilling angle and the burr thickness. The grinding method was also presented. Lastly, the experiments were conducted to verify the validation of the modification drill bit in minimizing hole-exit burr.
2017, 36(11): 1734-1739.
doi: 10.13433/j.cnki.1003-8728.2017.1116
Abstract:
Assembly is a key of product quality assurance, and assembly precision is an important measurement index in assembling process. There were four steps to predict assembly precision of NC machine. Firstly, the functional decomposition approach “function-motion-action” was used to analyze its assembly process structurally, then it was decomposed down into basic action, i.e. meta-action. Secondly, in order to express the assembly relationship between the assembly units and the logical relationship between the geometry features, the frame chart of assembly errors propagation via meta-action was constructed. Thirdly, the multi-level model for state space was built to predict final assembly precision of NC machine on the basis of the propagation and accumulation of geometry errors. Finally, the effectiveness of multi-level model for state space was demonstrated by an example of Z axis feed function assembly unit from a certain machining center.
Assembly is a key of product quality assurance, and assembly precision is an important measurement index in assembling process. There were four steps to predict assembly precision of NC machine. Firstly, the functional decomposition approach “function-motion-action” was used to analyze its assembly process structurally, then it was decomposed down into basic action, i.e. meta-action. Secondly, in order to express the assembly relationship between the assembly units and the logical relationship between the geometry features, the frame chart of assembly errors propagation via meta-action was constructed. Thirdly, the multi-level model for state space was built to predict final assembly precision of NC machine on the basis of the propagation and accumulation of geometry errors. Finally, the effectiveness of multi-level model for state space was demonstrated by an example of Z axis feed function assembly unit from a certain machining center.
2017, 36(11): 1740-1746.
doi: 10.13433/j.cnki.1003-8728.2017.1117
Abstract:
In order to analyze the influence of tool geometry on the milling temperature of the first deformation zone,the 3D simulation modelfor the milling process of U71Mn was established with AdvantEdge. At the same time, the K type artificial thermocouple was used to measure the temperature of the third deformation zone, the cutter and the working surface, and the influence of the processing parameters on the milling temperature was also studied. The results showed that milling temperature gradually increased with the increasing of cutter speed, feed rate and cutting depth. Among them, the cutter speed and cutting depth has a more significant influence on the cutting temperature, but the speed of the feed is little. Then using thermal infrared imager on the second deformation zone knife/chip surface milling temperature were measured in with all cutting parameters under the condition of artificial thermocouple and thermal infrared imager measured temperature and the simulation results were compared. The results showed that the effectiveness of the 3D simulation model. Finally, based on the above mentioned model, the effects of the cutting tool angles on the cutting temperature of the first deformation zone was simulated and analyzed. The simulation results provided a guidance for the structure design of the milling cutter.
In order to analyze the influence of tool geometry on the milling temperature of the first deformation zone,the 3D simulation modelfor the milling process of U71Mn was established with AdvantEdge. At the same time, the K type artificial thermocouple was used to measure the temperature of the third deformation zone, the cutter and the working surface, and the influence of the processing parameters on the milling temperature was also studied. The results showed that milling temperature gradually increased with the increasing of cutter speed, feed rate and cutting depth. Among them, the cutter speed and cutting depth has a more significant influence on the cutting temperature, but the speed of the feed is little. Then using thermal infrared imager on the second deformation zone knife/chip surface milling temperature were measured in with all cutting parameters under the condition of artificial thermocouple and thermal infrared imager measured temperature and the simulation results were compared. The results showed that the effectiveness of the 3D simulation model. Finally, based on the above mentioned model, the effects of the cutting tool angles on the cutting temperature of the first deformation zone was simulated and analyzed. The simulation results provided a guidance for the structure design of the milling cutter.
2017, 36(11): 1747-1753.
doi: 10.13433/j.cnki.1003-8728.2017.1118
Abstract:
To solve problems that traditional methods for analyzing the importance of a CNC machine tool failure mode faces, such as robust subjectivity, lack of essential data, rare analysis of the whole machine tool, this paper proposes a new method for analyzing the importance of computer numerical control（CNC) machine tool failure modes based on the fuzzy quantitative evaluation and Monte Carlo simulation of influence factors. This method evaluates the importance by taking into comprehensive consideration the influence factors of the importance of failure modes. The Delphi method is used to determine the influence factor evaluation grade and its corresponding evaluation criterion and the expert's weight to modify the factor grade by combining the variation coefficient method with the mean value. The fuzzy analytic hierarchy process is employed to determine the weight and priority of each influence factor. Then, a MATLAB program is written to do the Monte Carlo simulation. The linear weighting method is used to perform the statistical analysis of the importance of each failure mode. The order of importance of each CNC machine tool failure mode is ranked according to the overall unit. At last, a case study indicates that the method is rational and effective.
To solve problems that traditional methods for analyzing the importance of a CNC machine tool failure mode faces, such as robust subjectivity, lack of essential data, rare analysis of the whole machine tool, this paper proposes a new method for analyzing the importance of computer numerical control（CNC) machine tool failure modes based on the fuzzy quantitative evaluation and Monte Carlo simulation of influence factors. This method evaluates the importance by taking into comprehensive consideration the influence factors of the importance of failure modes. The Delphi method is used to determine the influence factor evaluation grade and its corresponding evaluation criterion and the expert's weight to modify the factor grade by combining the variation coefficient method with the mean value. The fuzzy analytic hierarchy process is employed to determine the weight and priority of each influence factor. Then, a MATLAB program is written to do the Monte Carlo simulation. The linear weighting method is used to perform the statistical analysis of the importance of each failure mode. The order of importance of each CNC machine tool failure mode is ranked according to the overall unit. At last, a case study indicates that the method is rational and effective.
2017, 36(11): 1754-1758.
doi: 10.13433/j.cnki.1003-8728.2017.1119
Abstract:
Austempered ductile iron(ADI) is a difficult machining material with excellent comprehensive properties, and its high speed milling force has an important influence on surface roughness of the work-piece. Based on the combined mechanical properties, the multi-factor orthogonal regression experiment theory is applied to establish the relationship between the milling force and the surface roughness. In the experiment, the spindle speed, feed per tooth rate, cutting depth and cutting width are regarded as the multi factors, and the milling force and surface roughness are regarded as the dependent variables. With the least squares method, a model of the milling force and the surface roughness about the three components(Fx,Fy,Fz) is established, and the significance of the regression model and its coefficient analysis are conducted to verify the model and the influence level of three components(Fx,Fy,Fz) of the milling force. Finally, some verification experiments are designed to check the effectiveness of the experimental model. The experimental results show that the influence order of the three force components on the surface roughness is in turn: tangential force, axial force, radial force. The verification experiments prove the credibility and validity of the model, and it will provide an important theoretical support and technical guidance in high-speed milling process of ADI.
Austempered ductile iron(ADI) is a difficult machining material with excellent comprehensive properties, and its high speed milling force has an important influence on surface roughness of the work-piece. Based on the combined mechanical properties, the multi-factor orthogonal regression experiment theory is applied to establish the relationship between the milling force and the surface roughness. In the experiment, the spindle speed, feed per tooth rate, cutting depth and cutting width are regarded as the multi factors, and the milling force and surface roughness are regarded as the dependent variables. With the least squares method, a model of the milling force and the surface roughness about the three components(Fx,Fy,Fz) is established, and the significance of the regression model and its coefficient analysis are conducted to verify the model and the influence level of three components(Fx,Fy,Fz) of the milling force. Finally, some verification experiments are designed to check the effectiveness of the experimental model. The experimental results show that the influence order of the three force components on the surface roughness is in turn: tangential force, axial force, radial force. The verification experiments prove the credibility and validity of the model, and it will provide an important theoretical support and technical guidance in high-speed milling process of ADI.
2017, 36(11): 1759-1763.
doi: 10.13433/j.cnki.1003-8728.2017.1120
Abstract:
Due to sliding motion errors of a four-wheeled skid-steer mobile robot, it is difficult to control the robot to follow its trajectory. Also the dynamical parameters of the skid-steer on different ground conditions are different, causing different sliding errors and increasing the difficulty in the control and prediction of the robot's turning linear velocity and angular velocity. The linear velocity and angular velocity calculation model of the four-wheeled skid-steer robot is built with two inertial measurement units, and the model is used to take the closed loop control of the four-wheeled skid-steer mobile robot for its motion control, dynamically adjust four wheels separately and make the robot operate more precisely and smoothly. The experimental results show that with the dynamic wheel-velocity adjustment strategy, the robot runs more accurately with less sliding motion error when its trajectory is followed.
Due to sliding motion errors of a four-wheeled skid-steer mobile robot, it is difficult to control the robot to follow its trajectory. Also the dynamical parameters of the skid-steer on different ground conditions are different, causing different sliding errors and increasing the difficulty in the control and prediction of the robot's turning linear velocity and angular velocity. The linear velocity and angular velocity calculation model of the four-wheeled skid-steer robot is built with two inertial measurement units, and the model is used to take the closed loop control of the four-wheeled skid-steer mobile robot for its motion control, dynamically adjust four wheels separately and make the robot operate more precisely and smoothly. The experimental results show that with the dynamic wheel-velocity adjustment strategy, the robot runs more accurately with less sliding motion error when its trajectory is followed.
2017, 36(11): 1764-1770.
doi: 10.13433/j.cnki.1003-8728.2017.1121
Abstract:
Aiming at the problem that early fault characteristic signal of rolling bearing is weak and affected by the environmental noise seriously, which makes the fault feature information difficult to be identified, a rolling bearing early fault diagnosis method is proposed in this study, based on ensemble local mean decomposition and maximum correlated kurtosis deconvolution. First of all, the ensemble local mean decomposition was adopted to decompose collected vibration signals, and obtains a finite number of product functions. Due to the interference of noise, it is difficult to make a correct judgment of the fault from the spectrum of the PF component. Then, the PF component that contains fault feature was processed by using maximum correlated kurtosis deconvolution to reduce the strong background noise and enhance the fault information. Finally, the fault frequency can be obtained accurately by Hilbert envelope spectrum. The bearing experimental signal and actual engineering data analysis has verified the effectiveness of the proposed method.
Aiming at the problem that early fault characteristic signal of rolling bearing is weak and affected by the environmental noise seriously, which makes the fault feature information difficult to be identified, a rolling bearing early fault diagnosis method is proposed in this study, based on ensemble local mean decomposition and maximum correlated kurtosis deconvolution. First of all, the ensemble local mean decomposition was adopted to decompose collected vibration signals, and obtains a finite number of product functions. Due to the interference of noise, it is difficult to make a correct judgment of the fault from the spectrum of the PF component. Then, the PF component that contains fault feature was processed by using maximum correlated kurtosis deconvolution to reduce the strong background noise and enhance the fault information. Finally, the fault frequency can be obtained accurately by Hilbert envelope spectrum. The bearing experimental signal and actual engineering data analysis has verified the effectiveness of the proposed method.
2017, 36(11): 1771-1777.
doi: 10.13433/j.cnki.1003-8728.2017.1122
Abstract:
Signal-to-noise rates（SNR) is very poor when incipient faults occur on rolling bearings, which makes it difficult to extract fault features and evaluate performance degradation of rolling bearings. Blind source separation（BSS) method is adapted to separate noise impulses mixed in measured signals of rolling bearings. Kurtosis values are sensitive features when measured signals are separated by BSS method. A performance evaluating model of incipient degradation of rolling bearings is built based on dynamic fuzzy neutral network（DFNN) and kurtosis values are input vectors of the evaluating model. The results of calculation show that the kurtosis is more sensitive to the performance and evaluation results of degradation performance of rolling bearings are more accurate. The method of performance degradation based on kurtosis and BSS is significant to solve engineering problems.
Signal-to-noise rates（SNR) is very poor when incipient faults occur on rolling bearings, which makes it difficult to extract fault features and evaluate performance degradation of rolling bearings. Blind source separation（BSS) method is adapted to separate noise impulses mixed in measured signals of rolling bearings. Kurtosis values are sensitive features when measured signals are separated by BSS method. A performance evaluating model of incipient degradation of rolling bearings is built based on dynamic fuzzy neutral network（DFNN) and kurtosis values are input vectors of the evaluating model. The results of calculation show that the kurtosis is more sensitive to the performance and evaluation results of degradation performance of rolling bearings are more accurate. The method of performance degradation based on kurtosis and BSS is significant to solve engineering problems.
2017, 36(11): 1778-1784.
doi: 10.13433/j.cnki.1003-8728.2017.1123
Abstract:
To increase the continuous driving mileage, a new regenerative braking control strategy of four-wheel-drive electric vehicles of different in-wheel-motors was proposed. The new control strategy based on constraint conditions for the ideal braking force distribution, ECE R13(Economic commission of europe regulations 13), the different characteristics of the in-wheel-motor and load variation in the front and rear shafts, the characteristics of the battery. Under the condition of stability braking performance, the vehicle's motor and friction braking force can be distributed reasonably, and enhance the utilization factor of in-wheel-motor to recapture more braking energy. A simulation model was built up with the software MATLAB/Simulink and CarSim, and the braking performances were simulated and compared of different braking conditions and control strategies. Simulation results show that the proposed strategy is applicable to four-wheel-drive electric vehicles of different in-wheel-motors and can receive more braking energy comparing with typical strategy, and it has a good performance of braking stability and can obviously improve the driving mileage of electric vehicles.
To increase the continuous driving mileage, a new regenerative braking control strategy of four-wheel-drive electric vehicles of different in-wheel-motors was proposed. The new control strategy based on constraint conditions for the ideal braking force distribution, ECE R13(Economic commission of europe regulations 13), the different characteristics of the in-wheel-motor and load variation in the front and rear shafts, the characteristics of the battery. Under the condition of stability braking performance, the vehicle's motor and friction braking force can be distributed reasonably, and enhance the utilization factor of in-wheel-motor to recapture more braking energy. A simulation model was built up with the software MATLAB/Simulink and CarSim, and the braking performances were simulated and compared of different braking conditions and control strategies. Simulation results show that the proposed strategy is applicable to four-wheel-drive electric vehicles of different in-wheel-motors and can receive more braking energy comparing with typical strategy, and it has a good performance of braking stability and can obviously improve the driving mileage of electric vehicles.
2017, 36(11): 1785-1790.
doi: 10.13433/j.cnki.1003-8728.2017.1124
Abstract:
For the cold-rolled strip that has various types of surface defects and complex form, there will be insensitive individual defects and low recognition rate if a single classification is used to identify classification. Therefore it probably results in data classification processing feature size is too large, the robustness and stability of the system is difficult to ensure. The method based on the the improved combination classifier is put forward. It will optimize BP neural network and probabilistic neural network, combining the improved support vector machine. Moreover, it will use complementary classification information to classify. Optimum classification system can be constituted. The experimental results show that the combination of the improved classifier makes up for the lack of a single classifier Network training. For each type of defect recognition, the accuracy is high. It can increase the overall classification generalization ability. The recognition accuracy rate is more than 95%. In short, there is efficient recognition and practical value.
For the cold-rolled strip that has various types of surface defects and complex form, there will be insensitive individual defects and low recognition rate if a single classification is used to identify classification. Therefore it probably results in data classification processing feature size is too large, the robustness and stability of the system is difficult to ensure. The method based on the the improved combination classifier is put forward. It will optimize BP neural network and probabilistic neural network, combining the improved support vector machine. Moreover, it will use complementary classification information to classify. Optimum classification system can be constituted. The experimental results show that the combination of the improved classifier makes up for the lack of a single classifier Network training. For each type of defect recognition, the accuracy is high. It can increase the overall classification generalization ability. The recognition accuracy rate is more than 95%. In short, there is efficient recognition and practical value.
2017, 36(11): 1791-1797.
doi: 10.13433/j.cnki.1003-8728.2017.1125
Abstract:
Fused silica glass is important as one of materials that compose space aircraft windows, which is placed on the surface of space aircraft, exposed in outer space and easily subjected to the impact of space debris. Inorder to bet ensurie space aircrafts and astronauts safe better, this paper simulated the impact experiment of fused silica glass in reference [1]. Through the comparison of the numerical simulation result with that of experiments, it was found that they matched well. In AUTODYN, it was obtained that fused silica glass responses to the hypervelocity impact of the ball in different diameters, shapes, incident velocities and incident angles.
Fused silica glass is important as one of materials that compose space aircraft windows, which is placed on the surface of space aircraft, exposed in outer space and easily subjected to the impact of space debris. Inorder to bet ensurie space aircrafts and astronauts safe better, this paper simulated the impact experiment of fused silica glass in reference [1]. Through the comparison of the numerical simulation result with that of experiments, it was found that they matched well. In AUTODYN, it was obtained that fused silica glass responses to the hypervelocity impact of the ball in different diameters, shapes, incident velocities and incident angles.
2017, 36(11): 1798-1804.
doi: 10.13433/j.cnki.1003-8728.2017.1126
Abstract:
This simulation study bases on one dynamic fatigue test and aims at the structural dynamic characteristics influenced by the static loads loading. The conclusions can be drawn that: 1) the influences of static loads loading prestress and the added stiffness to the inherent frequencies and acceleration responses of different orders were different, even some appeared totally opposite trend; 2) the static load-carrying area has little influence on the structural dynamic characteristics and can be neglected. At last, the real test was completed successfully by summarizing the simulation results.
This simulation study bases on one dynamic fatigue test and aims at the structural dynamic characteristics influenced by the static loads loading. The conclusions can be drawn that: 1) the influences of static loads loading prestress and the added stiffness to the inherent frequencies and acceleration responses of different orders were different, even some appeared totally opposite trend; 2) the static load-carrying area has little influence on the structural dynamic characteristics and can be neglected. At last, the real test was completed successfully by summarizing the simulation results.
