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RSS2017 Vol. 36, No. 8
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2017, 36(8): 1149-1154.
doi: 10.13433/j.cnki.1003-8728.2017.0801
PDF 1013KB
Abstract:
A turbo generator's coil strip slot needs to be strictly tested after its milling. While the traditional manual detection can cause missing and false detection, the correct detection rate is low. This paper presents a machine vision measurement algorithm. Firstly, by using the improved Otsu threshold segmentation method based on the Laplace transformation, the algorithm obtains the precise location of edges. Secondly, subpixel edges are obtained with the moving least square (MLS). Finally, experiments on sample coil strip slot test and verify the algorithm. The experimental results indicate that the algorithm proposed in this paper can fulfill coil strip slot online detection needs and acquire a higher accuracy of repeated measurement than the traditional methods, with the repeated measurement accuracy increasing by more than 50%.
A turbo generator's coil strip slot needs to be strictly tested after its milling. While the traditional manual detection can cause missing and false detection, the correct detection rate is low. This paper presents a machine vision measurement algorithm. Firstly, by using the improved Otsu threshold segmentation method based on the Laplace transformation, the algorithm obtains the precise location of edges. Secondly, subpixel edges are obtained with the moving least square (MLS). Finally, experiments on sample coil strip slot test and verify the algorithm. The experimental results indicate that the algorithm proposed in this paper can fulfill coil strip slot online detection needs and acquire a higher accuracy of repeated measurement than the traditional methods, with the repeated measurement accuracy increasing by more than 50%.
2017, 36(8): 1155-1160.
doi: 10.13433/j.cnki.1003-8728.2017.0802
Abstract:
In order to solve the serious pressure-drop problem of a common ECF (electro-conjugate fluid) jet generator when its output flow is small and also to improve its output performance, the structural optimization of the flow channel layer of the ECF jet generator is conducted. First, based on the principles of ion drag pumping and conduction pumping, the improved ECF jet generator's design is theoretically analyzed. Then, both common and improved ECF jet generators with less defects and good appearance are fabricated successfully based on MEMS technology. Finally, the experiments for the comparative verification of common and improved ECF jet generators are performed. The experimental results show that the ECF jet generators with bypass micro-channel have a stronger output performance, which verifies the feasibility of our design.
In order to solve the serious pressure-drop problem of a common ECF (electro-conjugate fluid) jet generator when its output flow is small and also to improve its output performance, the structural optimization of the flow channel layer of the ECF jet generator is conducted. First, based on the principles of ion drag pumping and conduction pumping, the improved ECF jet generator's design is theoretically analyzed. Then, both common and improved ECF jet generators with less defects and good appearance are fabricated successfully based on MEMS technology. Finally, the experiments for the comparative verification of common and improved ECF jet generators are performed. The experimental results show that the ECF jet generators with bypass micro-channel have a stronger output performance, which verifies the feasibility of our design.
2017, 36(8): 1161-1166.
doi: 10.13433/j.cnki.1003-8728.2017.0803
Abstract:
The essence of the dynamic stiffening/softening effect of flexible beams is the influence of the axial internal force caused by the large overall motion on the transverse vibration of the beams. A new method for accounting for the effect is presented. The central idea of this method is that the dynamic stiffening/softening effect of flexible beams is accounted for in the dynamic model by taking into consideration the influence of the axial internal force on the transverse vibration of the beams. Compared with other methods for accounting for the dynamic stiffening/softening effect of flexible beams, this method is more intuitive, clearer in physical concept, and simpler in symbol operation. A flexible beam clamped to a rotating rigid hub is taken as an example to show how to use the method to account for the dynamic stiffening effect of the beam. The dynamic modeling and numerical simulation of the beam confirm the validity and simplicity of the method.
The essence of the dynamic stiffening/softening effect of flexible beams is the influence of the axial internal force caused by the large overall motion on the transverse vibration of the beams. A new method for accounting for the effect is presented. The central idea of this method is that the dynamic stiffening/softening effect of flexible beams is accounted for in the dynamic model by taking into consideration the influence of the axial internal force on the transverse vibration of the beams. Compared with other methods for accounting for the dynamic stiffening/softening effect of flexible beams, this method is more intuitive, clearer in physical concept, and simpler in symbol operation. A flexible beam clamped to a rotating rigid hub is taken as an example to show how to use the method to account for the dynamic stiffening effect of the beam. The dynamic modeling and numerical simulation of the beam confirm the validity and simplicity of the method.
2017, 36(8): 1167-1174.
doi: 10.13433/j.cnki.1003-8728.2017.0804
Abstract:
To better realize the design of a machining center, reduce its iterative time and shorten its development cycle, the FMA (Function-Motion-Action) structural decomposition was used to decompose the machining center into its corresponding meta-action step by step according to the order of the FMA, the definitions of meta-action design structural unit were given on the basis of considering the coupling among design units, and the machining center design process planning driven by FMA structural decomposition was put forward. Then the double indexes for sensitivity and variability were introduced to express the coupling degree among design units, the design structure matrix was used to quantify the coupling strength among design units, and the tearing planning based on the index order was used to tear the coupled design units, thus the initial design sequence of design units was determined, and the machining center design process planning was implemented and can accelerate the design and development of the machining center. Finally, the automatic pallet changer of a machining center was taken as an example to prove the effectiveness of this paper.
To better realize the design of a machining center, reduce its iterative time and shorten its development cycle, the FMA (Function-Motion-Action) structural decomposition was used to decompose the machining center into its corresponding meta-action step by step according to the order of the FMA, the definitions of meta-action design structural unit were given on the basis of considering the coupling among design units, and the machining center design process planning driven by FMA structural decomposition was put forward. Then the double indexes for sensitivity and variability were introduced to express the coupling degree among design units, the design structure matrix was used to quantify the coupling strength among design units, and the tearing planning based on the index order was used to tear the coupled design units, thus the initial design sequence of design units was determined, and the machining center design process planning was implemented and can accelerate the design and development of the machining center. Finally, the automatic pallet changer of a machining center was taken as an example to prove the effectiveness of this paper.
2017, 36(8): 1175-1179.
doi: 10.13433/j.cnki.1003-8728.2017.0805
Abstract:
In lower limb rehabilitative training robot, the accuracy of the motor torque identification is seriously affected by the noise of AC servo motor current signal. In order to solve the problem of nonlinear and non-stationary noise signal denoising, an improved threshold wavelet filtering method based on Empirical Mode Decomposition (EMD) is proposed in this paper. The EMD denoising layers and the thresholding function of wavelet threshold are improved. The heavy sine signal in Matlab is used to do simulation experiments. The simulation results show that the improved method can effectively remove the noise of non-linear and non-stationary signal. Compared with other filtering methods, such as EMD and wavelet transforms, the improved method can obtain the maximum SNR (signal-to-noise ratio) and the minimum RMSE (root mean square error), and have better filtering effect.
In lower limb rehabilitative training robot, the accuracy of the motor torque identification is seriously affected by the noise of AC servo motor current signal. In order to solve the problem of nonlinear and non-stationary noise signal denoising, an improved threshold wavelet filtering method based on Empirical Mode Decomposition (EMD) is proposed in this paper. The EMD denoising layers and the thresholding function of wavelet threshold are improved. The heavy sine signal in Matlab is used to do simulation experiments. The simulation results show that the improved method can effectively remove the noise of non-linear and non-stationary signal. Compared with other filtering methods, such as EMD and wavelet transforms, the improved method can obtain the maximum SNR (signal-to-noise ratio) and the minimum RMSE (root mean square error), and have better filtering effect.
2017, 36(8): 1180-1186.
doi: 10.13433/j.cnki.1003-8728.2017.0806
Abstract:
The method of changing the dip angle of orifice plate is proposed in order to study the effect of orifice plate type on the inlet vortex backflow of high speed centrifugal pump. 25 different kinds of dip angle of orifice plate are designed and the flow field of a high-speed centrifugal pump is simulated based on ANSYS-CFX software. Three dip angle schemes that can improve the hydraulic performance of high-speed centrifugal pump are selected. The overall flow field of high-speed centrifugal pump, the changing of velocity vector, pressure and internal flow field are analyzed, and the performance curves of orifice plate with different dip angles are studied. The results show that orifice plates with -20°/10° dip angle can improve the backflow whirlpool of the inlet vortex backflow and control the swirling flow inside the idler, thus the hydraulic performance of high speed pump is improved.
The method of changing the dip angle of orifice plate is proposed in order to study the effect of orifice plate type on the inlet vortex backflow of high speed centrifugal pump. 25 different kinds of dip angle of orifice plate are designed and the flow field of a high-speed centrifugal pump is simulated based on ANSYS-CFX software. Three dip angle schemes that can improve the hydraulic performance of high-speed centrifugal pump are selected. The overall flow field of high-speed centrifugal pump, the changing of velocity vector, pressure and internal flow field are analyzed, and the performance curves of orifice plate with different dip angles are studied. The results show that orifice plates with -20°/10° dip angle can improve the backflow whirlpool of the inlet vortex backflow and control the swirling flow inside the idler, thus the hydraulic performance of high speed pump is improved.
2017, 36(8): 1187-1192.
doi: 10.13433/j.cnki.1003-8728.2017.0807
Abstract:
A new type of semi-submersible drilling platform of double floating body with four columns is designed and studied to demonstrate the new heave structure whether it can reduce the heave response of the platform effectively. The 3D Wet surface model of the new structure and the semi-submersible drilling platform of double floating body with four columns are created by using workbench software, the required data are obtained through simulation analysis and used for the comprehensive evaluation. The results show that the additional heave mass of the new heave structure is approximately doubled, and the minimum value, maximum value and mean value of the heave response are all reduced when the angle of wave is 0, 45° and 90°, respectively, in which the heave maximum response is reduced obviously. The designed new semi-submersible drilling platform can effectively reduce its heave motion and can be applied in the design practice.
A new type of semi-submersible drilling platform of double floating body with four columns is designed and studied to demonstrate the new heave structure whether it can reduce the heave response of the platform effectively. The 3D Wet surface model of the new structure and the semi-submersible drilling platform of double floating body with four columns are created by using workbench software, the required data are obtained through simulation analysis and used for the comprehensive evaluation. The results show that the additional heave mass of the new heave structure is approximately doubled, and the minimum value, maximum value and mean value of the heave response are all reduced when the angle of wave is 0, 45° and 90°, respectively, in which the heave maximum response is reduced obviously. The designed new semi-submersible drilling platform can effectively reduce its heave motion and can be applied in the design practice.
2017, 36(8): 1193-1197.
doi: 10.13433/j.cnki.1003-8728.2017.0808
Abstract:
The meshing interference state influences the tooth surface abrasion between the synchronous belt and the pulley. Combining the spatial differential geometry with thegear meshing theory, the complete meshing region for double helical synchronous beltwas investigated and the model for synchronous belt and pulley in complete meshing region was established. The paper studied the influence of the spiral angle and pitch difference on the meshing interference and the meshing interference expression in different meshing location. The 3D meshing interference morphology model in complete meshing region was established. The influence of the meshing interference on the meshing interference morphology and the relationship of spiral angle and interference were obtained. The result shows that the meshing interference is the main factor influencing the meshing transmission noise and vibration and the interference in complete meshing region is related to the synchronous belt and pulley profile. The interference and meshing surface abrasion reduces with the increasing of spiral angle. It laid a solid theoretical foundation for vibration and noise reduction design of double helical synchronous belt transmission.
The meshing interference state influences the tooth surface abrasion between the synchronous belt and the pulley. Combining the spatial differential geometry with thegear meshing theory, the complete meshing region for double helical synchronous beltwas investigated and the model for synchronous belt and pulley in complete meshing region was established. The paper studied the influence of the spiral angle and pitch difference on the meshing interference and the meshing interference expression in different meshing location. The 3D meshing interference morphology model in complete meshing region was established. The influence of the meshing interference on the meshing interference morphology and the relationship of spiral angle and interference were obtained. The result shows that the meshing interference is the main factor influencing the meshing transmission noise and vibration and the interference in complete meshing region is related to the synchronous belt and pulley profile. The interference and meshing surface abrasion reduces with the increasing of spiral angle. It laid a solid theoretical foundation for vibration and noise reduction design of double helical synchronous belt transmission.
2017, 36(8): 1198-1204.
doi: 10.13433/j.cnki.1003-8728.2017.0809
Abstract:
Denavit-Hartenberg (D-H) notation method and screw theory method are usually used to set up the kinematics model of a robot, but the D-H method doesn't have definite geometric meaning and the screw theory method has the structural constrain just as low DOF and the joint axes interesting to one point. A novel method for solving the 6-DOF robot inverse kinematics using conformal geometric algebra (CGA) is proposed in this paper. First the no coordinate robot model was set up based on the rotating joint axes and rotational planes, and three kinds of robot structural design frames were defined for shoulder, elbow and wrist. Then the conformal geometric objects just as lines, planes, circles and spheres were constructed by the conformal points based on the above model and the robot configure style, and the rotation angles were computed through the constrain relationship within the geometric objects based on the simple algebra computation. Furthermore, this method uniquely determined the rotation angles by using the constraint relationship between the constructed two lines objects and the normal vector of rotation plane based on the simplified algebra computation, thus the inverse kinematics was completed. Finally, the correctness of the algorithm was verified by the UR5 collaborative articulated robot with 6-DOF, whose kinematics model was set up by the proposed algorithm.
Denavit-Hartenberg (D-H) notation method and screw theory method are usually used to set up the kinematics model of a robot, but the D-H method doesn't have definite geometric meaning and the screw theory method has the structural constrain just as low DOF and the joint axes interesting to one point. A novel method for solving the 6-DOF robot inverse kinematics using conformal geometric algebra (CGA) is proposed in this paper. First the no coordinate robot model was set up based on the rotating joint axes and rotational planes, and three kinds of robot structural design frames were defined for shoulder, elbow and wrist. Then the conformal geometric objects just as lines, planes, circles and spheres were constructed by the conformal points based on the above model and the robot configure style, and the rotation angles were computed through the constrain relationship within the geometric objects based on the simple algebra computation. Furthermore, this method uniquely determined the rotation angles by using the constraint relationship between the constructed two lines objects and the normal vector of rotation plane based on the simplified algebra computation, thus the inverse kinematics was completed. Finally, the correctness of the algorithm was verified by the UR5 collaborative articulated robot with 6-DOF, whose kinematics model was set up by the proposed algorithm.
2017, 36(8): 1205-1211.
doi: 10.13433/j.cnki.1003-8728.2017.0810
Abstract:
This paper came up with a project on the new-mode 200 kN double-motor servo direct driving turret press, in which two AC servo motors with switches in magnetic flux directly drive two nuts to move independently. The press's working features from the perspective of dynamics and kinematics is analyzed. Besides, its working content and designing focus have also been expounded under two different operation conditions-changeover and punch-press. Finally, kinetic and dynamic models are established when main driving systems of turret presses conducted technical demand of mint-marking and stamping. With a turret press under the nominal pressure of 200 kN, the design and calculation of rated speed and rated load torque of two motors of magnetic flux are also finished. With the MATLAB software, engineering verification has been completed on the design results.
This paper came up with a project on the new-mode 200 kN double-motor servo direct driving turret press, in which two AC servo motors with switches in magnetic flux directly drive two nuts to move independently. The press's working features from the perspective of dynamics and kinematics is analyzed. Besides, its working content and designing focus have also been expounded under two different operation conditions-changeover and punch-press. Finally, kinetic and dynamic models are established when main driving systems of turret presses conducted technical demand of mint-marking and stamping. With a turret press under the nominal pressure of 200 kN, the design and calculation of rated speed and rated load torque of two motors of magnetic flux are also finished. With the MATLAB software, engineering verification has been completed on the design results.
2017, 36(8): 1212-1217.
doi: 10.13433/j.cnki.1003-8728.2017.0811
Abstract:
High feed milling is a new kind of rough machining method; which is important to study the tool wear mechanism for improving tool life and processing efficiency. High feed milling experiments of TC17 titanium alloy were carried out by using TiAlN-coated carbide indexable tool. The influence of the cutting parameters on the cutting force was studied. Comparing with cutting width and spindle speed, feed per tooth and cutting depth had a more significant effect on cutting force. Moreover, the prediction model for cutting force was established via multiple linear regression. By testing the flank wear, the tool wear morphology and wear mechanisms were analyzed, in whichthe main wear morphology were flank wear and material peeling off, and the main wear mechanism was adhesive wear and diffusion wear at the same time. Within the scope of the testing parameters, the selected cutting parameters are of:fz=0.8 mm/z, ap=0.5 mm, ae=20 mm, s=600 r/min.
High feed milling is a new kind of rough machining method; which is important to study the tool wear mechanism for improving tool life and processing efficiency. High feed milling experiments of TC17 titanium alloy were carried out by using TiAlN-coated carbide indexable tool. The influence of the cutting parameters on the cutting force was studied. Comparing with cutting width and spindle speed, feed per tooth and cutting depth had a more significant effect on cutting force. Moreover, the prediction model for cutting force was established via multiple linear regression. By testing the flank wear, the tool wear morphology and wear mechanisms were analyzed, in whichthe main wear morphology were flank wear and material peeling off, and the main wear mechanism was adhesive wear and diffusion wear at the same time. Within the scope of the testing parameters, the selected cutting parameters are of:fz=0.8 mm/z, ap=0.5 mm, ae=20 mm, s=600 r/min.
2017, 36(8): 1218-1223.
doi: 10.13433/j.cnki.1003-8728.2017.0812
Abstract:
Cutting width and the material removal rate in LS-WEDM (low speed wire electrical discharge machining) is important processing indicators. In precision manufacturing, the cutting width particularly influences on the dimensional accuracy, and the material removal rate is the most important indicator influencing the processing efficiency, which has a complex and mutual restraint relationship with cutting width, a set of processing parameters is difficult to obtain smaller cutting width and higher material removal at the same time. To solve this problem, multi-objective optimization model is established by using BP (Back Propagation)neural network and particle swarm optimization (PSO), and in which Ti6Al4V alloy is took as testing object, water pressure, pulse-on time, pulse-off time, servo voltage and wire tension are took as testing parameters, the material removal rate (MRR) and the cutting width (Kerf) are took as processing indicators via Taguchi experiment. The results illustrate the average relative error of Kerf and MRR are of 5.32% and 6.14% respectively. Meanwhile the single-objective and multi-objective optimal processing parameters are obtained, and Kerf decreases of 11.10%, MRR increases of 27.37% comparing with the previous results. The present multi-objective optimization model has a significant effect for predicting and optimizing cutting width and material removal rate.
Cutting width and the material removal rate in LS-WEDM (low speed wire electrical discharge machining) is important processing indicators. In precision manufacturing, the cutting width particularly influences on the dimensional accuracy, and the material removal rate is the most important indicator influencing the processing efficiency, which has a complex and mutual restraint relationship with cutting width, a set of processing parameters is difficult to obtain smaller cutting width and higher material removal at the same time. To solve this problem, multi-objective optimization model is established by using BP (Back Propagation)neural network and particle swarm optimization (PSO), and in which Ti6Al4V alloy is took as testing object, water pressure, pulse-on time, pulse-off time, servo voltage and wire tension are took as testing parameters, the material removal rate (MRR) and the cutting width (Kerf) are took as processing indicators via Taguchi experiment. The results illustrate the average relative error of Kerf and MRR are of 5.32% and 6.14% respectively. Meanwhile the single-objective and multi-objective optimal processing parameters are obtained, and Kerf decreases of 11.10%, MRR increases of 27.37% comparing with the previous results. The present multi-objective optimization model has a significant effect for predicting and optimizing cutting width and material removal rate.
2017, 36(8): 1224-1229.
doi: 10.13433/j.cnki.1003-8728.2017.0813
Abstract:
According to the industrial manipulator inverse kinematics problems, a new method combining screw theory and algebra method is proposed. The inverse kinematics problem of robot arm is decomposed by screw theory, the Paden-kahan inverse solution is used to solve the problem. Based on the structure characteristics of industrial manipulator, the algebra method is used to further simplify the solution of the three joints of the wrist. For example, the Yaskawa motoman-MH6, a 6 degrees of freedom industrial robot, is used to verify the correctness of the inverse kinematics algorithm. The experimental results show that the method can get 8 inverse solutions correctly and effectively to reduce the intermediate calculation steps and the time and space complexity compared with the existing methods.
According to the industrial manipulator inverse kinematics problems, a new method combining screw theory and algebra method is proposed. The inverse kinematics problem of robot arm is decomposed by screw theory, the Paden-kahan inverse solution is used to solve the problem. Based on the structure characteristics of industrial manipulator, the algebra method is used to further simplify the solution of the three joints of the wrist. For example, the Yaskawa motoman-MH6, a 6 degrees of freedom industrial robot, is used to verify the correctness of the inverse kinematics algorithm. The experimental results show that the method can get 8 inverse solutions correctly and effectively to reduce the intermediate calculation steps and the time and space complexity compared with the existing methods.
2017, 36(8): 1230-1236.
doi: 10.13433/j.cnki.1003-8728.2017.0814
Abstract:
Compared with conventional linear and circular interpolation, non-uniform rational B-spline (NURBS) interpolation has a greater advantage. However, it has the intense interpolation feedrate fluctuation problem that causes the excessive machining motion capability of a machine tool. In order to improve the kinematic performance of the NURBS interpolation and modify the saltation of acceleration and the jerk of motion, this paper proposes a smooth feedrate scheduling interpolation algorithm for the sensitive points of the NURBS curves based on their geometric characteristics. Through searching for the breakpoints, which are G1 or G2 discontinuity, and the critical points that have great curvature, the feedrate profile for these points are smoothed with the S-shaped acceleration by using the finite impulse response (FIR) cascade filter. Furthermore, this paper proposes an approximation method for fixing the feedrate of breakpoints to make their acceleration and jerk satisfy the desired requirements. Thus, this method can enhance the performance of NURBS interpolation. The simulation and experimental results verify that the algorithm proposed in the paper can smooth the feedrate and has a satisfactory kinematic performance in the sensitive points.
Compared with conventional linear and circular interpolation, non-uniform rational B-spline (NURBS) interpolation has a greater advantage. However, it has the intense interpolation feedrate fluctuation problem that causes the excessive machining motion capability of a machine tool. In order to improve the kinematic performance of the NURBS interpolation and modify the saltation of acceleration and the jerk of motion, this paper proposes a smooth feedrate scheduling interpolation algorithm for the sensitive points of the NURBS curves based on their geometric characteristics. Through searching for the breakpoints, which are G1 or G2 discontinuity, and the critical points that have great curvature, the feedrate profile for these points are smoothed with the S-shaped acceleration by using the finite impulse response (FIR) cascade filter. Furthermore, this paper proposes an approximation method for fixing the feedrate of breakpoints to make their acceleration and jerk satisfy the desired requirements. Thus, this method can enhance the performance of NURBS interpolation. The simulation and experimental results verify that the algorithm proposed in the paper can smooth the feedrate and has a satisfactory kinematic performance in the sensitive points.
2017, 36(8): 1237-1243.
doi: 10.13433/j.cnki.1003-8728.2017.0815
Abstract:
In five-axis machining, the drastic motion of rotation generated in post processing for inverse solving rotating angle in the singular area will cause large non-linear machining errors and induce damages to the workpiece and machine tool as well. To solve this problem, the paper taking five-axis table-tiliting horizontal type machine tool with two rotational axes AB as studying object, the post processing algorithm was deduced based on the structure and kinematic chain of the machine tool and homogeneous coordinate transformation theory. The feasible value range of cutter axis vector is simplified as a sphere. The corresponding detection method was obtained after analyzing the generation mechanism of the singular problem with an analogy of AB axis motion to the AB step on the sphere. The avoiding strategy for the singular problem is obtained with the method of CL point and tool axis vector interpolation for disintegrating B step and tool path regeneration after projecting by local zooming the tool axis vector. The experiment results show that the present method can effectively eliminate the singularity problem without any changing of the original cutter locus and improve the processing quality. At the same time, it can be extended to the similar structure of machine tool for eliminating singular problem.
In five-axis machining, the drastic motion of rotation generated in post processing for inverse solving rotating angle in the singular area will cause large non-linear machining errors and induce damages to the workpiece and machine tool as well. To solve this problem, the paper taking five-axis table-tiliting horizontal type machine tool with two rotational axes AB as studying object, the post processing algorithm was deduced based on the structure and kinematic chain of the machine tool and homogeneous coordinate transformation theory. The feasible value range of cutter axis vector is simplified as a sphere. The corresponding detection method was obtained after analyzing the generation mechanism of the singular problem with an analogy of AB axis motion to the AB step on the sphere. The avoiding strategy for the singular problem is obtained with the method of CL point and tool axis vector interpolation for disintegrating B step and tool path regeneration after projecting by local zooming the tool axis vector. The experiment results show that the present method can effectively eliminate the singularity problem without any changing of the original cutter locus and improve the processing quality. At the same time, it can be extended to the similar structure of machine tool for eliminating singular problem.
2017, 36(8): 1244-1249.
doi: 10.13433/j.cnki.1003-8728.2017.0816
Abstract:
Based on the contact geometry characteristics of taper roller and oilstone in the superfinishing process and the grinding principle, the mathematical models including the model of number of dynamically effective cutting edges per unit area and the model of number of dynamically effective integral cutting edges are established. The models and their parameter estimation are simulated with MATLAB. The influence of key elements on dynamically effective cutting edge distribution is analysed. The changing radius of the tape roller in the superfinishing region is the principal factor that causes the dynamical variation of number of cutting edges. Because of the influence of the radial contact arc length between tape roller and oilstone, the dynamically effective cutting edge distribution per unit area and the dynamically effective integral cutting edge distribution are different. The oilstone oscillation frequency obviously influences the integral cutting edge. With the fact that the contact area between tape roller and oilstone changes with the grinding depth considered, an ideal cutting edge distribution can be obtained.
Based on the contact geometry characteristics of taper roller and oilstone in the superfinishing process and the grinding principle, the mathematical models including the model of number of dynamically effective cutting edges per unit area and the model of number of dynamically effective integral cutting edges are established. The models and their parameter estimation are simulated with MATLAB. The influence of key elements on dynamically effective cutting edge distribution is analysed. The changing radius of the tape roller in the superfinishing region is the principal factor that causes the dynamical variation of number of cutting edges. Because of the influence of the radial contact arc length between tape roller and oilstone, the dynamically effective cutting edge distribution per unit area and the dynamically effective integral cutting edge distribution are different. The oilstone oscillation frequency obviously influences the integral cutting edge. With the fact that the contact area between tape roller and oilstone changes with the grinding depth considered, an ideal cutting edge distribution can be obtained.
2017, 36(8): 1250-1254.
doi: 10.13433/j.cnki.1003-8728.2017.0817
Abstract:
Focus on damage detection of highly reflective curved surface, a new method was put forward based on integrity analysis of reflected pattern. In this method, the dome light source was decorated with specific pattern on its inner wall. The pattern is reflected by the mirror-like surface of the steel balls inside. In this way, imperfection on the reflected pattern indicates defects exist on the steel ball. The inspection system is composed of three parts:computer, camera and illuminator. In our experiment, the dome diffused light source with inner wall decorated with circular pattern was employed as the illuminator. Images of reflected pattern are captured by cameras through the observation hole on the illuminator and sent to computer for further analysis. Experimental results show that, the inspection accuracy is of 96.7% to the steel balls made by a steel ball factory with 0.8mm diameter, which meets the steel ball inspection level of G10. The new method is effective for detecting and identifying the common defects on highly reflective curved surface.
Focus on damage detection of highly reflective curved surface, a new method was put forward based on integrity analysis of reflected pattern. In this method, the dome light source was decorated with specific pattern on its inner wall. The pattern is reflected by the mirror-like surface of the steel balls inside. In this way, imperfection on the reflected pattern indicates defects exist on the steel ball. The inspection system is composed of three parts:computer, camera and illuminator. In our experiment, the dome diffused light source with inner wall decorated with circular pattern was employed as the illuminator. Images of reflected pattern are captured by cameras through the observation hole on the illuminator and sent to computer for further analysis. Experimental results show that, the inspection accuracy is of 96.7% to the steel balls made by a steel ball factory with 0.8mm diameter, which meets the steel ball inspection level of G10. The new method is effective for detecting and identifying the common defects on highly reflective curved surface.
2017, 36(8): 1255-1259.
doi: 10.13433/j.cnki.1003-8728.2017.0818
Abstract:
Titanium alloy tubes are widely used in aerospace, nuclear industry and other fields, and the uniformity of wall thickness is strictly required, accurate and efficient detection for distribution of wall thickness in each section can provide a good guidance for correcting wall thickness. Thus this paper presents a coupling method that prob and tube are immersed in water based on the ultrasonic thickness measurement principle, non-uniform distribution of wall thickness of tube and bending after rolling are analyzed in order to facilitate the probe adjustment as the premise, and design the automatic measurement device. The results show that the device can accurately detect the distribution of wall thickness of tube and the system has good stability, reliability and practicability.
Titanium alloy tubes are widely used in aerospace, nuclear industry and other fields, and the uniformity of wall thickness is strictly required, accurate and efficient detection for distribution of wall thickness in each section can provide a good guidance for correcting wall thickness. Thus this paper presents a coupling method that prob and tube are immersed in water based on the ultrasonic thickness measurement principle, non-uniform distribution of wall thickness of tube and bending after rolling are analyzed in order to facilitate the probe adjustment as the premise, and design the automatic measurement device. The results show that the device can accurately detect the distribution of wall thickness of tube and the system has good stability, reliability and practicability.
2017, 36(8): 1260-1264.
doi: 10.13433/j.cnki.1003-8728.2017.0819
Abstract:
nondestructive measurement method via virtual slice has high accuracy, low cost of measurement, fast measurement and processing of data and which can be measured inside the object contour, due to high accuracy of mass measurement. The measurement accuracy of inspection system for precision slice massis one of the key technologies, directly affect the calculation accuracy of micro element body mass. Using the error compensation and orthogonal experiment of error influencing factors the error of inspection system of precision slice mass was analyzed and the system was optimized. The present results prove that the average relative error of slice mass decreased from 19.36% to 5.52%, and all of the relative error remain stable amplitude under various layer thickness.
nondestructive measurement method via virtual slice has high accuracy, low cost of measurement, fast measurement and processing of data and which can be measured inside the object contour, due to high accuracy of mass measurement. The measurement accuracy of inspection system for precision slice massis one of the key technologies, directly affect the calculation accuracy of micro element body mass. Using the error compensation and orthogonal experiment of error influencing factors the error of inspection system of precision slice mass was analyzed and the system was optimized. The present results prove that the average relative error of slice mass decreased from 19.36% to 5.52%, and all of the relative error remain stable amplitude under various layer thickness.
2017, 36(8): 1265-1271.
doi: 10.13433/j.cnki.1003-8728.2017.0820
Abstract:
The objective of this paper is to make a reasonable estimation on the combustion noise of internal combustion engine. According to the different transmission paths, the combustion noise can be divided into direct combustion noise and indirect combustion noise. Based on the fact that two kinds of combustion noise transfer function are not changing with engine working conditions, the multiple regression model of the cylinder pressure, the torque force caused by cylinder pressure and the combustion noise is built to solve the regression coefficients at each frequency. Then both the direct and indirect combustion noise transfer coefficients can be gotten at each corresponding frequency. The transfer functions of the two components of combustion noise between 20 Hz to 20 000 Hz are calculated and analyzed. The results show that the multiple regression model fitting degree is high at each frequency, so the direct and indirect combustion noise transfer functions obtained by this method are relatively accurate. The transfer functions of both the direct and indirect combustion noise exist peak at about 2 000 Hz. For this gasoline engine,the indirect combustion noise is higher than direct combustion noise between 25 Hz to 1 250 Hz; otherwise, the direct combustion noise is higher than indirect combustion noise between 1 250 Hz to 20 000 Hz.
The objective of this paper is to make a reasonable estimation on the combustion noise of internal combustion engine. According to the different transmission paths, the combustion noise can be divided into direct combustion noise and indirect combustion noise. Based on the fact that two kinds of combustion noise transfer function are not changing with engine working conditions, the multiple regression model of the cylinder pressure, the torque force caused by cylinder pressure and the combustion noise is built to solve the regression coefficients at each frequency. Then both the direct and indirect combustion noise transfer coefficients can be gotten at each corresponding frequency. The transfer functions of the two components of combustion noise between 20 Hz to 20 000 Hz are calculated and analyzed. The results show that the multiple regression model fitting degree is high at each frequency, so the direct and indirect combustion noise transfer functions obtained by this method are relatively accurate. The transfer functions of both the direct and indirect combustion noise exist peak at about 2 000 Hz. For this gasoline engine,the indirect combustion noise is higher than direct combustion noise between 25 Hz to 1 250 Hz; otherwise, the direct combustion noise is higher than indirect combustion noise between 1 250 Hz to 20 000 Hz.
2017, 36(8): 1272-1275.
doi: 10.13433/j.cnki.1003-8728.2017.0821
Abstract:
A* algorithm is a classical heuristic search algorithm, which is widely used in the path planning of intelligent vehicles. However, the efficiency of A* algorithm is low, and also it has no real time performance. Anytime repairing A*(ARA*), an efficient and real-time path searching algorithm, can solve the shortcoming of the A* algorithm. First, ARA* algorithm searches the suboptimal path in a relaxed constraint condition. Then, within the planning time, the constraint condition is gradually enhanced, and the solution is improved by using the information that has been searched until the optimal solution is found or planning time is run out. Next, because the path planned by ARA* algorithm is flaw with much broken lines, frequently turning points, we give a smooth method based on key points to make the path smoothly. The flow of smoothing ARA*algorithm is given, meanwhile, analyzing and comparing their respective characteristics. The theoretical analysis is verified by Matlab simulation results of path planning in the grid map. The simulation results also show that the smoothing ARA* algorithm is efficient and real-time.
A* algorithm is a classical heuristic search algorithm, which is widely used in the path planning of intelligent vehicles. However, the efficiency of A* algorithm is low, and also it has no real time performance. Anytime repairing A*(ARA*), an efficient and real-time path searching algorithm, can solve the shortcoming of the A* algorithm. First, ARA* algorithm searches the suboptimal path in a relaxed constraint condition. Then, within the planning time, the constraint condition is gradually enhanced, and the solution is improved by using the information that has been searched until the optimal solution is found or planning time is run out. Next, because the path planned by ARA* algorithm is flaw with much broken lines, frequently turning points, we give a smooth method based on key points to make the path smoothly. The flow of smoothing ARA*algorithm is given, meanwhile, analyzing and comparing their respective characteristics. The theoretical analysis is verified by Matlab simulation results of path planning in the grid map. The simulation results also show that the smoothing ARA* algorithm is efficient and real-time.
2017, 36(8): 1276-1283.
doi: 10.13433/j.cnki.1003-8728.2017.0822
Abstract:
A multi-objective optimization method of holistic components sizing for battery electric vehicles based on quality function deployment and radial basis functions was presented in order to improve the comprehensive performance of vehicles. With components cost, cycle energy consumption and cycle driving range as function objectives, components parameters as design variables, the multi-objective optimization method for powertrain parameters was proposed. The coupled model of the vehicle performance requirements and technical characteristics was set up based on quality function deployment, and the weight factors of sub-objective functions were build. Vehicle performance simulation model were built based on Modelica software. The response surface model of energy consumption and driving range were built based on radial basis functions and the simulated annealing was carried out to optimize the objective function. An electric vehicle was taken as an example and the simulation results showed that 6% of the vehicle comprehensive performance has improved compared with the baseline case, which proved the effectiveness of the proposed method.
A multi-objective optimization method of holistic components sizing for battery electric vehicles based on quality function deployment and radial basis functions was presented in order to improve the comprehensive performance of vehicles. With components cost, cycle energy consumption and cycle driving range as function objectives, components parameters as design variables, the multi-objective optimization method for powertrain parameters was proposed. The coupled model of the vehicle performance requirements and technical characteristics was set up based on quality function deployment, and the weight factors of sub-objective functions were build. Vehicle performance simulation model were built based on Modelica software. The response surface model of energy consumption and driving range were built based on radial basis functions and the simulated annealing was carried out to optimize the objective function. An electric vehicle was taken as an example and the simulation results showed that 6% of the vehicle comprehensive performance has improved compared with the baseline case, which proved the effectiveness of the proposed method.
2017, 36(8): 1284-1291.
doi: 10.13433/j.cnki.1003-8728.2017.0823
Abstract:
When interfered by the lateral acceleration or uneven road surface, the vehicle was prone to rollover. In this paper, the active anti-roll bar was adopted and the vehicle dynamic model with six degrees of freedom was established for rollover prevention. In order to prevent the rollover and ensure the comfortable riding of vehicle, the linear quadratic (LQ) optimal controller was designed and the weights of the controller were optimized by particle swarm optimization algorithm. However, this approach has a drawback in the loss of maneuverability because the active anti-roll bar for rollover prevention produces instability in vehicle. To overcome this drawback of the active anti-roll bar based method, ESP is designed. Furthermore, this paper carried out a series of simulation experiments which tested the validity of the proposed control strategy in maintaining yaw and roll stability of the vehicle. Simulation results showed that the integrated control method is effective in preventing the rollover and instability of the vehicle.
When interfered by the lateral acceleration or uneven road surface, the vehicle was prone to rollover. In this paper, the active anti-roll bar was adopted and the vehicle dynamic model with six degrees of freedom was established for rollover prevention. In order to prevent the rollover and ensure the comfortable riding of vehicle, the linear quadratic (LQ) optimal controller was designed and the weights of the controller were optimized by particle swarm optimization algorithm. However, this approach has a drawback in the loss of maneuverability because the active anti-roll bar for rollover prevention produces instability in vehicle. To overcome this drawback of the active anti-roll bar based method, ESP is designed. Furthermore, this paper carried out a series of simulation experiments which tested the validity of the proposed control strategy in maintaining yaw and roll stability of the vehicle. Simulation results showed that the integrated control method is effective in preventing the rollover and instability of the vehicle.
2017, 36(8): 1292-1297.
doi: 10.13433/j.cnki.1003-8728.2017.0824
Abstract:
In this paper, the processing ability and optimal processing parameters of quenched and tempered 45 steel in magnetic abrasive finishing (MAF) are studied. In this experiment, magnetic abrasive is mixed by using SiC abrasive and cast steel particles, magnetic pole was made by using Nb2Fe14B permanent magnet, and orthogonal experiment method was used to design four levels of each five factors, the type of the grinding fluid, abrasive mesh size, percentage weight of abrasive, working gap and magnetic field strength in the MAF process were optimized by comparing the change ratio in surface roughness before and after magnetic abrasive finishing. The results show that, the optimal processing parameters in theMAF process of quenched and tempered 45 steel were of:oleic acid as grinding fluid, 360# SiC abrasive, 30% abrasive weight percentage, 1 mm working gag and 0.359~0.133 T Magnetic field intensity (permanent magnet of Ø30 mm×20 mm); the surface roughness of the workpiece decreased from 1.941 μm before MAF to 1.053 μm after MAF; the surface texture of workpiece after MAF was eliminated.
In this paper, the processing ability and optimal processing parameters of quenched and tempered 45 steel in magnetic abrasive finishing (MAF) are studied. In this experiment, magnetic abrasive is mixed by using SiC abrasive and cast steel particles, magnetic pole was made by using Nb2Fe14B permanent magnet, and orthogonal experiment method was used to design four levels of each five factors, the type of the grinding fluid, abrasive mesh size, percentage weight of abrasive, working gap and magnetic field strength in the MAF process were optimized by comparing the change ratio in surface roughness before and after magnetic abrasive finishing. The results show that, the optimal processing parameters in theMAF process of quenched and tempered 45 steel were of:oleic acid as grinding fluid, 360# SiC abrasive, 30% abrasive weight percentage, 1 mm working gag and 0.359~0.133 T Magnetic field intensity (permanent magnet of Ø30 mm×20 mm); the surface roughness of the workpiece decreased from 1.941 μm before MAF to 1.053 μm after MAF; the surface texture of workpiece after MAF was eliminated.
2017, 36(8): 1298-1302.
doi: 10.13433/j.cnki.1003-8728.2017.0825
Abstract:
The manufacturing of superalloy K465 component with special cavity via laser additive manufacturing was studied, in order to meet the design requirement of aerospace component with special cavity and ensure the mechanical properties at high temperature. The results indicated that the crack occurred during the additive manufacturing of superalloy K465 structure, because of the poor deformability and the existence of eutectic phase with low melting point, which made it to difficultly manufacture alone via laser additive manufacturing. By addingthe Stellite 6 alloy reasonably and reliefing the stress and heating the substance, the crack in the laser additive manufacturing significantly decreased.
The manufacturing of superalloy K465 component with special cavity via laser additive manufacturing was studied, in order to meet the design requirement of aerospace component with special cavity and ensure the mechanical properties at high temperature. The results indicated that the crack occurred during the additive manufacturing of superalloy K465 structure, because of the poor deformability and the existence of eutectic phase with low melting point, which made it to difficultly manufacture alone via laser additive manufacturing. By addingthe Stellite 6 alloy reasonably and reliefing the stress and heating the substance, the crack in the laser additive manufacturing significantly decreased.
2017, 36(8): 1303-1306.
doi: 10.13433/j.cnki.1003-8728.2017.0826
Abstract:
To Mix different proportions of carbon nanotube (CNT) and Kaolin evenly and sinter them at 1 500℃ fabricate CNT/Kaolin micro porous ceramic material. It is found in experiment that the micro porous ceramic material show the semi-conductive character. When the temperature reaches a threshold, the ceramic material composite would be conductive. The resistivity of ceramic material will decrease with the increasing of temperature. The characteristic of ceramic material shows a new method to manufacture high temperature sensors. In this paper, the CNT/Kaolin micro porous ceramic material is incised into thin plate specimens and installed heat resisting electrodes to manufacture high temperature sensors. It's obvious that the high temperature sensors are competent for high temperature measurement from research results. The new high temperature sensor could be applied in many high temperature fields in the feature, such as aerospace engineering and jet engine.
To Mix different proportions of carbon nanotube (CNT) and Kaolin evenly and sinter them at 1 500℃ fabricate CNT/Kaolin micro porous ceramic material. It is found in experiment that the micro porous ceramic material show the semi-conductive character. When the temperature reaches a threshold, the ceramic material composite would be conductive. The resistivity of ceramic material will decrease with the increasing of temperature. The characteristic of ceramic material shows a new method to manufacture high temperature sensors. In this paper, the CNT/Kaolin micro porous ceramic material is incised into thin plate specimens and installed heat resisting electrodes to manufacture high temperature sensors. It's obvious that the high temperature sensors are competent for high temperature measurement from research results. The new high temperature sensor could be applied in many high temperature fields in the feature, such as aerospace engineering and jet engine.
2017, 36(8): 1307-1312.
doi: 10.13433/j.cnki.1003-8728.2017.0827
Abstract:
Micro-textures were made on the rake face of the cemented carbide tools by using laser processing method. Molybdenum disulfide-based solid lubricants were embedded into the micro-grooves to form micro-texturing self-lubricated cutting tools. Dry cutting tests on 304 austenite stainless steel were carried out with these self-lubricated cutting tools and conventional cemented carbide tools respectively. The results show that the cutting force, the friction coefficient of the rake face, the cutting temperature and the wear of the rake face with the micro-texturing self-lubricated cutting tools were greatly reduced compared with those of conventional cemented carbide tools. Meanwhile, MoS2/Sb2O3 complex solid lubricants could better improve the cutting performance of micro-texturing self-lubricated cutting tools and reduce the adhesive of the swarf.
Micro-textures were made on the rake face of the cemented carbide tools by using laser processing method. Molybdenum disulfide-based solid lubricants were embedded into the micro-grooves to form micro-texturing self-lubricated cutting tools. Dry cutting tests on 304 austenite stainless steel were carried out with these self-lubricated cutting tools and conventional cemented carbide tools respectively. The results show that the cutting force, the friction coefficient of the rake face, the cutting temperature and the wear of the rake face with the micro-texturing self-lubricated cutting tools were greatly reduced compared with those of conventional cemented carbide tools. Meanwhile, MoS2/Sb2O3 complex solid lubricants could better improve the cutting performance of micro-texturing self-lubricated cutting tools and reduce the adhesive of the swarf.
