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RSS2016 Vol. 35, No. 9
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2016, 35(9): 1313-1317.
doi: 10.13433/j.cnki.1003-8728.2016.0901
PDF 1814KB
Abstract:
This paper deals with singularity analysis of 3-UPU parallel manipulator (PM) with one translation and two rotations utilizing the line geometry tool and screw theory. Firstly, the static equilibrium condition of the moving platform is derived to obtain the full 6×6 matrix, which is set of governing lines of the manipulator. Based on linear dependency of these lines, the singular configurations of the manipulator can be identified. Secondly, architecture and constraint singularities associated with gain of DOFs (parallel singularity) are defined and analyzed using linear complex approximation algorithm (LCAA), which is employed to obtain the closest linear complex, presented by its screw coordinates, to the set of governing lines. The linear complex axis and pitch provide additional information of the manipulator's self-motion when in or closed to a singular configuration. Finally, various singularities of an example 3-UPU manipulator are presented and analyzed using the proposed methods.
This paper deals with singularity analysis of 3-UPU parallel manipulator (PM) with one translation and two rotations utilizing the line geometry tool and screw theory. Firstly, the static equilibrium condition of the moving platform is derived to obtain the full 6×6 matrix, which is set of governing lines of the manipulator. Based on linear dependency of these lines, the singular configurations of the manipulator can be identified. Secondly, architecture and constraint singularities associated with gain of DOFs (parallel singularity) are defined and analyzed using linear complex approximation algorithm (LCAA), which is employed to obtain the closest linear complex, presented by its screw coordinates, to the set of governing lines. The linear complex axis and pitch provide additional information of the manipulator's self-motion when in or closed to a singular configuration. Finally, various singularities of an example 3-UPU manipulator are presented and analyzed using the proposed methods.
2016, 35(9): 1318-1322.
doi: 10.13433/j.cnki.1003-8728.2016.0902
Abstract:
Conventional guided wave based damage detection often compares newly collected response to a prerecorded baseline directly, but these baseline signals are very sensitive to varying environmental and operational conditions. To overcome those deficiency, an instantaneous baseline method is proposed. Based on the nonlinear properties of fatigue damage varies with the amplitude of excitations, the instantaneous baseline is collected when a small amplitude excitation is applied and the current signal is collected when a large amplitude excitation is applied. A scaling subtraction method is adopted to get the difference between the current signal and the instantaneous baseline. Experimental tests are performed on an intact aluminum beam and a cracked beam, two PZT transducers which used to excite and sense the wave signals are bounded on two sides of each beam. Experimental results demonstrate the applicability and effectiveness of the instantaneous baseline method.
Conventional guided wave based damage detection often compares newly collected response to a prerecorded baseline directly, but these baseline signals are very sensitive to varying environmental and operational conditions. To overcome those deficiency, an instantaneous baseline method is proposed. Based on the nonlinear properties of fatigue damage varies with the amplitude of excitations, the instantaneous baseline is collected when a small amplitude excitation is applied and the current signal is collected when a large amplitude excitation is applied. A scaling subtraction method is adopted to get the difference between the current signal and the instantaneous baseline. Experimental tests are performed on an intact aluminum beam and a cracked beam, two PZT transducers which used to excite and sense the wave signals are bounded on two sides of each beam. Experimental results demonstrate the applicability and effectiveness of the instantaneous baseline method.
2016, 35(9): 1323-1329.
doi: 10.13433/j.cnki.1003-8728.2016.0903
Abstract:
The computational model of two stage planetary gear train was established, the system's dynamical differential equations were derived, the inherent characteristics of planetary transmission were analyzed. Directing at system's distinct eigenvalues and multiple eigenvalues, the sensitivity of natural frequencies to stiffness parameters was solved by the method of matrix perturbation theory. The results of the matrix perturbation method and the results of derivation method were compared, the comparison results show that the greatest stiffness impact parameters solved by the two method are basically the same, which prove the results solved by the matrix perturbation method are correct. By changing the maximum stiffness parameters of natural frequencies sensitivity, Natural frequencies can be modified to be away from the excitation frequency, which avoids resonance.
The computational model of two stage planetary gear train was established, the system's dynamical differential equations were derived, the inherent characteristics of planetary transmission were analyzed. Directing at system's distinct eigenvalues and multiple eigenvalues, the sensitivity of natural frequencies to stiffness parameters was solved by the method of matrix perturbation theory. The results of the matrix perturbation method and the results of derivation method were compared, the comparison results show that the greatest stiffness impact parameters solved by the two method are basically the same, which prove the results solved by the matrix perturbation method are correct. By changing the maximum stiffness parameters of natural frequencies sensitivity, Natural frequencies can be modified to be away from the excitation frequency, which avoids resonance.
2016, 35(9): 1330-1336.
doi: 10.13433/j.cnki.1003-8728.2016.0904
Abstract:
The calculation of the minimum distance between geometric objects has wide applications in robotics, video games and assembly simulation. For non-convex objects with smooth curved surfaces, most of the previous studies in this area have to decompose or discretize them into sets of polyhedra as approximations of original objects. The minimum distance obtained is approximate, being not precise. To address these issues, we propose a method of geometric object representation with R-functions; with the method, a geometric object can be defined with the implicit inequality g(x)≤0 based on the object's geometrical information and its constructive solid geometry. Then, according to their implicit equality,we derive certain non-linear constrained optimization models to calculate the minimum distance between the objects. Finally, the optimization models are solved with the exiting SQP algorithm, and the minimum distance is obtained. To verify the method proposed in the paper, a system named R-MinDist is developed. The verification results show the correctness and effectiveness of the calculation results.
The calculation of the minimum distance between geometric objects has wide applications in robotics, video games and assembly simulation. For non-convex objects with smooth curved surfaces, most of the previous studies in this area have to decompose or discretize them into sets of polyhedra as approximations of original objects. The minimum distance obtained is approximate, being not precise. To address these issues, we propose a method of geometric object representation with R-functions; with the method, a geometric object can be defined with the implicit inequality g(x)≤0 based on the object's geometrical information and its constructive solid geometry. Then, according to their implicit equality,we derive certain non-linear constrained optimization models to calculate the minimum distance between the objects. Finally, the optimization models are solved with the exiting SQP algorithm, and the minimum distance is obtained. To verify the method proposed in the paper, a system named R-MinDist is developed. The verification results show the correctness and effectiveness of the calculation results.
2016, 35(9): 1337-1342.
doi: 10.13433/j.cnki.1003-8728.2016.0905
Abstract:
A two-degree-of-freedom impact oscillator is considered. Routes from doubling-periodic bifurcations and Hopf bifurcations of period-n single-impact motions to chaotic motions are illustrated by numerical simulation. Bifurcation behavior and chaotic motions are suppressed by using a small-amplitude damping control law. The control signal is obtained by varying the damping coefficient according to the velocity direction of mass M1. Choosing the variable β*=2π or 4π in Poincaré section as the desired target, the control parameter is dynamically adjusted by applying the feedback control technique. The multi-impact periodic motions,quasi-periodic motions and chaotic behavior in the system are effectively controlled to the single-impact periodic motion. Numerical results show that the control input u=γ|x1| is a small-amplitude damping signal, it is necessary to apply a small quantity of energy to the control implementation.
A two-degree-of-freedom impact oscillator is considered. Routes from doubling-periodic bifurcations and Hopf bifurcations of period-n single-impact motions to chaotic motions are illustrated by numerical simulation. Bifurcation behavior and chaotic motions are suppressed by using a small-amplitude damping control law. The control signal is obtained by varying the damping coefficient according to the velocity direction of mass M1. Choosing the variable β*=2π or 4π in Poincaré section as the desired target, the control parameter is dynamically adjusted by applying the feedback control technique. The multi-impact periodic motions,quasi-periodic motions and chaotic behavior in the system are effectively controlled to the single-impact periodic motion. Numerical results show that the control input u=γ|x1| is a small-amplitude damping signal, it is necessary to apply a small quantity of energy to the control implementation.
2016, 35(9): 1343-1348.
doi: 10.13433/j.cnki.1003-8728.2016.0906
Abstract:
The reducing-dimensional kinematics and the statics singular configuration curves of 4-SPS/SP parallel mechanism were obtained respectively through analyzing the mechanism kinematics and statics. Positive and negative 90 degree lines were found from the comparison of the two curves. The positive and negative 90 degrees were proved to be the Euler angles' singular points who caused the singularity of the Euler kinematic equation instead of the singular configuration of the parallel mechanism, which was verified by examples. The two singular configuration curves were found to be the same after non-singular ones being eliminated, which was explained with physical principle. Finally, the posture singular configuration surface of the mechanism is acquired with the statics Jacobian matrix from which a special singular configuration group is found when the moving platform of the mechanism is rotated merely around Z axis. The special group was escaped through modifying the parameters of moving platform with the improvement of mechanism movement performance according to the correlation of force screw.
The reducing-dimensional kinematics and the statics singular configuration curves of 4-SPS/SP parallel mechanism were obtained respectively through analyzing the mechanism kinematics and statics. Positive and negative 90 degree lines were found from the comparison of the two curves. The positive and negative 90 degrees were proved to be the Euler angles' singular points who caused the singularity of the Euler kinematic equation instead of the singular configuration of the parallel mechanism, which was verified by examples. The two singular configuration curves were found to be the same after non-singular ones being eliminated, which was explained with physical principle. Finally, the posture singular configuration surface of the mechanism is acquired with the statics Jacobian matrix from which a special singular configuration group is found when the moving platform of the mechanism is rotated merely around Z axis. The special group was escaped through modifying the parameters of moving platform with the improvement of mechanism movement performance according to the correlation of force screw.
2016, 35(9): 1349-1353.
doi: 10.13433/j.cnki.1003-8728.2016.0907
Abstract:
In this paper, the seven link biped robot was researched, in order to study the complicate structure, nonlinear dynamical system and dynamic gait problem that were difficult to control, the mathematical model was established and the walking stability was also simulated. Then, the model can depict dynamic walking from the under actuated phase to fully drive phase switch and the impact of collision problem in walking, and it reflected the non-smooth dynamic characteristics of dynamic walking. Through the simulation platform, the rationality of the control algorithm and the validity of the parameterized computer simulation model were verified, and each joint motion parameters were analyzed. The results reflected the walking robot model changes in the stably walk and each motion parameters in the collision in the complete cycle, and the correctness of the parametric model was verified.
In this paper, the seven link biped robot was researched, in order to study the complicate structure, nonlinear dynamical system and dynamic gait problem that were difficult to control, the mathematical model was established and the walking stability was also simulated. Then, the model can depict dynamic walking from the under actuated phase to fully drive phase switch and the impact of collision problem in walking, and it reflected the non-smooth dynamic characteristics of dynamic walking. Through the simulation platform, the rationality of the control algorithm and the validity of the parameterized computer simulation model were verified, and each joint motion parameters were analyzed. The results reflected the walking robot model changes in the stably walk and each motion parameters in the collision in the complete cycle, and the correctness of the parametric model was verified.
2016, 35(9): 1354-1358.
doi: 10.13433/j.cnki.1003-8728.2016.0908
Abstract:
In this paper, the quaternion has been adopted to express orientation since the Euler angles attitude interpolation method has its singularity and may induce the unsmooth transition of attitude. The method of quaternion spherical linear interpolation has been used to interpolate the starting point and ending point, and obtained a direct inverse kinematics for attitude using quaternion with the process of converting attitude interpolation points to position and attitude transformation matrix being erased, thus, improved the efficiency of the robot control system software running. Taking the FANUC LR Mate 100i robot as an example, the inverse solutions of both the position-attitude transformation matrix and the quaternion were compared, the two methods got the same results, and thus the feasibility of this algorithm was verified.
In this paper, the quaternion has been adopted to express orientation since the Euler angles attitude interpolation method has its singularity and may induce the unsmooth transition of attitude. The method of quaternion spherical linear interpolation has been used to interpolate the starting point and ending point, and obtained a direct inverse kinematics for attitude using quaternion with the process of converting attitude interpolation points to position and attitude transformation matrix being erased, thus, improved the efficiency of the robot control system software running. Taking the FANUC LR Mate 100i robot as an example, the inverse solutions of both the position-attitude transformation matrix and the quaternion were compared, the two methods got the same results, and thus the feasibility of this algorithm was verified.
2016, 35(9): 1359-1364.
doi: 10.13433/j.cnki.1003-8728.2016.0909
Abstract:
The orthogonal experiment was used to chose the training sample data, and the sample data was calculated based on the model via finite element method in this paper.With the sample data, a non-linear mapping function from design variables to output structure features of the laser cutting machine beam was established by using the neural networks in MATLAB. As the fuzzy multiobjective optimization methods provided the objective function, the structural optimization of laser cutting machine beam was put forward via genetic algorithms. The computer simulation results showed that the multi-objective optimization technology based on the neural networks and genetic algorithms and combining the fuzzy methods, can achieve the structural optimization of laser cutting machine beam soa s to improve the mass and the rigidity of beam.
The orthogonal experiment was used to chose the training sample data, and the sample data was calculated based on the model via finite element method in this paper.With the sample data, a non-linear mapping function from design variables to output structure features of the laser cutting machine beam was established by using the neural networks in MATLAB. As the fuzzy multiobjective optimization methods provided the objective function, the structural optimization of laser cutting machine beam was put forward via genetic algorithms. The computer simulation results showed that the multi-objective optimization technology based on the neural networks and genetic algorithms and combining the fuzzy methods, can achieve the structural optimization of laser cutting machine beam soa s to improve the mass and the rigidity of beam.
2016, 35(9): 1365-1369.
doi: 10.13433/j.cnki.1003-8728.2016.0910
Abstract:
For the majority of current researches, the tool-path planning is only treated as a problem of geometry without considering the machining force, which cannot meet the high requirement of working accuracy. Therefore, the tool-path planning model for improving the working accuracy in belt grinding based on the removal depth is developed. Firstly, from the mechanical point of view and based on the Hertzian contact theory, a model for pressure distribution in the contact area between the belt and the workpiece was presented. And based on the Preston's equation, the calculation equation for the linear removal intensity, which was the removal depth per unit contact length along the grinding path, was presented, and the model for the overall removal depth was developed. Finally, based on the removal depth model and taking the scallop-height as a constraint, the planning algorithm for the interval between the adjacent grinding paths was developed and the calculation matrix of coordinates was presented. The experimental results show that the tool-path planning model can avoid the processing defects of overlapping and unprocessed region and effectively reduce the scallop-height so as to improve the processing quality.
For the majority of current researches, the tool-path planning is only treated as a problem of geometry without considering the machining force, which cannot meet the high requirement of working accuracy. Therefore, the tool-path planning model for improving the working accuracy in belt grinding based on the removal depth is developed. Firstly, from the mechanical point of view and based on the Hertzian contact theory, a model for pressure distribution in the contact area between the belt and the workpiece was presented. And based on the Preston's equation, the calculation equation for the linear removal intensity, which was the removal depth per unit contact length along the grinding path, was presented, and the model for the overall removal depth was developed. Finally, based on the removal depth model and taking the scallop-height as a constraint, the planning algorithm for the interval between the adjacent grinding paths was developed and the calculation matrix of coordinates was presented. The experimental results show that the tool-path planning model can avoid the processing defects of overlapping and unprocessed region and effectively reduce the scallop-height so as to improve the processing quality.
2016, 35(9): 1370-1374.
doi: 10.13433/j.cnki.1003-8728.2016.0911
Abstract:
Conventional experiment-based methods to extract the gears fault feature are time-consuming and lead to higher costs. This paper presents a rapid feature extraction approach that can obtain fault feature information through simulating the actual operation of gears by virtue of Virtual Prototyping Technology. Firstly, the gear models simulating various conditions, i.e. normal, mild and moderate wear, and fracture teeth are constructed in SolidWorks. Second, the models are imported into ADAMS (Automatic Dynamic Analysis of Mechanical Systems) for dynamic simulation from which the velocity and acceleration curves are obtained. Then, by comparing the curve derived from the normal gear with the other curves, the corresponding fault information in curves was revealed. The simulation results coincide with the actual operation of gears and agree with the experimental data, thus demonstrating the feasibility and effectiveness of this method.
Conventional experiment-based methods to extract the gears fault feature are time-consuming and lead to higher costs. This paper presents a rapid feature extraction approach that can obtain fault feature information through simulating the actual operation of gears by virtue of Virtual Prototyping Technology. Firstly, the gear models simulating various conditions, i.e. normal, mild and moderate wear, and fracture teeth are constructed in SolidWorks. Second, the models are imported into ADAMS (Automatic Dynamic Analysis of Mechanical Systems) for dynamic simulation from which the velocity and acceleration curves are obtained. Then, by comparing the curve derived from the normal gear with the other curves, the corresponding fault information in curves was revealed. The simulation results coincide with the actual operation of gears and agree with the experimental data, thus demonstrating the feasibility and effectiveness of this method.
2016, 35(9): 1375-1381.
doi: 10.13433/j.cnki.1003-8728.2016.0912
Abstract:
In the process of a Quad Flat No-Lead package is soldered to Printed Circuit Board (PCB) through Surface mount technology, molten solder joint forming a liquid bridge between package and PCB. With a view to increasing the success rate of the welding, not only is a reasonable size of the pad designed on the PCB, but also the shape and stress of the solder joints have to be understood. In this paper, employing the theory of the capillary mechanics and according to the shape characteristics of the molten solder joint, a mechanical model for the solder is developed. Under the condition of a molten solder joint with a constant volume, the differential equations defining the shape of the solder are solved. According to the changes of the shape parameters and the stiffness characteristic curves, the welding interval is analyzed. By comparing the Surface Evolver (SE) simulations with those of the method employed in this paper, the validity of the method is demonstrated.
In the process of a Quad Flat No-Lead package is soldered to Printed Circuit Board (PCB) through Surface mount technology, molten solder joint forming a liquid bridge between package and PCB. With a view to increasing the success rate of the welding, not only is a reasonable size of the pad designed on the PCB, but also the shape and stress of the solder joints have to be understood. In this paper, employing the theory of the capillary mechanics and according to the shape characteristics of the molten solder joint, a mechanical model for the solder is developed. Under the condition of a molten solder joint with a constant volume, the differential equations defining the shape of the solder are solved. According to the changes of the shape parameters and the stiffness characteristic curves, the welding interval is analyzed. By comparing the Surface Evolver (SE) simulations with those of the method employed in this paper, the validity of the method is demonstrated.
2016, 35(9): 1382-1386.
doi: 10.13433/j.cnki.1003-8728.2016.0913
Abstract:
Aiming at lower accuracy of classification for signal feature extraction of rolling bearing, firstly, some time domain indexes for online simple rapid discrimination are selected. Sensitivity of time domain index of fault is analyzed based on size of bearing fatigue damage and number of local damage. Secondly, the traditional time domain indexes are fused to calculate new sensitive time domain indexes ‘TALAF’ and ‘THIKAT’. Lastly, the data set including two new indicators are trained and tested based on probabilistic neural network (PNN) which has a good real-time. The training and testing results for the traditional time domain indexes are compared with results of the data set including two new indicators. Simulation results show that TALAF and THIKAT can effectively improve the accuracy of classification index in fault diagnosis of rolling bearing.
Aiming at lower accuracy of classification for signal feature extraction of rolling bearing, firstly, some time domain indexes for online simple rapid discrimination are selected. Sensitivity of time domain index of fault is analyzed based on size of bearing fatigue damage and number of local damage. Secondly, the traditional time domain indexes are fused to calculate new sensitive time domain indexes ‘TALAF’ and ‘THIKAT’. Lastly, the data set including two new indicators are trained and tested based on probabilistic neural network (PNN) which has a good real-time. The training and testing results for the traditional time domain indexes are compared with results of the data set including two new indicators. Simulation results show that TALAF and THIKAT can effectively improve the accuracy of classification index in fault diagnosis of rolling bearing.
2016, 35(9): 1387-1390.
doi: 10.13433/j.cnki.1003-8728.2016.0914
Abstract:
The authors use major principal stress around the weld nugget of spot welding to predict fatigue life for spot welded joints in automotive body structures. The finite element model for spot welding specimens are established by using shell and CWELD elements. The stress field in the spot welding specimens is analyzed via Nastran software. Based on the computed major principal stress, the fatigue life is estimated by using the S-N curve which is from linear fitting based on the finite element analysis and fatigue test data of spot welding. The calculated fatigue life for spot welding is compared with the experimental to verify the validity of the calculation method. The used method is proven an effective in consolidating a series of fatigue data for spot welding subjected to tensile shear load.
The authors use major principal stress around the weld nugget of spot welding to predict fatigue life for spot welded joints in automotive body structures. The finite element model for spot welding specimens are established by using shell and CWELD elements. The stress field in the spot welding specimens is analyzed via Nastran software. Based on the computed major principal stress, the fatigue life is estimated by using the S-N curve which is from linear fitting based on the finite element analysis and fatigue test data of spot welding. The calculated fatigue life for spot welding is compared with the experimental to verify the validity of the calculation method. The used method is proven an effective in consolidating a series of fatigue data for spot welding subjected to tensile shear load.
2016, 35(9): 1391-1395.
doi: 10.13433/j.cnki.1003-8728.2016.0915
Abstract:
In order to study the effects of the ultrasonic assistance on the joint property welded by filling friction stir spot welding, the thermal simulation about ultrasonic assisted filling type friction stir spot welding via ABAQUS is firstly presented; and then a spot welding equipment is developed, three aluminum alloys including 5A06, 2219 and 2A14 have been welded under no ultrasound, lateral ultrasonic and longitudinal ultrasonic assistance; and the welded spots have been undergone the metallographic, tensile and shear tests. The results show that the ultrasonic can provide extra heat input for filling friction stir spot welding process; the axial ultrasonic assisted welding can enhance the uniformity and consistency in the welded area, partly eliminate the weak link in the horizontal plane, and differently improve the shear performance according to the materials;the lateral ultrasound assisted welding can make the material flow and exchange with the surrounding material in the welded the area, eliminate vertical torus weak links to a certain extent, and differently improve the tensile strength according to the materials.
In order to study the effects of the ultrasonic assistance on the joint property welded by filling friction stir spot welding, the thermal simulation about ultrasonic assisted filling type friction stir spot welding via ABAQUS is firstly presented; and then a spot welding equipment is developed, three aluminum alloys including 5A06, 2219 and 2A14 have been welded under no ultrasound, lateral ultrasonic and longitudinal ultrasonic assistance; and the welded spots have been undergone the metallographic, tensile and shear tests. The results show that the ultrasonic can provide extra heat input for filling friction stir spot welding process; the axial ultrasonic assisted welding can enhance the uniformity and consistency in the welded area, partly eliminate the weak link in the horizontal plane, and differently improve the shear performance according to the materials;the lateral ultrasound assisted welding can make the material flow and exchange with the surrounding material in the welded the area, eliminate vertical torus weak links to a certain extent, and differently improve the tensile strength according to the materials.
2016, 35(9): 1396-1401.
doi: 10.13433/j.cnki.1003-8728.2016.0916
Abstract:
Noise signals, vibration signals and crank angle signal of 152QMI single cylinder engine were collected. The main distribution ranges of the single cylinder engine noise energy were calculated through spectrum analysis and wavelet transforms, using a module of the software LMS Test. Lab. The engine noise signals whose frequency does not change with speed resonance were screened out with order analysis and wavelet analysis. Then the signals were processed with wavelet analysis in angle domain. Considering the motion characteristics of valve-train, the engine noise sources of each frequency band were identified. Research results show that the bands of 0~800 Hz, 2 000 Hz, 4 000 Hz~5 000 Hz were the main noise frequency bands of this gasoline engine; the air inflow and exhaust noise, cylinder head cover resonance and the impact of the rocker arm and valve seat were identified to be the physical cause of each frequency band.
Noise signals, vibration signals and crank angle signal of 152QMI single cylinder engine were collected. The main distribution ranges of the single cylinder engine noise energy were calculated through spectrum analysis and wavelet transforms, using a module of the software LMS Test. Lab. The engine noise signals whose frequency does not change with speed resonance were screened out with order analysis and wavelet analysis. Then the signals were processed with wavelet analysis in angle domain. Considering the motion characteristics of valve-train, the engine noise sources of each frequency band were identified. Research results show that the bands of 0~800 Hz, 2 000 Hz, 4 000 Hz~5 000 Hz were the main noise frequency bands of this gasoline engine; the air inflow and exhaust noise, cylinder head cover resonance and the impact of the rocker arm and valve seat were identified to be the physical cause of each frequency band.
2016, 35(9): 1402-1407.
doi: 10.13433/j.cnki.1003-8728.2016.0917
Abstract:
Dynamic stability in vertical plane is critical for navigation safety and efficiency of the autonomous underwater vehicle (AUV) with measurement missions. In this paper, focused on the deep-sea AUV with the mission of measuring submarine topography developed by Tianjing University, the expression of the dynamic stability criterion in vertical plane was deduced by using Hurwitz discriminance. The hydrodynamic derivatives in the dynamic stability criterion were obtained by numerical simulation of tank tests. The influences of hydrodynamic shapes, such as main body shape, layout mode of the fixed rudder, on the dynamic stability of the AUV were discussed. Results showed that AUV with X rudder and with a larger horizontal projection area had a better dynamic stability in vertical plane.
Dynamic stability in vertical plane is critical for navigation safety and efficiency of the autonomous underwater vehicle (AUV) with measurement missions. In this paper, focused on the deep-sea AUV with the mission of measuring submarine topography developed by Tianjing University, the expression of the dynamic stability criterion in vertical plane was deduced by using Hurwitz discriminance. The hydrodynamic derivatives in the dynamic stability criterion were obtained by numerical simulation of tank tests. The influences of hydrodynamic shapes, such as main body shape, layout mode of the fixed rudder, on the dynamic stability of the AUV were discussed. Results showed that AUV with X rudder and with a larger horizontal projection area had a better dynamic stability in vertical plane.
2016, 35(9): 1408-1413.
doi: 10.13433/j.cnki.1003-8728.2016.0918
Abstract:
In order to solve the problem that traditional methods have poor performance to analyze frequency modulated (FM) signal, a new method based on singular value analysis is proposed. the singular value mutation characteristics of common signal is studied based on Hankel matrix and the correspondence relationship between the relevant singular value and the specific characteristics of signal is analyzed to provide the selection basis of effective singular value for signal reconstruction. Considering the problem that singular value mutation characteristics of the FM signal is not obvious, polynomial fitting is used to describe frequency modulation regularity of the FM signal according to the Weierstrass approximation theorem.; the minimum singular value distribution difference criterion is proposed to achieve the optimal estimation of the parameters of signal instantaneous frequency function; Then, signal demodulation is accomplished with the use of the established demodulation operator and its singular value owns obvious mutation characteristics; Finally, the FM signal is restructured by demodulation signal and modulation term. Analysis of simulation signal and actual measurement of aircraft engines shows the method of polynomial fitting demodulation and singular value decomposition (SVD) is effective for FM signal noise reduction and component extraction.
In order to solve the problem that traditional methods have poor performance to analyze frequency modulated (FM) signal, a new method based on singular value analysis is proposed. the singular value mutation characteristics of common signal is studied based on Hankel matrix and the correspondence relationship between the relevant singular value and the specific characteristics of signal is analyzed to provide the selection basis of effective singular value for signal reconstruction. Considering the problem that singular value mutation characteristics of the FM signal is not obvious, polynomial fitting is used to describe frequency modulation regularity of the FM signal according to the Weierstrass approximation theorem.; the minimum singular value distribution difference criterion is proposed to achieve the optimal estimation of the parameters of signal instantaneous frequency function; Then, signal demodulation is accomplished with the use of the established demodulation operator and its singular value owns obvious mutation characteristics; Finally, the FM signal is restructured by demodulation signal and modulation term. Analysis of simulation signal and actual measurement of aircraft engines shows the method of polynomial fitting demodulation and singular value decomposition (SVD) is effective for FM signal noise reduction and component extraction.
2016, 35(9): 1414-1420.
doi: 10.13433/j.cnki.1003-8728.2016.0919
Abstract:
The stability control strategy with hierarchical structure based on sliding mode control of yawing moment is developed to improve the stability control for wheel drive electric vehicle. For the case of excessive status estimation error of the vehicle at limiting conditions, a status estimation method which is appropriate for wheel drive electric cars is designed based on the unscented kalman filter(UKF) theory. According to the vehicle status calculation estimated by UKF, the yawing moment for calculation of motion controller is designed. Allocation controller is designed when considering the practical constraints of torque distribution, and quadratic programming method is adopted to optimize the distribution of the driving/braking torque on each wheel. The simulation results show that the driving/braking force can be applied rapidly, and the yaw rate and the sideslip angle are also controlled accurately and timely using the stability controller. The vehicle driving stability is improved effectively.
The stability control strategy with hierarchical structure based on sliding mode control of yawing moment is developed to improve the stability control for wheel drive electric vehicle. For the case of excessive status estimation error of the vehicle at limiting conditions, a status estimation method which is appropriate for wheel drive electric cars is designed based on the unscented kalman filter(UKF) theory. According to the vehicle status calculation estimated by UKF, the yawing moment for calculation of motion controller is designed. Allocation controller is designed when considering the practical constraints of torque distribution, and quadratic programming method is adopted to optimize the distribution of the driving/braking torque on each wheel. The simulation results show that the driving/braking force can be applied rapidly, and the yaw rate and the sideslip angle are also controlled accurately and timely using the stability controller. The vehicle driving stability is improved effectively.
2016, 35(9): 1421-1425.
doi: 10.13433/j.cnki.1003-8728.2016.0920
Abstract:
In order to improve the robustness of double wishbone suspension, a multi-objective robust design method for double wishbone suspension system is presented based on the Kriging and particle swarm optimization. To achieve a group of hard point coordinates which had a great influence on the performance of suspension, the sensitivity analysis is carried out on the suspension hard point coordinates. These coordinates are considered as the design variables and the performance of kinematics of suspension are considered as a response, and the Kriging model for double wishbone suspension is established. The particle swarm optimization method is applied to optimize the design variables within the feasible space and consider the factors of noise that affect the performance of suspension kinematics. Furthermore, the scheme of double wishbone suspension of robust optimization design is achieved.
In order to improve the robustness of double wishbone suspension, a multi-objective robust design method for double wishbone suspension system is presented based on the Kriging and particle swarm optimization. To achieve a group of hard point coordinates which had a great influence on the performance of suspension, the sensitivity analysis is carried out on the suspension hard point coordinates. These coordinates are considered as the design variables and the performance of kinematics of suspension are considered as a response, and the Kriging model for double wishbone suspension is established. The particle swarm optimization method is applied to optimize the design variables within the feasible space and consider the factors of noise that affect the performance of suspension kinematics. Furthermore, the scheme of double wishbone suspension of robust optimization design is achieved.
2016, 35(9): 1426-1431.
doi: 10.13433/j.cnki.1003-8728.2016.0921
Abstract:
Under windows operation system, a system for rolling-stock axle structural design and strength check (RAxleDVS) is developed on NX platform to improve the flexibility of existing axle design algorithm. The system is developed by using C#, Fortran and C++ languages, and the user interface, numeric calculation part and nephogram part are written in C#, Fortran and C++ languages, respectively. The system consists of three parts: preprocessing module, solution module and post-process module. Meshing and parametric modeling are implemented by preprocessing module, force apply and solution are completed by preprocessing module, and post-process module displays the results by curves and nephograms. Accomplishing the whole process from structural design to strength check, the system is very practical for efficient and reliable design of rolling-stock axle.
Under windows operation system, a system for rolling-stock axle structural design and strength check (RAxleDVS) is developed on NX platform to improve the flexibility of existing axle design algorithm. The system is developed by using C#, Fortran and C++ languages, and the user interface, numeric calculation part and nephogram part are written in C#, Fortran and C++ languages, respectively. The system consists of three parts: preprocessing module, solution module and post-process module. Meshing and parametric modeling are implemented by preprocessing module, force apply and solution are completed by preprocessing module, and post-process module displays the results by curves and nephograms. Accomplishing the whole process from structural design to strength check, the system is very practical for efficient and reliable design of rolling-stock axle.
2016, 35(9): 1432-1438.
doi: 10.13433/j.cnki.1003-8728.2016.0922
Abstract:
The vibration of the vehicle seats is a multidimensional vibration. A new kind of multi-dimensional vibration damping vehicle seat, based on parallel mechanism, can provide a form of three degrees of freedom vibration. Then, the dynamic equation of parallel mechanism of the vibration damping vehicle seat was established, and reasonable elasticity and damping of seating systems were determined by modal analysis. Finally, combined vibration curves of vehicle vibration seat were plotted by MATLAB and the simulation of ADAMS verifies the theoretical analysis result and the vehicle seat has a good damping performance.
The vibration of the vehicle seats is a multidimensional vibration. A new kind of multi-dimensional vibration damping vehicle seat, based on parallel mechanism, can provide a form of three degrees of freedom vibration. Then, the dynamic equation of parallel mechanism of the vibration damping vehicle seat was established, and reasonable elasticity and damping of seating systems were determined by modal analysis. Finally, combined vibration curves of vehicle vibration seat were plotted by MATLAB and the simulation of ADAMS verifies the theoretical analysis result and the vehicle seat has a good damping performance.
2016, 35(9): 1439-1443.
doi: 10.13433/j.cnki.1003-8728.2016.0923
Abstract:
Based on the 1T15M-2 reversible sleeve air spring manufactured by Firestone corp., an air spring damping system with auxiliary chamber was built, which mainly consists of an air spring, an auxiliary chamber with volume of 22 L and a controllable orifice valve. Based on the acceleration response characteristics of the air spring damping system, a kind of vibration control program was designed by frequency indicator. The air spring was set with three different levels of inner pressure during the test respectively. The exciting frequency of generator was changed from 0.5 Hz to 10 Hz randomly. The acceleration signals of sprung mass were purified by butterworth low pass filter, and then the signal was processed by using the fast Fourier transform (FFT). The frequency of acceleration signal with the maximum excitation energy was picked up in every sampling period. The open area of throttle valve was switched quickly to the one of the two relative optimized acceleration response zones according to the extracted frequency indicator. The experiment results showed that the shortest transition time was about 2 seconds when the air spring damping system got to a steady response state. The acceleration amplitude of air spring damping system was almost reduced by 50% compared to the max acceleration value. The research results provide a basis for developing the electrical control unit of semi-active air suspension system with continuous-adjustable stiffness and damping.
Based on the 1T15M-2 reversible sleeve air spring manufactured by Firestone corp., an air spring damping system with auxiliary chamber was built, which mainly consists of an air spring, an auxiliary chamber with volume of 22 L and a controllable orifice valve. Based on the acceleration response characteristics of the air spring damping system, a kind of vibration control program was designed by frequency indicator. The air spring was set with three different levels of inner pressure during the test respectively. The exciting frequency of generator was changed from 0.5 Hz to 10 Hz randomly. The acceleration signals of sprung mass were purified by butterworth low pass filter, and then the signal was processed by using the fast Fourier transform (FFT). The frequency of acceleration signal with the maximum excitation energy was picked up in every sampling period. The open area of throttle valve was switched quickly to the one of the two relative optimized acceleration response zones according to the extracted frequency indicator. The experiment results showed that the shortest transition time was about 2 seconds when the air spring damping system got to a steady response state. The acceleration amplitude of air spring damping system was almost reduced by 50% compared to the max acceleration value. The research results provide a basis for developing the electrical control unit of semi-active air suspension system with continuous-adjustable stiffness and damping.
2016, 35(9): 1444-1449.
doi: 10.13433/j.cnki.1003-8728.2016.0924
Abstract:
In order to improve the fatigue resistance of 2060-T8E30 aluminum lithium alloy, the effect of the shot peening on the surface integrity and fatigue property of this alloy were investigated. The variations of the surface integrity before and after shot peening were observed and analyzed by using the surface profiler, X-ray stress instrument, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The influence of the shot peening treatments on the fatigue life was studied by using the high frequency fatigue testing machine. The internal relationship between the surface integrity and the fatigue property were discussed. The results indicated that the shot peening with rational intensity can effectively improve the fatigue life of 2060-T8E30 alloy, however the best anti-fatigue performance of the aluminum lithium alloy can not be obtained by excessively increasing or decreasing the intensity of shot peening. It should be attributed to the non-monotonic influence of the shot peening on the surface integrity of aluminum lithium alloy.
In order to improve the fatigue resistance of 2060-T8E30 aluminum lithium alloy, the effect of the shot peening on the surface integrity and fatigue property of this alloy were investigated. The variations of the surface integrity before and after shot peening were observed and analyzed by using the surface profiler, X-ray stress instrument, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The influence of the shot peening treatments on the fatigue life was studied by using the high frequency fatigue testing machine. The internal relationship between the surface integrity and the fatigue property were discussed. The results indicated that the shot peening with rational intensity can effectively improve the fatigue life of 2060-T8E30 alloy, however the best anti-fatigue performance of the aluminum lithium alloy can not be obtained by excessively increasing or decreasing the intensity of shot peening. It should be attributed to the non-monotonic influence of the shot peening on the surface integrity of aluminum lithium alloy.
2016, 35(9): 1450-1454.
doi: 10.13433/j.cnki.1003-8728.2016.0925
Abstract:
Plasma Carbonitriding in liquid is used to improve the surface properties and the abrasion performance of titanium alloy. The uniformity of flow fileds in electrolyzer is an important factor to influence the stability of Plasma Carbonitriding and the surface quality. By simulating the flow fields in electrolyzer, the effects of the direction, speed, flow of electrolyte and the area of electrode plate on the uniformity of flow fields were studied. The results showed that the direction of electrolyte has a great influence on the uniformity of flow fields. The speed and flow of electrolyte can only affect the pressure and speed in reactive tank, the area of electrode plate can affect the move of electrolyte between two plates.
Plasma Carbonitriding in liquid is used to improve the surface properties and the abrasion performance of titanium alloy. The uniformity of flow fileds in electrolyzer is an important factor to influence the stability of Plasma Carbonitriding and the surface quality. By simulating the flow fields in electrolyzer, the effects of the direction, speed, flow of electrolyte and the area of electrode plate on the uniformity of flow fields were studied. The results showed that the direction of electrolyte has a great influence on the uniformity of flow fields. The speed and flow of electrolyte can only affect the pressure and speed in reactive tank, the area of electrode plate can affect the move of electrolyte between two plates.
2016, 35(9): 1455-1460.
doi: 10.13433/j.cnki.1003-8728.2016.0926
Abstract:
A numerical model for predicting low-velocity impact induced force and damage in laminated composites is developed. The stacked continuum shell elements are employed to model the laminate plies with discrete cohesive elements being placed in pre-determined potential damage zones to model the initiation and propagation of in-plane matrix cracks and interlaminar delamination. The contact friction is introduced between two adjacent plies, and the friction shear stress at the delamination crack wake will inhibit/reduce delamination growth. For a clustered cross-ply laminate, the model accurately calculated the impact load and damage area. It is shown that matrix cracks should be included in the model in order to simulate the delamination in adjacent interface. The practical outcome of this research is a validated finite element modelling approach that can be further improved for predicting low-velocity impact damage.
A numerical model for predicting low-velocity impact induced force and damage in laminated composites is developed. The stacked continuum shell elements are employed to model the laminate plies with discrete cohesive elements being placed in pre-determined potential damage zones to model the initiation and propagation of in-plane matrix cracks and interlaminar delamination. The contact friction is introduced between two adjacent plies, and the friction shear stress at the delamination crack wake will inhibit/reduce delamination growth. For a clustered cross-ply laminate, the model accurately calculated the impact load and damage area. It is shown that matrix cracks should be included in the model in order to simulate the delamination in adjacent interface. The practical outcome of this research is a validated finite element modelling approach that can be further improved for predicting low-velocity impact damage.
2016, 35(9): 1461-1465.
doi: 10.13433/j.cnki.1003-8728.2016.0927
Abstract:
This paper investigates the effect of Micro Vortex Generators (MVGs) on the supercritical airfoil aerodynamics using the wind tunnel. The results indicated that when installed co-rotating MVGs, the drag coefficient was decreased, and the lift and stall angle of attack changed little. The drag decreased more when the size of MVGs was smaller. As the height of MVGs was below 0.4 δ(δ is the velocity boundary-layer thickness), the optimal location was about 3.5δ~4.5δ downstream from the baseline separation point.
This paper investigates the effect of Micro Vortex Generators (MVGs) on the supercritical airfoil aerodynamics using the wind tunnel. The results indicated that when installed co-rotating MVGs, the drag coefficient was decreased, and the lift and stall angle of attack changed little. The drag decreased more when the size of MVGs was smaller. As the height of MVGs was below 0.4 δ(δ is the velocity boundary-layer thickness), the optimal location was about 3.5δ~4.5δ downstream from the baseline separation point.
2016, 35(9): 1466-1469.
doi: 10.13433/j.cnki.1003-8728.2016.0928
Abstract:
The change laws in the tenon stress distribution of turbine blade versus slight change in arc radius were studied by photoelastic experiment. Firstly, the photoelastic model blanks were poured by the vacuum casting, then, models were made by the broaching machine, finally photoelastic frozen experiments were finished on the multi-function model loading equipment, the change curves in the tenon stress of turbine blade versus arc radius were obtained, the effectiveness of photoelastic experiment was verified by finite element analysis. The study shows that slight change in arc radius will cause great change in the stress distribution, and the research results will provide references and bases for improving the design of gas turbine blade and possess practical value in engineering.
The change laws in the tenon stress distribution of turbine blade versus slight change in arc radius were studied by photoelastic experiment. Firstly, the photoelastic model blanks were poured by the vacuum casting, then, models were made by the broaching machine, finally photoelastic frozen experiments were finished on the multi-function model loading equipment, the change curves in the tenon stress of turbine blade versus arc radius were obtained, the effectiveness of photoelastic experiment was verified by finite element analysis. The study shows that slight change in arc radius will cause great change in the stress distribution, and the research results will provide references and bases for improving the design of gas turbine blade and possess practical value in engineering.
2016, 35(9): 1470-1476.
doi: 10.13433/j.cnki.1003-8728.2016.0929
Abstract:
In order to obtain the effect of pump source structure on the thermal characteristics of aircraft hydraulic system, the thermal model for aircraft hydraulic systems with different pump source structure is established, and the simulation calculation and comparing analysis are carried out. Four different kinds of pump source structure in aircraft hydraulic system including constant pressure variable pump, double stage constant pressure variable pump, the work load sensitive pump and intelligent pump are analyzed. The thermal characteristics model for aircraft hydraulic system with different pump source structure is established based on the thermal characteristics simulation method of aircraft hydraulic system presented by Modelica. The simulation and comparing analysis are carried out, considering thermal characteristics of aircraft hydraulic system with the two different mission profile of air defense interception and maneuver flight. The results show that the intelligent pump significantly reduce the hydraulic system temperature, and this advantage is more obvious under the operation condition which demands the less power.
