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RSS2017 Vol. 36, No. 5
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2017, 36(5): 657-664.
doi: 10.13433/j.cnki.1003-8728.2017.0501
PDF 1361KB
Abstract:
In order to study of the general method for the intergrated representation of the wind turbine blade parameters, the integrated expression of control parameters model of airfoil, chord legnth and twist angle distribution was established based on the airfoil profile integration theory and the Bezier curve fitting method. The convergence properties of fitting wind turbine blade was studied by the wind turbine aerodynamic and noise calculation model. The research shows that corresponding wind turbine of control parameters which obtained by the proposed method in the paper is in good agreement with the original one, therefore in terms of power, load and noise meet the accuracy requirements of convergence.
In order to study of the general method for the intergrated representation of the wind turbine blade parameters, the integrated expression of control parameters model of airfoil, chord legnth and twist angle distribution was established based on the airfoil profile integration theory and the Bezier curve fitting method. The convergence properties of fitting wind turbine blade was studied by the wind turbine aerodynamic and noise calculation model. The research shows that corresponding wind turbine of control parameters which obtained by the proposed method in the paper is in good agreement with the original one, therefore in terms of power, load and noise meet the accuracy requirements of convergence.
Acoustic Performance Analysis of Resonant Muffler based on Three-dimensional Time-domain Computation
2017, 36(5): 665-669.
doi: 10.13433/j.cnki.1003-8728.2017.0502
Abstract:
The resonant muffler is an important measure to improve the intake and exhaust noise. The interaction between the flow and the sound is significant. The acoustic performance of resonant muffler was calculated with the three-dimensional time domain impulse method, which is based on the computational fluid dynamics (CFD) simulation. The CFD simulation results were verified by experimental results. The acoustic performances varying with different flow rates and temperature were analyzed. The results show that the peak at the resonance frequency declines and the transmission loss at the pass frequency moves gradually close to the resonance peak along with the increasing flow rate. Besides, the frequency characteristics shift to the higher frequency and the overall noise reduction effect declines. The resonance frequency shifts to the higher frequency, and the peak decreases with the temperature increase. Both the flow and temperature has more obvious effect on low frequency transmission loss than high frequency.
The resonant muffler is an important measure to improve the intake and exhaust noise. The interaction between the flow and the sound is significant. The acoustic performance of resonant muffler was calculated with the three-dimensional time domain impulse method, which is based on the computational fluid dynamics (CFD) simulation. The CFD simulation results were verified by experimental results. The acoustic performances varying with different flow rates and temperature were analyzed. The results show that the peak at the resonance frequency declines and the transmission loss at the pass frequency moves gradually close to the resonance peak along with the increasing flow rate. Besides, the frequency characteristics shift to the higher frequency and the overall noise reduction effect declines. The resonance frequency shifts to the higher frequency, and the peak decreases with the temperature increase. Both the flow and temperature has more obvious effect on low frequency transmission loss than high frequency.
2017, 36(5): 670-678.
doi: 10.13433/j.cnki.1003-8728.2017.0503
Abstract:
We aim to develop a parallel mechanism with four degrees of freedom (DOFs) and design a 3D printing parallel robot, which shares actuated joints and can produce two or more identical products at the same time. Firstly, we analysed the kinematics, work space, Jacobian matrix and singularity of the 4-DOF parallel mechanism and then obtained the optimal design parameters of the 3D printing parallel robot. Secondly, in order to provide basis for the control of the 3D printing parallel robot, we carried out its simulation analysis by planning the motion track of its moving platform to find the real-time positional relationship between the actuated joints and the moving platform. Finally, we did experimental analysis of the designed 3D Printer's control characteristics of the parallel mechanism. The experimental results show that because of the traits of this 4-DOFs parallel mechanism, the control of the 3D printer is easier and the 3D printing parallel robot can produce objects on a sloping surface. Under certain conditions, the production has a higher surface accuracy.
We aim to develop a parallel mechanism with four degrees of freedom (DOFs) and design a 3D printing parallel robot, which shares actuated joints and can produce two or more identical products at the same time. Firstly, we analysed the kinematics, work space, Jacobian matrix and singularity of the 4-DOF parallel mechanism and then obtained the optimal design parameters of the 3D printing parallel robot. Secondly, in order to provide basis for the control of the 3D printing parallel robot, we carried out its simulation analysis by planning the motion track of its moving platform to find the real-time positional relationship between the actuated joints and the moving platform. Finally, we did experimental analysis of the designed 3D Printer's control characteristics of the parallel mechanism. The experimental results show that because of the traits of this 4-DOFs parallel mechanism, the control of the 3D printer is easier and the 3D printing parallel robot can produce objects on a sloping surface. Under certain conditions, the production has a higher surface accuracy.
2017, 36(5): 679-684.
doi: 10.13433/j.cnki.1003-8728.2017.0504
Abstract:
When solving the parallel mechanisms based on screw theory, the kinematic screws are usually expressed with six coordinates. However, for some parallel mechanisms, all the kinematic screws have the same constant zero coordinates. When solving these special parallel mechanisms, the same constant zero coordinates can be removed to reduce the coordinates. Using the reduced coordinates expressing kinematic joints to solve the parallel mechanisms is equivalent to lowering the dimensions of the problem, thus simplifying the solving procedure. The special axis configuration of revolute joints and the special moving direction of prismatic joints can make some coordinates of the kinematic screws, which denote these kinematic joints be constant zero. The kinematic joints are categorized based on different counts and order of constant zero coordinates of the kinematic screws. Single open chains are formed by these types of kinematic joints and then all 3-DOF parallel mechanisms which can be reduced to three coordinates are synthesized. The reduced coordinates which denotes the kinematic screws of the parallel mechanisms and the formula of reciprocal screws based on the reduced coordinates are presented. Some sketches of the parallel mechanisms are also proposed. Solving these parallel mechanisms based on the reduced coordinates can efficiently simplify the analyzing procedure and decrease the difficulty of solving.
When solving the parallel mechanisms based on screw theory, the kinematic screws are usually expressed with six coordinates. However, for some parallel mechanisms, all the kinematic screws have the same constant zero coordinates. When solving these special parallel mechanisms, the same constant zero coordinates can be removed to reduce the coordinates. Using the reduced coordinates expressing kinematic joints to solve the parallel mechanisms is equivalent to lowering the dimensions of the problem, thus simplifying the solving procedure. The special axis configuration of revolute joints and the special moving direction of prismatic joints can make some coordinates of the kinematic screws, which denote these kinematic joints be constant zero. The kinematic joints are categorized based on different counts and order of constant zero coordinates of the kinematic screws. Single open chains are formed by these types of kinematic joints and then all 3-DOF parallel mechanisms which can be reduced to three coordinates are synthesized. The reduced coordinates which denotes the kinematic screws of the parallel mechanisms and the formula of reciprocal screws based on the reduced coordinates are presented. Some sketches of the parallel mechanisms are also proposed. Solving these parallel mechanisms based on the reduced coordinates can efficiently simplify the analyzing procedure and decrease the difficulty of solving.
2017, 36(5): 685-689.
doi: 10.13433/j.cnki.1003-8728.2017.0505
Abstract:
The influence factors of brake drag, such as brake fluid viscosity, temperature, hydroscopicity, vapor lock are all analyzed, and the relationships between brake fluid viscosity and brake drag are concluded. Using the hydraulic simulation software MSC.EASY5, the visual braking process model of brake system is built, the braking process is simulated, and the brake drag from the angle of the piston displacement is analyzed. Using the existed bench test, the brake drag experiment is made by selecting several brake fluid that the boiling point is close to in-use oil, focused on analyzing the influence of brake viscosity on brake drag. The influence of configuration of brake fluid to brake drag is obtained.
The influence factors of brake drag, such as brake fluid viscosity, temperature, hydroscopicity, vapor lock are all analyzed, and the relationships between brake fluid viscosity and brake drag are concluded. Using the hydraulic simulation software MSC.EASY5, the visual braking process model of brake system is built, the braking process is simulated, and the brake drag from the angle of the piston displacement is analyzed. Using the existed bench test, the brake drag experiment is made by selecting several brake fluid that the boiling point is close to in-use oil, focused on analyzing the influence of brake viscosity on brake drag. The influence of configuration of brake fluid to brake drag is obtained.
2017, 36(5): 690-696.
doi: 10.13433/j.cnki.1003-8728.2017.0506
Abstract:
Aiming at the problem of large friction between the drill string and borehole, a hydraulic oscillator of axial vibration antifriction was put forward in this paper. According to the working principles and structural design of hydraulic oscillator, its equations of motion and mechanical properties were analyzed, and the vibration equation of hydraulic oscillator was established in the horizontal well. The analysis of calculation example indicated the frequency of flow area change was proportional to the flow rate, the flow area increased with the increase of the static valve hole diameter, the total axial force decreased with the increase of the static valve hole diameter, the vibration displacement decreased with the increase of static valve hole diameter and installation location and coefficient of friction. The conclusions provide important references for reducing friction, increasing speed and field applications of hydraulic oscillator.
Aiming at the problem of large friction between the drill string and borehole, a hydraulic oscillator of axial vibration antifriction was put forward in this paper. According to the working principles and structural design of hydraulic oscillator, its equations of motion and mechanical properties were analyzed, and the vibration equation of hydraulic oscillator was established in the horizontal well. The analysis of calculation example indicated the frequency of flow area change was proportional to the flow rate, the flow area increased with the increase of the static valve hole diameter, the total axial force decreased with the increase of the static valve hole diameter, the vibration displacement decreased with the increase of static valve hole diameter and installation location and coefficient of friction. The conclusions provide important references for reducing friction, increasing speed and field applications of hydraulic oscillator.
2017, 36(5): 697-703.
doi: 10.13433/j.cnki.1003-8728.2017.0507
Abstract:
To meet the demands of rehabilitation training for patients with lower limb paralysis, a lower extremity exoskeleton rehabilitation robot is designed. The composition of the designed robot is described and the kinematics analysis of the robot mechanism is conducted. Based on the joint angular displacements, a closed loop control system was designed. As a reference input information, while the subject is walking or walking up and down the stairs with the exoskeleton, the movement of the lower-extremity's joint ankles during normal human walking is acquired by the VICON motion capture system. With the commissioned system, the gait data of normal human is compared with that captured by using the VICON motion capture system and the control algorithm is verified. In addition, the range of motion with perception (RMP) is defined. Training experiments are conducted on the patient with the rehabilitation exoskeleton, which proves the effectiveness of the designed rehabilitation robot.
To meet the demands of rehabilitation training for patients with lower limb paralysis, a lower extremity exoskeleton rehabilitation robot is designed. The composition of the designed robot is described and the kinematics analysis of the robot mechanism is conducted. Based on the joint angular displacements, a closed loop control system was designed. As a reference input information, while the subject is walking or walking up and down the stairs with the exoskeleton, the movement of the lower-extremity's joint ankles during normal human walking is acquired by the VICON motion capture system. With the commissioned system, the gait data of normal human is compared with that captured by using the VICON motion capture system and the control algorithm is verified. In addition, the range of motion with perception (RMP) is defined. Training experiments are conducted on the patient with the rehabilitation exoskeleton, which proves the effectiveness of the designed rehabilitation robot.
2017, 36(5): 704-710.
doi: 10.13433/j.cnki.1003-8728.2017.0508
Abstract:
In order to reveal the effects of the fluid compressibility on the piston pump volumetric efficiency, one simulation model is established considering the trapped oil, compression volume loss resulting the fluid compressibility. Then the internal flow of the piston pump is simulated by using the FLUENT software. The simulation results show that trapped oil ratio and compression volume loss increase with the increasing of pressure and speed while the proportion of volumetric efficiency loss due to compression in total volume losses increases with speed and load raise. Finally, the comparison between the simulation and experimental results indicates that the bias is less than 2.1%, and which validates the simulation of mechanism.
In order to reveal the effects of the fluid compressibility on the piston pump volumetric efficiency, one simulation model is established considering the trapped oil, compression volume loss resulting the fluid compressibility. Then the internal flow of the piston pump is simulated by using the FLUENT software. The simulation results show that trapped oil ratio and compression volume loss increase with the increasing of pressure and speed while the proportion of volumetric efficiency loss due to compression in total volume losses increases with speed and load raise. Finally, the comparison between the simulation and experimental results indicates that the bias is less than 2.1%, and which validates the simulation of mechanism.
2017, 36(5): 711-716.
doi: 10.13433/j.cnki.1003-8728.2017.0509
Abstract:
In order to deal with the problem such as slow convergence speed etc. of basic genetic algorithm for mobile robot path planning, an improved adaptive genetic algorithm is proposed. This algorithm can adjust the crossover probability and mutation probability automatically according to the change of the fitness value in the evolutionary process, thus to avoid falling into local optimal solution and overcome the shortcoming of prematurity. Meanwhile, the grid method is used to model the robot working space. The simulation for mobile robot path planning is performed and the comparison results show that this method is valid and the quality of robot path planning can be improved effectively by using the proposed genetic algorithm.
In order to deal with the problem such as slow convergence speed etc. of basic genetic algorithm for mobile robot path planning, an improved adaptive genetic algorithm is proposed. This algorithm can adjust the crossover probability and mutation probability automatically according to the change of the fitness value in the evolutionary process, thus to avoid falling into local optimal solution and overcome the shortcoming of prematurity. Meanwhile, the grid method is used to model the robot working space. The simulation for mobile robot path planning is performed and the comparison results show that this method is valid and the quality of robot path planning can be improved effectively by using the proposed genetic algorithm.
2017, 36(5): 717-721.
doi: 10.13433/j.cnki.1003-8728.2017.0510
Abstract:
As the core component of gas turbine, the structure of combined rotor is relatively special and its force condition is complex. At present, the study on its dynamic characteristics is fundamentally based on finite element mode. Therefore, to conduct systematic study on its deep mechanism is difficult. In this paper, the Timoshenko beam lumped parameter model of combined rotor was developed. According to the discontinuity of combined rotor, which is one of the structural features, the combined rotor was central parameterized using the disk as the unit, and the bending vibration mode was modeled. Then, MATLAB was used to calculate the natural frequency and mode of vibration of the centrally parametric model, and analyze harmonic response; the results were contrastively analyzed with the results of finite element model. The results show that the natural frequency the combined rotor can be accurately reflected by the centrally parametric model and it can be used to study and analyze the dynamics of combined rotor. Compared to finite element model, the internal mechanism of the combined rotor was reflected by this centrally parametric model more accurately and the calculation time was shortened over three orders of magnitude.
As the core component of gas turbine, the structure of combined rotor is relatively special and its force condition is complex. At present, the study on its dynamic characteristics is fundamentally based on finite element mode. Therefore, to conduct systematic study on its deep mechanism is difficult. In this paper, the Timoshenko beam lumped parameter model of combined rotor was developed. According to the discontinuity of combined rotor, which is one of the structural features, the combined rotor was central parameterized using the disk as the unit, and the bending vibration mode was modeled. Then, MATLAB was used to calculate the natural frequency and mode of vibration of the centrally parametric model, and analyze harmonic response; the results were contrastively analyzed with the results of finite element model. The results show that the natural frequency the combined rotor can be accurately reflected by the centrally parametric model and it can be used to study and analyze the dynamics of combined rotor. Compared to finite element model, the internal mechanism of the combined rotor was reflected by this centrally parametric model more accurately and the calculation time was shortened over three orders of magnitude.
2017, 36(5): 722-728.
doi: 10.13433/j.cnki.1003-8728.2017.0511
Abstract:
It is important to meet drive requirements of the high precision, high speed and long-stroke for robotic driving system. An investigation on the theory of tooth profile and meshing characteristics of a new type of trochoidal roller pinion rack transmission was made in this paper. Firstly, based on forming principle of the trochoidal and meshing rule, the theoretic and practical tooth profile equations were derived, and the changes of curvature and curvature radius of the trochoidal tooth profile were analyzed. Then, according to the analysis and meshing principle, the undercut condition of practical tooth profile was concluded, and the calculating formulae of the pressure angle and contact ratio were established. Finally, an example was given, and the validity of theoretical deduction was proved by three-dimensional modeling and mesh simulation. The results show that, by choosing the trochoidal tooth and reasonable structural parameters in design, the undercutting phenomenon was solved and the contact ratio was increased.
It is important to meet drive requirements of the high precision, high speed and long-stroke for robotic driving system. An investigation on the theory of tooth profile and meshing characteristics of a new type of trochoidal roller pinion rack transmission was made in this paper. Firstly, based on forming principle of the trochoidal and meshing rule, the theoretic and practical tooth profile equations were derived, and the changes of curvature and curvature radius of the trochoidal tooth profile were analyzed. Then, according to the analysis and meshing principle, the undercut condition of practical tooth profile was concluded, and the calculating formulae of the pressure angle and contact ratio were established. Finally, an example was given, and the validity of theoretical deduction was proved by three-dimensional modeling and mesh simulation. The results show that, by choosing the trochoidal tooth and reasonable structural parameters in design, the undercutting phenomenon was solved and the contact ratio was increased.
2017, 36(5): 729-735.
doi: 10.13433/j.cnki.1003-8728.2017.0512
Abstract:
The dynamic performance of high speed motorized spindle was governed by both bearing and high frequency harmonic torque. Aiming at extracting their characteristic frequencies for proper control, the calculation formulae for steady and ripple harmonic electromagnetic torque were derived from different electromagnetic force on the basis of Fourier Transform of the waveform of the air gap magnetic field. The conclusion was that the steady harmonic torque only affected the output torque of the spindle when the ripple harmonic torque generated periodical vibration with frequency of integer multiple of six times fundamental frequency. Based on the above-mentioned results, it is easy to extinguish the vibration frequency from the bearing and that from the harmonic torque, as well as their effect on the dynamic performance of the spindle system. In addition, the different control methods can be applied as the system dynamic requirement. Finally, the conclusion has been validated via an experiment on a 170MD15Y20 high speed motorized spindle.
The dynamic performance of high speed motorized spindle was governed by both bearing and high frequency harmonic torque. Aiming at extracting their characteristic frequencies for proper control, the calculation formulae for steady and ripple harmonic electromagnetic torque were derived from different electromagnetic force on the basis of Fourier Transform of the waveform of the air gap magnetic field. The conclusion was that the steady harmonic torque only affected the output torque of the spindle when the ripple harmonic torque generated periodical vibration with frequency of integer multiple of six times fundamental frequency. Based on the above-mentioned results, it is easy to extinguish the vibration frequency from the bearing and that from the harmonic torque, as well as their effect on the dynamic performance of the spindle system. In addition, the different control methods can be applied as the system dynamic requirement. Finally, the conclusion has been validated via an experiment on a 170MD15Y20 high speed motorized spindle.
2017, 36(5): 736-740.
doi: 10.13433/j.cnki.1003-8728.2017.0513
Abstract:
For the disadvantages of contact power transmission in rotary ultrasonic vibration machining, a contactless power transmission system is proposed in this paper. A loosely coupled inductive model of contactless power transmission is established. The influence factors of energy utilization are analyzed based on theoretical analysis. Impedance matching is implemented on primary and secondary of loosely coupled transformer. The variation rules of voltage gain, primary/secondary side power and transmission efficiency with the load and design parameters of loosely coupled transformer are simulated. The relationship between the system transmission efficiency and power frequency, magnetic core spacing is studied by experiment. The feasibility of the proposed scheme is proved from experimental results.
For the disadvantages of contact power transmission in rotary ultrasonic vibration machining, a contactless power transmission system is proposed in this paper. A loosely coupled inductive model of contactless power transmission is established. The influence factors of energy utilization are analyzed based on theoretical analysis. Impedance matching is implemented on primary and secondary of loosely coupled transformer. The variation rules of voltage gain, primary/secondary side power and transmission efficiency with the load and design parameters of loosely coupled transformer are simulated. The relationship between the system transmission efficiency and power frequency, magnetic core spacing is studied by experiment. The feasibility of the proposed scheme is proved from experimental results.
2017, 36(5): 741-748.
doi: 10.13433/j.cnki.1003-8728.2017.0514
Abstract:
In order to promote the effectiveness of model segmentation, an improved method of model segmentation for 3D CAD model retrieval is proposed in this paper. Firstly, 3D CAD models are transformed to attribute adjacency labelled graphs (AALGs) based on the boundary representation (B-Rep) information such as geometry and topology attributes. Secondly, the models are decomposed into surface regions initially according to the convexity-concavity of nodes and links in AALGs. The segmented sub-graphs corresponding to the decomposed regions are merged to constructthe optimal region decomposition which makes the defined segmentation cohesion be maximal. When there are several optional combined sub-graphs, the optimal one is selected and merged according to the maximal region coupling factors. Finally, the similarity between the models is assessed by optimal-matching of decomposed regions. The experimental results show that the present method of model segmentation is effective for 3D model retrieval so as to support the effective reuse of CAD model.
In order to promote the effectiveness of model segmentation, an improved method of model segmentation for 3D CAD model retrieval is proposed in this paper. Firstly, 3D CAD models are transformed to attribute adjacency labelled graphs (AALGs) based on the boundary representation (B-Rep) information such as geometry and topology attributes. Secondly, the models are decomposed into surface regions initially according to the convexity-concavity of nodes and links in AALGs. The segmented sub-graphs corresponding to the decomposed regions are merged to constructthe optimal region decomposition which makes the defined segmentation cohesion be maximal. When there are several optional combined sub-graphs, the optimal one is selected and merged according to the maximal region coupling factors. Finally, the similarity between the models is assessed by optimal-matching of decomposed regions. The experimental results show that the present method of model segmentation is effective for 3D model retrieval so as to support the effective reuse of CAD model.
2017, 36(5): 749-754.
doi: 10.13433/j.cnki.1003-8728.2017.0515
Abstract:
This paper uses the Geobel model to study the plasma performance of the ion source of an electron cyclotron resonance ion thruster. It analyzes the relationship between mass utilization efficiency and discharge loss, electron temperature and ion source performance, influence of ion source length and grid effective transparency on the discharge loss and mass utilization efficiency. The calculation results of the ion source performance show that the mass utilization efficiency and the discharge loss are 90% and 203 W/A respectively for 20 cm ECRIT ion source with 100 mm axial length and the 80% grid effective transparency; the mass utilization efficiency and discharge loss are 86% and 300 W/A respectively for 10 cm ECRIT ion source with 40 mm axial length and the 80% grid effective transparency. The performance analysis demonstrates that the ion source performance data calculated with the Geobel model has a relative error of less than 5% compared with the data published in the open literature.
This paper uses the Geobel model to study the plasma performance of the ion source of an electron cyclotron resonance ion thruster. It analyzes the relationship between mass utilization efficiency and discharge loss, electron temperature and ion source performance, influence of ion source length and grid effective transparency on the discharge loss and mass utilization efficiency. The calculation results of the ion source performance show that the mass utilization efficiency and the discharge loss are 90% and 203 W/A respectively for 20 cm ECRIT ion source with 100 mm axial length and the 80% grid effective transparency; the mass utilization efficiency and discharge loss are 86% and 300 W/A respectively for 10 cm ECRIT ion source with 40 mm axial length and the 80% grid effective transparency. The performance analysis demonstrates that the ion source performance data calculated with the Geobel model has a relative error of less than 5% compared with the data published in the open literature.
2017, 36(5): 755-760.
doi: 10.13433/j.cnki.1003-8728.2017.0516
Abstract:
The two-phase mixing effect of spiral oval mixer was studied with the CFD technology when liquid in duct has insufficient natural flow. The mixing effects on the change of cross-sectional shape, radius of curvature and pitch of mixer were discussed and the cloud chart of the distribution phase was obtained based on the FLUENT software. The simulation results on the distribution of liquid have good adaptability with the experimental results. The data on the COV (Coefficient of variation) of liquid in relevant cross-sectional shape shows that there is a narrow area when the cross-sectional shape changes, producing a big impact to the mixing effect. There is a negative influence if the pitch of spiral oval duct increases; the mixing performance obtains its best state when the radius of curvature has a value. At the same time, simulation results show that the flow rate does not have important mixing effects on the liquid in the spiral oval duct mixer. Based on the previous research, the mixing process of different kinds of liquid in the spiral oval duct mixer was analyzed according to strain rate, the distribution of flow streamline and velocity field of a particle. The key factor of full mixing with the spiral oval duct mixer is that the distribution of particles is not in good order.
The two-phase mixing effect of spiral oval mixer was studied with the CFD technology when liquid in duct has insufficient natural flow. The mixing effects on the change of cross-sectional shape, radius of curvature and pitch of mixer were discussed and the cloud chart of the distribution phase was obtained based on the FLUENT software. The simulation results on the distribution of liquid have good adaptability with the experimental results. The data on the COV (Coefficient of variation) of liquid in relevant cross-sectional shape shows that there is a narrow area when the cross-sectional shape changes, producing a big impact to the mixing effect. There is a negative influence if the pitch of spiral oval duct increases; the mixing performance obtains its best state when the radius of curvature has a value. At the same time, simulation results show that the flow rate does not have important mixing effects on the liquid in the spiral oval duct mixer. Based on the previous research, the mixing process of different kinds of liquid in the spiral oval duct mixer was analyzed according to strain rate, the distribution of flow streamline and velocity field of a particle. The key factor of full mixing with the spiral oval duct mixer is that the distribution of particles is not in good order.
2017, 36(5): 761-766.
doi: 10.13433/j.cnki.1003-8728.2017.0517
Abstract:
The alignment torque changes significantly on different road, which leads to insufficient/overshoot return ability. Return-to-center control based on the estimation of actual aligning moment is discussed to overcome the negative effects of adhesion coefficients on return ability. The dynamic model of electric power steering system (EPS) was established. The ideal aligning moment is determined according to speed and steering wheel angle. The motor speed is estimated based on motor model with variable resistance and back-electromotive force (EMF) coefficient, and the actual aligning moment is obtained from the vehicle dynamics equations with motor current, estimated motor angular velocity and measured steering torque. With the actual and ideal aligning moment, the return-to-center compensation is implemented by a segmented PID controller. A hardware-in-loop test bench for EPS was established to validate the proposed algorithm. The results show that the vehicle equipped with the presented EPS has a good steering wheel return ability on different road surfaces.
The alignment torque changes significantly on different road, which leads to insufficient/overshoot return ability. Return-to-center control based on the estimation of actual aligning moment is discussed to overcome the negative effects of adhesion coefficients on return ability. The dynamic model of electric power steering system (EPS) was established. The ideal aligning moment is determined according to speed and steering wheel angle. The motor speed is estimated based on motor model with variable resistance and back-electromotive force (EMF) coefficient, and the actual aligning moment is obtained from the vehicle dynamics equations with motor current, estimated motor angular velocity and measured steering torque. With the actual and ideal aligning moment, the return-to-center compensation is implemented by a segmented PID controller. A hardware-in-loop test bench for EPS was established to validate the proposed algorithm. The results show that the vehicle equipped with the presented EPS has a good steering wheel return ability on different road surfaces.
2017, 36(5): 767-772.
doi: 10.13433/j.cnki.1003-8728.2017.0518
Abstract:
For the conventional vehicle steering system, the driver's mistake operations can not be corrected, and the driver needs to constantly amend direction to eliminate internal or external disturbances on vehicle during driving. An additional front wheel angle being independent to the driver's action is provided by active front steering (AFS), so lateral force of the vehicle is changed to overcome the shortages of traditional steering system. In this paper, the desired yaw rate is dynamically tracked by AFS using active disturbance rejection (ADR) technique according to the input and output of the system, and vehicle runs in yaw rate security margin. Active disturbance rejection controller (ADRC) algorithm was realized in MATLAB, and CarSim vehicle model was controlled by ADRC to carry out straight driving anti-disturbance test and double lane change test. Anti-disturbance performance, path tracking performance and robustness to parameter variations of active disturbance rejection control steering system were investigated, and compared with PID control test results. The test results show that controllability and stability of vehicle with ADRC was improved by the AFS that has strong disturbance rejection, good tracking performance and robustness, and various performances are better than PID controller.
For the conventional vehicle steering system, the driver's mistake operations can not be corrected, and the driver needs to constantly amend direction to eliminate internal or external disturbances on vehicle during driving. An additional front wheel angle being independent to the driver's action is provided by active front steering (AFS), so lateral force of the vehicle is changed to overcome the shortages of traditional steering system. In this paper, the desired yaw rate is dynamically tracked by AFS using active disturbance rejection (ADR) technique according to the input and output of the system, and vehicle runs in yaw rate security margin. Active disturbance rejection controller (ADRC) algorithm was realized in MATLAB, and CarSim vehicle model was controlled by ADRC to carry out straight driving anti-disturbance test and double lane change test. Anti-disturbance performance, path tracking performance and robustness to parameter variations of active disturbance rejection control steering system were investigated, and compared with PID control test results. The test results show that controllability and stability of vehicle with ADRC was improved by the AFS that has strong disturbance rejection, good tracking performance and robustness, and various performances are better than PID controller.
2017, 36(5): 773-778.
doi: 10.13433/j.cnki.1003-8728.2017.0519
Abstract:
Due to the presence of geometric error, installation error, the actual hard point has certain fluctuation and uncertainty which cause the suspension K&C characteristic fluctuation bigger compared with the standard K&C characteristic. In view of the uncertainty analysis problem, mathematical models for Mcpherson suspension are built by using the attitude coordinate transformation based on the rigid body kinematics theory. Sobol method is used to analyze the suspension K&C characteristics sensitivity and find out the hard point of the impact. The interval analysis method is used to optimize parameters of the suspension structure which will improve the suspension K&C characteristic robustness and reduce the suspension K&C fluctuation compared with the standard K&C characteristic. The results show that this method has high robustness and practicability.
Due to the presence of geometric error, installation error, the actual hard point has certain fluctuation and uncertainty which cause the suspension K&C characteristic fluctuation bigger compared with the standard K&C characteristic. In view of the uncertainty analysis problem, mathematical models for Mcpherson suspension are built by using the attitude coordinate transformation based on the rigid body kinematics theory. Sobol method is used to analyze the suspension K&C characteristics sensitivity and find out the hard point of the impact. The interval analysis method is used to optimize parameters of the suspension structure which will improve the suspension K&C characteristic robustness and reduce the suspension K&C fluctuation compared with the standard K&C characteristic. The results show that this method has high robustness and practicability.
2017, 36(5): 779-786.
doi: 10.13433/j.cnki.1003-8728.2017.0520
Abstract:
Compared with conventional bogies, the main technical measures, including low axel-box longitudinal stiffness, wheelsets with high tread conicity and inter-axel shear system, should be used to self-steering bogie for electric vehicles. Aiming at the best curving, the principles of matching design between axel-box longitudinal stiffness of wheelsets and its gravity stiffness proposed by Scheffel were discussed based on linear steady state analysis. The nonlinear analysis on curving simulation for single bogie and whole car were carried out. By comparing the results of wheelsets transverse displacement, yaw angle and loads of inter-axel shear system obtained from simulation and theoretical analysis, the rationality of design method of axel-box longitudinal stiffness was verified. Considering the requirements of other vehicle running stability, the specific application recommendations were given for engineering practice.
Compared with conventional bogies, the main technical measures, including low axel-box longitudinal stiffness, wheelsets with high tread conicity and inter-axel shear system, should be used to self-steering bogie for electric vehicles. Aiming at the best curving, the principles of matching design between axel-box longitudinal stiffness of wheelsets and its gravity stiffness proposed by Scheffel were discussed based on linear steady state analysis. The nonlinear analysis on curving simulation for single bogie and whole car were carried out. By comparing the results of wheelsets transverse displacement, yaw angle and loads of inter-axel shear system obtained from simulation and theoretical analysis, the rationality of design method of axel-box longitudinal stiffness was verified. Considering the requirements of other vehicle running stability, the specific application recommendations were given for engineering practice.
2017, 36(5): 787-792.
doi: 10.13433/j.cnki.1003-8728.2017.0521
Abstract:
In order to achieve energy recovery and utilization of an engine's cooling system and improve its internal combustion engine efficiency, we develop an optimization design method for the energy recovery of the thermoelectric generator of the internal combustion engine's cooling system by using the numerical method, the finite volume method and a three-dimensional model. Its validation is done by experiments. The results on the cooling system temperature distribution show that the difference between the simulation and experimental results is less than 3.5%, while the residential pressure difference of energy recovery pipe is 1.5%. This indicates that the simulation method for cooling system and the energy recovery pipe analysis based on numerical simulation are feasible. More experimental results indicate that it is feasible to recover and recycle the energy from the internal combustion engine's cooling system based on commercial thermoelectric chips but the thermoelectric generator is not economical because the current generator has only a small temperature difference between its hot and cold ends.
In order to achieve energy recovery and utilization of an engine's cooling system and improve its internal combustion engine efficiency, we develop an optimization design method for the energy recovery of the thermoelectric generator of the internal combustion engine's cooling system by using the numerical method, the finite volume method and a three-dimensional model. Its validation is done by experiments. The results on the cooling system temperature distribution show that the difference between the simulation and experimental results is less than 3.5%, while the residential pressure difference of energy recovery pipe is 1.5%. This indicates that the simulation method for cooling system and the energy recovery pipe analysis based on numerical simulation are feasible. More experimental results indicate that it is feasible to recover and recycle the energy from the internal combustion engine's cooling system based on commercial thermoelectric chips but the thermoelectric generator is not economical because the current generator has only a small temperature difference between its hot and cold ends.
2017, 36(5): 793-797.
doi: 10.13433/j.cnki.1003-8728.2017.0522
Abstract:
In the microscopic environment, analysis and research on the size effect of indentation can provide a powerful theoretical basis and technical guidance for exploring the characteristics of thin film and micro mechanical materials. Using two kinds of test methods, the nano-indentation tests are performed on the 3J21 alloy foil of 100 μm thickness, from which the mechanic parameters of the 3J21 alloy foil are obtained. The experimental data indicates that there is significant indentation size effect in the micro-nano scale. Three kinds of models are used to describe and analyze the indentation size effect of the 3J21 alloy foil. The results show that these three models can effectively describe the indentation size effect and the latter two models can accurately predict the true hardness value of the 3J21 alloy foil.
In the microscopic environment, analysis and research on the size effect of indentation can provide a powerful theoretical basis and technical guidance for exploring the characteristics of thin film and micro mechanical materials. Using two kinds of test methods, the nano-indentation tests are performed on the 3J21 alloy foil of 100 μm thickness, from which the mechanic parameters of the 3J21 alloy foil are obtained. The experimental data indicates that there is significant indentation size effect in the micro-nano scale. Three kinds of models are used to describe and analyze the indentation size effect of the 3J21 alloy foil. The results show that these three models can effectively describe the indentation size effect and the latter two models can accurately predict the true hardness value of the 3J21 alloy foil.
2017, 36(5): 798-804.
doi: 10.13433/j.cnki.1003-8728.2017.0523
Abstract:
In order to study the mechanical properties of a commercial aluminum foam and simulate its filling structure. The material parameters of aluminum foam and alloys are identified based on the material quasi-static compression experiments and material constitutive model. The identified results are validated by using the experiment data. Then, as the composite structure, the parameter analysis of the foam-filled tube is conducted, such as thickness, cone angle and foam density. The finite element code LS-DYNA is used to study effect of these factors on the energy absorbed prosperity of foam-filled taper thin-walled tube via virtual test. The results show that the identification method can obtain the accurate material parameters, aluminum-foam density and tube thickness are the main factors on the average force and easier to control the energy absorption than that via cone angle. Through the computer simulation, the tube thickness is the main factor for influencing the initial peak force. The filling of aluminum foam can not only improve the thin-walled tube's deformation mode, increase the specific energy absorption, but also has few influence on the initial peak force. The present results can provide the reference for the structural design of energy absorber such as automobile energy absorption box.
In order to study the mechanical properties of a commercial aluminum foam and simulate its filling structure. The material parameters of aluminum foam and alloys are identified based on the material quasi-static compression experiments and material constitutive model. The identified results are validated by using the experiment data. Then, as the composite structure, the parameter analysis of the foam-filled tube is conducted, such as thickness, cone angle and foam density. The finite element code LS-DYNA is used to study effect of these factors on the energy absorbed prosperity of foam-filled taper thin-walled tube via virtual test. The results show that the identification method can obtain the accurate material parameters, aluminum-foam density and tube thickness are the main factors on the average force and easier to control the energy absorption than that via cone angle. Through the computer simulation, the tube thickness is the main factor for influencing the initial peak force. The filling of aluminum foam can not only improve the thin-walled tube's deformation mode, increase the specific energy absorption, but also has few influence on the initial peak force. The present results can provide the reference for the structural design of energy absorber such as automobile energy absorption box.
2017, 36(5): 805-810.
doi: 10.13433/j.cnki.1003-8728.2017.0524
Abstract:
In order to enhance the dynamic characteristics of the rudder loop system of an electro-mechanical actuator with the planetary roller screw mechanism, this paper develops a closed-loop coupling model that combines the one-dimensional servo control model with the three-dimensional dynamic model. Comprehensive simulations are performed with the real-time interaction of information on variables, and the influence of nonlinear factors of a planetary roller screw such as frictional moment, stiffness and clearance on the dynamic characteristics of the rudder loop system is analyzed. The results indicate that the frictional moment is the main factor that influences the steady-state value of the system's step response. Stiffness and clearance can cause the oscillation of the system when its step signal is input signal, and the tracking precision and response speed of the system decreases when the frictional moment is taken into account. Furthermore, increasing stiffness can avoid the oscillation of the system, thus improving its stability. The fluctuation amplitude of the step response can be decreased and the time for regulating the system can also be increased by decreasing the clearance of the planetary roller screw.
In order to enhance the dynamic characteristics of the rudder loop system of an electro-mechanical actuator with the planetary roller screw mechanism, this paper develops a closed-loop coupling model that combines the one-dimensional servo control model with the three-dimensional dynamic model. Comprehensive simulations are performed with the real-time interaction of information on variables, and the influence of nonlinear factors of a planetary roller screw such as frictional moment, stiffness and clearance on the dynamic characteristics of the rudder loop system is analyzed. The results indicate that the frictional moment is the main factor that influences the steady-state value of the system's step response. Stiffness and clearance can cause the oscillation of the system when its step signal is input signal, and the tracking precision and response speed of the system decreases when the frictional moment is taken into account. Furthermore, increasing stiffness can avoid the oscillation of the system, thus improving its stability. The fluctuation amplitude of the step response can be decreased and the time for regulating the system can also be increased by decreasing the clearance of the planetary roller screw.
2017, 36(5): 811-815.
doi: 10.13433/j.cnki.1003-8728.2017.0525
Abstract:
Nose landing gear shimmy model because of week fuselage local stiffness is established. The model can analyze the contribution of fuselage local stiffness on the shimmy critical damping coefficient and dynamic swinging response. The results show that shimmy critical damping coefficient can increase to 2 times because of contribution of fuselage local stiffness. The swinging angle response of a landing gear is convergent, but the response of swinging angle considering fuselage local stiffness is divergent. The analysis results accord to the test.
Nose landing gear shimmy model because of week fuselage local stiffness is established. The model can analyze the contribution of fuselage local stiffness on the shimmy critical damping coefficient and dynamic swinging response. The results show that shimmy critical damping coefficient can increase to 2 times because of contribution of fuselage local stiffness. The swinging angle response of a landing gear is convergent, but the response of swinging angle considering fuselage local stiffness is divergent. The analysis results accord to the test.
2017, 36(5): 816-820.
doi: 10.13433/j.cnki.1003-8728.2017.0526
Abstract:
The sensitivity analysis plays a critical role in super large-scale optimization problem. The analytic method for sensitivity analysis has been investigated deeply,and the analytical expression of differential stiffness matrix is derived for shell elements and the displacement constraints sensitivity is obtained by using virtual displacement method. The method was programmed based on the HAJIF system with FORTRAN language. Validation examples showed that the proposed method has a high reliability in solving super large-scale optimization problem, and the efficiency of the present method is almost 70 times of that of the differential method.
The sensitivity analysis plays a critical role in super large-scale optimization problem. The analytic method for sensitivity analysis has been investigated deeply,and the analytical expression of differential stiffness matrix is derived for shell elements and the displacement constraints sensitivity is obtained by using virtual displacement method. The method was programmed based on the HAJIF system with FORTRAN language. Validation examples showed that the proposed method has a high reliability in solving super large-scale optimization problem, and the efficiency of the present method is almost 70 times of that of the differential method.
