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RSS2013 Vol. 32, No. 6
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2013, 32(6): 781-784.
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Abstract:
The dynamic performances, such as natural frequencies and modes, of track structure for low-speed ma-glev train were obtained by finite element method.The sensitive vibration frequency range of track subject to ran-dom vibration excitation was analyzed and the structure was optimized on the basis of the numerical calculation re-sults.The results showed that the finite element analysis of track not only had the inspection and checking role the-orectically to provide data for test running of maglev train, but also provided the basis for further design and im-provement for track performance.
The dynamic performances, such as natural frequencies and modes, of track structure for low-speed ma-glev train were obtained by finite element method.The sensitive vibration frequency range of track subject to ran-dom vibration excitation was analyzed and the structure was optimized on the basis of the numerical calculation re-sults.The results showed that the finite element analysis of track not only had the inspection and checking role the-orectically to provide data for test running of maglev train, but also provided the basis for further design and im-provement for track performance.
2013, 32(6): 785-790.
Abstract:
To enhance the tracking control accuracy and disturbance-resistance of a multi-steering vehicle, the pa-per proposes a method for robust control of multi-steering vehicle with no static error tracking based on the Internal Model Principle (IMP).The linear model of the multi-steering vehicle with two degrees of freedom is established.The tracking controller is designed and solved with the pole assignment method.The tracking control system of a certain three-wheel steering vehicle is designed, and its simulation is carried out; the simulation results are com-pared with those of the PID control method.With some disturbance, the internal model controller tracks the contin-uous step and the ramp signal respectively.The tracking results show that the static errors for both are zero and that their settling time is within 0.09 s.With the PID control method, the maximum static error is 0.2 �s and the max-imum settling time is 0.6 s.The tracking results also indicate that the robust control method can make yaw rate track its reference input with zero static error and has certain robustness compared with the PID control method.Meanwhile, the response of sideslip angle is improved.
To enhance the tracking control accuracy and disturbance-resistance of a multi-steering vehicle, the pa-per proposes a method for robust control of multi-steering vehicle with no static error tracking based on the Internal Model Principle (IMP).The linear model of the multi-steering vehicle with two degrees of freedom is established.The tracking controller is designed and solved with the pole assignment method.The tracking control system of a certain three-wheel steering vehicle is designed, and its simulation is carried out; the simulation results are com-pared with those of the PID control method.With some disturbance, the internal model controller tracks the contin-uous step and the ramp signal respectively.The tracking results show that the static errors for both are zero and that their settling time is within 0.09 s.With the PID control method, the maximum static error is 0.2 �s and the max-imum settling time is 0.6 s.The tracking results also indicate that the robust control method can make yaw rate track its reference input with zero static error and has certain robustness compared with the PID control method.Meanwhile, the response of sideslip angle is improved.
2013, 32(6): 791-795.
Abstract:
For structural element under multi-level loads, the fatigue reliability has been analyzed based on the re-sidual strength model.Firstly, residual strength formula considered multi-level loads is derived by principle of equal strength degradation, and from this formula using moments method the mean and variance of residual strength with load cycles can be obtained, when takes into account the randomness of the number of equivalent role.Final-ly, using the numerical characteristics of residual strength, based on the assumptions of normal distribution, fatigue reliability can be calculated by FOSM method.The feasibility and effectiveness of method is investigated.through an example.
For structural element under multi-level loads, the fatigue reliability has been analyzed based on the re-sidual strength model.Firstly, residual strength formula considered multi-level loads is derived by principle of equal strength degradation, and from this formula using moments method the mean and variance of residual strength with load cycles can be obtained, when takes into account the randomness of the number of equivalent role.Final-ly, using the numerical characteristics of residual strength, based on the assumptions of normal distribution, fatigue reliability can be calculated by FOSM method.The feasibility and effectiveness of method is investigated.through an example.
2013, 32(6): 796-800.
Abstract:
In this paper, the insufficiency of serial robot structure was introduced.The characteristics, application and basic components of parallel robots were summarized.The parallel robot as variable length shaft driving meth-od, swinging rod driving method, soft cable driving method and other driving method were classified.Then the difference in each structure is analyzed.By the contrast of several driving method, such as hydraulic driving sys-tem, servo driving system applied on parallel robot, it is concluded that at this stage the AC servo motor driving system has more competitive strength than any other systems.The rationality of the transmission mechanism applied in parallel robot was discussed.Then this article looks into the further of the development of parallel robot driving method.
In this paper, the insufficiency of serial robot structure was introduced.The characteristics, application and basic components of parallel robots were summarized.The parallel robot as variable length shaft driving meth-od, swinging rod driving method, soft cable driving method and other driving method were classified.Then the difference in each structure is analyzed.By the contrast of several driving method, such as hydraulic driving sys-tem, servo driving system applied on parallel robot, it is concluded that at this stage the AC servo motor driving system has more competitive strength than any other systems.The rationality of the transmission mechanism applied in parallel robot was discussed.Then this article looks into the further of the development of parallel robot driving method.
2013, 32(6): 801-804.
Abstract:
In order to study the spindle movement of precision centrifuge to improve its accuracy, this paper ana-lyzed the fixed gyroscopic movement of precision centrifuge's main spindle based on the rigid rotor dynamics, and built up the vector acceleration model at the test point of the load pan with the consideration of spindle revolution; then the vector acceleration model and vector acceleration error model for two different dynamic radius measurement ways i.e.on/off board measurements were put forward; lastly the acceleration error is evaluated considering the revolutionary effect with the given parameters.The results show if the centripetal acceleration is 100g, the absolute acceleration error would be 5.89 m/s 2 and the relative error is 6‰; in this way with the relative accuracy require-ment for 10－5～10 －6, the revolution of the spindle fixed gyroscopic movement is important.
In order to study the spindle movement of precision centrifuge to improve its accuracy, this paper ana-lyzed the fixed gyroscopic movement of precision centrifuge's main spindle based on the rigid rotor dynamics, and built up the vector acceleration model at the test point of the load pan with the consideration of spindle revolution; then the vector acceleration model and vector acceleration error model for two different dynamic radius measurement ways i.e.on/off board measurements were put forward; lastly the acceleration error is evaluated considering the revolutionary effect with the given parameters.The results show if the centripetal acceleration is 100g, the absolute acceleration error would be 5.89 m/s 2 and the relative error is 6‰; in this way with the relative accuracy require-ment for 10－5～10 －6, the revolution of the spindle fixed gyroscopic movement is important.
2013, 32(6): 805-808.
Abstract:
Taking the stages of the motion of the automatic system of an antiaircraft gun into consideration, we es-tablish its fault diagnosis fusion model based on the D-S evidence theory.First, we extract feature vectors from the test data of multi-sensors.Then, we propose the revised Minkowski distance to create evidences.Finally, we fuse them according to the Dempster combination rule.The diagnosis results verify the feasibility and effectiveness of our fault diagnosis method.
Taking the stages of the motion of the automatic system of an antiaircraft gun into consideration, we es-tablish its fault diagnosis fusion model based on the D-S evidence theory.First, we extract feature vectors from the test data of multi-sensors.Then, we propose the revised Minkowski distance to create evidences.Finally, we fuse them according to the Dempster combination rule.The diagnosis results verify the feasibility and effectiveness of our fault diagnosis method.
2013, 32(6): 809-813.
Abstract:
Aiming at the problem that how to select the wavelet basis used in denoising the steering wheel angle ex-perimental data, a selection method of wavelet basis is researched.First of all, the features of wavelet basis which is suitable for the steering wheel angle experimental data processing are summarized based on the parameter charac-teristics of wavelet basis and the requirement of processing effects of steering wheel angle experimental data.Then Daubechies (dbN) and Symlet (symN) are selected as the suitable types of wavelet basis.Second, the reconstruc-tion factor is introduced to judge the processing effect of each wavelet basis so that the proper order numbers of wavelet basis are precisely selected.After that, taking a group of steering wheel angle experimental data that col-lected from a vehicle double lane change running test as example, the wavelet bases db5, db6, sym4 and sym5 are selected as the suitable wavelet bases for this test data through calculating and comparing the reconstruction factor of all wavelet bases of dbN and symN.Finally their processing effects are also verified by using the selected wavelet bases to denoise steering wheel angle experimental data.
Aiming at the problem that how to select the wavelet basis used in denoising the steering wheel angle ex-perimental data, a selection method of wavelet basis is researched.First of all, the features of wavelet basis which is suitable for the steering wheel angle experimental data processing are summarized based on the parameter charac-teristics of wavelet basis and the requirement of processing effects of steering wheel angle experimental data.Then Daubechies (dbN) and Symlet (symN) are selected as the suitable types of wavelet basis.Second, the reconstruc-tion factor is introduced to judge the processing effect of each wavelet basis so that the proper order numbers of wavelet basis are precisely selected.After that, taking a group of steering wheel angle experimental data that col-lected from a vehicle double lane change running test as example, the wavelet bases db5, db6, sym4 and sym5 are selected as the suitable wavelet bases for this test data through calculating and comparing the reconstruction factor of all wavelet bases of dbN and symN.Finally their processing effects are also verified by using the selected wavelet bases to denoise steering wheel angle experimental data.
2013, 32(6): 814-818.
Abstract:
The friction force of the hydraulic cylinder of an excavator arm deteriorates its dynamic properties.Therefore, the effective friction compensation for the hydraulic cylinder is important for improving its control per-formance.In order to construct a precise friction model of the hydraulic cylinder, we build the dynamic function for the bucket joint and use in it the coulomb friction, the coulomb-viscous friction and the stribeck friction respective-ly.Due to the colored noise in the hydraulic cylinder, we use the improved recursive least squares method to esti-mate the unknown parameters.The comparison results on the three friction models show that the identified Stribeck model is the most accurate one and that it can effectively predict the actuation force of the hydraulic cylinder.The identification errors of the stribeck model are about 8% and 18% less than those of the coulomb-viscous model and the coulomb model.
The friction force of the hydraulic cylinder of an excavator arm deteriorates its dynamic properties.Therefore, the effective friction compensation for the hydraulic cylinder is important for improving its control per-formance.In order to construct a precise friction model of the hydraulic cylinder, we build the dynamic function for the bucket joint and use in it the coulomb friction, the coulomb-viscous friction and the stribeck friction respective-ly.Due to the colored noise in the hydraulic cylinder, we use the improved recursive least squares method to esti-mate the unknown parameters.The comparison results on the three friction models show that the identified Stribeck model is the most accurate one and that it can effectively predict the actuation force of the hydraulic cylinder.The identification errors of the stribeck model are about 8% and 18% less than those of the coulomb-viscous model and the coulomb model.
2013, 32(6): 819-823.
Abstract:
An autonomous mobile robot system for indoor environment is presented, primarily for family and office and other regional work environment, instead of people to complete tasks such as housework, goods handling and so on.The system can establish an appropriate environment model by a priori map and information which is collected by the sensors, making the robot independently complete the functions of the planning of the shortest path, obstacle detection and motion control and so on.The robot's moving speed and angle data are real-time transmitted to the host computer by the wireless chip for analysis, and then the control instructions are real-time transmitted to the ro-bot to adjust the robot's forward movement.The simulation test of the planning of the shortest path, obstacle detec-tion and the deviation of moving trajectory showed that the designed system is stable and reliable and achieves the expected goals.
An autonomous mobile robot system for indoor environment is presented, primarily for family and office and other regional work environment, instead of people to complete tasks such as housework, goods handling and so on.The system can establish an appropriate environment model by a priori map and information which is collected by the sensors, making the robot independently complete the functions of the planning of the shortest path, obstacle detection and motion control and so on.The robot's moving speed and angle data are real-time transmitted to the host computer by the wireless chip for analysis, and then the control instructions are real-time transmitted to the ro-bot to adjust the robot's forward movement.The simulation test of the planning of the shortest path, obstacle detec-tion and the deviation of moving trajectory showed that the designed system is stable and reliable and achieves the expected goals.
2013, 32(6): 824-828.
Abstract:
This paper presents a new approach with cutter-contact (CC) curves of cross sections for the determina-tion of tool paths in the machining of discrete data points using 3-axis ball end milling.Firstly, a set of cutting planes are defined to compute the intersection curves with the point cloud and the curves are seen as CC point traces.Because the CC point traces consists of a series of intersection points, this paper presents a constant step-er-ror method to calculate CC points, and the K-nearest points of a CC point are obtained to fit a plane.The normal vector of the plane is seen as the normal vector of the CC point.The CC point is offset by the radius size along the normal vector to calculate the corresponding CL point.Finally, after detecting and eliminating all the CL points, the interference-free tool paths are generated.The tool paths generated by this approach meet the step error require-ment and keep the step error constant, and the CL points are fewer.The experiment result indicates that the ap-proach is feasible and efficient.
This paper presents a new approach with cutter-contact (CC) curves of cross sections for the determina-tion of tool paths in the machining of discrete data points using 3-axis ball end milling.Firstly, a set of cutting planes are defined to compute the intersection curves with the point cloud and the curves are seen as CC point traces.Because the CC point traces consists of a series of intersection points, this paper presents a constant step-er-ror method to calculate CC points, and the K-nearest points of a CC point are obtained to fit a plane.The normal vector of the plane is seen as the normal vector of the CC point.The CC point is offset by the radius size along the normal vector to calculate the corresponding CL point.Finally, after detecting and eliminating all the CL points, the interference-free tool paths are generated.The tool paths generated by this approach meet the step error require-ment and keep the step error constant, and the CL points are fewer.The experiment result indicates that the ap-proach is feasible and efficient.
2013, 32(6): 829-833.
Abstract:
In order to solve the safety problem happened in a car offset impact test, vehicle front key structure were improved to achieve the stiffness-matching of vehicle front parts and reasonable deformation of the whole structure.According to the simulation results and the deficiency of original car crashworthiness, energy-absorbing guidance slot was designed in front parts to improve energy-absorbing deformation, and the thickness of a pillar strengthen pieces was increased to improve the longitudinal stiffness and the crew cabin frame strength.The simulation results show that the peak acceleration of automobile reduces by 6 g, the deformation of cabin was reduced with a mass in-creasing by only 2.24 kg, and the whole vehicle crashworthiness was improved effectively.
In order to solve the safety problem happened in a car offset impact test, vehicle front key structure were improved to achieve the stiffness-matching of vehicle front parts and reasonable deformation of the whole structure.According to the simulation results and the deficiency of original car crashworthiness, energy-absorbing guidance slot was designed in front parts to improve energy-absorbing deformation, and the thickness of a pillar strengthen pieces was increased to improve the longitudinal stiffness and the crew cabin frame strength.The simulation results show that the peak acceleration of automobile reduces by 6 g, the deformation of cabin was reduced with a mass in-creasing by only 2.24 kg, and the whole vehicle crashworthiness was improved effectively.
2013, 32(6): 834-838.
Abstract:
Owing to the characteristics of the parameter variation and external disturbance of the electro-hydraulic proportional system of a hydraulic manipulator, it is hard for ordinary methods to completely meet the performance requirements.Though the conventional PID control method has simple algorithm, high reliability and good robust-ness, it also has many disadvantages, such as miscellaneous parameters and bad adaptability.To improve its per-formance, we designed a fuzzy PID controller by combining fuzzy logic control with PID control.The output of the fuzzy PID controller can adjust online the parameters of the conventional PID controller.We use the MATLAB/Sim-ulink to simulate the performance of our fuzzy PID controller, which is then compared with that of the conventional PID controller; the simulation results show preliminarily that our fuzzy PID controller is more capable of overcoming the nonlinear and external disturbance of the electro-hydraulic proportional system and can greatly improve its sta-bility and dynamic performance.
Owing to the characteristics of the parameter variation and external disturbance of the electro-hydraulic proportional system of a hydraulic manipulator, it is hard for ordinary methods to completely meet the performance requirements.Though the conventional PID control method has simple algorithm, high reliability and good robust-ness, it also has many disadvantages, such as miscellaneous parameters and bad adaptability.To improve its per-formance, we designed a fuzzy PID controller by combining fuzzy logic control with PID control.The output of the fuzzy PID controller can adjust online the parameters of the conventional PID controller.We use the MATLAB/Sim-ulink to simulate the performance of our fuzzy PID controller, which is then compared with that of the conventional PID controller; the simulation results show preliminarily that our fuzzy PID controller is more capable of overcoming the nonlinear and external disturbance of the electro-hydraulic proportional system and can greatly improve its sta-bility and dynamic performance.
2013, 32(6): 839-844.
Abstract:
To estimate the fatigue life for a wide-band random vibration fatigue problem, several frequency domain analysis methods are introduced and studied in this paper, which are presented by P.H.Wirsching, Dirlik, T.T.Fu and the authors.The vibration fatigue tests of several groups of cantilever beams with significant bi-modal re-sponse are proposed, then their fatigue lives are estimated with these frequency-domain analysis methods using test-ed strain data, and the test life results and estimated life results are compared to verify the accuracy and application range of the mentioned frequency-domain analysis methods.
To estimate the fatigue life for a wide-band random vibration fatigue problem, several frequency domain analysis methods are introduced and studied in this paper, which are presented by P.H.Wirsching, Dirlik, T.T.Fu and the authors.The vibration fatigue tests of several groups of cantilever beams with significant bi-modal re-sponse are proposed, then their fatigue lives are estimated with these frequency-domain analysis methods using test-ed strain data, and the test life results and estimated life results are compared to verify the accuracy and application range of the mentioned frequency-domain analysis methods.
2013, 32(6): 845-852.
Abstract:
The spindle of motorized spindle and rotor transmit torque through the interference fit.The reliability of interference fit is designed by seeing the actual interference quantity of the fitting surface and the effective combina-tion radius as random variables with normal distribution.The general stress and general strength series can be simu-lated by using the Monte Carlo method, then that is verified through chi-square goodness-of-fit testing that they con-form to the normal distribution, combining the stress-strength interference theory, the reliability model is estab-lished.Through the comparison of the numerical characters of the random variables both by the Monte Carlo method and the First Order Second Moment method, the correctness of the mathematic model is verified.The effect of radi-us of fitting surface, actual interference quantity, spindle speed on the system reliability is analyzed.
The spindle of motorized spindle and rotor transmit torque through the interference fit.The reliability of interference fit is designed by seeing the actual interference quantity of the fitting surface and the effective combina-tion radius as random variables with normal distribution.The general stress and general strength series can be simu-lated by using the Monte Carlo method, then that is verified through chi-square goodness-of-fit testing that they con-form to the normal distribution, combining the stress-strength interference theory, the reliability model is estab-lished.Through the comparison of the numerical characters of the random variables both by the Monte Carlo method and the First Order Second Moment method, the correctness of the mathematic model is verified.The effect of radi-us of fitting surface, actual interference quantity, spindle speed on the system reliability is analyzed.
2013, 32(6): 853-856.
Abstract:
We design a new circulation ball power steering gear for a brushless DC motor.The design consists of prototype circulation ball power steering gear and its controller.According to the open-loop control theory, the tar-get torque should not exceed 30 Nom when providing assistant power.Static steering power tests were carried out on a CA1037K2L light goods vehicle (LGV) to verify the steering power characteristics of the power steering gear.The response curves calibrated by a torque sensor and the test curves of the power steering gear were obtained.The test results show that the circulation ball power steering gear for the brushless DC motor can meet the requirements for the power steering of the LGV.
We design a new circulation ball power steering gear for a brushless DC motor.The design consists of prototype circulation ball power steering gear and its controller.According to the open-loop control theory, the tar-get torque should not exceed 30 Nom when providing assistant power.Static steering power tests were carried out on a CA1037K2L light goods vehicle (LGV) to verify the steering power characteristics of the power steering gear.The response curves calibrated by a torque sensor and the test curves of the power steering gear were obtained.The test results show that the circulation ball power steering gear for the brushless DC motor can meet the requirements for the power steering of the LGV.
2013, 32(6): 857-862.
Abstract:
The platform of humanoid robot SJTU-HR1 is composed of parallel manipulator joints with 34 DOFs.In the paper, the robot joints are designed according to the construction of human being joints.The parallel manipula-tor joint is taken as a module, and the input angle and output angle are defined.By establishing the coordinates of the whole body, the forward and inverse solution of every end effectors are formulated.The results are important for the study on motion planning, motion design, and control system design of SJTU-HR1.
The platform of humanoid robot SJTU-HR1 is composed of parallel manipulator joints with 34 DOFs.In the paper, the robot joints are designed according to the construction of human being joints.The parallel manipula-tor joint is taken as a module, and the input angle and output angle are defined.By establishing the coordinates of the whole body, the forward and inverse solution of every end effectors are formulated.The results are important for the study on motion planning, motion design, and control system design of SJTU-HR1.
2013, 32(6): 863-867.
Abstract:
According to the suture laminated plates of the mesoscopic damage in characteristics, analyzed the ten-sile properties of materials of the two factors, in view of the two factors of different characteristics and make two dif-ferent hypothesis, with T700/QY8911 laminated plate materials as an example, that the analysis model method were established based on the assumption, and compared with the experimental results, and then analyzed the sam-ple drawn the fracture along the stitches, in place of the stitches caused fiber bending, fiber breakage and micro-scopic damage is the tensile strength of the main characteristics of influence factors, among which the elastic con-stants of composite material stitched before and after the change of the main and fiber fracture are concerned, and tensile load with both the limit of the relevant.
According to the suture laminated plates of the mesoscopic damage in characteristics, analyzed the ten-sile properties of materials of the two factors, in view of the two factors of different characteristics and make two dif-ferent hypothesis, with T700/QY8911 laminated plate materials as an example, that the analysis model method were established based on the assumption, and compared with the experimental results, and then analyzed the sam-ple drawn the fracture along the stitches, in place of the stitches caused fiber bending, fiber breakage and micro-scopic damage is the tensile strength of the main characteristics of influence factors, among which the elastic con-stants of composite material stitched before and after the change of the main and fiber fracture are concerned, and tensile load with both the limit of the relevant.
2013, 32(6): 868-872.
Abstract:
A virtual machine can adapt to the parallel development of hardware to a certain extent through the oper-ating system-level parallelism.However, it causes the loss of stack performance and increases energy consumption.This paper analyzes the shortcomings of the current virtual machine, introduces the space division multiplexing, and re-designs the architecture of a multi-core platform by binding different functions to specific parts of the processor, and the break between processors completes function calls.This mechanism avoids switching costs caused by the time division multiplexing.The explicit message passing during processing takes the place of cache coherence proto-cols because it is difficult to determine the execution time.Because the processor status is inconsistent with the NU-MA architecture, we propose the corresponding distribution and transfer strategies.
A virtual machine can adapt to the parallel development of hardware to a certain extent through the oper-ating system-level parallelism.However, it causes the loss of stack performance and increases energy consumption.This paper analyzes the shortcomings of the current virtual machine, introduces the space division multiplexing, and re-designs the architecture of a multi-core platform by binding different functions to specific parts of the processor, and the break between processors completes function calls.This mechanism avoids switching costs caused by the time division multiplexing.The explicit message passing during processing takes the place of cache coherence proto-cols because it is difficult to determine the execution time.Because the processor status is inconsistent with the NU-MA architecture, we propose the corresponding distribution and transfer strategies.
The Modal Analysis of Drum System for Horizontal Worm Screen Centrifuge Based on Hypermesh and Ansys
2013, 32(6): 873-878.
Abstract:
Drum system of the horizontal worm screen centrifuge as the vibration source of the whole machine is the key study object of the centrifuge's dynamic load and mechanical vibration.Structural resonance and material une-ven distribution are the main causes of vibration of the drum system.The structural resonance can be avoided by modal analysis for the drum system using finite element method.The geometric model of drum system is founded by UG, then it is partitioned by hypermesh using hex grid meshing method.Contact pair and MPC(multipoint con-straint) algorithm are used to achieve a connection between two components with discontinuous grids.The eigenval-ues of drum system are extracted in ansys based on block lanczos algorithm and the solution offers the first eight nat-ural frequencies and vibration modes of the drum system under both the conditions with and without centrifugal pre-stress.The results demonstrate that the structural resonace will not occur at the rated working speed.The centrifu-gal prestress has an obvious effect on the lower natural frequencies.The conclusions provide the basis for research and design on the transient dynamic response of the whole machine and the structure optimization of drum system.
Drum system of the horizontal worm screen centrifuge as the vibration source of the whole machine is the key study object of the centrifuge's dynamic load and mechanical vibration.Structural resonance and material une-ven distribution are the main causes of vibration of the drum system.The structural resonance can be avoided by modal analysis for the drum system using finite element method.The geometric model of drum system is founded by UG, then it is partitioned by hypermesh using hex grid meshing method.Contact pair and MPC(multipoint con-straint) algorithm are used to achieve a connection between two components with discontinuous grids.The eigenval-ues of drum system are extracted in ansys based on block lanczos algorithm and the solution offers the first eight nat-ural frequencies and vibration modes of the drum system under both the conditions with and without centrifugal pre-stress.The results demonstrate that the structural resonace will not occur at the rated working speed.The centrifu-gal prestress has an obvious effect on the lower natural frequencies.The conclusions provide the basis for research and design on the transient dynamic response of the whole machine and the structure optimization of drum system.
2013, 32(6): 879-883.
Abstract:
It becomes a tendency to combine experiments and Finite Element Analysis in Ground Vibration Test (GVT) for improving its effectiveness and precision.This paper studied finite-element model based modern aircraft GVT preparation and GVT design techniques, including collocation of the measuring points, the optimal configura-tion of the exciting force, the scheme of the support and the evaluation approaches.Moreover, the feasibility of the test scheme was verified by the GVT of a type of aircraft.By utilization of these techniques, the optimal test scheme can be obtained so that the test period can be shortened and the costs can be drastically decreased as well, which will finally achieve a great jump from a simplex physical test to a synthesized research of experiment and analysis.
It becomes a tendency to combine experiments and Finite Element Analysis in Ground Vibration Test (GVT) for improving its effectiveness and precision.This paper studied finite-element model based modern aircraft GVT preparation and GVT design techniques, including collocation of the measuring points, the optimal configura-tion of the exciting force, the scheme of the support and the evaluation approaches.Moreover, the feasibility of the test scheme was verified by the GVT of a type of aircraft.By utilization of these techniques, the optimal test scheme can be obtained so that the test period can be shortened and the costs can be drastically decreased as well, which will finally achieve a great jump from a simplex physical test to a synthesized research of experiment and analysis.
2013, 32(6): 884-887.
Abstract:
Aiming at complex nonlinear dynamic behaviors of stone-cutting with circular saw blade, according to hard-brittle materials fracture mechanism, a dynamic simulation model of circular saw blade-stone materials system was established by finite element numerical simulation technology, based on ANSYS/LS-DYNA.The process of failure and fracture of the stone with kerfs generation is simulated.The symmetric penalty function contact algorithm and the explicit central difference method were used to solve dynamic equations.The dynamic responses of saw blade-stone materials during the process of cutting were acquired based on LS-PREPOSTD.The results show the stress distributions of circular saw blade and stone at different periods, and reveal stone's micro-crack creation and chip generation mechanism.At the same time, the simulation results prove the feasibility and the validity of the model and methods in this paper.
Aiming at complex nonlinear dynamic behaviors of stone-cutting with circular saw blade, according to hard-brittle materials fracture mechanism, a dynamic simulation model of circular saw blade-stone materials system was established by finite element numerical simulation technology, based on ANSYS/LS-DYNA.The process of failure and fracture of the stone with kerfs generation is simulated.The symmetric penalty function contact algorithm and the explicit central difference method were used to solve dynamic equations.The dynamic responses of saw blade-stone materials during the process of cutting were acquired based on LS-PREPOSTD.The results show the stress distributions of circular saw blade and stone at different periods, and reveal stone's micro-crack creation and chip generation mechanism.At the same time, the simulation results prove the feasibility and the validity of the model and methods in this paper.
2013, 32(6): 888-894.
Abstract:
Large-stroke and high-resolution drive position system is one of the key technology for precision positio-ning.This paper reviews the advances in the study of large-stroke and high-resolution drive system structure.And then for the problems of complex structure, big volume and drive control difficulty for large-stroke and high-resolution macro/micro two-stage positioning system, it is proposed that the research on a single-stage structure which has dual function of micro/macro motion will be the development direction of large-stroke and high-resolution drive positioning system, and the ultrasonic motor as a single driver will be a research topic of the single stage mac-ro/micro drive system.Finally, the development of modeling method and position control strategy of the single stage ultrasonic motor macro/micro drive system are reviewed and difficulties in the research of modeling and control for single stage ultrasonic motor are suggested.
Large-stroke and high-resolution drive position system is one of the key technology for precision positio-ning.This paper reviews the advances in the study of large-stroke and high-resolution drive system structure.And then for the problems of complex structure, big volume and drive control difficulty for large-stroke and high-resolution macro/micro two-stage positioning system, it is proposed that the research on a single-stage structure which has dual function of micro/macro motion will be the development direction of large-stroke and high-resolution drive positioning system, and the ultrasonic motor as a single driver will be a research topic of the single stage mac-ro/micro drive system.Finally, the development of modeling method and position control strategy of the single stage ultrasonic motor macro/micro drive system are reviewed and difficulties in the research of modeling and control for single stage ultrasonic motor are suggested.
2013, 32(6): 895-898.
Abstract:
Due to the strong nonlinearity of a cleaning machine's digging chain guide groove, the PD control meth-od may easily cause large overshoots or even shaking when its parameters change.The digging chain guide groove often shows a big difference between its static performance and dynamic performance.To improve its control effect, we design a gravity compensation fuzzy PD controller that combines the advantages of gravity compensation PD con-trol with those of fuzzy control and then introduce the fuzzy PD controller into the RM80 cleaning machine's digging chain guide groove.We use the MATLAB/Simulink to simulate the control effect.The simulation results show that, compared with the traditional PD controller, the gravity compensation fuzzy PD controller can improve the dynamic performance of the digging chain guide groove and produce a better robustness.
Due to the strong nonlinearity of a cleaning machine's digging chain guide groove, the PD control meth-od may easily cause large overshoots or even shaking when its parameters change.The digging chain guide groove often shows a big difference between its static performance and dynamic performance.To improve its control effect, we design a gravity compensation fuzzy PD controller that combines the advantages of gravity compensation PD con-trol with those of fuzzy control and then introduce the fuzzy PD controller into the RM80 cleaning machine's digging chain guide groove.We use the MATLAB/Simulink to simulate the control effect.The simulation results show that, compared with the traditional PD controller, the gravity compensation fuzzy PD controller can improve the dynamic performance of the digging chain guide groove and produce a better robustness.
2013, 32(6): 899-904.
Abstract:
By the use of combining digital image encryption with chaotic dynamical system which has stochastic、certainty and sensitivity to initial value of chaos conditions and parameters, we can get an extremely good pictorial information cryptographic system.A new digital image encryption method based on different structure chaos syn-chronization system was putted forward in this paper for encrypting and decrypting all of your images on the base of the drive-response method (DRM).The simulative test results show that the encrypted images information cannot be abstracted or restored true faces of the original images, however, the decrypted image can achieve the same effect as the original image by the right password.In order to realize security of data in communication systems be-tween two different chaotic systems within a limited time, the image decryption key sensitivity was analyzed by changing the linear mapping parameters and the control law parameters separately, the original images and plain-texts are very different in the experimental results.Hence, it was proved that the new encryption method above has a very good safety.
By the use of combining digital image encryption with chaotic dynamical system which has stochastic、certainty and sensitivity to initial value of chaos conditions and parameters, we can get an extremely good pictorial information cryptographic system.A new digital image encryption method based on different structure chaos syn-chronization system was putted forward in this paper for encrypting and decrypting all of your images on the base of the drive-response method (DRM).The simulative test results show that the encrypted images information cannot be abstracted or restored true faces of the original images, however, the decrypted image can achieve the same effect as the original image by the right password.In order to realize security of data in communication systems be-tween two different chaotic systems within a limited time, the image decryption key sensitivity was analyzed by changing the linear mapping parameters and the control law parameters separately, the original images and plain-texts are very different in the experimental results.Hence, it was proved that the new encryption method above has a very good safety.
2013, 32(6): 905-908.
Abstract:
This paper presents a polishing technique that uses rotational magnetic polishing liquid, which can pro-duce vortex motion under the action of a magnetic stirrer.The use of a strong external magnetic field increases its viscosity and shear yield stress when a work-piece is introduced into the magnetic polishing liquid.The magnetic polishing liquid contacts the work-piece surface grinding so as to achieve work-piece surface finishing.Experiments were carried out to study the relationship between the surface roughness of the work-piece, its polishing time and its polishing position.The experimental results show that the rotational magnetic polishing liquid can polish the super-smooth surface and that the longer the polishing time and the closer the surface roughness at various locations, the better the surface roughness is, which is also better than that by using abrasive polishing alone.
This paper presents a polishing technique that uses rotational magnetic polishing liquid, which can pro-duce vortex motion under the action of a magnetic stirrer.The use of a strong external magnetic field increases its viscosity and shear yield stress when a work-piece is introduced into the magnetic polishing liquid.The magnetic polishing liquid contacts the work-piece surface grinding so as to achieve work-piece surface finishing.Experiments were carried out to study the relationship between the surface roughness of the work-piece, its polishing time and its polishing position.The experimental results show that the rotational magnetic polishing liquid can polish the super-smooth surface and that the longer the polishing time and the closer the surface roughness at various locations, the better the surface roughness is, which is also better than that by using abrasive polishing alone.
2013, 32(6): 909-913.
Abstract:
In view of the important role of tire force in the simulation of vehicle dynamics and the development of control system, the system-function in Matlab/Simulink software was used to establish the Gim theoretical tire model in this paper.The tire model was built in Simulink, and this tire module can be directly called as a sub-module of Simulink to calculate tire longitudinal and lateral force applied by ground.Finally, By the comparison between re-sults of dynamics simulation and experiments, it indicates that the Gim theoretical tire model has high precision, and it can accurately predict the mechanical properties of the tire.The tire sub-module established has a wide appli-cability with few parameters and it can be directly applied to the analysis of vehicles dynamics and control system.
In view of the important role of tire force in the simulation of vehicle dynamics and the development of control system, the system-function in Matlab/Simulink software was used to establish the Gim theoretical tire model in this paper.The tire model was built in Simulink, and this tire module can be directly called as a sub-module of Simulink to calculate tire longitudinal and lateral force applied by ground.Finally, By the comparison between re-sults of dynamics simulation and experiments, it indicates that the Gim theoretical tire model has high precision, and it can accurately predict the mechanical properties of the tire.The tire sub-module established has a wide appli-cability with few parameters and it can be directly applied to the analysis of vehicles dynamics and control system.
2013, 32(6): 914-918.
Abstract:
Due to the shortcoming of the LQG(linear quadratic gaussian) when defining the weight matrices, a method using the genetic algorithm is designed to optimize the LQG.This method utilizes the global optimization al-gorithm of the genetic algorithm to optimize and design the weight matrices with the target function of chassis per-formance indexes.This method improves the design efficiency and control performance of the LQG control.And a simulation is provided to vehicle active chassis control.The result shows that the actively controlled chassis using LQG optimized by the genetic algorithm compared to the chassis controlled by the normal LQG and the passive one, canimprove the chassis performance greatly.Meanwhile, the problem of defining the weight matrices is greatly solved based on the advantage of the normal LQG is sufficiently utilized.
Due to the shortcoming of the LQG(linear quadratic gaussian) when defining the weight matrices, a method using the genetic algorithm is designed to optimize the LQG.This method utilizes the global optimization al-gorithm of the genetic algorithm to optimize and design the weight matrices with the target function of chassis per-formance indexes.This method improves the design efficiency and control performance of the LQG control.And a simulation is provided to vehicle active chassis control.The result shows that the actively controlled chassis using LQG optimized by the genetic algorithm compared to the chassis controlled by the normal LQG and the passive one, canimprove the chassis performance greatly.Meanwhile, the problem of defining the weight matrices is greatly solved based on the advantage of the normal LQG is sufficiently utilized.
2013, 32(6): 919-922,927.
Abstract:
Key structure parameters were verified and optimized through Kinematic analysis and mechanical analysis for the lifting mechanism of a common scissor-fork lifter.The whole movement of the mechanism was described firstly, and then detailed analysis was performed for the lift cylinder and the lifting platform.The maximum stress point was obtained through load bearing analysis for the lifting mechanism.Finally, optimizing scheme was presen-ted based on strength checking for the scissor rod and adjusting installation point of the lift cylinder.The results of in-situ test showed that the stability of lifting mechanism was improved and the demand on the driving force of hy-draulic cylinder was greatly reduced.
Key structure parameters were verified and optimized through Kinematic analysis and mechanical analysis for the lifting mechanism of a common scissor-fork lifter.The whole movement of the mechanism was described firstly, and then detailed analysis was performed for the lift cylinder and the lifting platform.The maximum stress point was obtained through load bearing analysis for the lifting mechanism.Finally, optimizing scheme was presen-ted based on strength checking for the scissor rod and adjusting installation point of the lift cylinder.The results of in-situ test showed that the stability of lifting mechanism was improved and the demand on the driving force of hy-draulic cylinder was greatly reduced.
2013, 32(6): 923-927.
Abstract:
The fastener flexibility plays an important role in the factors influencing the fatigue life of the aircraft joints, and is often used as a main parameter when modeling and analyzing aircraft fatigue and life-span.This pa-per, based on the verification of the effectiveness of Elastoplasticity Finite Element Method (EFEM) to the fastener flexibility, analyses the single lap joints connected to different fasteners using the EFEM.The flexibility of the fas-teners are calculated using the load-displacement curves of the fastener details.The results show that the smaller the head of the oval-head rivets, the greater of its flexibility, the flexibility value of countersunk rivet is bigger than that of the flat-head rivet; and the flexibility of cross recessed countersunk bolt is a little bigger than that of the flat-head rivet.The fastener flexibility is drastically reduced with interference fit.
The fastener flexibility plays an important role in the factors influencing the fatigue life of the aircraft joints, and is often used as a main parameter when modeling and analyzing aircraft fatigue and life-span.This pa-per, based on the verification of the effectiveness of Elastoplasticity Finite Element Method (EFEM) to the fastener flexibility, analyses the single lap joints connected to different fasteners using the EFEM.The flexibility of the fas-teners are calculated using the load-displacement curves of the fastener details.The results show that the smaller the head of the oval-head rivets, the greater of its flexibility, the flexibility value of countersunk rivet is bigger than that of the flat-head rivet; and the flexibility of cross recessed countersunk bolt is a little bigger than that of the flat-head rivet.The fastener flexibility is drastically reduced with interference fit.
2013, 32(6): 928-931,936.
Abstract:
In order to solve the problem of the significant difference between ΔE 76 and visual evaluation for small color-difference proofs of digital proofing machine, new evaluation methods have been put forward in this paper based on visual characteristics.First, small color-difference proofs are designed in this experiment for digital proo-fing machine.Then, a visual perceptibility assessment method is applied on small color-difference proofs, and the just-noticeable-differences were evaluated with the model of ΔE76, ΔE 94, ΔE cmc, ΔE 00 and ΔI m .The measured data were appraised using color root-mean-squared errors (RMSE), performance evaluation factors (PF/3), sample decisive coefficients (R2 ) in order to obtain their prediction performance.The results show that the ΔE 00 and ΔI m are closer to the subjective color difference, and the ΔE 76 is the worst one.Benefited from its simple calculation method, the ΔI m method is better than other models as the color-difference evaluation model of digital proofing ma-chine for production.
In order to solve the problem of the significant difference between ΔE 76 and visual evaluation for small color-difference proofs of digital proofing machine, new evaluation methods have been put forward in this paper based on visual characteristics.First, small color-difference proofs are designed in this experiment for digital proo-fing machine.Then, a visual perceptibility assessment method is applied on small color-difference proofs, and the just-noticeable-differences were evaluated with the model of ΔE76, ΔE 94, ΔE cmc, ΔE 00 and ΔI m .The measured data were appraised using color root-mean-squared errors (RMSE), performance evaluation factors (PF/3), sample decisive coefficients (R2 ) in order to obtain their prediction performance.The results show that the ΔE 00 and ΔI m are closer to the subjective color difference, and the ΔE 76 is the worst one.Benefited from its simple calculation method, the ΔI m method is better than other models as the color-difference evaluation model of digital proofing ma-chine for production.
2013, 32(6): 932-936.
Abstract:
We computed the transient state of a side-branch resonant hydraulic pulsation damper with CFD (com-putational fluid dynamics) codes to analyze the relationship between its dynamic characteristics and cavity struc-ture.Under the laminar condition, we used the M-sequence pressure signal to simulate the pressure wave that acts as boundary in order to simulate the transient state of the pulsation damper with fluid compressibility.We trans-formed its transient pressure sequences into its frequency characteristics through the fast Fourier transform.We compared the frequency responses of the pulsation damper and insert loss among pulsation dampers with the same cavity volume but different diameters and lengths.We simulated the pressure impact with the step pressure and showed the flow field.We designed pulsation dampers with different cavity volume, and compared their perform-ance.We analyzed the relationship between the base frequency of the pulsation damper and the diameter-to-length ratio by using the distributive parameter model.The analysis results show that: 1) the pulsation damper's dynamic characteristics have relations with its cavity's diameter-to-length ratio and decrease when the ratio is less than 1 and decreasing; 2) the pulsation damper's base frequency is smaller and increases little when the ratio is larger than 1 and increasing.Therefore designers should decrease the volume of the pulsation damper that has a smaller cavity and lower diameter-to-length ratio so as to keep its resonance frequency stable.
We computed the transient state of a side-branch resonant hydraulic pulsation damper with CFD (com-putational fluid dynamics) codes to analyze the relationship between its dynamic characteristics and cavity struc-ture.Under the laminar condition, we used the M-sequence pressure signal to simulate the pressure wave that acts as boundary in order to simulate the transient state of the pulsation damper with fluid compressibility.We trans-formed its transient pressure sequences into its frequency characteristics through the fast Fourier transform.We compared the frequency responses of the pulsation damper and insert loss among pulsation dampers with the same cavity volume but different diameters and lengths.We simulated the pressure impact with the step pressure and showed the flow field.We designed pulsation dampers with different cavity volume, and compared their perform-ance.We analyzed the relationship between the base frequency of the pulsation damper and the diameter-to-length ratio by using the distributive parameter model.The analysis results show that: 1) the pulsation damper's dynamic characteristics have relations with its cavity's diameter-to-length ratio and decrease when the ratio is less than 1 and decreasing; 2) the pulsation damper's base frequency is smaller and increases little when the ratio is larger than 1 and increasing.Therefore designers should decrease the volume of the pulsation damper that has a smaller cavity and lower diameter-to-length ratio so as to keep its resonance frequency stable.
