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RSS2017 Vol. 36, No. 9
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2017, 36(9): 1313-1319.
doi: 10.13433/j.cnki.1003-8728.2017.0901
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Abstract:
Based on the kinematics and dynamics of a tracked robot under skid condition when its tracks on both sides contact ground evenly, the formulas of traction force and steering resistance moment were derived when the outer grousers contact the ground, and the influence of mass center shift was analyzed. Then the steering condition of the tracked robot under skid condition was obtained. The influence of the steering rate on the skid ratio of pivot steering was discussed. The discussion results show that:the traction force and steering resistance moment are the same when the outer grousers are grounded and the tracks are evenly grounded, the steering rate range that satisfies the steering condition under skid condition increases, the skid ratios on both sides increase with increasing steering ratio when the tracked robot turns.
Based on the kinematics and dynamics of a tracked robot under skid condition when its tracks on both sides contact ground evenly, the formulas of traction force and steering resistance moment were derived when the outer grousers contact the ground, and the influence of mass center shift was analyzed. Then the steering condition of the tracked robot under skid condition was obtained. The influence of the steering rate on the skid ratio of pivot steering was discussed. The discussion results show that:the traction force and steering resistance moment are the same when the outer grousers are grounded and the tracks are evenly grounded, the steering rate range that satisfies the steering condition under skid condition increases, the skid ratios on both sides increase with increasing steering ratio when the tracked robot turns.
2017, 36(9): 1320-1326.
doi: 10.13433/j.cnki.1003-8728.2017.0902
Abstract:
Based on the variable density method, the interpolation model for multiphase materials is established, and the topology optimization model for the compliant mechanisms with the maximum displacement of the structure and the material volume as the constraint is established. The miniature flexible clamp for example, with the Method of moving asymptotes(MMA) to complete the calculation, and the topology results are analyzed. The results show that the topology optimization method of compliant mechanisms for multiphase materials is feasible, which can significantly reduce the maximum stress level of the topology structure, but also to a certain extent, the displacement of the output point of the structure is reduced. As a whole, the method is feasible, and can effectively solve the problem of structural failure caused by excessive stress in the project.
Based on the variable density method, the interpolation model for multiphase materials is established, and the topology optimization model for the compliant mechanisms with the maximum displacement of the structure and the material volume as the constraint is established. The miniature flexible clamp for example, with the Method of moving asymptotes(MMA) to complete the calculation, and the topology results are analyzed. The results show that the topology optimization method of compliant mechanisms for multiphase materials is feasible, which can significantly reduce the maximum stress level of the topology structure, but also to a certain extent, the displacement of the output point of the structure is reduced. As a whole, the method is feasible, and can effectively solve the problem of structural failure caused by excessive stress in the project.
2017, 36(9): 1327-1332.
doi: 10.13433/j.cnki.1003-8728.2017.0903
Abstract:
To better evaluate the ergonomics of an exoskeleton, this paper proposes a method for evaluating man's lower extremity exoskeleton coupling roughness based on a three-dimensional motion capture system. This method derives a wearer's hip and knee trajectory changes from the motion capture system to establish the man's lower extremity exoskeleton coupling surface roughness model which can perform the ergonomics of the exoskeleton quantitatively to some extent. By introducing the Gaussian bandpass filters, the method can obtain the center line, enhancing the accuracy of the model. The experimental results prove that the method can obtain the mismatch between the wearer and his lower extremity exoskeleton on three kinds of gaits and be used as a reference for the comprehensive evaluation of exoskeleton.
To better evaluate the ergonomics of an exoskeleton, this paper proposes a method for evaluating man's lower extremity exoskeleton coupling roughness based on a three-dimensional motion capture system. This method derives a wearer's hip and knee trajectory changes from the motion capture system to establish the man's lower extremity exoskeleton coupling surface roughness model which can perform the ergonomics of the exoskeleton quantitatively to some extent. By introducing the Gaussian bandpass filters, the method can obtain the center line, enhancing the accuracy of the model. The experimental results prove that the method can obtain the mismatch between the wearer and his lower extremity exoskeleton on three kinds of gaits and be used as a reference for the comprehensive evaluation of exoskeleton.
2017, 36(9): 1333-1339.
doi: 10.13433/j.cnki.1003-8728.2017.0904
Abstract:
Aiming at the technical difficulties of strong abrasion resistance, poor drillability and low rate of penetration of the stratum, a torsional vibration generator is designed. According to the structure and operating principle of the torsional vibration generator, its kinematics and mathematical models are established. The expression of the collision period, angular velocity, angular displacement of the hydraulic hammer are derived, and the variation relationships of these parameters with respect to time are obtained with the aid of numerical examples, and the effect of the inlet pressure and inlet flow on them are also achieved. The accuracy and reliability of the calculation method are verified by experiments. The results show that its collision period increases with the inlet flow and decreases with the inlet pressure. With the increasing of inlet pressure and the decreasing of inlet flow, the angular velocity and angular displacement of the hydraulic hammer are increased.
Aiming at the technical difficulties of strong abrasion resistance, poor drillability and low rate of penetration of the stratum, a torsional vibration generator is designed. According to the structure and operating principle of the torsional vibration generator, its kinematics and mathematical models are established. The expression of the collision period, angular velocity, angular displacement of the hydraulic hammer are derived, and the variation relationships of these parameters with respect to time are obtained with the aid of numerical examples, and the effect of the inlet pressure and inlet flow on them are also achieved. The accuracy and reliability of the calculation method are verified by experiments. The results show that its collision period increases with the inlet flow and decreases with the inlet pressure. With the increasing of inlet pressure and the decreasing of inlet flow, the angular velocity and angular displacement of the hydraulic hammer are increased.
2017, 36(9): 1340-1344.
doi: 10.13433/j.cnki.1003-8728.2017.0905
Abstract:
The method of calculating the top Lyapunov exponent of a Duffing system in the multi-parameter space is given, and the distribution characteristic of the top Lyapunov exponent of the Duffing system in its two-parameter plane is calculated. Bifurcation characteristics of the Duffing system are discussed with the single parameter bifurcation diagram. The discussion results show that the Duffing system has various bifurcation curves including periodic jump, pitchfork bifurcation and period-doubling bifurcation in its two-parameter plane. The period-doubling bifurcation curve cycles constantly appear and nest each other, making the system finally evolve the chaotic state via period-doubling bifurcation sequences. These periodic bifurcation curves are truncated by the periodic jumping curve, making the system move into different periodic states via the cycle jump curve. The intersection of various bifurcation curves in the two-parameter plane makes the local bifurcation characteristic of the system become very complex. The calculation and analysis of the Duffing system prove that this method is effective and feasible in terms of computational chaos.
The method of calculating the top Lyapunov exponent of a Duffing system in the multi-parameter space is given, and the distribution characteristic of the top Lyapunov exponent of the Duffing system in its two-parameter plane is calculated. Bifurcation characteristics of the Duffing system are discussed with the single parameter bifurcation diagram. The discussion results show that the Duffing system has various bifurcation curves including periodic jump, pitchfork bifurcation and period-doubling bifurcation in its two-parameter plane. The period-doubling bifurcation curve cycles constantly appear and nest each other, making the system finally evolve the chaotic state via period-doubling bifurcation sequences. These periodic bifurcation curves are truncated by the periodic jumping curve, making the system move into different periodic states via the cycle jump curve. The intersection of various bifurcation curves in the two-parameter plane makes the local bifurcation characteristic of the system become very complex. The calculation and analysis of the Duffing system prove that this method is effective and feasible in terms of computational chaos.
2017, 36(9): 1345-1350.
doi: 10.13433/j.cnki.1003-8728.2017.0906
Abstract:
In order to better realize the efficiency of dexterous hand grasping and collision avoidance in virtual environment, the variables of objects are introduced to multi-fingered grasping, then the kinematic trajectory based on the idea of automatic grasping are established and verified. According to the structure of hand, the movement characteristics are analyzed, and the fingertip kinematic trajectory model with size and position of objects as variables is established. The forward and inverse kinematics analysis of hand is conducted and the grasping rule is set to ensure the stability of grasping. The fingertip kinematic trajectory is simulated based on SolidWorks and MATLAB. The correctness of simulation is verified by grasping experiments, the results of simulation reflect the character of hand grasping and demonstrate the effectiveness of the present method.
In order to better realize the efficiency of dexterous hand grasping and collision avoidance in virtual environment, the variables of objects are introduced to multi-fingered grasping, then the kinematic trajectory based on the idea of automatic grasping are established and verified. According to the structure of hand, the movement characteristics are analyzed, and the fingertip kinematic trajectory model with size and position of objects as variables is established. The forward and inverse kinematics analysis of hand is conducted and the grasping rule is set to ensure the stability of grasping. The fingertip kinematic trajectory is simulated based on SolidWorks and MATLAB. The correctness of simulation is verified by grasping experiments, the results of simulation reflect the character of hand grasping and demonstrate the effectiveness of the present method.
2017, 36(9): 1351-1356.
doi: 10.13433/j.cnki.1003-8728.2017.0907
Abstract:
An adaptive sliding mode controller is presented for the feed servo system with nonlinear friction and bounded external disturbances. The controller has a sliding control input to compensate the friction and external disturbances so that the tracking error convergences asymptotically to the preassigned boundary. The gain of the sliding control input is adjusted using adaptive algorithms to estimate the linear bound of the friction. The global stability of the closed loop control system is established via Lyapunov's stability theorem. Finally, simulation results have verified that the proposed controller can compensate the friction and external disturbances effectively. Compared with the traditional Proportional-integral-differential (PD and PID) controllers, it enhances significantly the tracking accuracy of the servo system, and has robustness to the uncertainty of the system parameters and friction characteristics.
An adaptive sliding mode controller is presented for the feed servo system with nonlinear friction and bounded external disturbances. The controller has a sliding control input to compensate the friction and external disturbances so that the tracking error convergences asymptotically to the preassigned boundary. The gain of the sliding control input is adjusted using adaptive algorithms to estimate the linear bound of the friction. The global stability of the closed loop control system is established via Lyapunov's stability theorem. Finally, simulation results have verified that the proposed controller can compensate the friction and external disturbances effectively. Compared with the traditional Proportional-integral-differential (PD and PID) controllers, it enhances significantly the tracking accuracy of the servo system, and has robustness to the uncertainty of the system parameters and friction characteristics.
2017, 36(9): 1357-1361.
doi: 10.13433/j.cnki.1003-8728.2017.0908
Abstract:
On diesel engine main bearing hole roundness, the displacement of main bearing hole via original model and splitting model are simulated when it is assembled, at 150℃ and under explosion pressure. The stress difference around the main bearing hole is analyzed. With contrast test analysis, RuT450 materials and HT250 materials were used respectively to create specimen. With the comparison method, the influence of the material quality, the splitting surface quality and the change of main bearing hole precision on the fracture splitting technology of the main bearing hole among the Ru450, the HT250 specimen and the German company MAN D26 alloy material was studied. The results show that Ru450 can meet the performance requirements of hardness and strength for the diesel engine, and it is suitable for the use of splitting technology. The splitting surface of Ru450 specimen is very smooth and the material organization is very compact. The change in all main bearing hole detected in specimens does not exceed the setting value of 0.1 mm. It shows that the precision of the expanding hole after splitting is very high.
On diesel engine main bearing hole roundness, the displacement of main bearing hole via original model and splitting model are simulated when it is assembled, at 150℃ and under explosion pressure. The stress difference around the main bearing hole is analyzed. With contrast test analysis, RuT450 materials and HT250 materials were used respectively to create specimen. With the comparison method, the influence of the material quality, the splitting surface quality and the change of main bearing hole precision on the fracture splitting technology of the main bearing hole among the Ru450, the HT250 specimen and the German company MAN D26 alloy material was studied. The results show that Ru450 can meet the performance requirements of hardness and strength for the diesel engine, and it is suitable for the use of splitting technology. The splitting surface of Ru450 specimen is very smooth and the material organization is very compact. The change in all main bearing hole detected in specimens does not exceed the setting value of 0.1 mm. It shows that the precision of the expanding hole after splitting is very high.
2017, 36(9): 1362-1366.
doi: 10.13433/j.cnki.1003-8728.2017.0909
Abstract:
The dynamics model of a two-DOF vibration system with two kinds of friction which is considered by the differences of working condition of contact surface and clearance is established. The system in different stages of exercise judgment and stick-slip-impact behavior transition rules are given, then using the numerical simulation method to solve the differential equations of system, combined with the judgment condition to analyze the non-smooth movement characteristics caused by the friction and the complex dynamic behavior, and the influence of different friction models on the dynamics of the system. The results show that the system exists the friction vibration phenomenon including the instantaneous friction induced vibration, period flutter, flutter transition to sticking and among the conversion of stick-slip-impact.
The dynamics model of a two-DOF vibration system with two kinds of friction which is considered by the differences of working condition of contact surface and clearance is established. The system in different stages of exercise judgment and stick-slip-impact behavior transition rules are given, then using the numerical simulation method to solve the differential equations of system, combined with the judgment condition to analyze the non-smooth movement characteristics caused by the friction and the complex dynamic behavior, and the influence of different friction models on the dynamics of the system. The results show that the system exists the friction vibration phenomenon including the instantaneous friction induced vibration, period flutter, flutter transition to sticking and among the conversion of stick-slip-impact.
Influence of Time-varying Cutting Load on Dynamic Control Accuracy of Asynchronous Motorized Spindle
2017, 36(9): 1367-1374.
doi: 10.13433/j.cnki.1003-8728.2017.0910
Abstract:
To study the instability of dynamic accuracy control of motorized spindle in high-speed cutting process, a method to predict the output torque and speed of motorized spindle based on the voltage and current value of the input terminal of stator is put forward. The method is based on the principle of speed-sensorless vector control and combined with the electromagnetic parameters such as spindle resistance and inductance. And it takes the rotor flux linkage amplitude and phase angle as a bridge to establish mathematical model between the three-phase voltage and current of the stator input and the speed and torque of rotor output. A double closed-loop control system of speed outer loop and current inner loop on speed sensorless vector control is constructed. With the double closed-loop system, the three-phase voltage and current of the stator input during the cutting process are converted into the voltage and current in the two-phase rotating coordinate system. On this basis, the current loop is further decomposed into two independent control subsystems:flux linkage loop and torque loop to control the rotor flux linkage and the electromagnetic torque respectively. The output stability of torque and speed of the spindle can be determined by observing the current trends of flux linkage loop and torque loop. Finally, the method above is verified by cutting experiments.
To study the instability of dynamic accuracy control of motorized spindle in high-speed cutting process, a method to predict the output torque and speed of motorized spindle based on the voltage and current value of the input terminal of stator is put forward. The method is based on the principle of speed-sensorless vector control and combined with the electromagnetic parameters such as spindle resistance and inductance. And it takes the rotor flux linkage amplitude and phase angle as a bridge to establish mathematical model between the three-phase voltage and current of the stator input and the speed and torque of rotor output. A double closed-loop control system of speed outer loop and current inner loop on speed sensorless vector control is constructed. With the double closed-loop system, the three-phase voltage and current of the stator input during the cutting process are converted into the voltage and current in the two-phase rotating coordinate system. On this basis, the current loop is further decomposed into two independent control subsystems:flux linkage loop and torque loop to control the rotor flux linkage and the electromagnetic torque respectively. The output stability of torque and speed of the spindle can be determined by observing the current trends of flux linkage loop and torque loop. Finally, the method above is verified by cutting experiments.
2017, 36(9): 1375-1380.
doi: 10.13433/j.cnki.1003-8728.2017.0911
Abstract:
The three-dimensional model of the hollow spindle unit is established with Pro/E. And the vibration characteristics of the hollow spindle unit are studied with ANSYS. Six key nodes on the hollow spindle and different positions of the front bearing are selected and the vibration characteristics are comparatively studied. The results show that the rod machining precision is greatly influenced by the vibration of the nodes of knives and knife pouches. Based on the results, the structure of hollow spindle is optimized and the machining accuracy is improved.
The three-dimensional model of the hollow spindle unit is established with Pro/E. And the vibration characteristics of the hollow spindle unit are studied with ANSYS. Six key nodes on the hollow spindle and different positions of the front bearing are selected and the vibration characteristics are comparatively studied. The results show that the rod machining precision is greatly influenced by the vibration of the nodes of knives and knife pouches. Based on the results, the structure of hollow spindle is optimized and the machining accuracy is improved.
2017, 36(9): 1381-1387.
doi: 10.13433/j.cnki.1003-8728.2017.0912
Abstract:
In order to predict the durability of car front suspension structure, a finite element model was built, the strength with the maximum load of real road spectrum was analyzed and the durability with the dynamical real road spectrum was analyzed. By contrast, the maximum stress value and the position of the vehicle are fully consistent with the experimental result, fatigue analysis also showed severe fatigue damage. The example shows the strength and fatigue analysis with finite element can predict the durability of front suspension structural parts. In the early days no actual load conditions, with correlation road load maximum, the strength analysis can predict the durability. Finally, to optimize front suspension structure design showed that to enhance the material properties was more pronounced than to increase the thickness. There are not obvious improvement by reducing the bushing stiffness.
In order to predict the durability of car front suspension structure, a finite element model was built, the strength with the maximum load of real road spectrum was analyzed and the durability with the dynamical real road spectrum was analyzed. By contrast, the maximum stress value and the position of the vehicle are fully consistent with the experimental result, fatigue analysis also showed severe fatigue damage. The example shows the strength and fatigue analysis with finite element can predict the durability of front suspension structural parts. In the early days no actual load conditions, with correlation road load maximum, the strength analysis can predict the durability. Finally, to optimize front suspension structure design showed that to enhance the material properties was more pronounced than to increase the thickness. There are not obvious improvement by reducing the bushing stiffness.
2017, 36(9): 1388-1395.
doi: 10.13433/j.cnki.1003-8728.2017.0913
Abstract:
In order to improve the static and dynamic performance of machine tool column, the stiffened plate structure of column was designed, and four kinds of preferred structure were preliminarily screened out. Orthogonal test was designed with three levels and four factors, including the structure of stiffened plate, rib thickness, the diameter of column lifting hole and the weight, maximum coupling deformation, the first order frequency and maximum coupling stress are taken as evaluation indexes. Considering the objective and subjective factors, Gray correlation method and combination weighting method were used to get the optimal parameter combination. The results show that the best combination of parameters for column are the "十" type rib structure with rib plate thickness of 20 mm and lifting hole diameter of 180 mm. After optimized, the weight is reduced by 503 kg, the maximum stress is reduced by 6%, and the first natural frequency is increased, while the maximum deformation is substantially unchanged. The present study expands the applications of orthogonal test, grey correlation method and the combination weighting method, and it also provides a useful method for the design of other machine parts.
In order to improve the static and dynamic performance of machine tool column, the stiffened plate structure of column was designed, and four kinds of preferred structure were preliminarily screened out. Orthogonal test was designed with three levels and four factors, including the structure of stiffened plate, rib thickness, the diameter of column lifting hole and the weight, maximum coupling deformation, the first order frequency and maximum coupling stress are taken as evaluation indexes. Considering the objective and subjective factors, Gray correlation method and combination weighting method were used to get the optimal parameter combination. The results show that the best combination of parameters for column are the "十" type rib structure with rib plate thickness of 20 mm and lifting hole diameter of 180 mm. After optimized, the weight is reduced by 503 kg, the maximum stress is reduced by 6%, and the first natural frequency is increased, while the maximum deformation is substantially unchanged. The present study expands the applications of orthogonal test, grey correlation method and the combination weighting method, and it also provides a useful method for the design of other machine parts.
2017, 36(9): 1396-1401.
doi: 10.13433/j.cnki.1003-8728.2017.0914
Abstract:
A novel method of micro-tools preparation with wire electro discharge grinding(WEDG) technology was presented. The method combines the manufacturing with the use of micro-milling tool, so the preparation and use process of micro-cutter would complete together on the same micro-EDM machine. In this way, the set-up errors caused by micro-cutter tilt and eccentricity errors could be avoided, and the overall quality of the parts would be increased. In order to verify the feasibility of on-site preparation technology of micro-milling tool via WEDG, a series of experiments were carried out based on the self-development μEM-200CDS2 double spindle three-position micro EDM platform. The influence of the tool material and geometric structure of micro-milling tool tip was analyzed, meanwhile, the carbide materials and the geometric structural of D shape were acquired which are suitable for WEDG processing. Finally the micro-milling tool with cutting edge diameter less than 100 μm were fabricated via WEDG, and a group of thin-walled structures with a minimum thickness less than 20 μm were machined with micro-milling. The results showed that the on-site preparation technology of micro-milling tool via WEDG is feasible.
A novel method of micro-tools preparation with wire electro discharge grinding(WEDG) technology was presented. The method combines the manufacturing with the use of micro-milling tool, so the preparation and use process of micro-cutter would complete together on the same micro-EDM machine. In this way, the set-up errors caused by micro-cutter tilt and eccentricity errors could be avoided, and the overall quality of the parts would be increased. In order to verify the feasibility of on-site preparation technology of micro-milling tool via WEDG, a series of experiments were carried out based on the self-development μEM-200CDS2 double spindle three-position micro EDM platform. The influence of the tool material and geometric structure of micro-milling tool tip was analyzed, meanwhile, the carbide materials and the geometric structural of D shape were acquired which are suitable for WEDG processing. Finally the micro-milling tool with cutting edge diameter less than 100 μm were fabricated via WEDG, and a group of thin-walled structures with a minimum thickness less than 20 μm were machined with micro-milling. The results showed that the on-site preparation technology of micro-milling tool via WEDG is feasible.
2017, 36(9): 1402-1407.
doi: 10.13433/j.cnki.1003-8728.2017.0915
Abstract:
The rolling bearing fault vibration signals have low signal-to-noise ratio. Aiming at diagnosing the fault of rolling bearing accurately, a method based on local characteristic-scale decomposition(LCD), k-means cluster analysis and independent component analysis(ICA) was proposed. Firstly, the vibration signal was decomposed into some intrinsic mode components (ISC) by LCD. Then the correlation coefficients of every ISC and the original signal and the kurtosis value of every ISC were calculated, the efficient components were selected by means of k-means cluster analysis. The efficient components were processed by ICA to separate the signal from the noise, and the signal components were selected according to the kurtosis values. Finally, the Hilbert envelope aptitude envelope spectrum was used for fault diagnosis. The analysis of the bearing fault data shows that the method can realize weak signal detection and fault diagnosis effectively.
The rolling bearing fault vibration signals have low signal-to-noise ratio. Aiming at diagnosing the fault of rolling bearing accurately, a method based on local characteristic-scale decomposition(LCD), k-means cluster analysis and independent component analysis(ICA) was proposed. Firstly, the vibration signal was decomposed into some intrinsic mode components (ISC) by LCD. Then the correlation coefficients of every ISC and the original signal and the kurtosis value of every ISC were calculated, the efficient components were selected by means of k-means cluster analysis. The efficient components were processed by ICA to separate the signal from the noise, and the signal components were selected according to the kurtosis values. Finally, the Hilbert envelope aptitude envelope spectrum was used for fault diagnosis. The analysis of the bearing fault data shows that the method can realize weak signal detection and fault diagnosis effectively.
2017, 36(9): 1408-1413.
doi: 10.13433/j.cnki.1003-8728.2017.0916
Abstract:
Gear thermo-elastic coupling analysis was carried out with finite element indirect coupling method, and the thermo-elastic deformation distribution along tooth width direction was obtained. The function fitting of thermo-elastic deformation data points along tooth width direction was carried out with MATLAB. Based on gear profile modification, a new style of gear modification was presented. The elastic deformation showed uneven distribution, and thermo-elastic deformation in middle region was less than the gear end-faces along tooth width direction. The new style of gear modification met different deformations along tooth width direction, and the problem that the modification amount was larger or less in local for the Walker gear profile modification was avoided. The new style of gear modification design was more accurate.
Gear thermo-elastic coupling analysis was carried out with finite element indirect coupling method, and the thermo-elastic deformation distribution along tooth width direction was obtained. The function fitting of thermo-elastic deformation data points along tooth width direction was carried out with MATLAB. Based on gear profile modification, a new style of gear modification was presented. The elastic deformation showed uneven distribution, and thermo-elastic deformation in middle region was less than the gear end-faces along tooth width direction. The new style of gear modification met different deformations along tooth width direction, and the problem that the modification amount was larger or less in local for the Walker gear profile modification was avoided. The new style of gear modification design was more accurate.
2017, 36(9): 1414-1420.
doi: 10.13433/j.cnki.1003-8728.2017.0917
Abstract:
With the finite element analysis software of COMSOL Multiphysics, a finite element model of water-cooling system for 170SD30-SY motorized spindle was built, and the temperature field of water-cooling system under different water flows was simulated; furthermore, a temperature experiment platform of water-cooling system was built, then the experiments were carried out respectively under different water flow speeds to validate the relationship between the cooling system parameters and temperature rise. The results showed that under different speeds, the spindle temperature was reduced in different degrees with the increase of the cooling water flow rate; and it achieved the best cooling effect when the cooling water flow rate was 0.28 m3/h~0.30 m3/h; meanwhile, it had a more direct effect to change the initial temperature of cooling water so as to control the spindle temperature rise.
With the finite element analysis software of COMSOL Multiphysics, a finite element model of water-cooling system for 170SD30-SY motorized spindle was built, and the temperature field of water-cooling system under different water flows was simulated; furthermore, a temperature experiment platform of water-cooling system was built, then the experiments were carried out respectively under different water flow speeds to validate the relationship between the cooling system parameters and temperature rise. The results showed that under different speeds, the spindle temperature was reduced in different degrees with the increase of the cooling water flow rate; and it achieved the best cooling effect when the cooling water flow rate was 0.28 m3/h~0.30 m3/h; meanwhile, it had a more direct effect to change the initial temperature of cooling water so as to control the spindle temperature rise.
2017, 36(9): 1421-1427.
doi: 10.13433/j.cnki.1003-8728.2017.0918
Abstract:
A seven degree of freedom (7-DOF) nonlinear vehicle model which included vertical, pitch and roll motions were built in MATLAB/SIMULINK, the nonlinear effects of the shock absorber on the vehicle under the random excitation was discussed. The vehicle test results proved that the analysis were correct. Then the influences of the nonlinear shock absorber damping on the vehicle total weighted RMS vibration acceleration was studied. The results show that different rebound stroke damping variation coefficient nr and compression stroke damping variation coefficient nc will affect vehicle vibration on varying degrees, and small variation coefficient will increase the total weighted RMS vibration acceleration, while large variation coefficient do not improve the ride comfort. At the same time, the results show that the same variation coefficients of the double-side damping value nrc and ncr have little effect on the vehicle vibration. This paper considered the sensitive direction to human body, it provides a guidance to design a good ride comfort vehicle suspension.
A seven degree of freedom (7-DOF) nonlinear vehicle model which included vertical, pitch and roll motions were built in MATLAB/SIMULINK, the nonlinear effects of the shock absorber on the vehicle under the random excitation was discussed. The vehicle test results proved that the analysis were correct. Then the influences of the nonlinear shock absorber damping on the vehicle total weighted RMS vibration acceleration was studied. The results show that different rebound stroke damping variation coefficient nr and compression stroke damping variation coefficient nc will affect vehicle vibration on varying degrees, and small variation coefficient will increase the total weighted RMS vibration acceleration, while large variation coefficient do not improve the ride comfort. At the same time, the results show that the same variation coefficients of the double-side damping value nrc and ncr have little effect on the vehicle vibration. This paper considered the sensitive direction to human body, it provides a guidance to design a good ride comfort vehicle suspension.
2017, 36(9): 1428-1433.
doi: 10.13433/j.cnki.1003-8728.2017.0919
Abstract:
In order to solve the problem of lacking SIR particle filter algorithm diversity, the SIR particle filter algorithm is improved to estimate electric vehicle battery state of charge (SOC), with system state continuous approximate distribution sampling regularization filtering algorithm. By the ampere hour method to build the state space model of the battery and identify the battery model parameter, the simulation experiment is finished combined with the particle filter algorithm and improved particle filter algorithm in MATLAB. Simulation results show that, the SIR particle filter algorithm estimation errors of SOC becomes larger with the time increasing, the improved particle filtering algorithm to estimate the battery state of charge (SOC) has been close to the true value. Compared with the SIR particle filter, the improved particle filtering algorithm is of high accuracy and better adaptability than the SIR particle filter algorithm, providing a new idea for estimating SOC of batteries used in electric vehicles.
In order to solve the problem of lacking SIR particle filter algorithm diversity, the SIR particle filter algorithm is improved to estimate electric vehicle battery state of charge (SOC), with system state continuous approximate distribution sampling regularization filtering algorithm. By the ampere hour method to build the state space model of the battery and identify the battery model parameter, the simulation experiment is finished combined with the particle filter algorithm and improved particle filter algorithm in MATLAB. Simulation results show that, the SIR particle filter algorithm estimation errors of SOC becomes larger with the time increasing, the improved particle filtering algorithm to estimate the battery state of charge (SOC) has been close to the true value. Compared with the SIR particle filter, the improved particle filtering algorithm is of high accuracy and better adaptability than the SIR particle filter algorithm, providing a new idea for estimating SOC of batteries used in electric vehicles.
2017, 36(9): 1434-1440.
doi: 10.13433/j.cnki.1003-8728.2017.0920
Abstract:
Adopting the extend Kalman filter theory, a key target distinguishing method is researched in order to avoid the goal confusion or missing of automobile cruise control system (ACC) on the curve road. An extend Kalman filter on yaw rate and a key target distinguishing model are established to estimate the road curvature in real time and decide the critical target based on a nonlinear three-DOF vehicle model including the longitudinal, lateral and yaw direction. Adopting the fuzzy control theory, a multi-object lane-changing controller is presented to prejudge the danger lane-changing objects and distinguish out the key target on the straight road. A simulation model is elaborated with MATLAB/Simulink to validate the estimation of yaw rate and side slip angle under high-speed double lane input conditions. Simulation experiments are given for multiple targets in the curve road by adopting Carsim and MATLAB/Simulink co-simulation under building vehicle, sensor and road models in the Carsim conditions. The simulation results show that the key target distinguishing methods can identify accurately the key target, and avoid effectively rear-end collisions owing to the goal confusion or missing on the curve road, and prejudge the danger lane-changing objects on the straight road.
Adopting the extend Kalman filter theory, a key target distinguishing method is researched in order to avoid the goal confusion or missing of automobile cruise control system (ACC) on the curve road. An extend Kalman filter on yaw rate and a key target distinguishing model are established to estimate the road curvature in real time and decide the critical target based on a nonlinear three-DOF vehicle model including the longitudinal, lateral and yaw direction. Adopting the fuzzy control theory, a multi-object lane-changing controller is presented to prejudge the danger lane-changing objects and distinguish out the key target on the straight road. A simulation model is elaborated with MATLAB/Simulink to validate the estimation of yaw rate and side slip angle under high-speed double lane input conditions. Simulation experiments are given for multiple targets in the curve road by adopting Carsim and MATLAB/Simulink co-simulation under building vehicle, sensor and road models in the Carsim conditions. The simulation results show that the key target distinguishing methods can identify accurately the key target, and avoid effectively rear-end collisions owing to the goal confusion or missing on the curve road, and prejudge the danger lane-changing objects on the straight road.
2017, 36(9): 1441-1446.
doi: 10.13433/j.cnki.1003-8728.2017.0921
Abstract:
A calculation model for heat transfer analysis of internal combustion engines composite materials connecting rod was established with the element-free galerkin (EFG) method, and the heat transfer governing equation for the orthotropic structure based on the meshless method was deduced. The numerical example of composite materials plate was used to verify that the meshless model has a good adaptability for the heat transfer problem under the mixed boundary conditions. The temperature field of the composite materials connecting rod with different anisotropy factor was calculated with EFG method, and the effect of the EFG node number on the calculation accuracy was discussed. The result shows that the temperature based on the EFG method has a higher accuracy than that via FEM, and the temperature distribution of connecting rod small end can be greatly improved when the anisotropy factor is less than 1. The composite materials with the transverse thermal conductivity more than the vertical should be chosen for designing the internal combustion engines connecting rod.
A calculation model for heat transfer analysis of internal combustion engines composite materials connecting rod was established with the element-free galerkin (EFG) method, and the heat transfer governing equation for the orthotropic structure based on the meshless method was deduced. The numerical example of composite materials plate was used to verify that the meshless model has a good adaptability for the heat transfer problem under the mixed boundary conditions. The temperature field of the composite materials connecting rod with different anisotropy factor was calculated with EFG method, and the effect of the EFG node number on the calculation accuracy was discussed. The result shows that the temperature based on the EFG method has a higher accuracy than that via FEM, and the temperature distribution of connecting rod small end can be greatly improved when the anisotropy factor is less than 1. The composite materials with the transverse thermal conductivity more than the vertical should be chosen for designing the internal combustion engines connecting rod.
2017, 36(9): 1447-1451.
doi: 10.13433/j.cnki.1003-8728.2017.0922
Abstract:
To apply the wireless charging technology to an electric vehicle, a design method for power transmitter has been put forward. Rectangular coils and spiral windings are specially selected for evaluation. The compound winding is chosen for optimization. The magnetic flux density is studied by calculating the mutual inductance per area. By optimally choosing the turns and pitch distances of the spiral winding, a uniform magnetic field is achieved. Using finite element analysis, the performances of the transmitter are evaluated, including its tolerance to misalignment, thus effectively improving the inductive power transmission. The magnetic flux density distribution model of the designed transmitting terminal is simulated, and the simulation results are basically consistent with the calculation amount of the pre-designed model. In the transmitting terminal of a compound structure, when the spiral winding adopts non-uniform pitch, although the magnetic flux density at the edge of transmitting terminal is unavoidably reduced, the magnetic flux densities in most other charging areas still remain uniform.
To apply the wireless charging technology to an electric vehicle, a design method for power transmitter has been put forward. Rectangular coils and spiral windings are specially selected for evaluation. The compound winding is chosen for optimization. The magnetic flux density is studied by calculating the mutual inductance per area. By optimally choosing the turns and pitch distances of the spiral winding, a uniform magnetic field is achieved. Using finite element analysis, the performances of the transmitter are evaluated, including its tolerance to misalignment, thus effectively improving the inductive power transmission. The magnetic flux density distribution model of the designed transmitting terminal is simulated, and the simulation results are basically consistent with the calculation amount of the pre-designed model. In the transmitting terminal of a compound structure, when the spiral winding adopts non-uniform pitch, although the magnetic flux density at the edge of transmitting terminal is unavoidably reduced, the magnetic flux densities in most other charging areas still remain uniform.
2017, 36(9): 1452-1457.
doi: 10.13433/j.cnki.1003-8728.2017.0923
Abstract:
Because of the flow separation of the corner region of compressor cascade, a little blade installed in leading edge of cascades was proposed to control the separation of corner region. After confirming the reliability of numerical simulation method with experimental data, numerical simulations were carried out to explore the effects of little blade on the performance of cascade. The results show that the aerodynamic performance at the attack angle range of -6° and 9° is improved by the use of little blade. It also decreases the total pressure loss, arises the static pressure ratio. Furthermore, little blade makes leading edge separation point of cascades corner move back, the area of the reverse flow is decreased and corner flow is improved. More fluid converges to middle of cascade, which improves the diffusion capacity of the cascade.
Because of the flow separation of the corner region of compressor cascade, a little blade installed in leading edge of cascades was proposed to control the separation of corner region. After confirming the reliability of numerical simulation method with experimental data, numerical simulations were carried out to explore the effects of little blade on the performance of cascade. The results show that the aerodynamic performance at the attack angle range of -6° and 9° is improved by the use of little blade. It also decreases the total pressure loss, arises the static pressure ratio. Furthermore, little blade makes leading edge separation point of cascades corner move back, the area of the reverse flow is decreased and corner flow is improved. More fluid converges to middle of cascade, which improves the diffusion capacity of the cascade.
2017, 36(9): 1458-1463.
doi: 10.13433/j.cnki.1003-8728.2017.0924
Abstract:
A three-degree-of-freedom (3-DOF) rotational redundant-actuation flight simulator is proposed. It includes three degrees of freedom, six actuators and 3 redundant actuators. Based on the 3-DOF RRR spherical parallel manipulator, the parallelogram mechanism is introduced to accomplish the redundant actuation so that the flight simulator can be manipulated by enough power. The use of the parallelogram mechanism improves the stiffness and overcomes the drawback of the low power of an electric motor compared with hydraulic power. The parameters of 3-DOF spherical parallel manipulator are changed to gain the smallest volume of the manipulator of the flight simulator relatively. Direction-cosine is built with the analytically spherical theory; then the Jacobian matrix is established based on the direction-cosine. The inverse kinematics is solved with the constant intersection angle principle and the constraint equations are established at the same time. The interference that limits the input angles of the parallelogram mechanism is considered, so that the ranges of input angle are gained by the cross vector product theorem. Based on the range of input angles, an effective numerical algorithm of forward kinematics and inversely kinematical equations and the workspace volume are obtained. The results show that the volume of flight simulator proposed in this paper is apparently larger than the Stewart parallel manipulator.
A three-degree-of-freedom (3-DOF) rotational redundant-actuation flight simulator is proposed. It includes three degrees of freedom, six actuators and 3 redundant actuators. Based on the 3-DOF RRR spherical parallel manipulator, the parallelogram mechanism is introduced to accomplish the redundant actuation so that the flight simulator can be manipulated by enough power. The use of the parallelogram mechanism improves the stiffness and overcomes the drawback of the low power of an electric motor compared with hydraulic power. The parameters of 3-DOF spherical parallel manipulator are changed to gain the smallest volume of the manipulator of the flight simulator relatively. Direction-cosine is built with the analytically spherical theory; then the Jacobian matrix is established based on the direction-cosine. The inverse kinematics is solved with the constant intersection angle principle and the constraint equations are established at the same time. The interference that limits the input angles of the parallelogram mechanism is considered, so that the ranges of input angle are gained by the cross vector product theorem. Based on the range of input angles, an effective numerical algorithm of forward kinematics and inversely kinematical equations and the workspace volume are obtained. The results show that the volume of flight simulator proposed in this paper is apparently larger than the Stewart parallel manipulator.
2017, 36(9): 1464-1471.
doi: 10.13433/j.cnki.1003-8728.2017.0925
Abstract:
The integrated micro-vibration modeling and control scheme are thus investigated to achieve high accuracy and high stability control of the spacecraft payload. At first, the integrated model including the dynamics and control of the spacecraft body containing typical vibration sources is derived. The attitude control simulation of the spacecraft is implemented. Then, using the proposed model of the spacecraft body, the integrated model of the whole spacecraft containing the payload-body vibration isolator is derived. To compare the performance of the passive vibration isolation and passive-active hybrid isolation, the attitude control of payload is simulated. The simulation results confirm that the passive-active hybrid isolation improves the accuracy and stability of the payload attitude control by two orders. The high accuracy and high stability control of the spacecraft payload is thus achieved.
The integrated micro-vibration modeling and control scheme are thus investigated to achieve high accuracy and high stability control of the spacecraft payload. At first, the integrated model including the dynamics and control of the spacecraft body containing typical vibration sources is derived. The attitude control simulation of the spacecraft is implemented. Then, using the proposed model of the spacecraft body, the integrated model of the whole spacecraft containing the payload-body vibration isolator is derived. To compare the performance of the passive vibration isolation and passive-active hybrid isolation, the attitude control of payload is simulated. The simulation results confirm that the passive-active hybrid isolation improves the accuracy and stability of the payload attitude control by two orders. The high accuracy and high stability control of the spacecraft payload is thus achieved.
2017, 36(9): 1472-1476.
doi: 10.13433/j.cnki.1003-8728.2017.0926
Abstract:
The equivalent stiffness of the aero-clamps for a certain type aircraft hydraulic pipeline was determined by experiments. The effects of temperature and pipe-diameter on the equivalent stiffness of the clamps were investigated. The tensile experiments of one-point-fixed clamps (containing cushion) with different pipe-diameter were designed. The experiments were carried out by INSTRON 5567 tester with a temperature box. The tested temperature range was -50℃~125℃. The experimental results showed that:1) The stiffness of the clamps in Y-direction was 25% of that in X-direction approximately; 2) At the room temperature, when the pipe-diameter increased from 6 mm to 12 mm, the equivalent stiffness in X-direction decreased by 33.6%, and the stiffness in Y-direction decreased by 49.6%; 3) The stiffness of one-point-fixed clamp decreased dramatically with increasing temperature. The clamping force declined when the temperature was greater than 80℃, and the slipping phenomenon was observed. Finally, a FEM model (considering the detailed-contacts between cushion and clamp-strap) for the aero-clamps was established, the numerical predictions are in good agreements with the experimental data.
The equivalent stiffness of the aero-clamps for a certain type aircraft hydraulic pipeline was determined by experiments. The effects of temperature and pipe-diameter on the equivalent stiffness of the clamps were investigated. The tensile experiments of one-point-fixed clamps (containing cushion) with different pipe-diameter were designed. The experiments were carried out by INSTRON 5567 tester with a temperature box. The tested temperature range was -50℃~125℃. The experimental results showed that:1) The stiffness of the clamps in Y-direction was 25% of that in X-direction approximately; 2) At the room temperature, when the pipe-diameter increased from 6 mm to 12 mm, the equivalent stiffness in X-direction decreased by 33.6%, and the stiffness in Y-direction decreased by 49.6%; 3) The stiffness of one-point-fixed clamp decreased dramatically with increasing temperature. The clamping force declined when the temperature was greater than 80℃, and the slipping phenomenon was observed. Finally, a FEM model (considering the detailed-contacts between cushion and clamp-strap) for the aero-clamps was established, the numerical predictions are in good agreements with the experimental data.
