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RSS2015 Vol. 34, No. 6
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2015, 34(6): 821-826.
doi: 10.13433/j.cnki.1003-8728.2015.0601
PDF 1886KB
Abstract:
Referred to the characteristics of intermittent crawl gait, the continuous crawl gait was optimized with a lateral movement of the center of gravity (COG) to get a balance of speed and stability. Besides, the stability margin affected by lateral movement of COG was depicted quantitatively. The improvement of optimized crawl gait in stability and speed was analyzed based on Adams simulation. Finally the optimized crawl gait was verified by a quadruped robot prototype test.
Referred to the characteristics of intermittent crawl gait, the continuous crawl gait was optimized with a lateral movement of the center of gravity (COG) to get a balance of speed and stability. Besides, the stability margin affected by lateral movement of COG was depicted quantitatively. The improvement of optimized crawl gait in stability and speed was analyzed based on Adams simulation. Finally the optimized crawl gait was verified by a quadruped robot prototype test.
2015, 34(6): 827-831.
doi: 10.13433/j.cnki.1003-8728.2015.0602
Abstract:
The diesel particulate trap technology can effectively reduce black smoke emissions. But as the amount of trap increases, exhaust back pressure increases accordingly. Adopting the regeneration of fuel injection combustion mode, we can remove deposited particles and lower exhaust back pressure. Aiming at reducing the high cost and difficulty in developing the current regeneration control system of injection combustion, we adopt the STC89C52 single-chip microcomputer to design an automatic and efficient closed loop control system. With the control system,the fuzzy control algorithm is applied to adjusting the quantity of fuel injection and air compensation timely to realize the intelligent control of the inlet temperature of the DPF (diesel particle filter) so as to reduce the secondary pollution during regeneration and to improve the regeneration efficiency and prolong the service life of the diesel particle filter.
The diesel particulate trap technology can effectively reduce black smoke emissions. But as the amount of trap increases, exhaust back pressure increases accordingly. Adopting the regeneration of fuel injection combustion mode, we can remove deposited particles and lower exhaust back pressure. Aiming at reducing the high cost and difficulty in developing the current regeneration control system of injection combustion, we adopt the STC89C52 single-chip microcomputer to design an automatic and efficient closed loop control system. With the control system,the fuzzy control algorithm is applied to adjusting the quantity of fuel injection and air compensation timely to realize the intelligent control of the inlet temperature of the DPF (diesel particle filter) so as to reduce the secondary pollution during regeneration and to improve the regeneration efficiency and prolong the service life of the diesel particle filter.
2015, 34(6): 832-835.
doi: 10.13433/j.cnki.1003-8728.2015.0603
Abstract:
Based on the analysis of power matching between diesel engine and HST, a new curve extraction method based on first-order linear fitting is presented. Based on the most economical working curve obtained with the method, a new fuel optimal control method of diesel engine-HST system is designed. A simulation model is established in AMEsim; speed characteristic in closed loop feedback system is analyzed. The results show that power matching and joint control between diesel engine and HST is an effective way for improving the vehicle's matching identity and ensure its working point in the economic region.
Based on the analysis of power matching between diesel engine and HST, a new curve extraction method based on first-order linear fitting is presented. Based on the most economical working curve obtained with the method, a new fuel optimal control method of diesel engine-HST system is designed. A simulation model is established in AMEsim; speed characteristic in closed loop feedback system is analyzed. The results show that power matching and joint control between diesel engine and HST is an effective way for improving the vehicle's matching identity and ensure its working point in the economic region.
2015, 34(6): 836-839.
doi: 10.13433/j.cnki.1003-8728.2015.0604
Abstract:
In order to analyze the characteristics of collision between ratchet and pawl of a synchronous-self-shifting clutch, this paper studies the core component of ratchet and pawl of the 4.5MW synchronous-self-shifting clutch and uses the RECURDYN software to build the ratchet and pawl simulation analysis model, which is based on a general contact problem solution. The ratchet and pawl collision process is simulated and analyzed. The influences of the differential angular speed of the ratchet and pawl and the contact stiffness coefficient on the impact force of the ratchet and its speed are studied, thus obtaining the collision characteristics of the ratchet and pawl.
In order to analyze the characteristics of collision between ratchet and pawl of a synchronous-self-shifting clutch, this paper studies the core component of ratchet and pawl of the 4.5MW synchronous-self-shifting clutch and uses the RECURDYN software to build the ratchet and pawl simulation analysis model, which is based on a general contact problem solution. The ratchet and pawl collision process is simulated and analyzed. The influences of the differential angular speed of the ratchet and pawl and the contact stiffness coefficient on the impact force of the ratchet and its speed are studied, thus obtaining the collision characteristics of the ratchet and pawl.
2015, 34(6): 840-843.
doi: 10.13433/j.cnki.1003-8728.2015.0605
Abstract:
Aiming at welded structure inevitably cracks phenomenon, we build tower crane boom finite element model, taking into account the effect of residual stress, which is used to calculate QTZ40 tower crane jib bottom chord and horizontal web welding rod at full load and no-load state car horn, different crack lengths corresponding to the stress intensity factor, through simulation analysis. Then we establish stress intensity factor range as a function of the crack length, and then estimate the tower crane arm fatigue life. The results show that: with the stress intensity factor range crack length increases, when the crack length reaches a certain value, the stress intensity factor range exponentially accelerated form, so to take effective measures to prevent the rapid expansion of the crack can improve the fatigue life.
Aiming at welded structure inevitably cracks phenomenon, we build tower crane boom finite element model, taking into account the effect of residual stress, which is used to calculate QTZ40 tower crane jib bottom chord and horizontal web welding rod at full load and no-load state car horn, different crack lengths corresponding to the stress intensity factor, through simulation analysis. Then we establish stress intensity factor range as a function of the crack length, and then estimate the tower crane arm fatigue life. The results show that: with the stress intensity factor range crack length increases, when the crack length reaches a certain value, the stress intensity factor range exponentially accelerated form, so to take effective measures to prevent the rapid expansion of the crack can improve the fatigue life.
2015, 34(6): 844-847.
doi: 10.13433/j.cnki.1003-8728.2015.0606
Abstract:
In order to attenuate hydraulic pressure pulsation, the structure of modal resonance hydraulic pulsation attenuator is proposed based on the principle of resonance attenuation. The resonance plate has multiple modes which widen the attenuation frequency range. When the pulsation frequency of the hydraulic system approaches to one of the modal frequencies, the corresponding mode will be aroused to attenuate the pulsation energy. Selecting suitable materials and designing the resonant structure can make its natural frequencies distributed evenly and densely, so that the pulsation attenuator has perfect performance for wide frequency range. The acoustic-vibration coupling simulation and experimental tests show that the modal resonance hydraulic pulsation attenuator has the advantages of compact structure, wide attenuation frequency range, and excellent silencing performance.
In order to attenuate hydraulic pressure pulsation, the structure of modal resonance hydraulic pulsation attenuator is proposed based on the principle of resonance attenuation. The resonance plate has multiple modes which widen the attenuation frequency range. When the pulsation frequency of the hydraulic system approaches to one of the modal frequencies, the corresponding mode will be aroused to attenuate the pulsation energy. Selecting suitable materials and designing the resonant structure can make its natural frequencies distributed evenly and densely, so that the pulsation attenuator has perfect performance for wide frequency range. The acoustic-vibration coupling simulation and experimental tests show that the modal resonance hydraulic pulsation attenuator has the advantages of compact structure, wide attenuation frequency range, and excellent silencing performance.
2015, 34(6): 848-852.
doi: 10.13433/j.cnki.1003-8728.2015.0607
Abstract:
In normal operation of swing bar of LED Bonder, there exist the questions of the non-stability, large amplitude and long settling time. These questions affect the efficiency and accuracy of LED Bonder. By analyzing the whole swing bar movement a new design method is proposed. Firstly, the quintic polynomial motion curve is used instead of trapezoid motion curve to ensure the stability of the swing bar in the moving process. Secondly, the shape of the swing bar is optimized with the results of the static analysis, modal analysis and transient dynamics analysis. Then, topology optimization is carried out on the structural design of the swing bar to reduce the influence of moment of inertia and get the optimization model. Finally, the feasiblity and effectiveness of this method are verified with the results of transient dynamics analysis.
In normal operation of swing bar of LED Bonder, there exist the questions of the non-stability, large amplitude and long settling time. These questions affect the efficiency and accuracy of LED Bonder. By analyzing the whole swing bar movement a new design method is proposed. Firstly, the quintic polynomial motion curve is used instead of trapezoid motion curve to ensure the stability of the swing bar in the moving process. Secondly, the shape of the swing bar is optimized with the results of the static analysis, modal analysis and transient dynamics analysis. Then, topology optimization is carried out on the structural design of the swing bar to reduce the influence of moment of inertia and get the optimization model. Finally, the feasiblity and effectiveness of this method are verified with the results of transient dynamics analysis.
2015, 34(6): 853-857.
doi: 10.13433/j.cnki.1003-8728.2015.0608
Abstract:
Aiming at the issues that the traveling of the continuous ability to work on the curved pipes between home and abroad, we propose a turning mechanism that the tube peristaltic robot with a spring coupling can move in different curvature pipeline. With the analysis of the robot's structure, working principle, position posture and motion geometry, we obtain the related formulas of movement characteristics in different curvature pipes. Simulation analysis is made on the robots to verify the related theoretical analysis so as to determine all design parameters of the turning mechanism' relating theory principles of the crawling in-pipe robot with a spring coupling.
Aiming at the issues that the traveling of the continuous ability to work on the curved pipes between home and abroad, we propose a turning mechanism that the tube peristaltic robot with a spring coupling can move in different curvature pipeline. With the analysis of the robot's structure, working principle, position posture and motion geometry, we obtain the related formulas of movement characteristics in different curvature pipes. Simulation analysis is made on the robots to verify the related theoretical analysis so as to determine all design parameters of the turning mechanism' relating theory principles of the crawling in-pipe robot with a spring coupling.
2015, 34(6): 858-862.
doi: 10.13433/j.cnki.1003-8728.2015.0609
Abstract:
Upper non-contact magnetic bearing used in flywheel energy storage system should relief 80%~90% weights to reduce friction and consumption of under bracing and bearing. Based on Finite Element Method (FEM), an armored NdFeB (Neodymium Ferrum Boron) permanent magnetic bearing (PMB) design method was proposed and was applied in 400 kW flywheel energy storage system prototype design and experiment. In the simple structure, rotor without permanent magnet could avoid vibration and heat deposition. Permanent Magnetic (PM) rings assembled with tile-shaped blocks were suitable for huge unloading force requirement without any worry about the non-uniform magnetic field. Bearing suction was approximately linear relational to the gap size near working gap. Bearing suction could reach the maximum when the ratio of magnetic yoke and magnetic ring was near 2. According to optimizing process, we concluded an efficient design process, making the PM volume reduced by 24.4%, and gave several more designs of armored PMB with max unloading force under different rotary speed.
Upper non-contact magnetic bearing used in flywheel energy storage system should relief 80%~90% weights to reduce friction and consumption of under bracing and bearing. Based on Finite Element Method (FEM), an armored NdFeB (Neodymium Ferrum Boron) permanent magnetic bearing (PMB) design method was proposed and was applied in 400 kW flywheel energy storage system prototype design and experiment. In the simple structure, rotor without permanent magnet could avoid vibration and heat deposition. Permanent Magnetic (PM) rings assembled with tile-shaped blocks were suitable for huge unloading force requirement without any worry about the non-uniform magnetic field. Bearing suction was approximately linear relational to the gap size near working gap. Bearing suction could reach the maximum when the ratio of magnetic yoke and magnetic ring was near 2. According to optimizing process, we concluded an efficient design process, making the PM volume reduced by 24.4%, and gave several more designs of armored PMB with max unloading force under different rotary speed.
2015, 34(6): 863-866.
doi: 10.13433/j.cnki.1003-8728.2015.0610
Abstract:
Combining the features of Intrinsic Time-scale Decomposition (ITD) and Denoising Source Separation (DSS), we propose an underdetermined DSS method based on ITD. This method is used to deal with the blind source separation problem of rotating machinery in the case of the number of observed mixtures being less than that of contributing sources. The observed signals are decomposed into some proper rotation component with the ITD, which is an effective way to solve the problem of the dimension insufficient in underdetermined blind source separation. As the same time, the Gerschgorin Disk Estimator (GDE) is used to estimate the number of the types of observed signals, and the mixed sources are separated by DSS algorithm. Applying ITD-GDE-DSS method to the rotor fault detection, we have diagnosed the sudden unbalance phenomenon through the measured fault signals of the rotor. The first critical speed signals and the second critical speed signals are separated by this method.
Combining the features of Intrinsic Time-scale Decomposition (ITD) and Denoising Source Separation (DSS), we propose an underdetermined DSS method based on ITD. This method is used to deal with the blind source separation problem of rotating machinery in the case of the number of observed mixtures being less than that of contributing sources. The observed signals are decomposed into some proper rotation component with the ITD, which is an effective way to solve the problem of the dimension insufficient in underdetermined blind source separation. As the same time, the Gerschgorin Disk Estimator (GDE) is used to estimate the number of the types of observed signals, and the mixed sources are separated by DSS algorithm. Applying ITD-GDE-DSS method to the rotor fault detection, we have diagnosed the sudden unbalance phenomenon through the measured fault signals of the rotor. The first critical speed signals and the second critical speed signals are separated by this method.
2015, 34(6): 867-871.
doi: 10.13433/j.cnki.1003-8728.2015.0611
Abstract:
This paper explains a load sensitive pump response performance theoretically and builds its mathematical and simulation model. Then, AMESim batch function is used to explore the response speed of the main parameters. After theoretical and simulation analysis, the structural optimization of the load sensitive pump is carried out. The simulation results show that: the response speed of the optimized load sensitive pump increases by 33.2%. Finally, 28-type rotary drilling rig is used for test research. The test results also show that the response speed of the optimized load sensitive pump increases by 33.2%. The simulation results agree well with the test results.
This paper explains a load sensitive pump response performance theoretically and builds its mathematical and simulation model. Then, AMESim batch function is used to explore the response speed of the main parameters. After theoretical and simulation analysis, the structural optimization of the load sensitive pump is carried out. The simulation results show that: the response speed of the optimized load sensitive pump increases by 33.2%. Finally, 28-type rotary drilling rig is used for test research. The test results also show that the response speed of the optimized load sensitive pump increases by 33.2%. The simulation results agree well with the test results.
Influence of the Surface Integrity on the Fatigue Life for High-speed Milling of 7055 Aluminum Alloy
2015, 34(6): 872-876.
doi: 10.13433/j.cnki.1003-8728.2015.0612
Abstract:
To optimize the process parameters in the high-speed milling of high strength aluminum alloys, and to improve the fatigue life of components, the effect of the process parameters on the surface integrity and the effect of the surface integrity on the fatigue life were investigated through high-speed milling experiments and fatigue tests of aluminum alloys 7055. The results show that the compressive residual stress can be detected on all the machining surface, the effect of the feed per tooth on the surface roughness is greater than the milling speed, the milling speed and feed per tooth slightly affect the surface micro hardness. The fatigue life decreases with the increasing of the surface roughness, and increases with the increasing of the surface compressive residual stress. Within the experiments limits, the best process parameters are the milling speed of 1 100 m/min, feed per tooth of 0.06 mm/z, and the machining surface roughness is of Ra 0.327 μm, surface micro hardness be of 187.44HV0.025, surface residual stress be of -177.7 MPa, fatigue life be of 1.275×105 cycles.
To optimize the process parameters in the high-speed milling of high strength aluminum alloys, and to improve the fatigue life of components, the effect of the process parameters on the surface integrity and the effect of the surface integrity on the fatigue life were investigated through high-speed milling experiments and fatigue tests of aluminum alloys 7055. The results show that the compressive residual stress can be detected on all the machining surface, the effect of the feed per tooth on the surface roughness is greater than the milling speed, the milling speed and feed per tooth slightly affect the surface micro hardness. The fatigue life decreases with the increasing of the surface roughness, and increases with the increasing of the surface compressive residual stress. Within the experiments limits, the best process parameters are the milling speed of 1 100 m/min, feed per tooth of 0.06 mm/z, and the machining surface roughness is of Ra 0.327 μm, surface micro hardness be of 187.44HV0.025, surface residual stress be of -177.7 MPa, fatigue life be of 1.275×105 cycles.
2015, 34(6): 877-880.
doi: 10.13433/j.cnki.1003-8728.2015.0613
Abstract:
The whole system including software and hardware is constructed in this paper. In order to realize the optimization design and control for servo press, a servo press mechanical loads emulation experimental platform using servo motor to emulate the dynamic characteristics of different mechanical loads is constructed. The experimental platform which uses feedforward control combined with speed-tracking control in design can realize the emulation of different mechanical loads in laboratory environment based on the flexible control of servo motor by realizing the servo motor load equivalent to different mechanical loads. It is expected that the system might have better dynamic response than the ordinary dynamometer as it avoids introducing the inverse dynamic control.
The whole system including software and hardware is constructed in this paper. In order to realize the optimization design and control for servo press, a servo press mechanical loads emulation experimental platform using servo motor to emulate the dynamic characteristics of different mechanical loads is constructed. The experimental platform which uses feedforward control combined with speed-tracking control in design can realize the emulation of different mechanical loads in laboratory environment based on the flexible control of servo motor by realizing the servo motor load equivalent to different mechanical loads. It is expected that the system might have better dynamic response than the ordinary dynamometer as it avoids introducing the inverse dynamic control.
2015, 34(6): 881-891.
doi: 10.13433/j.cnki.1003-8728.2015.0614
Abstract:
To deal with problems of monitoring complex and assembly data out of touch with the management, the monitoring technology for complex product assembly was studied. Firstly, the business processes and organization personnel's monitoring data in complex product assembly process were analyzed and the method of the grading monitoring for complex product assembly process based on the information flow model was presented. Some key techniques in the present method were studied, such as real-time data acquisition and real-time monitoring for assembly process, the assembly schedule variance grading adjust, the control of working hours based on the organization regulation, and so on. Finally, the system was developed, and the satisfactory results of the system were obtained.
To deal with problems of monitoring complex and assembly data out of touch with the management, the monitoring technology for complex product assembly was studied. Firstly, the business processes and organization personnel's monitoring data in complex product assembly process were analyzed and the method of the grading monitoring for complex product assembly process based on the information flow model was presented. Some key techniques in the present method were studied, such as real-time data acquisition and real-time monitoring for assembly process, the assembly schedule variance grading adjust, the control of working hours based on the organization regulation, and so on. Finally, the system was developed, and the satisfactory results of the system were obtained.
2015, 34(6): 892-897.
doi: 10.13433/j.cnki.1003-8728.2015.0615
Abstract:
To solve the reuse of parts process knowledge in the Computer Aided Process Planning(CAPP) system, the knowledge based modeling and similarity measurement method for the reuse of Three-Dimensional(3D) process knowledge is proposed. According to analyze the evolvement law of 3D geometric feature in parts process knowledge, we introduce the concept of machining cell and its sequence consequently. Based on the factor space theory, the information essence of process knowledge is analyzed, the concept of knowledge element is defined and its factor set is subsequently provided. According to the above-mentioned, we contruct the space expression model of process knowledge. According to the data type of the factor's status value, we contruct the measurement space which is the projection of the high-dimensional factor space of knowledge element onto 3D space and present the similarity measurment function of each dimension. The space distance among knowledge elements using Euclidean distance is calculated and then the similarity of knowledge element is gotten. The effectiveness of the method has been confirmed in the prototype system for knowledge reuse.
To solve the reuse of parts process knowledge in the Computer Aided Process Planning(CAPP) system, the knowledge based modeling and similarity measurement method for the reuse of Three-Dimensional(3D) process knowledge is proposed. According to analyze the evolvement law of 3D geometric feature in parts process knowledge, we introduce the concept of machining cell and its sequence consequently. Based on the factor space theory, the information essence of process knowledge is analyzed, the concept of knowledge element is defined and its factor set is subsequently provided. According to the above-mentioned, we contruct the space expression model of process knowledge. According to the data type of the factor's status value, we contruct the measurement space which is the projection of the high-dimensional factor space of knowledge element onto 3D space and present the similarity measurment function of each dimension. The space distance among knowledge elements using Euclidean distance is calculated and then the similarity of knowledge element is gotten. The effectiveness of the method has been confirmed in the prototype system for knowledge reuse.
2015, 34(6): 898-902.
doi: 10.13433/j.cnki.1003-8728.2015.0616
Abstract:
A three-dimensional finite element model closer to the actual milling cutter structure is established. The chip forming process of high-speed milling titanium alloy Ti6Al4V is simulated, obtaining the distribution cloud atlas of temperature, analyzing the distribution of surface residual stress. A surface roughness evaluation method using the contour arithmetic average deviation as the parameters, though simulating the size of surface displacement of milling workpiece by the finite element, is put forward. The results reveal that the highest temperature in the cutting zone locates on the tool-chip interface at a distance of 0.01~0.03 mm from the tool tip. The cutting temperature decreases when the spindle speed is 9 500 r/min. The tensile residual stress in the surface of the workpiece rapidly transformed into compressive stress,whose magnitude is found at 100~200 μm. The surface roughness obtains the minimum when the spindle speed is 9 500 r/min and the feed per tooth is 0.02 mm.
A three-dimensional finite element model closer to the actual milling cutter structure is established. The chip forming process of high-speed milling titanium alloy Ti6Al4V is simulated, obtaining the distribution cloud atlas of temperature, analyzing the distribution of surface residual stress. A surface roughness evaluation method using the contour arithmetic average deviation as the parameters, though simulating the size of surface displacement of milling workpiece by the finite element, is put forward. The results reveal that the highest temperature in the cutting zone locates on the tool-chip interface at a distance of 0.01~0.03 mm from the tool tip. The cutting temperature decreases when the spindle speed is 9 500 r/min. The tensile residual stress in the surface of the workpiece rapidly transformed into compressive stress,whose magnitude is found at 100~200 μm. The surface roughness obtains the minimum when the spindle speed is 9 500 r/min and the feed per tooth is 0.02 mm.
2015, 34(6): 903-909.
doi: 10.13433/j.cnki.1003-8728.2015.0617
Abstract:
The flow characteristics of the hydraulic cylinder are analyzed with the pulse width modulation (PWM), and the equations of flow-pressure and force balance are studied in the environment of MATLAB/Simulink. This compound algorithm is proposed to realize the precise position control, under the condition that the duty ratio is given ahead. The PI algorithm is designed and utilized to deal with the position error with adjusting to the frequency and duty ratio of the high-speed on-off valve (HSV). The genetic algorithm (GA) is used to tune the control parameters such as speed-forward coefficient, proportional and integral coefficient of displacement feedback and output coefficient to obtain optimization results on the performance of the position control system. The hydraulic loop is established on the FESTO platform for verification through comparing simulation results with optimization results. The results and analysis preliminary show that: 1) HSV can realize the flow control with PWM method; 2) the compound algorithm of PI and speed feedforward-displacement feedback effectively reduces the position control error; 3) the position control algorithm optimized with GA can realize the precise position control, and the position error can be reduced within -0.6 mm~0.6 mm.
The flow characteristics of the hydraulic cylinder are analyzed with the pulse width modulation (PWM), and the equations of flow-pressure and force balance are studied in the environment of MATLAB/Simulink. This compound algorithm is proposed to realize the precise position control, under the condition that the duty ratio is given ahead. The PI algorithm is designed and utilized to deal with the position error with adjusting to the frequency and duty ratio of the high-speed on-off valve (HSV). The genetic algorithm (GA) is used to tune the control parameters such as speed-forward coefficient, proportional and integral coefficient of displacement feedback and output coefficient to obtain optimization results on the performance of the position control system. The hydraulic loop is established on the FESTO platform for verification through comparing simulation results with optimization results. The results and analysis preliminary show that: 1) HSV can realize the flow control with PWM method; 2) the compound algorithm of PI and speed feedforward-displacement feedback effectively reduces the position control error; 3) the position control algorithm optimized with GA can realize the precise position control, and the position error can be reduced within -0.6 mm~0.6 mm.
2015, 34(6): 910-913.
doi: 10.13433/j.cnki.1003-8728.2015.0618
Abstract:
The dispersion in Lamb wave complicates the signal shape and analysis procedure and this phenomena also bring difficulties in mode packet extraction during damage monitoring. Extraction the wave packet via Hilbert-Huang Transform(HHT)can simplify the raw signal and improve precision and efficiency of damage monitoring. Compared with Short Time Fourier Transform(STFT), the HHT is more suitable for Lamb wave analysis with higher self-adaptivity and efficiency. The experiment of crack expansion monitoring on aluminum plate showed that the damage index combined with HHT can extract the lamb wave packet with higher accuracy and higher sensitivity to the crack expansion than those obtained by STFT appraoch.
The dispersion in Lamb wave complicates the signal shape and analysis procedure and this phenomena also bring difficulties in mode packet extraction during damage monitoring. Extraction the wave packet via Hilbert-Huang Transform(HHT)can simplify the raw signal and improve precision and efficiency of damage monitoring. Compared with Short Time Fourier Transform(STFT), the HHT is more suitable for Lamb wave analysis with higher self-adaptivity and efficiency. The experiment of crack expansion monitoring on aluminum plate showed that the damage index combined with HHT can extract the lamb wave packet with higher accuracy and higher sensitivity to the crack expansion than those obtained by STFT appraoch.
2015, 34(6): 914-918.
doi: 10.13433/j.cnki.1003-8728.2015.0619
Abstract:
This paper describes the driving system and its fractional order PID (FOPID) control algorithm for DC motor velocity control in a two-wheeled self-balancing vehicle (TWSBV) which is a nonlinear system. The proposed control algorithm aims to provide consistent driving performance for TWSBV on the condition of uncertainty and various velocities caused by different payload. The equations of motion of the motor are established and the FOPID control algorithm is presented. The motor's driving system is developed based on the STM32 embedded system. The simulation results indicate that the overshoot is minimized to 28.6% and that the settling time is reduced to 1.25 second. These parameters prove that the dynamic response performance of the FOPID controller is better than the conventional PID controller, thus being able to achieve the stable driving control.
This paper describes the driving system and its fractional order PID (FOPID) control algorithm for DC motor velocity control in a two-wheeled self-balancing vehicle (TWSBV) which is a nonlinear system. The proposed control algorithm aims to provide consistent driving performance for TWSBV on the condition of uncertainty and various velocities caused by different payload. The equations of motion of the motor are established and the FOPID control algorithm is presented. The motor's driving system is developed based on the STM32 embedded system. The simulation results indicate that the overshoot is minimized to 28.6% and that the settling time is reduced to 1.25 second. These parameters prove that the dynamic response performance of the FOPID controller is better than the conventional PID controller, thus being able to achieve the stable driving control.
2015, 34(6): 919-924.
doi: 10.13433/j.cnki.1003-8728.2015.0620
Abstract:
To improve the mechanical performances and reduce the weight of a semi_trailer towing vehicle frame, the uncertain optimization theory is introduced into the optimization of the frame. Based on the finite element model of the frame, an approximate model among design variables, uncertain variables and objective function is built. Upper and lower bounds of the objective function are solved with interval analysis method; target evaluation function serves as a fitness value of multi-objective optimization problem. The stress and mass of the frame are optimized with non-dominating sorting genetic algorithm (NSGA-Ⅱ), which is improved by adding elitist preservation strategy and removing duplicate individuals. The results compared with those of the multi-objective double nested optimization show that the computational efficiency is greatly improved and the mass of the frame is reduced under the premise of mechanical performances and accuracy requirements.
To improve the mechanical performances and reduce the weight of a semi_trailer towing vehicle frame, the uncertain optimization theory is introduced into the optimization of the frame. Based on the finite element model of the frame, an approximate model among design variables, uncertain variables and objective function is built. Upper and lower bounds of the objective function are solved with interval analysis method; target evaluation function serves as a fitness value of multi-objective optimization problem. The stress and mass of the frame are optimized with non-dominating sorting genetic algorithm (NSGA-Ⅱ), which is improved by adding elitist preservation strategy and removing duplicate individuals. The results compared with those of the multi-objective double nested optimization show that the computational efficiency is greatly improved and the mass of the frame is reduced under the premise of mechanical performances and accuracy requirements.
2015, 34(6): 925-929.
doi: 10.13433/j.cnki.1003-8728.2015.0621
Abstract:
In order to investigate the fatigue reliability of the welded position in bogie frame, with the methods the probabilistic fatigue S-N curves are constructed for the lateral butt welded joint, lateral T welded joint, and longitudinal T welded joint from the former test data of Q345 welded joints. For the high-speed bogie frame of passenger car, the bogie of CRH2 EMU is selected as the research object. Local stresses of 31 locations for welded joints around the connections are obtained from former calculations for the frame. Fatigue life prediction and reliability evaluation are performed with the probabilistic curves. The results reveal that the joint close to connection of gear box on the frame lateral beam is a critical location, which has a life of 3.88×108 cycles under a confidence of 97.5% and a survival probability of 0.975; if a life of 109 cycles is required under the same confidence level, the survival probability decreases to about 0.948 2.
In order to investigate the fatigue reliability of the welded position in bogie frame, with the methods the probabilistic fatigue S-N curves are constructed for the lateral butt welded joint, lateral T welded joint, and longitudinal T welded joint from the former test data of Q345 welded joints. For the high-speed bogie frame of passenger car, the bogie of CRH2 EMU is selected as the research object. Local stresses of 31 locations for welded joints around the connections are obtained from former calculations for the frame. Fatigue life prediction and reliability evaluation are performed with the probabilistic curves. The results reveal that the joint close to connection of gear box on the frame lateral beam is a critical location, which has a life of 3.88×108 cycles under a confidence of 97.5% and a survival probability of 0.975; if a life of 109 cycles is required under the same confidence level, the survival probability decreases to about 0.948 2.
2015, 34(6): 930-933.
doi: 10.13433/j.cnki.1003-8728.2015.0622
Abstract:
In order to obtain the MFI zeolite that has highly efficient adsorption properties, the Monte Carlo simulation and the hydrocarbon emissions in diesel cold start were used to simulate the effects of modified MFI zeolite on its adsorption performance. The experimental results demonstrate that the adsorption performances of both propylene and ethylene increase significantly, but the adsorption performance of ethylene is better. The study shows that with the decrease of the silica alumina ratio, the adsorption performance of propylene first decreases and then increases with the temperature rise and the adsorption performance of ethylene shows, on the whole, a trend of gradual increase when silica alumina ratio is 23, which is the largest adsorption performance of ethylene and propylene.
In order to obtain the MFI zeolite that has highly efficient adsorption properties, the Monte Carlo simulation and the hydrocarbon emissions in diesel cold start were used to simulate the effects of modified MFI zeolite on its adsorption performance. The experimental results demonstrate that the adsorption performances of both propylene and ethylene increase significantly, but the adsorption performance of ethylene is better. The study shows that with the decrease of the silica alumina ratio, the adsorption performance of propylene first decreases and then increases with the temperature rise and the adsorption performance of ethylene shows, on the whole, a trend of gradual increase when silica alumina ratio is 23, which is the largest adsorption performance of ethylene and propylene.
2015, 34(6): 934-939.
doi: 10.13433/j.cnki.1003-8728.2015.0623
Abstract:
The seriousness of injury and the mass of door trim can be reduced effectively by designing the shape of door trim reasonably. The implicit parametric technology was applied in progress of developing door trim and a parametric FE model of door subsystem was built. The shape of armrest and the thickness of door trim were optimized with multi-objective genetic algorithm in approximate model. The example indicated that the method can successfully solve the multi-objective problem about door trim's requirements in safety and lightweighting, and the development period was shortened greatly.
The seriousness of injury and the mass of door trim can be reduced effectively by designing the shape of door trim reasonably. The implicit parametric technology was applied in progress of developing door trim and a parametric FE model of door subsystem was built. The shape of armrest and the thickness of door trim were optimized with multi-objective genetic algorithm in approximate model. The example indicated that the method can successfully solve the multi-objective problem about door trim's requirements in safety and lightweighting, and the development period was shortened greatly.
2015, 34(6): 940-944.
doi: 10.13433/j.cnki.1003-8728.2015.0624
Abstract:
This paper investigated the reliability evaluation process of crack propagation life of marine diesel engine body material QT400-18 with probabilistic fracture mechanics method. Based on the crack propagation experiments of QT400-18 and considering the dispersion of crack propagation rate, we obtain the Paris formula parameters with statistical analysis, and establish a random probability model of crack propagation rate of QT400-18. Furthermore, a residual life reliability prediction model is also built. Through the numerical sampling simulation, the residual life and its distribution in different initial crack length are achieved and the correlation curve of reliability with residual life is drawn. In the condition of, the threshold of fatigue crack growth is obtained with an inversion approach.
This paper investigated the reliability evaluation process of crack propagation life of marine diesel engine body material QT400-18 with probabilistic fracture mechanics method. Based on the crack propagation experiments of QT400-18 and considering the dispersion of crack propagation rate, we obtain the Paris formula parameters with statistical analysis, and establish a random probability model of crack propagation rate of QT400-18. Furthermore, a residual life reliability prediction model is also built. Through the numerical sampling simulation, the residual life and its distribution in different initial crack length are achieved and the correlation curve of reliability with residual life is drawn. In the condition of, the threshold of fatigue crack growth is obtained with an inversion approach.
2015, 34(6): 945-948.
doi: 10.13433/j.cnki.1003-8728.2015.0625
Abstract:
The springback prediction for cold stretch bending of T8 aluminum-lithium alloys profiles and the die correction technique are researched. The stretch bending experiment of 2196-T8511 and 2099-T83 aluminum-lithium alloys profiles with T-section and Z-section is carried out. The present correction algorithm is used for dies of stretch bending. Its maximum error is 2 mm. The results show that cold stretch bending of T8 aluminium-lithium alloys profiles is feasible and the algorithms of springback prediction and compensation are effective. It can be taken as a reliable approach for stretch bending and die design of T8 aluminum-lithium alloys profiles.
The springback prediction for cold stretch bending of T8 aluminum-lithium alloys profiles and the die correction technique are researched. The stretch bending experiment of 2196-T8511 and 2099-T83 aluminum-lithium alloys profiles with T-section and Z-section is carried out. The present correction algorithm is used for dies of stretch bending. Its maximum error is 2 mm. The results show that cold stretch bending of T8 aluminium-lithium alloys profiles is feasible and the algorithms of springback prediction and compensation are effective. It can be taken as a reliable approach for stretch bending and die design of T8 aluminum-lithium alloys profiles.
2015, 34(6): 949-952.
doi: 10.13433/j.cnki.1003-8728.2015.0626
Abstract:
In order to select the optimum fixture materials for vacuum diffusion bonding of 00Cr18Ni10N stainless steel, joints with boron nitride (BN) and graphite as fixture material were prepared. The effect of the fixture materials on the corrosion behavior of joints was studied by neutral salt spray corrosion test and electrochemical impedance spectroscopy (EIS) test. The experimental results show that the joint with BN as fixture material maintained similar corrosion resistance with the substrate, and no corrosion occurred. However, the corrosion resistance of the joint with graphite as fixture material decreased significantly and the joint suffered severe intergranular corrosion. Furthermore, the electrochemical tests indicated that the corrosion current density of the joint with graphite as fixture material is higher than that of stainless steel substrate and the joint manufactured with BN fixture by an order of magnitude. While its resistance is lower than that of substrate with two orders of magnitude. The reason lies in the fact that carbon atoms of graphite fixture diffused to the surface of stainless steel and it led to the formation of a supersaturated solid solution of carbon during the bonding process. In the cooling process, carbon, chromium and iron formed carbide (CrFe)7C3 in grain boundary, which caused intergranular chromium depletion on the surface of stainless steel. So the corrosion resistance of bonding area was reduced and intergranular corrosion occurred.
In order to select the optimum fixture materials for vacuum diffusion bonding of 00Cr18Ni10N stainless steel, joints with boron nitride (BN) and graphite as fixture material were prepared. The effect of the fixture materials on the corrosion behavior of joints was studied by neutral salt spray corrosion test and electrochemical impedance spectroscopy (EIS) test. The experimental results show that the joint with BN as fixture material maintained similar corrosion resistance with the substrate, and no corrosion occurred. However, the corrosion resistance of the joint with graphite as fixture material decreased significantly and the joint suffered severe intergranular corrosion. Furthermore, the electrochemical tests indicated that the corrosion current density of the joint with graphite as fixture material is higher than that of stainless steel substrate and the joint manufactured with BN fixture by an order of magnitude. While its resistance is lower than that of substrate with two orders of magnitude. The reason lies in the fact that carbon atoms of graphite fixture diffused to the surface of stainless steel and it led to the formation of a supersaturated solid solution of carbon during the bonding process. In the cooling process, carbon, chromium and iron formed carbide (CrFe)7C3 in grain boundary, which caused intergranular chromium depletion on the surface of stainless steel. So the corrosion resistance of bonding area was reduced and intergranular corrosion occurred.
2015, 34(6): 953-956.
doi: 10.13433/j.cnki.1003-8728.2015.0627
Abstract:
Because the data points of a closed NURBS curve are non-uniform, the interpolated curve is not smooth. This paper proposes the closed NURBS curve smoothing method based on genetic algorithm to solve the curve unfairness caused by reverse curvature in the process of NURBS curve interpolation. Finally, this paper takes the body section of a turbine blade line as an example to verify the effectiveness and applicability of this smoothing method.
Because the data points of a closed NURBS curve are non-uniform, the interpolated curve is not smooth. This paper proposes the closed NURBS curve smoothing method based on genetic algorithm to solve the curve unfairness caused by reverse curvature in the process of NURBS curve interpolation. Finally, this paper takes the body section of a turbine blade line as an example to verify the effectiveness and applicability of this smoothing method.
2015, 34(6): 957-962.
doi: 10.13433/j.cnki.1003-8728.2015.0628
Abstract:
A full-scale nonlinear finite element model (FEM) was developed to obtain the crash performance of civil aircraft fuselage section. The FEM included the cargo door structures, as well as the airframes, skins, luggages, overhead baggage bay and seats in cabin. The FEM was used to simulate the vertical crash of the aircraft fuselage section. The initial impact velocity of the fuselage section was 9.14 m/s. The FEM was solved in MSC.Dytran and exported the deformation results of the fuselage section and the acceleration of all the measure points defined in the corresponding experiments. The FEM was validated by the agreement of the simulation results and the experiments data. The dynamic responses of the fuselage section with different roll angles were calculated with the validated FEM in the same initial velocity. The simulation results show that the damage of fuselage structures was most severe and the overloads of the passengers were largest in both cases of roll left 12° and roll right 8°. The deformation of the right hand side (RHS) fuselage was smaller than the left hand side (LHS) fuselage because the stiffness of the RHS fuselage structures was increased by the cargo door structures. The overloads of passengers on the RHS seats were also larger than the LHS due to the cargo door structures.
A full-scale nonlinear finite element model (FEM) was developed to obtain the crash performance of civil aircraft fuselage section. The FEM included the cargo door structures, as well as the airframes, skins, luggages, overhead baggage bay and seats in cabin. The FEM was used to simulate the vertical crash of the aircraft fuselage section. The initial impact velocity of the fuselage section was 9.14 m/s. The FEM was solved in MSC.Dytran and exported the deformation results of the fuselage section and the acceleration of all the measure points defined in the corresponding experiments. The FEM was validated by the agreement of the simulation results and the experiments data. The dynamic responses of the fuselage section with different roll angles were calculated with the validated FEM in the same initial velocity. The simulation results show that the damage of fuselage structures was most severe and the overloads of the passengers were largest in both cases of roll left 12° and roll right 8°. The deformation of the right hand side (RHS) fuselage was smaller than the left hand side (LHS) fuselage because the stiffness of the RHS fuselage structures was increased by the cargo door structures. The overloads of passengers on the RHS seats were also larger than the LHS due to the cargo door structures.
2015, 34(6): 963-968.
doi: 10.13433/j.cnki.1003-8728.2015.0629
Abstract:
The traditional method is that LORA (Level of Repair Analysis) and spare parts inventory are solved respectively, and then each minimum value is obtained, but the sum of them will not be the necessarily smallest. Aiming at this problem, we treat the equipment availability as the constraint condition, serve the smallest sum of cost of equipment LORA and spare parts inventory as the optimization objective, and present a nonlinear integer programming joint optimizing model based on the multi-echelon-multi-indenture, theory for recoverable item control (VARI-METRIC). On this basis, the relation between spare parts inventory's costs and variable costs of LORA is analyzed, further, an iterative-greedy heuristic algorithm is presented and the problem is solved by the algorithm. Compared with the respective optimization of LORA and spare parts inventory, the joint optimizing method of equipment LORA and spare parts inventory can save maintenance cost.
The traditional method is that LORA (Level of Repair Analysis) and spare parts inventory are solved respectively, and then each minimum value is obtained, but the sum of them will not be the necessarily smallest. Aiming at this problem, we treat the equipment availability as the constraint condition, serve the smallest sum of cost of equipment LORA and spare parts inventory as the optimization objective, and present a nonlinear integer programming joint optimizing model based on the multi-echelon-multi-indenture, theory for recoverable item control (VARI-METRIC). On this basis, the relation between spare parts inventory's costs and variable costs of LORA is analyzed, further, an iterative-greedy heuristic algorithm is presented and the problem is solved by the algorithm. Compared with the respective optimization of LORA and spare parts inventory, the joint optimizing method of equipment LORA and spare parts inventory can save maintenance cost.
2015, 34(6): 969-973.
doi: 10.13433/j.cnki.1003-8728.2015.0630
Abstract:
Through the sensitivity study in different object's pose in monocular vision measurement system, the influencing factors and the corresponding proportion can be found. At first, a theoretical model for the sensitivity of image point is proposed in this paper. Then a series of the numerical analysis experiments are designed. The results show that the sensitivity of image point is inversely proportional to the target plate angle and the distance between the camera and the object. The object's pose will always be in the direction of the camera's optical axis when the sensitivity of image point reaches the maximum value.
Through the sensitivity study in different object's pose in monocular vision measurement system, the influencing factors and the corresponding proportion can be found. At first, a theoretical model for the sensitivity of image point is proposed in this paper. Then a series of the numerical analysis experiments are designed. The results show that the sensitivity of image point is inversely proportional to the target plate angle and the distance between the camera and the object. The object's pose will always be in the direction of the camera's optical axis when the sensitivity of image point reaches the maximum value.
2015, 34(6): 974-977.
doi: 10.13433/j.cnki.1003-8728.2015.0631
Abstract:
In this paper, the connected plates are simulated by shell elements, and the bolts are simulated by beam elements. Gap elements and MPC in PATRAN are used to simulate the contacts and constrains between the bolts and plates, which are capable of simulating the warping deformation of multi-bolt composite joints by external forces. It is verified that the results of bolt load distribution are relatively accurate for both single-lap and double-lap models. On the basis of this kind of two-dimensional finite element models, we establish a common approach to meshing the model according to the geometric features of multi-bolt composite joints. The procedure of parametric modeling is programmed with PCL, and the program can build FE models of this kind of structures automatically and rapidly with reading the data in the corresponding data files, so as to realize the fast calculations for the bolt load distribution.
In this paper, the connected plates are simulated by shell elements, and the bolts are simulated by beam elements. Gap elements and MPC in PATRAN are used to simulate the contacts and constrains between the bolts and plates, which are capable of simulating the warping deformation of multi-bolt composite joints by external forces. It is verified that the results of bolt load distribution are relatively accurate for both single-lap and double-lap models. On the basis of this kind of two-dimensional finite element models, we establish a common approach to meshing the model according to the geometric features of multi-bolt composite joints. The procedure of parametric modeling is programmed with PCL, and the program can build FE models of this kind of structures automatically and rapidly with reading the data in the corresponding data files, so as to realize the fast calculations for the bolt load distribution.
2015, 34(6): 978-981.
doi: 10.13433/j.cnki.1003-8728.2015.0632
Abstract:
The aim of the present work is focused on the vibration isolation design for certain airborne equipment installing platform under environmental exciting of a propeller plane. Firstly, the phenomenon was analyzed for the vibration problem of the airborne equipment, and then a complex design for vibration suppression was proposed by introducing damping material, silicified rubber and industrial felt, on both sides of the installing platform. The vibration environment for the installing platform was recorded during a flight test. Based on this recorded signal, vibration test was conducted to determine the best complex design for the vibration suppression of airborne equipment, and the design parameters were obtained for the most effective vibration isolator.
The aim of the present work is focused on the vibration isolation design for certain airborne equipment installing platform under environmental exciting of a propeller plane. Firstly, the phenomenon was analyzed for the vibration problem of the airborne equipment, and then a complex design for vibration suppression was proposed by introducing damping material, silicified rubber and industrial felt, on both sides of the installing platform. The vibration environment for the installing platform was recorded during a flight test. Based on this recorded signal, vibration test was conducted to determine the best complex design for the vibration suppression of airborne equipment, and the design parameters were obtained for the most effective vibration isolator.
2015, 34(6): 982-984.
doi: 10.13433/j.cnki.1003-8728.2015.0633
Abstract:
As an important part to realize the lock and release function of loop antenna, the deployment characteristic of LHA (Launch Hold-Down Assembly) is a very important criterion to evaluate the deploying process of loop antenna. According to the design requirement, we conduct numerical simulation of the deployment of LHA. Simulation results and analysis show that requirement of the LHA to release quickly and stop slowly can be easily achieved by appropriate combination of the stiffness of drive spring and stop spring.
As an important part to realize the lock and release function of loop antenna, the deployment characteristic of LHA (Launch Hold-Down Assembly) is a very important criterion to evaluate the deploying process of loop antenna. According to the design requirement, we conduct numerical simulation of the deployment of LHA. Simulation results and analysis show that requirement of the LHA to release quickly and stop slowly can be easily achieved by appropriate combination of the stiffness of drive spring and stop spring.
