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RSS2022 Vol. 41, No. 7
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2022, 41(7): 985-991.
doi: 10.13433/j.cnki.1003-8728.20200421
PDF 3230KB
Abstract:
In order to study the cooling effect in the cutting of superalloy GH4169 with spray cooling, the cutting temperature in the cutting of superalloy GH4169 under the condition of spray cooling is experimentally and simulated. Firstly, the thermocouple is used to measure the temperature, and the reverse heat conduction method is used to convert the temperature measured by thermocouple into the actual cutting temperature to analyze the cutting temperature under dry cutting and spray cooling. Secondly, a simulation model for spray cooling was established, and the influence of the spray cooling parameters on the cutting temperature and the influencing reasons were analyzed under the same cutting parameters as the experiment. It is found that the spray cooling can significantly reduce the cutting temperature; the cutting temperature decreases with the increase of pressure, and has no obvious change with the increase of flow.
In order to study the cooling effect in the cutting of superalloy GH4169 with spray cooling, the cutting temperature in the cutting of superalloy GH4169 under the condition of spray cooling is experimentally and simulated. Firstly, the thermocouple is used to measure the temperature, and the reverse heat conduction method is used to convert the temperature measured by thermocouple into the actual cutting temperature to analyze the cutting temperature under dry cutting and spray cooling. Secondly, a simulation model for spray cooling was established, and the influence of the spray cooling parameters on the cutting temperature and the influencing reasons were analyzed under the same cutting parameters as the experiment. It is found that the spray cooling can significantly reduce the cutting temperature; the cutting temperature decreases with the increase of pressure, and has no obvious change with the increase of flow.
2022, 41(7): 992-997.
doi: 10.13433/j.cnki.1003-8728.20200427
Abstract:
In order to detect the failure of bolt looseness of the structure simply and effectively, a method for detecting bolt looseness by using average vibration response energy was proposed. Firstly, the bolt loosening damage indicator related to vibration response energy was established. Secondly, in order to reduce the influence of the noise on the results, the average vibration response energy was proposed as the bolt loosening damage indicator. Finally, the relative change in the damage norm before and after bolt loosening was used to construct damage index, and the location of the loose bolt was judged according to the damage index. The experimental results show that the present method can effectively detect the bolt loosening position.
In order to detect the failure of bolt looseness of the structure simply and effectively, a method for detecting bolt looseness by using average vibration response energy was proposed. Firstly, the bolt loosening damage indicator related to vibration response energy was established. Secondly, in order to reduce the influence of the noise on the results, the average vibration response energy was proposed as the bolt loosening damage indicator. Finally, the relative change in the damage norm before and after bolt loosening was used to construct damage index, and the location of the loose bolt was judged according to the damage index. The experimental results show that the present method can effectively detect the bolt loosening position.
2022, 41(7): 998-1002.
doi: 10.13433/j.cnki.1003-8728.20200437
Abstract:
In order to solve problem that the organ pipe nozzle, Helmholtz nozzle and cavitation nozzle are little suitable for the low frequency occasions such as drilling fluid transportation, a self-excited oscillation pulsed jet nozzle was developed based on the wall attachment effect and the back-flow feedback principle in this paper. The internal flow field of the nozzle was simulated with FLUENT software, the mechanism of self-excited pulsating jet was revealed, and the pulsating frequency characteristic of the self-excited oscillating nozzle was obtained. The simulation results show that the pulsating range of outlet velocity of the basic nozzle is 22-39 m/s and the pulsating frequency is 67.1 Hz. The pulsation is stable and the frequency is relatively low. Under a certain pressure difference, the pulsating frequency changes little with the confining pressure varying and decreases with the oscillating cavity length increasing. Variant design is easy for this kind of nozzle. These research results are helpful for the development of a new self-excited oscillating pulsed jet nozzle.
In order to solve problem that the organ pipe nozzle, Helmholtz nozzle and cavitation nozzle are little suitable for the low frequency occasions such as drilling fluid transportation, a self-excited oscillation pulsed jet nozzle was developed based on the wall attachment effect and the back-flow feedback principle in this paper. The internal flow field of the nozzle was simulated with FLUENT software, the mechanism of self-excited pulsating jet was revealed, and the pulsating frequency characteristic of the self-excited oscillating nozzle was obtained. The simulation results show that the pulsating range of outlet velocity of the basic nozzle is 22-39 m/s and the pulsating frequency is 67.1 Hz. The pulsation is stable and the frequency is relatively low. Under a certain pressure difference, the pulsating frequency changes little with the confining pressure varying and decreases with the oscillating cavity length increasing. Variant design is easy for this kind of nozzle. These research results are helpful for the development of a new self-excited oscillating pulsed jet nozzle.
2022, 41(7): 1003-1008.
doi: 10.13433/j.cnki.1003-8728.20200417
Abstract:
Rolling electromagnetic vibration energy harvester uses magnetic attraction force as restoring force. An equivalent dynamic model of the rolling electromagnetic vibration energy harvester is constructed based on the nonlinear analysis method, and the motion equation of the moving magnet in the system is re-evaluated. The finite element method was used to calculate the nonlinear magnetic force, the system damping was estimated through experiments, and the influence of damping on the output performance was analyzed. Connected the resistive load at both ends of the coils, the effect of the Lorentz force on the output is analyzed by comparing the calculation results and experimental results of the energy harvester. The results showed that the maximum error between the calculated value and the experimental value of the load voltage was reduced from 20% to 9% under the condition of 13.5 Hz, after considering the effect of the Lorentz force on the output performance; the resistive load value corresponding to the maximum power is changed from 114 to 160. By comparing the results of simulation and experiment, it is proved that the equivalent model considering nonlinear effects can guide the experimental research of such structures.
Rolling electromagnetic vibration energy harvester uses magnetic attraction force as restoring force. An equivalent dynamic model of the rolling electromagnetic vibration energy harvester is constructed based on the nonlinear analysis method, and the motion equation of the moving magnet in the system is re-evaluated. The finite element method was used to calculate the nonlinear magnetic force, the system damping was estimated through experiments, and the influence of damping on the output performance was analyzed. Connected the resistive load at both ends of the coils, the effect of the Lorentz force on the output is analyzed by comparing the calculation results and experimental results of the energy harvester. The results showed that the maximum error between the calculated value and the experimental value of the load voltage was reduced from 20% to 9% under the condition of 13.5 Hz, after considering the effect of the Lorentz force on the output performance; the resistive load value corresponding to the maximum power is changed from 114 to 160. By comparing the results of simulation and experiment, it is proved that the equivalent model considering nonlinear effects can guide the experimental research of such structures.
2022, 41(7): 1009-1017.
doi: 10.13433/j.cnki.1003-8728.20200407
Abstract:
The occurrences of torsional vibration and torque ripple at the joints of industrial robots during its operation are notoriously known for negatively impacting the actuating precision and responsiveness of robot joint drive system. Following this context, this paper addresses the vibration issues in the servo drive systems of robot joints by establishing a dynamic electromechanical coupling model of such system and then analyzing the resulting torsional vibration and electromechanical coupling vibration. Subsequently, the influencing relationships of various parameters, such as drive stiffness and moment of inertia on the system's resonant frequency, as well as electrical parameters (e.g., flux linkage) and the current's harmonic frequency on the vibration amplitude and conditioning time, were studied using numerical simulation methods. Lastly, the contributions of every component at the joint on the vibration of the drive system were analyzed. The results show that the established electromechanical coupling model, as well as the efforts made to analyze the system's vibration characteristics, such as the torsional vibration and electromechanical coupling, can effectively simulate the joints drive system dynamic characteristics of industrial robots.
The occurrences of torsional vibration and torque ripple at the joints of industrial robots during its operation are notoriously known for negatively impacting the actuating precision and responsiveness of robot joint drive system. Following this context, this paper addresses the vibration issues in the servo drive systems of robot joints by establishing a dynamic electromechanical coupling model of such system and then analyzing the resulting torsional vibration and electromechanical coupling vibration. Subsequently, the influencing relationships of various parameters, such as drive stiffness and moment of inertia on the system's resonant frequency, as well as electrical parameters (e.g., flux linkage) and the current's harmonic frequency on the vibration amplitude and conditioning time, were studied using numerical simulation methods. Lastly, the contributions of every component at the joint on the vibration of the drive system were analyzed. The results show that the established electromechanical coupling model, as well as the efforts made to analyze the system's vibration characteristics, such as the torsional vibration and electromechanical coupling, can effectively simulate the joints drive system dynamic characteristics of industrial robots.
2022, 41(7): 1018-1022.
doi: 10.13433/j.cnki.1003-8728.20200385
Abstract:
In order to realize the automatic target recognition and grasping of the vision manipulator, research work is carried out based on the deep learning detection algorithm DarkNet-53, and a target grasping experimental platform combined with the vision manipulator is established. Feature extraction is performed under the deep learning framework. Adopt YOLOv3 to complete the rapid target classification detection. The five-parameter method based on the DarkNet-53 is used to complete the prediction of the target pose. The experiments on the physical prototype are carried out. The research results show that the deep learning algorithm can achieve the rapid classification and recognition of a target and the analysis of a grasping area and can realize automatic recognition and grasping.
In order to realize the automatic target recognition and grasping of the vision manipulator, research work is carried out based on the deep learning detection algorithm DarkNet-53, and a target grasping experimental platform combined with the vision manipulator is established. Feature extraction is performed under the deep learning framework. Adopt YOLOv3 to complete the rapid target classification detection. The five-parameter method based on the DarkNet-53 is used to complete the prediction of the target pose. The experiments on the physical prototype are carried out. The research results show that the deep learning algorithm can achieve the rapid classification and recognition of a target and the analysis of a grasping area and can realize automatic recognition and grasping.
2022, 41(7): 1023-1030.
doi: 10.13433/j.cnki.1003-8728.20220141
Abstract:
In order to improve the hydraulic performance of small high speed centrifugal pump in aviation field, reduce its weight and simplify its mechanical structure, and have better axial force balance ability, a new type of centrifugal pump with single stage small specific revolution rotor groove structure was designed. The hydraulic performance test bench of centrifugal pump was set up to study the influence of groove structure on hydraulic performance and pressure fluctuation of centrifugal pump under different working conditions, and the numerical simulation was compared and analyzed. The results show that compared with the traditional centrifugal pump, the outlet pressure, head and effective power of the rotor groove centrifugal pump are increased by 7.89%, 7.53% and 11.1%, respectively. The experimental and numerical simulation results show that the errors of outlet pressure, head and effective power are all less than 1.5%, the critical cavitation margin is 1.488 m, and the overall pressure pulsation amplitude is less than 0.2, and the peak value occurs near the impeller frequency twice. It is proved that it is reasonable to introduce spiral groove into rotor of high speed small specific revolution centrifugal pump motor.
In order to improve the hydraulic performance of small high speed centrifugal pump in aviation field, reduce its weight and simplify its mechanical structure, and have better axial force balance ability, a new type of centrifugal pump with single stage small specific revolution rotor groove structure was designed. The hydraulic performance test bench of centrifugal pump was set up to study the influence of groove structure on hydraulic performance and pressure fluctuation of centrifugal pump under different working conditions, and the numerical simulation was compared and analyzed. The results show that compared with the traditional centrifugal pump, the outlet pressure, head and effective power of the rotor groove centrifugal pump are increased by 7.89%, 7.53% and 11.1%, respectively. The experimental and numerical simulation results show that the errors of outlet pressure, head and effective power are all less than 1.5%, the critical cavitation margin is 1.488 m, and the overall pressure pulsation amplitude is less than 0.2, and the peak value occurs near the impeller frequency twice. It is proved that it is reasonable to introduce spiral groove into rotor of high speed small specific revolution centrifugal pump motor.
2022, 41(7): 1031-1038.
doi: 10.13433/j.cnki.1003-8728.20200456
Abstract:
Supercritical carbon dioxide (sCO2) Brayton cycle as the next generation energy conversion technology has received extensive attention in recent years. In order to optimize the support and cooling system parameters of Brayton cycle shafting, based on Riccati transfer matrix, the multi-objective optimization model of high-speed shafting is established by considering the unbalance response, critical speed and the derivative of unbalance response at the working speed point. The concept of chaotic interval is introduced by using chaotic mapping for nonlinear stiffness of gas bearings, and chaos interval multi-objective particle swarm optimization algorithm (CIMPSO) was proposed to solve the optimization problem of two-dimensional nonlinear variables under the condition of multi-objective functions. The CIMPSO algorithm is applied to optimize the parameters of the bearing spacing and the stiffness, damping and vibration mass of the bearing pedestal and the stiffness of sCO2 cooling unit of the micro supercritical carbon dioxide turbine. The results show that the resonance amplitude of the optimized model is effectively attenuated, and the critical speed point is far away from the working speed, which shows the robustness of the proposed optimization algorithm. Finally, based on an arbitrary set of optimization solutions and empirical parameters, the finite element model of shafting is established for simulation, and the results show that the optimized solution has certain guiding significance for the design of the rotor system.
Supercritical carbon dioxide (sCO2) Brayton cycle as the next generation energy conversion technology has received extensive attention in recent years. In order to optimize the support and cooling system parameters of Brayton cycle shafting, based on Riccati transfer matrix, the multi-objective optimization model of high-speed shafting is established by considering the unbalance response, critical speed and the derivative of unbalance response at the working speed point. The concept of chaotic interval is introduced by using chaotic mapping for nonlinear stiffness of gas bearings, and chaos interval multi-objective particle swarm optimization algorithm (CIMPSO) was proposed to solve the optimization problem of two-dimensional nonlinear variables under the condition of multi-objective functions. The CIMPSO algorithm is applied to optimize the parameters of the bearing spacing and the stiffness, damping and vibration mass of the bearing pedestal and the stiffness of sCO2 cooling unit of the micro supercritical carbon dioxide turbine. The results show that the resonance amplitude of the optimized model is effectively attenuated, and the critical speed point is far away from the working speed, which shows the robustness of the proposed optimization algorithm. Finally, based on an arbitrary set of optimization solutions and empirical parameters, the finite element model of shafting is established for simulation, and the results show that the optimized solution has certain guiding significance for the design of the rotor system.
2022, 41(7): 1039-1047.
doi: 10.13433/j.cnki.1003-8728.20200448
Abstract:
In order to improve the side structure crashworthiness of an automobile, the Latin hypercube experimental design method and the finite element model (FEM) were employed to establish the thirteen design variables and seven responses for sample data. Then, the third-order polynomial response surface model (RSM) were constructed instead of FEM to reflect the function correlation between variables and responses. Finally, the simulated annealing optimization algorithm was implemented in RSM for the multi-objective optimization of the side structures of an automobile to seek optimal and reliable solutions. The optimization results indicate that in the areas of B-pillar and doorsill, the increase of the thickness of the high-strength steel plate can effectively improve the crashworthiness. The optimization process was changed from the traditional combination of design experience, simulation and experimental validation to the mathematical optimization problem, reducing the dependence of design experience and effectively improving optimization efficiency and solution accuracy.
In order to improve the side structure crashworthiness of an automobile, the Latin hypercube experimental design method and the finite element model (FEM) were employed to establish the thirteen design variables and seven responses for sample data. Then, the third-order polynomial response surface model (RSM) were constructed instead of FEM to reflect the function correlation between variables and responses. Finally, the simulated annealing optimization algorithm was implemented in RSM for the multi-objective optimization of the side structures of an automobile to seek optimal and reliable solutions. The optimization results indicate that in the areas of B-pillar and doorsill, the increase of the thickness of the high-strength steel plate can effectively improve the crashworthiness. The optimization process was changed from the traditional combination of design experience, simulation and experimental validation to the mathematical optimization problem, reducing the dependence of design experience and effectively improving optimization efficiency and solution accuracy.
2022, 41(7): 1048-1054.
doi: 10.13433/j.cnki.1003-8728.20200428
Abstract:
In order to solve the problem that it is difficult to insulate the sidewall of the tool and the insulating layer coated by the tool is easy to wear during electrochemical machining, a method of real-time generating an insulating layer on the sidewall of the tungsten tool electrode is proposed. In order to realize the above mentioned, an electrolysis power supply capable of outputting double pulses whose positive and negative voltages and duty cycles are independently adjustable was designed. The present circuit uses two MOSFET (Metal-oxide-semiconductor field effect transistor) tubes to control two independent DC(Direct current) power supplies, and uses STM32 to control two MOSFET tubes. The experimental results show that the actual output voltage waveform meets the design requirements, and the output voltage frequency has a better waveform when the frequency is below 240 kHz. The research uses 1 mm tungsten rod as tool electrode. Comparing the processing of the sidewall of the tungsten rod without insulation, a double-pulse power supply with a positive voltage of 12 V (duty cycle of 20%) is used, a negative voltage of 19 V (duty cycle of 50%) and a positive pulse time accounting for 90% of the total pulse time to process the stainless steel, its localization is significantly improved.
In order to solve the problem that it is difficult to insulate the sidewall of the tool and the insulating layer coated by the tool is easy to wear during electrochemical machining, a method of real-time generating an insulating layer on the sidewall of the tungsten tool electrode is proposed. In order to realize the above mentioned, an electrolysis power supply capable of outputting double pulses whose positive and negative voltages and duty cycles are independently adjustable was designed. The present circuit uses two MOSFET (Metal-oxide-semiconductor field effect transistor) tubes to control two independent DC(Direct current) power supplies, and uses STM32 to control two MOSFET tubes. The experimental results show that the actual output voltage waveform meets the design requirements, and the output voltage frequency has a better waveform when the frequency is below 240 kHz. The research uses 1 mm tungsten rod as tool electrode. Comparing the processing of the sidewall of the tungsten rod without insulation, a double-pulse power supply with a positive voltage of 12 V (duty cycle of 20%) is used, a negative voltage of 19 V (duty cycle of 50%) and a positive pulse time accounting for 90% of the total pulse time to process the stainless steel, its localization is significantly improved.
2022, 41(7): 1055-1061.
doi: 10.13433/j.cnki.1003-8728.20200434
Abstract:
Production scheduling and equipment maintenance are two important activities in the manufacturing workshop. The combination of the predictive maintenance with the production scheduling can not only ensure the normal operation of workshop production scheduling, improving workshop processing efficiency and product quality; but also effectively control the cost of machine maintenance and integrate internal resources within the company to make reasonable allocations. An integrated optimization method for predictive maintenance and production scheduling for flow shop is proposed. Based on the predictive state of the machine failure, considering both of the perfect and imperfect maintenance strategy, an integrated optimization model is established for the flow shop with the goal of minimizing the make-span, and an improved bat algorithm is designed to solve the model. Finally, an example is used to verify the effectiveness and feasibility of the present method.
Production scheduling and equipment maintenance are two important activities in the manufacturing workshop. The combination of the predictive maintenance with the production scheduling can not only ensure the normal operation of workshop production scheduling, improving workshop processing efficiency and product quality; but also effectively control the cost of machine maintenance and integrate internal resources within the company to make reasonable allocations. An integrated optimization method for predictive maintenance and production scheduling for flow shop is proposed. Based on the predictive state of the machine failure, considering both of the perfect and imperfect maintenance strategy, an integrated optimization model is established for the flow shop with the goal of minimizing the make-span, and an improved bat algorithm is designed to solve the model. Finally, an example is used to verify the effectiveness and feasibility of the present method.
Evolution Mechanism of Sub-surface Defects in Nanocutting of Nickel-based Single Crystal Super Alloy
2022, 41(7): 1062-1069.
doi: 10.13433/j.cnki.1003-8728.20200445
Abstract:
The generation and evolution of surface defects in the process of parts processing directly affect the surface quality and service life, which has always been the focus of attention in the business and academic fields. From the point of view of defect evolution and energy change, combining with molecular dynamics method, the evolution mechanism of subsurface defects in the cutting of nickel based single crystal Superalloy by using the silicon nitride ceramics tool was studied. The mixed potential function is used to describe the interatomic force in the cutting of nickel based single crystal Superalloy. The process of nucleation, propagation and transformation of various dislocations and stacking faults are analyzed. The influence of the type, quantity, depth and area of subsurface defects, system potential energy and crystal structure change induced by the change of cutting speed on the machined surface quality is discussed. The results show that to increase the cutting speed can effectively reduce the number and area of subsurface defects and improve the quality of machined parts.
The generation and evolution of surface defects in the process of parts processing directly affect the surface quality and service life, which has always been the focus of attention in the business and academic fields. From the point of view of defect evolution and energy change, combining with molecular dynamics method, the evolution mechanism of subsurface defects in the cutting of nickel based single crystal Superalloy by using the silicon nitride ceramics tool was studied. The mixed potential function is used to describe the interatomic force in the cutting of nickel based single crystal Superalloy. The process of nucleation, propagation and transformation of various dislocations and stacking faults are analyzed. The influence of the type, quantity, depth and area of subsurface defects, system potential energy and crystal structure change induced by the change of cutting speed on the machined surface quality is discussed. The results show that to increase the cutting speed can effectively reduce the number and area of subsurface defects and improve the quality of machined parts.
2022, 41(7): 1070-1075.
doi: 10.13433/j.cnki.1003-8728.20200634
Abstract:
The change in the stiffness and redistribution of internal stress of extra large split spiral bevel gear during gear cutting lead to serious deformation of the blank. The deformation caused by gear cutting is closely related to the residual stress distribution of the blank. In order to solve this problem, the simulation analysis via finite element software is carried out, the stress nephogram of the surface and internal section of the gear blank is extracted, the evolution of the stress distribution in the machining is explored, and the internal mechanism of the internal stress evolution of the gear blank in the gear cutting and its influence on its deformation are studied. Finally, the actual gear cutting and deformation measurement experiments of the split gear blank is carried out. The results show that the deformation law of simulation and machining experiment is consistent, and the deformation characteristics of gear blank are consistent with the change law of initial residual stress.
The change in the stiffness and redistribution of internal stress of extra large split spiral bevel gear during gear cutting lead to serious deformation of the blank. The deformation caused by gear cutting is closely related to the residual stress distribution of the blank. In order to solve this problem, the simulation analysis via finite element software is carried out, the stress nephogram of the surface and internal section of the gear blank is extracted, the evolution of the stress distribution in the machining is explored, and the internal mechanism of the internal stress evolution of the gear blank in the gear cutting and its influence on its deformation are studied. Finally, the actual gear cutting and deformation measurement experiments of the split gear blank is carried out. The results show that the deformation law of simulation and machining experiment is consistent, and the deformation characteristics of gear blank are consistent with the change law of initial residual stress.
2022, 41(7): 1076-1084.
doi: 10.13433/j.cnki.1003-8728.20200431
Abstract:
In order to improve the prediction accuracy and calculation efficiency of tool wear state in the micro milling, an online monitoring method of tool wear in the micro milling based on the wavelet packet decomposition (WPD) and support vector machine-particle swarm optimization (SVM-PSO) is put forward. Firstly, the wear of tool in the micro milling can be divided into the five states: initial wear, light wear, medium wear, heavy wear and tool failure. Secondly, the collected vibration signals are transformed by using WPD, and the energy ratio and kurtosis of key nodes of wavelet packet are extracted as the wear features, and the influence of the different cutting parameters on the two features is analyzed. Finally, SVM-PSO model is used to classify and predict the wear state of tool in the micro milling. The results show that, comparing with the grid search method, the online wear monitoring method of tool in the micro milling proposed in this paper has comprehensive advantages in the calculation accuracy and efficiency, and can provide the necessary basis and guidance for monitoring the other tool wear.
In order to improve the prediction accuracy and calculation efficiency of tool wear state in the micro milling, an online monitoring method of tool wear in the micro milling based on the wavelet packet decomposition (WPD) and support vector machine-particle swarm optimization (SVM-PSO) is put forward. Firstly, the wear of tool in the micro milling can be divided into the five states: initial wear, light wear, medium wear, heavy wear and tool failure. Secondly, the collected vibration signals are transformed by using WPD, and the energy ratio and kurtosis of key nodes of wavelet packet are extracted as the wear features, and the influence of the different cutting parameters on the two features is analyzed. Finally, SVM-PSO model is used to classify and predict the wear state of tool in the micro milling. The results show that, comparing with the grid search method, the online wear monitoring method of tool in the micro milling proposed in this paper has comprehensive advantages in the calculation accuracy and efficiency, and can provide the necessary basis and guidance for monitoring the other tool wear.
2022, 41(7): 1085-1094.
doi: 10.13433/j.cnki.1003-8728.20200435
Abstract:
closed-loop trajectory tracking control system with the fixed/finite sliding mode variable structural algorithm. The double closed-loop control system uses the outer loop position controller to output the desired linear velocity and the inner loop attitude controller to output the desired angular velocity. According to the wall-climbing robot's kinematics equation and kinematic error equation, the fixed-time sliding mode control and the finite-time sliding mode control are designed to achieve the tracking of the trajectory of the wall-climbing robot; the simulation of the linear, sine, and circular trajectory tracking has been completed. The simulation results show that the tracking accuracy, convergence speed and convergence time of the fixed/finite sliding mode control is better than those of the ordinary sliding mode control, thus improving the tracking performance of a wall-climbing robot.
closed-loop trajectory tracking control system with the fixed/finite sliding mode variable structural algorithm. The double closed-loop control system uses the outer loop position controller to output the desired linear velocity and the inner loop attitude controller to output the desired angular velocity. According to the wall-climbing robot's kinematics equation and kinematic error equation, the fixed-time sliding mode control and the finite-time sliding mode control are designed to achieve the tracking of the trajectory of the wall-climbing robot; the simulation of the linear, sine, and circular trajectory tracking has been completed. The simulation results show that the tracking accuracy, convergence speed and convergence time of the fixed/finite sliding mode control is better than those of the ordinary sliding mode control, thus improving the tracking performance of a wall-climbing robot.
2022, 41(7): 1095-1101.
doi: 10.13433/j.cnki.1003-8728.20200426
Abstract:
To solve the current path planning problem of a mobile robot, a new adaptive mechanism is proposed to establish the pheromone update strategy. By increasing adaptive thresholds and optimizing the path generated with the ant colony algorithm, the generated path conforms to the real motion trajectory and improves the adaptability and efficiency of a mobile robot to its unknown environment during walking. Firstly, the raster map is established, the initial pheromone is input, and the parameters of the algorithm are set. Ants are placed at the starting point and the transition probability of the current state is calculated. Then we compare the obtained current adaptive threshold with the state transition probability, select the next node for ants to walk according to comparison results and update the path until the ants reach their end point and until all the ants of this generation traverse. Finally, we dynamically update the information heuristic factor α, the expected heuristic factor β and the pheromone. We repeat these steps until the iteration is completed, optimize the generated path and output the optimal path. Experimental and application results show that the optimization method solves the lack of pheromones at the beginning of a mobile robot′s path planning, accelerates convergence speed, conforms to its motion trajectory, being suitable for the path planning of a mobile robot in its unknown dynamic environment.
To solve the current path planning problem of a mobile robot, a new adaptive mechanism is proposed to establish the pheromone update strategy. By increasing adaptive thresholds and optimizing the path generated with the ant colony algorithm, the generated path conforms to the real motion trajectory and improves the adaptability and efficiency of a mobile robot to its unknown environment during walking. Firstly, the raster map is established, the initial pheromone is input, and the parameters of the algorithm are set. Ants are placed at the starting point and the transition probability of the current state is calculated. Then we compare the obtained current adaptive threshold with the state transition probability, select the next node for ants to walk according to comparison results and update the path until the ants reach their end point and until all the ants of this generation traverse. Finally, we dynamically update the information heuristic factor α, the expected heuristic factor β and the pheromone. We repeat these steps until the iteration is completed, optimize the generated path and output the optimal path. Experimental and application results show that the optimization method solves the lack of pheromones at the beginning of a mobile robot′s path planning, accelerates convergence speed, conforms to its motion trajectory, being suitable for the path planning of a mobile robot in its unknown dynamic environment.
2022, 41(7): 1102-1111.
doi: 10.13433/j.cnki.1003-8728.20200432
Abstract:
The spatial straightness error evaluation calculation problem is essentially a nonlinear optimization one, which is difficult to solve with the traditional mathematical calculation methods; its solution accuracy is not high. The intelligent optimization algorithm has great advantages in solving such problems. Therefore, we propose to apply the improved whale optimization algorithm to the spatial straightness error evaluation. Our method satisfies the minimum area condition. First, the mathematical model of the minimum area method for spatial straightness error evaluation is established, thus obtaining the objective function of spatial straightness. Secondly, the principles of the basic whale optimization algorithm are explained. Its shortcomings are addressed; three aspects of whale optimization algorithm are improved. The population using the Latin hypercube sampling are initialized; the population diversity is enhanced. The nonlinear convergence factor is replaced with the linear convergence factor in the basic whale optimization algorithm. The nonlinear inertia weight is introduced into the whale optimization algorithm. The simulation results show that the algorithm has been effectively improved in convergence speed, accuracy and stability. It is also verified by two examples of spatial straightness error evaluation. The results show that the improved whale optimization algorithm has more advantages in evaluation accuracy than the two-point connection method, the whale optimization algorithm, the genetic algorithm and the particle swarm optimization algorithm.
The spatial straightness error evaluation calculation problem is essentially a nonlinear optimization one, which is difficult to solve with the traditional mathematical calculation methods; its solution accuracy is not high. The intelligent optimization algorithm has great advantages in solving such problems. Therefore, we propose to apply the improved whale optimization algorithm to the spatial straightness error evaluation. Our method satisfies the minimum area condition. First, the mathematical model of the minimum area method for spatial straightness error evaluation is established, thus obtaining the objective function of spatial straightness. Secondly, the principles of the basic whale optimization algorithm are explained. Its shortcomings are addressed; three aspects of whale optimization algorithm are improved. The population using the Latin hypercube sampling are initialized; the population diversity is enhanced. The nonlinear convergence factor is replaced with the linear convergence factor in the basic whale optimization algorithm. The nonlinear inertia weight is introduced into the whale optimization algorithm. The simulation results show that the algorithm has been effectively improved in convergence speed, accuracy and stability. It is also verified by two examples of spatial straightness error evaluation. The results show that the improved whale optimization algorithm has more advantages in evaluation accuracy than the two-point connection method, the whale optimization algorithm, the genetic algorithm and the particle swarm optimization algorithm.
2022, 41(7): 1112-1120.
doi: 10.13433/j.cnki.1003-8728.20200439
Abstract:
In order to improve the fuel economy of extended-range electric vehicle(E-REV) under complex driving condition, a rule energy management strategy based on BP neural network optimized by genetic algorithm is proposed. The genetic algorithm is used to optimize BP neural network for overcoming the shortcomings of slow convergence speed and poor generalization ability of BP neural network. City cycle of China include urban, suburban and expressway driving circle are used as the velocity curves of the three driving circles for training samples. Then, the rule energy management strategy is optimized under the identified driving pattern. The results show that the accuracy rate of driving pattern recognition of BP neural network optimized by genetic algorithm is 99.99%, which is higher than that without genetic algorithm. And the fuel economy of E-REV is improved under the energy management strategy based on driving pattern recognition, which is reasonable distribution of the working mode of the E-REV.
In order to improve the fuel economy of extended-range electric vehicle(E-REV) under complex driving condition, a rule energy management strategy based on BP neural network optimized by genetic algorithm is proposed. The genetic algorithm is used to optimize BP neural network for overcoming the shortcomings of slow convergence speed and poor generalization ability of BP neural network. City cycle of China include urban, suburban and expressway driving circle are used as the velocity curves of the three driving circles for training samples. Then, the rule energy management strategy is optimized under the identified driving pattern. The results show that the accuracy rate of driving pattern recognition of BP neural network optimized by genetic algorithm is 99.99%, which is higher than that without genetic algorithm. And the fuel economy of E-REV is improved under the energy management strategy based on driving pattern recognition, which is reasonable distribution of the working mode of the E-REV.
2022, 41(7): 1121-1127.
doi: 10.13433/j.cnki.1003-8728.20200433
Abstract:
Aiming at the rolling stability of heavy dump truck in extreme conditions, a differential braking control algorithm was proposed based on model predictive control(MPC). The control matrix was established according to the reference model of the heavy-duty dump truck. The decision is based on the center of mass slip angle, the yaw velocity and the roll angle. And the lateral load transfer rate is taken as the rollover evaluation index. The additional stabilizing torque is provided for the vehicle through differential braking, thereby improving the driving stability of the vehicle. After that, the joint simulation of MATLAB/Simulink and Trucksim was used to conduct simulation tests under two typical rollover working conditions. The simulation results show that the anti-rollover control system based on model predictive control can effectively inhibit the rollover of vehicles, ensure driving safety, and improve the rolling stability of heavy dump trucks.
Aiming at the rolling stability of heavy dump truck in extreme conditions, a differential braking control algorithm was proposed based on model predictive control(MPC). The control matrix was established according to the reference model of the heavy-duty dump truck. The decision is based on the center of mass slip angle, the yaw velocity and the roll angle. And the lateral load transfer rate is taken as the rollover evaluation index. The additional stabilizing torque is provided for the vehicle through differential braking, thereby improving the driving stability of the vehicle. After that, the joint simulation of MATLAB/Simulink and Trucksim was used to conduct simulation tests under two typical rollover working conditions. The simulation results show that the anti-rollover control system based on model predictive control can effectively inhibit the rollover of vehicles, ensure driving safety, and improve the rolling stability of heavy dump trucks.
2022, 41(7): 1128-1135.
doi: 10.13433/j.cnki.1003-8728.20200430
Abstract:
In this paper, the dynamic models for carbon/epoxy prepreg system was studied by nonisothermal and isothermal differential scanning calorimetry (DSC). The glass transition temperature (Tg) was firstly determined with DSC analysis as a function of curing degree of the samples. Subsequently, three kinetics mechanism equations consist of nth order reaction model, autocatalytic model as well as modified Kamal model were used to describe the curing process under dynamic condition. The modified Kamal model was finally adopted in view of the existence of two reactions in DSC curve. In addition, the prediction of modified Kamal model shows highly in accordance with the experimental via isothermal scans.
In this paper, the dynamic models for carbon/epoxy prepreg system was studied by nonisothermal and isothermal differential scanning calorimetry (DSC). The glass transition temperature (Tg) was firstly determined with DSC analysis as a function of curing degree of the samples. Subsequently, three kinetics mechanism equations consist of nth order reaction model, autocatalytic model as well as modified Kamal model were used to describe the curing process under dynamic condition. The modified Kamal model was finally adopted in view of the existence of two reactions in DSC curve. In addition, the prediction of modified Kamal model shows highly in accordance with the experimental via isothermal scans.
2022, 41(7): 1136-1141.
doi: 10.13433/j.cnki.1003-8728.20220077
Abstract:
In order to analyze the aerodynamic characteristics of a new spin-stabilized trajectory correction projectile with air-ducts structure, the flow field of the projectile under different Mach numbers and angles of attack is studied by using the computational fluid dynamics method. By analyzing the pressure and velocity distributions of the internal and external flow field of the projectile, the structural characteristics of the flow field are studied, and the change laws of the aerodynamic characteristics of the projectile under different flight conditions are obtained. The numerical simulation results show that when the flight Mach number of the projectile is in the range of Ma 0.4~1.4 and the angle of attack is in the range of 6 degrees, the high-speed oncoming airflow can be derived smoothly from the air ducts, and the radial correction effect can be produced. Compared with subsonic speed, the drag characteristic of the projectile during supersonic flight is more affected by Mach number. There is an obvious obstruction area at the inlet of the air duct, where the pressure increases.
In order to analyze the aerodynamic characteristics of a new spin-stabilized trajectory correction projectile with air-ducts structure, the flow field of the projectile under different Mach numbers and angles of attack is studied by using the computational fluid dynamics method. By analyzing the pressure and velocity distributions of the internal and external flow field of the projectile, the structural characteristics of the flow field are studied, and the change laws of the aerodynamic characteristics of the projectile under different flight conditions are obtained. The numerical simulation results show that when the flight Mach number of the projectile is in the range of Ma 0.4~1.4 and the angle of attack is in the range of 6 degrees, the high-speed oncoming airflow can be derived smoothly from the air ducts, and the radial correction effect can be produced. Compared with subsonic speed, the drag characteristic of the projectile during supersonic flight is more affected by Mach number. There is an obvious obstruction area at the inlet of the air duct, where the pressure increases.
2022, 41(7): 1142-1148.
doi: 10.13433/j.cnki.1003-8728.20220139
Abstract:
The problem of static aeroelasticity is a mechanical problem that must be considered in the structural design of aerospace aircraft. The solution functions of SABRE software system cover static analysis, dynamic analysis, thermal analysis and aeroelastic analysis. This article first introduces the basic theoretical methods of SABRE software static aeroelastic analysis, and then based on the Qt and C++ development framework and human-computer interaction mode and combining the analysis process in engineering practice, designs and achieves three-dimensional graphical user interface and method for efficient and supportable static aeroelastic analysis, in which the system includes static aeroelastic geometric parameters, automatic generation of aerodynamic partitions, solution response and two-dimensional curve post-processing templates, etc. This software can easily and quickly complete the construction, simulation and evaluation of the static aeroelastic analysis model of the wing structure. Tested and verified by engineering examples, the software solidifies the static aeroelastic analysis process, improves analysis efficiency, and has reliable performance.
The problem of static aeroelasticity is a mechanical problem that must be considered in the structural design of aerospace aircraft. The solution functions of SABRE software system cover static analysis, dynamic analysis, thermal analysis and aeroelastic analysis. This article first introduces the basic theoretical methods of SABRE software static aeroelastic analysis, and then based on the Qt and C++ development framework and human-computer interaction mode and combining the analysis process in engineering practice, designs and achieves three-dimensional graphical user interface and method for efficient and supportable static aeroelastic analysis, in which the system includes static aeroelastic geometric parameters, automatic generation of aerodynamic partitions, solution response and two-dimensional curve post-processing templates, etc. This software can easily and quickly complete the construction, simulation and evaluation of the static aeroelastic analysis model of the wing structure. Tested and verified by engineering examples, the software solidifies the static aeroelastic analysis process, improves analysis efficiency, and has reliable performance.
