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RSS2020 Vol. 39, No. 6
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2020, 39(6): 821-828.
doi: 10.13433/j.cnki.1003-8728.20190217
PDF 2935KB
Abstract:
The high temperature in the ultrasonic vibration grinding is likely to cause thermal damage of carbon fiber reinforced plastic (CFRP). In order to resolve the temperature problem in the ultrasonic vibration assisted grinding of CFRP, the temperature field is studied by using finite element method. Firstly, the ultrasonic vibration assisted grinding temperature is measured online by semi-manual thermocouple. The heat distribution ratio in the unidirectional CFRP with a fiber orientation of 0, 45°, 90° and 135° is studied by combing the experiment and simulation. Then, according to the heat distribution ratio of each unidirectional CFRP, a simulation model for temperature field in the ultrasonic vibration assisted grinding of multi-directional CFRP is established. Finally, the finite element model is verified by using ultrasonic vibration assisted grinding experiments performed on multi-directional CFRP.
The high temperature in the ultrasonic vibration grinding is likely to cause thermal damage of carbon fiber reinforced plastic (CFRP). In order to resolve the temperature problem in the ultrasonic vibration assisted grinding of CFRP, the temperature field is studied by using finite element method. Firstly, the ultrasonic vibration assisted grinding temperature is measured online by semi-manual thermocouple. The heat distribution ratio in the unidirectional CFRP with a fiber orientation of 0, 45°, 90° and 135° is studied by combing the experiment and simulation. Then, according to the heat distribution ratio of each unidirectional CFRP, a simulation model for temperature field in the ultrasonic vibration assisted grinding of multi-directional CFRP is established. Finally, the finite element model is verified by using ultrasonic vibration assisted grinding experiments performed on multi-directional CFRP.
2020, 39(6): 829-835.
doi: 10.13433/j.cnki.1003-8728.20190169
Abstract:
To study the conveying characteristics of deep-sea ore conveying equipment, the three-dimensional simulation of solid-liquid two-phase flow in ore conveying equipment was carried out with the computational fluid dynamics theory and the Fluent software. The effects of jet velocity, pumping speed, jet height and particle size on the discharge mass flow rate and average velocity of particles at the outlet was studied. The simulation results show that with the increase of injection velocity, the discharge mass flow first increases and then decreases, there is an optimal injection speed, and the average velocity of ore particles at the outlet increases linearly and increases substantially linearly as the pumping speed increases, but the discharge mass flow does not change much. The discharge mass flow rate rises first and then decreases with the change in injection height, and has an optimal value when the injection height is 500 mm. The change in injection height has no effect on the average velocity of the ore particle at the exit. With the increase of particle size, the discharge mass flow rate increases sharply. When the particle size exceeds 15 mm, it slowly rises and finally decreases slowly. The average velocity of the ore particles at the outlet is basically not affected by particle size.
To study the conveying characteristics of deep-sea ore conveying equipment, the three-dimensional simulation of solid-liquid two-phase flow in ore conveying equipment was carried out with the computational fluid dynamics theory and the Fluent software. The effects of jet velocity, pumping speed, jet height and particle size on the discharge mass flow rate and average velocity of particles at the outlet was studied. The simulation results show that with the increase of injection velocity, the discharge mass flow first increases and then decreases, there is an optimal injection speed, and the average velocity of ore particles at the outlet increases linearly and increases substantially linearly as the pumping speed increases, but the discharge mass flow does not change much. The discharge mass flow rate rises first and then decreases with the change in injection height, and has an optimal value when the injection height is 500 mm. The change in injection height has no effect on the average velocity of the ore particle at the exit. With the increase of particle size, the discharge mass flow rate increases sharply. When the particle size exceeds 15 mm, it slowly rises and finally decreases slowly. The average velocity of the ore particles at the outlet is basically not affected by particle size.
2020, 39(6): 836-843.
doi: 10.13433/j.cnki.1003-8728.20190214
Abstract:
In order to weaken the strict geometric constraint relationship between the axes of the kinematic pairs in the overconstrained mechanism and reduce the assembly error and difficulty of the mechanism, a single closed-loop non-overconstrained mechanism configuration design method with inactive joints is proposed. The degree of freedom analysis method of non-overconstrained mechanism with inactive joints is presented. For overconstrained Goldberg mechanism, the non-overconstrained Goldberg mechanism RSRRR is obtained by adding two inactive joints to a single rotation pair. The screw theory proves that the overconstrained/non-overconstrained Goldberg mechanism is completely equivalent in kinematics, and input and output motion parameters of non-overconstrained Goldberg mechanism is studied, so as to verify the correctness of the single closed-loop configuration design method of the non-overconstrained Goldberg mechanism proposed in this paper.
In order to weaken the strict geometric constraint relationship between the axes of the kinematic pairs in the overconstrained mechanism and reduce the assembly error and difficulty of the mechanism, a single closed-loop non-overconstrained mechanism configuration design method with inactive joints is proposed. The degree of freedom analysis method of non-overconstrained mechanism with inactive joints is presented. For overconstrained Goldberg mechanism, the non-overconstrained Goldberg mechanism RSRRR is obtained by adding two inactive joints to a single rotation pair. The screw theory proves that the overconstrained/non-overconstrained Goldberg mechanism is completely equivalent in kinematics, and input and output motion parameters of non-overconstrained Goldberg mechanism is studied, so as to verify the correctness of the single closed-loop configuration design method of the non-overconstrained Goldberg mechanism proposed in this paper.
2020, 39(6): 844-851.
doi: 10.13433/j.cnki.1003-8728.20190162
Abstract:
This paper proposes an improved CMA-ES algorithm. Firstly, the original algorithm randomly generates the initial mean point, which is modified to the weighted sum of excellent individuals in good point sets. Then, the cross-border sensitivity factor and step-size scaling factor are added to adjust step size updates, when the new individuals have cross-border behaviour. Taking the 7-DOF humanoid arm as an example, the inverse kinematic solution is obtained with the improved CMA-ES algorithm. The simulation results show that the improved CMA-ES algorithm can solve the inverse kinematics of 7-DOF humanoid arm in real-time and with high-precision. In point-to-point motion, the single solution time is about 9.7 ms, and the fitness function is stable at the 10−8 level. In the continuous trajectory of workspace, the position tracking error is stable at the 10−5 mm level, and the single average solution time is about 14.1 ms.
This paper proposes an improved CMA-ES algorithm. Firstly, the original algorithm randomly generates the initial mean point, which is modified to the weighted sum of excellent individuals in good point sets. Then, the cross-border sensitivity factor and step-size scaling factor are added to adjust step size updates, when the new individuals have cross-border behaviour. Taking the 7-DOF humanoid arm as an example, the inverse kinematic solution is obtained with the improved CMA-ES algorithm. The simulation results show that the improved CMA-ES algorithm can solve the inverse kinematics of 7-DOF humanoid arm in real-time and with high-precision. In point-to-point motion, the single solution time is about 9.7 ms, and the fitness function is stable at the 10−8 level. In the continuous trajectory of workspace, the position tracking error is stable at the 10−5 mm level, and the single average solution time is about 14.1 ms.
2020, 39(6): 858-864.
doi: 10.13433/j.cnki.1003-8728.20190152
Abstract:
In order to explore the influence of the loading force and other factors on the quality and efficiency in the rotating ultrasonic micro-hole machining of hard and brittle materials, the ultrasonic machining system and air floatation load-matching system with loading force control function were used to conduct the rotating ultrasonic micro-hole machining experiments. Orthogonal experimental design method was used to design the scheme. Ferrite and quartz glass were used as workpiece materials. The influence laws of the loading force, ultrasonic power percentage and free abrasive on the diameter and depth of micro-holes on different materials were analyzed and compared. The results show that excessive loading force leads to low machining efficiency; energy input is mainly based on ultrasonic energy in machining; the influence area of the ultrasonic on the workpiece is slightly larger than the tool itself; too large free abrasive particles are not easy to enter the machining area, while too small particles cannot carry enough energy. Hence, too large or too small diameter of free abrasive will lead to low quality and efficiency in machining.
In order to explore the influence of the loading force and other factors on the quality and efficiency in the rotating ultrasonic micro-hole machining of hard and brittle materials, the ultrasonic machining system and air floatation load-matching system with loading force control function were used to conduct the rotating ultrasonic micro-hole machining experiments. Orthogonal experimental design method was used to design the scheme. Ferrite and quartz glass were used as workpiece materials. The influence laws of the loading force, ultrasonic power percentage and free abrasive on the diameter and depth of micro-holes on different materials were analyzed and compared. The results show that excessive loading force leads to low machining efficiency; energy input is mainly based on ultrasonic energy in machining; the influence area of the ultrasonic on the workpiece is slightly larger than the tool itself; too large free abrasive particles are not easy to enter the machining area, while too small particles cannot carry enough energy. Hence, too large or too small diameter of free abrasive will lead to low quality and efficiency in machining.
2020, 39(6): 865-872.
doi: 10.13433/j.cnki.1003-8728.20190167
Abstract:
In order to improve the effect of the spindle-type barrel finishing process for large and medium-sized disc parts, a vertical cross-spindle type buffing finishing technique was proposed and its theoretical analysis was carried out. By detailing the processing principle of the technique, a mathematical model was established. The cutting speed and cutting angle formula of any point on the disk workpiece were derived. The MATLAB software and the control variable method were used to analyze the variation of cutting speed and cutting angle of the vertical cross-spindle finishing of the workpiece when it was rolling. The results show that with the increase of the parameters of the drum rotation speed, the workpiece rotation speed, and the rotation axis of the drum to the center of the workpiece, the variation of the cutting speed at any point with the workpiece increases. The change in cutting angle is mainly affected by the swing amplitude and swing frequency of two swing angles. The peak value of the outer surface cutting angle increases as the amplitude of the two swings increases.
In order to improve the effect of the spindle-type barrel finishing process for large and medium-sized disc parts, a vertical cross-spindle type buffing finishing technique was proposed and its theoretical analysis was carried out. By detailing the processing principle of the technique, a mathematical model was established. The cutting speed and cutting angle formula of any point on the disk workpiece were derived. The MATLAB software and the control variable method were used to analyze the variation of cutting speed and cutting angle of the vertical cross-spindle finishing of the workpiece when it was rolling. The results show that with the increase of the parameters of the drum rotation speed, the workpiece rotation speed, and the rotation axis of the drum to the center of the workpiece, the variation of the cutting speed at any point with the workpiece increases. The change in cutting angle is mainly affected by the swing amplitude and swing frequency of two swing angles. The peak value of the outer surface cutting angle increases as the amplitude of the two swings increases.
2020, 39(6): 879-883.
doi: 10.13433/j.cnki.1003-8728.20190172
Abstract:
In terms of the principle of ultrasonic vibration polishing, the material removal method in the elastoplastic material polishing process is analyzed. The material removal model for elastoplastic material is established, and the mathematical expressions of abrasive particle velocity, impact load and force on the surface of the workpiece are given. The effects of the polishing processing parameters on the material removal were discussed and analyzed, and the rationality of the model was verified by using the existing experiments.
In terms of the principle of ultrasonic vibration polishing, the material removal method in the elastoplastic material polishing process is analyzed. The material removal model for elastoplastic material is established, and the mathematical expressions of abrasive particle velocity, impact load and force on the surface of the workpiece are given. The effects of the polishing processing parameters on the material removal were discussed and analyzed, and the rationality of the model was verified by using the existing experiments.
2020, 39(6): 884-890.
doi: 10.13433/j.cnki.1003-8728.20190219
Abstract:
Aiming at the low processing efficiency of spiral bevel gears with small modulus by means of five-step method and the difficulty of obtaining good contact area by Two-step method, a cutting method of spiral bevel gears with small modulus by using double rolling is presented. Designing NC double rolling process, the calculation model for tool position and the phase compensation model for automatic tool alignment are established, NC software for the double rolling is developed, the processing of concave and convex sides of gear pair through two rolling in a cutting cycle without manual tool alignment is realized. The experiments of cutting teeth and rolling inspection have been carried out. The results show that the double-rolling method can ensure the good contact and obtain the high processing efficiency for spiral bevel gears with small modulus.
Aiming at the low processing efficiency of spiral bevel gears with small modulus by means of five-step method and the difficulty of obtaining good contact area by Two-step method, a cutting method of spiral bevel gears with small modulus by using double rolling is presented. Designing NC double rolling process, the calculation model for tool position and the phase compensation model for automatic tool alignment are established, NC software for the double rolling is developed, the processing of concave and convex sides of gear pair through two rolling in a cutting cycle without manual tool alignment is realized. The experiments of cutting teeth and rolling inspection have been carried out. The results show that the double-rolling method can ensure the good contact and obtain the high processing efficiency for spiral bevel gears with small modulus.
2020, 39(6): 891-897.
doi: 10.13433/j.cnki.1003-8728.20190170
Abstract:
In order to meet the dual requirements of the aesthetics of the lower extremity rehabilitation exoskeleton and the lightweight structure, a comprehensive design method of modeling design and structural optimization is proposed. Using the principles of kansei engineering and design aesthetics, the general characteristics of lower extremity rehabilitation exoskeleton design are summarized and applied to the design of lower extremity rehabilitation exoskeleton. Then the 7-point scale semantic differential scale is used to select the modeling scheme. In order to verify the rationality of the structure of the modeling scheme, the SolidWorks software is used to carry out the three-dimensional modeling and finite element analysis of the preferred scheme and on the basis of not changing the aesthetics of the contour of the preferred scheme, the topology optimization method is used to reduce the exoskeleton weight. The final design of the design scheme is outstanding in terms of aesthetic appearance and structural performance, indicating the effectiveness of the method.
In order to meet the dual requirements of the aesthetics of the lower extremity rehabilitation exoskeleton and the lightweight structure, a comprehensive design method of modeling design and structural optimization is proposed. Using the principles of kansei engineering and design aesthetics, the general characteristics of lower extremity rehabilitation exoskeleton design are summarized and applied to the design of lower extremity rehabilitation exoskeleton. Then the 7-point scale semantic differential scale is used to select the modeling scheme. In order to verify the rationality of the structure of the modeling scheme, the SolidWorks software is used to carry out the three-dimensional modeling and finite element analysis of the preferred scheme and on the basis of not changing the aesthetics of the contour of the preferred scheme, the topology optimization method is used to reduce the exoskeleton weight. The final design of the design scheme is outstanding in terms of aesthetic appearance and structural performance, indicating the effectiveness of the method.
2020, 39(6): 898-903.
doi: 10.13433/j.cnki.1003-8728.20190163
Abstract:
The fast identification of cutting coefficients by using oblique cutting has been widely used in cutting force modeling, which neglects uncertainties in the identification of cutting coefficients. A method for identification of cutting coefficients based on the Bayesian inference was proposed to solve this problem. The analytical model of surface milling with inserted cutters was deduced and the linear regression method based on the fast identification of cutting coefficients by using oblique cutting was also presented. The cutting coefficients were sampled from their posterior distribution. The variations of cutting coefficients were estimated based on the Bayesian inference. The cutting coefficients obtained with the linear regression method and the Bayesian method under given experimental conditions were used to calculate milling forces respectively. Experiments on milling were performed to validate the effectiveness of these two methods. The results show that the Bayesian method can obtain more accurate predictions.
The fast identification of cutting coefficients by using oblique cutting has been widely used in cutting force modeling, which neglects uncertainties in the identification of cutting coefficients. A method for identification of cutting coefficients based on the Bayesian inference was proposed to solve this problem. The analytical model of surface milling with inserted cutters was deduced and the linear regression method based on the fast identification of cutting coefficients by using oblique cutting was also presented. The cutting coefficients were sampled from their posterior distribution. The variations of cutting coefficients were estimated based on the Bayesian inference. The cutting coefficients obtained with the linear regression method and the Bayesian method under given experimental conditions were used to calculate milling forces respectively. Experiments on milling were performed to validate the effectiveness of these two methods. The results show that the Bayesian method can obtain more accurate predictions.
2020, 39(6): 910-918.
doi: 10.13433/j.cnki.1003-8728.20190211
Abstract:
In order to improve the ultrasonic dry-coupled performance of rough contact interface, the interaction between the ultrasonic wave and the rough interface is studied. The contact stiffness expression with fractal parameters is obtained by establishing the interface fractal model, and the change in acoustic reflection coefficient under different coupling conditions is analyzed by combining the interface acoustic model. The ultrasonic dry-coupling experimental platform is established to measure the surface profile of rough aluminum plate. The fractal dimension is measured with structural function method, and the reflection coefficient of rough aluminum plate with different fractal dimension under pressure is measured. The results show that the coupling performance can be improved by increasing the pressure between the solid surfaces, and the rough aluminum plate with larger fractal dimension needs less load to achieve good acoustic coupling effect, which is more convenient for the implementation of ultrasonic dry coupling detection.
In order to improve the ultrasonic dry-coupled performance of rough contact interface, the interaction between the ultrasonic wave and the rough interface is studied. The contact stiffness expression with fractal parameters is obtained by establishing the interface fractal model, and the change in acoustic reflection coefficient under different coupling conditions is analyzed by combining the interface acoustic model. The ultrasonic dry-coupling experimental platform is established to measure the surface profile of rough aluminum plate. The fractal dimension is measured with structural function method, and the reflection coefficient of rough aluminum plate with different fractal dimension under pressure is measured. The results show that the coupling performance can be improved by increasing the pressure between the solid surfaces, and the rough aluminum plate with larger fractal dimension needs less load to achieve good acoustic coupling effect, which is more convenient for the implementation of ultrasonic dry coupling detection.
2020, 39(6): 926-936.
doi: 10.13433/j.cnki.1003-8728.20190226
Abstract:
In the past, the impact of battery performance evaluation and electric vehicles on the grid has often neglected the impact of battery charging energy, and the charging energy of the battery is also an important indicator in the charging process. To this end, a prediction method of electric charging energy based on the stacking model for machine learning is proposed. The method performs data processing, feature extraction and model screening on the data of charging, and selects the RMSE as the evaluation index of the prediction result. Finally, the stacking model is used to predict the charging energy. In order to verify the prediction results of the Stacking model, the stacking model is compared with the prediction results with a single algorithm model to ensure the feasibility of the scheme. The results show that with the present model for prediction, the RMSE score of the prediction result is 0.104 1, which achieves better prediction than that via single algorithm model.
In the past, the impact of battery performance evaluation and electric vehicles on the grid has often neglected the impact of battery charging energy, and the charging energy of the battery is also an important indicator in the charging process. To this end, a prediction method of electric charging energy based on the stacking model for machine learning is proposed. The method performs data processing, feature extraction and model screening on the data of charging, and selects the RMSE as the evaluation index of the prediction result. Finally, the stacking model is used to predict the charging energy. In order to verify the prediction results of the Stacking model, the stacking model is compared with the prediction results with a single algorithm model to ensure the feasibility of the scheme. The results show that with the present model for prediction, the RMSE score of the prediction result is 0.104 1, which achieves better prediction than that via single algorithm model.
2020, 39(6): 948-953.
doi: 10.13433/j.cnki.1003-8728.20190216
Abstract:
Taking a micro-pure electric vehicle（BEV） as the research object, the paper analyzes the structural characteristics of the high-voltage system（HVS）, refines modeling of the high-voltage harness, establishes the finite element model of the vehicle with HVS components, selects the rear-end crash and the rear-cylinder crash. By simulation, as a results, the high-voltage harness is damaged and the strength of the mounting bracket is insufficient in the high-voltage electrical components. After the improved design, according to the damage condition of the HVS in crash, the control conditions of the crash and power-off protection of the BEV were established, and the high-voltage electric safety protection control strategy was formulated to ensure the safety of the high-voltage electric power of the vehicle.
Taking a micro-pure electric vehicle（BEV） as the research object, the paper analyzes the structural characteristics of the high-voltage system（HVS）, refines modeling of the high-voltage harness, establishes the finite element model of the vehicle with HVS components, selects the rear-end crash and the rear-cylinder crash. By simulation, as a results, the high-voltage harness is damaged and the strength of the mounting bracket is insufficient in the high-voltage electrical components. After the improved design, according to the damage condition of the HVS in crash, the control conditions of the crash and power-off protection of the BEV were established, and the high-voltage electric safety protection control strategy was formulated to ensure the safety of the high-voltage electric power of the vehicle.
2020, 39(6): 954-959.
doi: 10.13433/j.cnki.1003-8728.20200091
Abstract:
A simple and efficient method is proposed to evaluate the vibration behavior of the laminated composite beams under elastic boundary conditions with Haar wavelet discretization method, in terms of the first order shear deformation theory and the Hamilton principle. The basis functions for the displacement variables and their derivatives are expressed in terms of Haar wavelet and their integral, respectively. On the basis, the boundary conditions are used to obtain the constants in the integration process, and then the equations of motion and the boundary conditions of the laminated beams are further converted into a group of linear algebraic equations. The natural frequencies of laminated composite beams are obtained by solving the algebraic equations. The correctness and efficiency of the present method is verified by a series of numerical examples. Some new results for the laminated composite beams are presented, which may serve as benchmark solutions.
A simple and efficient method is proposed to evaluate the vibration behavior of the laminated composite beams under elastic boundary conditions with Haar wavelet discretization method, in terms of the first order shear deformation theory and the Hamilton principle. The basis functions for the displacement variables and their derivatives are expressed in terms of Haar wavelet and their integral, respectively. On the basis, the boundary conditions are used to obtain the constants in the integration process, and then the equations of motion and the boundary conditions of the laminated beams are further converted into a group of linear algebraic equations. The natural frequencies of laminated composite beams are obtained by solving the algebraic equations. The correctness and efficiency of the present method is verified by a series of numerical examples. Some new results for the laminated composite beams are presented, which may serve as benchmark solutions.
