The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of sc...The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of screening efficiency.Based on the reverse engineering technology,using the wavy geometry formed during the earthworm(Pheretima guillelmi)moving as a bionic prototype,a bionic screen was designed to make the maize mixture migrate backward rapidly in the front of the screen.The contour curve of earthworm’s head in an axial contracted state was extracted and fitted to obtain its equation.Based on the difference of concave position of the lower surface’s wavy geometry during the earthworm moving,the motion of the bionic screen was divided into four postures,and the conversion between different postures of the bionic screen was realized by the cam drive mechanism.The kinematics simulation of the bionic screen was carried out through ADAMS,and the displacement and velocity of the bionic screen were analyzed.When the feeding mass of the maize mixture was set at 5 kg/s,6 kg/s and 7 kg/s,the test results showed that the time of the maize mixture migrated(TOMMM)in the front of the bionic screen was shortened by 0.18 s,0.71 s,and 1.36 s,respectively,compared with that of planar reciprocating vibrating screen.The total screening time(TST)of the bionic screen was shortened by 1.28 s,1.33 s,and 1.53 s,respectively.The ability of the maize mixture to be migrated backward was improved.This study can provide a reference for the innovative design of the cleaning screen.展开更多
A launch and recovery system for a seafloor drill was studied using a dynamic model that considered the influences of seawater resistance and the elastic deformation of the cable based on the lumped mass method.The in...A launch and recovery system for a seafloor drill was studied using a dynamic model that considered the influences of seawater resistance and the elastic deformation of the cable based on the lumped mass method.The influence of wave direction angle on heave,roll,and pitch motions of the ship was analyzed,and those motion characteristics were then used to assess the tension response of the armored umbilical cable at the lifting point under different wave direction angles.By analyzing the different wave direction angles we found that,when a ship experiences longitudinal waves it will express longitudinal movement.When a ship encounters transverse waves,it will have transverse movement.Under oblique waves from bow or stern,a ship will have both longitudinal and transverse movement,exhibiting obvious heave and pitch movements.Oblique waves,in this study,produced the most obvious impact on armored umbilical cable tension.However,the tension of the armored umbilical cable will change based on the weight of the armored umbilical cable and the seafloor drill in the water.This analysis has provided a useful reference for the study of heave compensation and the constant tension automatic control.展开更多
A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-R...A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-RPU-UPR rigid parallel mechanism with the method of optimization of motion/force transfer characteristic.R,P and U represent rotation,translation and universal pairs,respectively.Firstly,inverse kinematics and Jacobian matrix are analyzed for the dimensional synthesis.Then,output transmission indexes of branches in the parallel mechanism are given.Dimensional synthesis is completed based on the normalized design parameter.And optimization of flexure joints based on constrained energy is carried out.Afterwards,the novel compliant mechanism is obtained by direct replacing method.Mechanical model of the compliant mechanism including static stiffness and input stiffness is built based on the pseudo-rigid body modeling method and virtual work principle.Finally,FEA simulation by Ansys Workbench is carried out to verify DOF,effectiveness of the dimension synthesis,and compliant model.Optimization of motion/force transfer characteristic is first applied for the design of compliant mechanisms to suppress drift of rotation axis in the paper.展开更多
An online detection device that used the capacitance method to detect the moisture content of rice in a combine harvester was designed and found a low detection accuracy because of the high impurity content of the sam...An online detection device that used the capacitance method to detect the moisture content of rice in a combine harvester was designed and found a low detection accuracy because of the high impurity content of the samples.To solve this problem,a screening and impurity removal device was designed in this study,and the structural parameter range of the screw conveyor was the focus of the design.To determine the best structural parameters and operating parameters of the device,models of rice grains and short stems were established by the discrete element method.The Discrete Element Method(DEM)simulation test was carried out according to the Box-Behnken response surface method.When the rotating speed was 300 r/min,the diameter of spiral blade was 146 mm,the pitch was 80 mm,the diameter of rotating shaft was 30.6 mm,and the minimum impurity content was 0.27%.The density distributions and movement characteristics of the rice grains and short stems in the optimized screening and impurity removal device were studied.An experiment was carried out to compare data for the moisture content of rice measured by the online moisture content detection device before and after the installation of the screening and impurity removal device and the results of the 105°C drying method.The results showed that the impurity content of rice ranged from 0.26%to 0.37%,and the maximum effective screening rate was 90.99%after screening.The screening and impurity removal device significantly reduced the error in the moisture content measured by the online detection device,the error range was 0.12%-2.55%.This study provides a method for accurate online detection of moisture content and provides a reference for the design and simulation of related screening devices.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.52075091,51475090)the Heilongjiang Provincial Natural Science Foundation of China(Grant No.E2017004).
文摘The maize mixture feeding with a large mass cannot be migrated backward rapidly along the planar reciprocating vibrating screen,and it is easy to accumulate in the front of the screen,which leads to the decrease of screening efficiency.Based on the reverse engineering technology,using the wavy geometry formed during the earthworm(Pheretima guillelmi)moving as a bionic prototype,a bionic screen was designed to make the maize mixture migrate backward rapidly in the front of the screen.The contour curve of earthworm’s head in an axial contracted state was extracted and fitted to obtain its equation.Based on the difference of concave position of the lower surface’s wavy geometry during the earthworm moving,the motion of the bionic screen was divided into four postures,and the conversion between different postures of the bionic screen was realized by the cam drive mechanism.The kinematics simulation of the bionic screen was carried out through ADAMS,and the displacement and velocity of the bionic screen were analyzed.When the feeding mass of the maize mixture was set at 5 kg/s,6 kg/s and 7 kg/s,the test results showed that the time of the maize mixture migrated(TOMMM)in the front of the bionic screen was shortened by 0.18 s,0.71 s,and 1.36 s,respectively,compared with that of planar reciprocating vibrating screen.The total screening time(TST)of the bionic screen was shortened by 1.28 s,1.33 s,and 1.53 s,respectively.The ability of the maize mixture to be migrated backward was improved.This study can provide a reference for the innovative design of the cleaning screen.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51705145 and 51779092)the special funding support for the construction of innovative provinces in Hunan Province (Grant Nos. 2020GK1021, 2019SK2271, and 2019GK1012)
文摘A launch and recovery system for a seafloor drill was studied using a dynamic model that considered the influences of seawater resistance and the elastic deformation of the cable based on the lumped mass method.The influence of wave direction angle on heave,roll,and pitch motions of the ship was analyzed,and those motion characteristics were then used to assess the tension response of the armored umbilical cable at the lifting point under different wave direction angles.By analyzing the different wave direction angles we found that,when a ship experiences longitudinal waves it will express longitudinal movement.When a ship encounters transverse waves,it will have transverse movement.Under oblique waves from bow or stern,a ship will have both longitudinal and transverse movement,exhibiting obvious heave and pitch movements.Oblique waves,in this study,produced the most obvious impact on armored umbilical cable tension.However,the tension of the armored umbilical cable will change based on the weight of the armored umbilical cable and the seafloor drill in the water.This analysis has provided a useful reference for the study of heave compensation and the constant tension automatic control.
基金National Natural Science Foundation of China(Grant No.51975007).
文摘A novel compliant mechanism with RPR degrees of freedom(DOF)is proposed where R and P represent rotation and translation DOFs,respectively.The proposed compliant mechanism is obtained from dimension synthesizing a 2-RPU-UPR rigid parallel mechanism with the method of optimization of motion/force transfer characteristic.R,P and U represent rotation,translation and universal pairs,respectively.Firstly,inverse kinematics and Jacobian matrix are analyzed for the dimensional synthesis.Then,output transmission indexes of branches in the parallel mechanism are given.Dimensional synthesis is completed based on the normalized design parameter.And optimization of flexure joints based on constrained energy is carried out.Afterwards,the novel compliant mechanism is obtained by direct replacing method.Mechanical model of the compliant mechanism including static stiffness and input stiffness is built based on the pseudo-rigid body modeling method and virtual work principle.Finally,FEA simulation by Ansys Workbench is carried out to verify DOF,effectiveness of the dimension synthesis,and compliant model.Optimization of motion/force transfer characteristic is first applied for the design of compliant mechanisms to suppress drift of rotation axis in the paper.
基金supported by the Program on Industrial Technology System of National Rice(CN)(CARS-01-48).
文摘An online detection device that used the capacitance method to detect the moisture content of rice in a combine harvester was designed and found a low detection accuracy because of the high impurity content of the samples.To solve this problem,a screening and impurity removal device was designed in this study,and the structural parameter range of the screw conveyor was the focus of the design.To determine the best structural parameters and operating parameters of the device,models of rice grains and short stems were established by the discrete element method.The Discrete Element Method(DEM)simulation test was carried out according to the Box-Behnken response surface method.When the rotating speed was 300 r/min,the diameter of spiral blade was 146 mm,the pitch was 80 mm,the diameter of rotating shaft was 30.6 mm,and the minimum impurity content was 0.27%.The density distributions and movement characteristics of the rice grains and short stems in the optimized screening and impurity removal device were studied.An experiment was carried out to compare data for the moisture content of rice measured by the online moisture content detection device before and after the installation of the screening and impurity removal device and the results of the 105°C drying method.The results showed that the impurity content of rice ranged from 0.26%to 0.37%,and the maximum effective screening rate was 90.99%after screening.The screening and impurity removal device significantly reduced the error in the moisture content measured by the online detection device,the error range was 0.12%-2.55%.This study provides a method for accurate online detection of moisture content and provides a reference for the design and simulation of related screening devices.
