Contour error is the deviation between the actual displacement and reference trajectory,which is directly related to the machining accuracy.Contour error compensation poses substantial challenges because of the time-v...Contour error is the deviation between the actual displacement and reference trajectory,which is directly related to the machining accuracy.Contour error compensation poses substantial challenges because of the time-varying,nonlinear,and strongly coupled characteristics of parallel machining modules.In addition,the time delay in the system reduces the timeliness of the feedback data,thereby making online contour error calculations and compensation particularly difficult.To solve this problem,the generation mechanism of the time delay of the feedback data and contour error is revealed,and a systematic method for the identification of the time-delay parameter based on Beckhoff’s tracking error calculation mechanism is proposed.The temporal alignment between the position commands and feedback data enables the online calculation of the contour error.On this basis,the tracking error of the drive axes(an important factor resulting in end-effector contour errors)is used for the contour error calculation.Considering the ambiguous parameter-setting logic of the servo drive,the servo parameter is calculated in reverse using the steady-state error to obtain the tracking error model of the drive axes.Furthermore,combined with the system time-delay model,an online correction method for the tracking error estimation model is established.To achieve an accurate mapping of the drive-axis tracking error and end-effector contour error,a bounded iterative search method for the nearest contour point and online calculation model for the contour error are respectively established.Finally,an online compensation controller for contour error is designed.Its effectiveness is verified by a machining experiment on a frame workpiece.The machining results show that the contour error reduces from 68μm to 45μm,and the finish machining accuracy increases by 34%.This study provides a feasible method for online compensation of contour error in a system with time delay.展开更多
Gibberella stalk rot(GSR)caused by Fusarium graminearum is one of the most devastating diseases of maize,seriously impacting maize yield and quality,as well as the ability to use technology of mechanical harvesting.En...Gibberella stalk rot(GSR)caused by Fusarium graminearum is one of the most devastating diseases of maize,seriously impacting maize yield and quality,as well as the ability to use technology of mechanical harvesting.Environmental conditions including photoperiod affect crop disease resistance.However,the mechanism underlying photoperiod-regulated maize GSR resistance remains unexplored.We found in this study that GSR resistance is regulated by the ZmPIF4.1(Phytochrome-Interacting Factor4)-ZmPTI1c(Pto-Interacting 1)-ZmMYB31 module coupled with photoperiod.The functional analysis of zmpti1c mutant indicated that ZmPTI1c negatively regulates maize GSR resistance.Short day promoted the disease progression in both zmpti1c and wild-type plants.ZmPTI1c promoter contains multiple predicted cis-acting elements for light responses.Yeast one-hybrid assay(Y1H),Electrophoretic mobility shift analysis(EMSA),and Dual-luciferase(LUC)reporter assays demonstrated that ZmPIF4.1 binds to the G-box in ZmPTI1c promoter and activates its expression.Moreover,expression levels of ZmPIF4 and ZmPTI1c were significantly higher under short day than under long day.ZmPTI1c interacted with and phosphorylated ZmMYB31.GSR resistance in zmmyb31 mutant was significantly increased than in wild type,indicating that ZmMYB31 also negatively regulated GSR resistance.Furthermore,ZmMYB31 suppressed the transcriptional activation of ZmPTI1c by ZmPIF4.1.Overall,ZmPIF4.1-ZmPTI1c-ZmMYB31negatively regulates maize immunity to GSR,which is likely modulated by photoperiod.展开更多
Accurate kinematic calibration is the very foundation for robots'application in industry demanding high precision such as machining.Considering the complex error characteristic and severe ill-posed identification ...Accurate kinematic calibration is the very foundation for robots'application in industry demanding high precision such as machining.Considering the complex error characteristic and severe ill-posed identification issues of a 5-DoF parallel machining robot,this paper proposes an adaptive and weighted identification method to achieve high-precision kinematic calibration while maintaining reliable stability.First,a kinematic error propagation mechanism model considering the non-ideal constraints and the screw self-rotation is formulated by incorporating the intricate structure of multiple chains and a unique driven screw arrangement of the robot.To address the challenge of accurately identifying such a sophisticated error model,a novel adaptive and weighted identification method based on generalized cross validation(GCV)is proposed.Specifically,this approach innovatively introduces Gauss-Markov estimation into the GCV algorithm and utilizes prior physical information to construct both a weighted identification model and a weighted cross-validation function,thus eliminating the inaccuracy caused by significant differences in dimensional magnitudes of pose errors and achieving accurate identification with flexible numerical stability.Finally,the kinematic calibration experiment is conducted.The comparative experimental results demonstrate that the presented approach is effective and has enhanced accuracy performance over typical least squares methods,with maximum position and orientation errors reduced from 2.279 mm to 0.028 mm and from 0.206°to 0.017°,respectively.展开更多
The world is currently undergoing profound changes which have never happened within the past century.Global competition in the technology and industry fields is becoming increasingly fierce.The strategic competition o...The world is currently undergoing profound changes which have never happened within the past century.Global competition in the technology and industry fields is becoming increasingly fierce.The strategic competition of the major powers further focuses on the manufacturing industry.Developed countries such as the United States,Germany,and Japan have successively put forward strategic plans such as“re-industrialization”and“return of manufacturing industry”,aiming to seize the commanding heights of a new round of global high-end technology competition and expand international market share.Standing at the historic intersection of a new round of scientific and technological revolution and China's accelerated high-quality development,the“14th Five-Year Plan”clearly pointed out that intelligent manufacturing is the main development trend to promote China's manufacturing to the medium-high end of the global value chain.This reflects the importance of advanced manufacturing for national strategic layout.To better grasp the development direction of advanced manufacturing equipment,the development process and current application status of manufacturing equipment are summarized,and thereafter the characteristics of manufacturing equipment in different development stages of the manufacturing industry are analyzed.Finally,the development trend of advanced milling equipment is prospected.展开更多
Positioning and navigation technology is a new trend of research in mobile robot area.Existing researches focus on the indoor industrial problems,while many application fields are in the outdoor environment,which put ...Positioning and navigation technology is a new trend of research in mobile robot area.Existing researches focus on the indoor industrial problems,while many application fields are in the outdoor environment,which put forward higher requirements for sensor selection and navigation scheme.In this paper,a complete hybrid navigation system for a class of mobile robots with load tasks and docking tasks is presented.The work can realize large-range autonomous positioning and path planning for mobile robots in unstructured scenarios.The autonomous positioning is achieved by adopting suitable guidance methods to meet different application requirements and accuracy requirements in conditions of different distances.Based on the Bezier curve,a path planning scheme is proposed and a motion controller is designed to make the mobile robot follow the target path.The Kalman filter is established to process the guidance signals and control outputs of the motion controller.Finally,the autonomous positioning and docking experiment are carried out.The results of the research verify the effectiveness of the hybrid navigation,which can be used in autonomous warehousing logistics and multi-mobile robot system.展开更多
Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure ...Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure the reliability and determinism of system execution,a flexible real-time control system architecture and interaction algorithm are required.The ROS framework was designed to improve the reusability of robotic software development by providing a distributed structure,hardware abstraction,message-passing mechanism,and application prototypes.Rich ecosystems for robotic development have been built around ROS1 and ROS2 architectures based on the Linux system.However,because of the fairness scheduling principle of the default Linux system design and the complexity of the kernel,the system does not have real-time computing.To achieve a balance between real-time and non-real-time computing,this paper uses the transmission mechanism of ROS2,combines it with the scheduling mechanism of the Linux operating system,and uses Preempt_RT to enhance the real-time computing of ROS1 and ROS2.The real-time performance evaluation of ROS1 and ROS2 is conducted from multiple perspectives,including throughput,transmission mode,QoS service quality,frequency,number of subscription nodes and EtherCAT master.This paper makes two significant contributions:firstly,it employs Preempt_RT to optimize the native ROS2 system,effectively enhancing the real-time performance of native ROS2 message transmission;secondly,it conducts a comprehensive evaluation of the real-time performance of both native and optimized ROS2 systems.This comparison elucidates the benefits of the optimized ROS2 architecture regarding real-time performance,with results vividly demonstrated through illustrative figures.展开更多
The teleoperation of a 6 degrees-of-freedom(DOF)manipulator is one of the basic methods to extend people’s capabilities in the wide variety of applications.The master interface based on the force/torque(FT)sensor cou...The teleoperation of a 6 degrees-of-freedom(DOF)manipulator is one of the basic methods to extend people’s capabilities in the wide variety of applications.The master interface based on the force/torque(FT)sensor could provide the full-dimension intuitive teleoperation of a 6-DOF robot since it has the ability to trigger 6-DOF command input.However,due to the force coupling,noise disturbance and unlimited input signals of the FT sensor,this force-sensed interface could not be widely used in practice.In this paper,we present an intuitive teleoperation method based on the FT sensor to overcome these challenges.In this method,the input signals from the force-sensed joystick were filtered and then processed to the force commands by force limit algorithm,with the merits of anti-interference,output limitation,and online velocity adjustment.Furthermore,based on the admittance control and position controller,the manipulator could be teleoperated by the force commands.Three experiments were conducted on our self-designed robotic system.The result of the first experiment shows that the interfered force from the force coupling could be effectively suppressed with the limitation of the input force through force limit algorithm.Then,a parameter was introduced in the other two experiments to adjust the velocity online practically with force limit algorithm.The proposed method could give a practical solution to the intuitive teleoperation based on the FT sensor.展开更多
High-speed parallel robots have been extensively utilized in the light industry.However,the influence of the nonlinear dynamic characteristics of high-speed parallel robots on system’s dynamic response and stable ope...High-speed parallel robots have been extensively utilized in the light industry.However,the influence of the nonlinear dynamic characteristics of high-speed parallel robots on system’s dynamic response and stable operation cannot be ignored during the high-speed reciprocating motion.Thus,trajectory planning is essential for efficiency and stability from pick-and-place(PAP)actions.This paper presents a method for planning the equal-height pick-and-place trajectory considering velocity constraints to improve the PAP efficiency and stability of high-speed parallel robots.The velocity constraints in the start-and-end points can reduce vibration from picking and placing,making the trajectory more suitable to complex beltline situations.Based on velocity constraints,trajectory optimization includes trajectory smoothness and joint torque to optimize cycle time is carried out.This paper proposes an online trajectory optimization solution.By using back propagation(BP)neural networks,the solution is simplified and can be solved in real-time.Simulation and experiments were carried out on the SR4 parallel robot.The results show that the proposed method improves the efficiency,smoothness,and stability of the robot.This paper proposes an online trajectory planning method which is velocity constraints based and can improve the efficiency and stability of high-speed parallel robots.The work of this research is conducive to finely applying high-speed parallel robots.展开更多
The health of people around the world and the global economy are under substantial threat from the outbreak of pandemics[1].Controlling pandemics is extremely challenging,with preventing the spread of pathogens the mo...The health of people around the world and the global economy are under substantial threat from the outbreak of pandemics[1].Controlling pandemics is extremely challenging,with preventing the spread of pathogens the most important and critical step.Of all preventative actions,body temperature screening is undoubtedly highly necessary and effective[2].展开更多
This paper deals with the conceptual design, kinematic analysis and workspace identification of a novel four degrees-of-freedom （DOFs） high-speed spatial parallel robot for pick-and-place operations. The proposed sp...This paper deals with the conceptual design, kinematic analysis and workspace identification of a novel four degrees-of-freedom （DOFs） high-speed spatial parallel robot for pick-and-place operations. The proposed spatial parallel robot consists of a base, four arms and a 11/2 mobile platform. The mobile platform is a major innova- tion that avoids output singularity and offers the advantages of both single and double platforms. To investigate the characteristics of the robot＇s DOFs, a line graph method based on Grassmann line geometry is adopted in mobility analysis. In addition, the inverse kinematics is derived, and the constraint conditions to identify the correct solution are also provided. On the basis of the proposed concept, the workspace of the robot is identified using a set of presupposed parameters by taking input and output transmission index as the performance evaluation criteria.展开更多
This study introduces a high-speed parallel robot with Schonflies motion. This robot exhibits a promising prospect in realizing high-speed pick-and- place manipulation for packaging production lines. The robot has fou...This study introduces a high-speed parallel robot with Schonflies motion. This robot exhibits a promising prospect in realizing high-speed pick-and- place manipulation for packaging production lines. The robot has four identical limbs and a single platform. Its compact structure and single-platform concept provides this robot with good dynamic response potential. A line graph method based on Grassmann line geometry is used to investigate the mobility characteristics of the proposed robot. A generalized Blanding rule is also introduced into this procedure to realize mutual conversion between the line graphs for motions and constraints. Subsequently, the inverse kinematics is derived, and the singularity issue of the robot is investigated using both qualitative and quantitative approaches. Input and output transmission singularity indices are defined based on the reciprocal product in screw theory and the virtual coefficient by considering motion/force transmission performance. Thereafter, the singular loci of the proposed robot with specific geometric parameters are derived. The mobility analysis, inverse kinematics modeling, and singularity analysis conducted in this study are helpful in developing the robot.展开更多
An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot du...An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. After- ward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low- power-consumption workspace is selected for the robot.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52375018,92148301).
文摘Contour error is the deviation between the actual displacement and reference trajectory,which is directly related to the machining accuracy.Contour error compensation poses substantial challenges because of the time-varying,nonlinear,and strongly coupled characteristics of parallel machining modules.In addition,the time delay in the system reduces the timeliness of the feedback data,thereby making online contour error calculations and compensation particularly difficult.To solve this problem,the generation mechanism of the time delay of the feedback data and contour error is revealed,and a systematic method for the identification of the time-delay parameter based on Beckhoff’s tracking error calculation mechanism is proposed.The temporal alignment between the position commands and feedback data enables the online calculation of the contour error.On this basis,the tracking error of the drive axes(an important factor resulting in end-effector contour errors)is used for the contour error calculation.Considering the ambiguous parameter-setting logic of the servo drive,the servo parameter is calculated in reverse using the steady-state error to obtain the tracking error model of the drive axes.Furthermore,combined with the system time-delay model,an online correction method for the tracking error estimation model is established.To achieve an accurate mapping of the drive-axis tracking error and end-effector contour error,a bounded iterative search method for the nearest contour point and online calculation model for the contour error are respectively established.Finally,an online compensation controller for contour error is designed.Its effectiveness is verified by a machining experiment on a frame workpiece.The machining results show that the contour error reduces from 68μm to 45μm,and the finish machining accuracy increases by 34%.This study provides a feasible method for online compensation of contour error in a system with time delay.
基金supported financially by the grants from the JBGS[2021]002 project from the Jiangsu Governmentthe National Nature Science Foundation of China(32472095)+2 种基金the National Key Research and Development Program of China(2020YFE02029002)Collaborative Innovation Center for Modern Crop Production(CIC-MCP)to Xiquan Gaosupported in part by the high-performance computing platform of Bioinformatics Center,Nanjing Agricultural University。
文摘Gibberella stalk rot(GSR)caused by Fusarium graminearum is one of the most devastating diseases of maize,seriously impacting maize yield and quality,as well as the ability to use technology of mechanical harvesting.Environmental conditions including photoperiod affect crop disease resistance.However,the mechanism underlying photoperiod-regulated maize GSR resistance remains unexplored.We found in this study that GSR resistance is regulated by the ZmPIF4.1(Phytochrome-Interacting Factor4)-ZmPTI1c(Pto-Interacting 1)-ZmMYB31 module coupled with photoperiod.The functional analysis of zmpti1c mutant indicated that ZmPTI1c negatively regulates maize GSR resistance.Short day promoted the disease progression in both zmpti1c and wild-type plants.ZmPTI1c promoter contains multiple predicted cis-acting elements for light responses.Yeast one-hybrid assay(Y1H),Electrophoretic mobility shift analysis(EMSA),and Dual-luciferase(LUC)reporter assays demonstrated that ZmPIF4.1 binds to the G-box in ZmPTI1c promoter and activates its expression.Moreover,expression levels of ZmPIF4 and ZmPTI1c were significantly higher under short day than under long day.ZmPTI1c interacted with and phosphorylated ZmMYB31.GSR resistance in zmmyb31 mutant was significantly increased than in wild type,indicating that ZmMYB31 also negatively regulated GSR resistance.Furthermore,ZmMYB31 suppressed the transcriptional activation of ZmPTI1c by ZmPIF4.1.Overall,ZmPIF4.1-ZmPTI1c-ZmMYB31negatively regulates maize immunity to GSR,which is likely modulated by photoperiod.
基金Supported by National Key R&D Program of China(Grant No.2022YFB3404101)National Natural Science Foundation of China(Grant Nos.52375018,92148301)。
文摘Accurate kinematic calibration is the very foundation for robots'application in industry demanding high precision such as machining.Considering the complex error characteristic and severe ill-posed identification issues of a 5-DoF parallel machining robot,this paper proposes an adaptive and weighted identification method to achieve high-precision kinematic calibration while maintaining reliable stability.First,a kinematic error propagation mechanism model considering the non-ideal constraints and the screw self-rotation is formulated by incorporating the intricate structure of multiple chains and a unique driven screw arrangement of the robot.To address the challenge of accurately identifying such a sophisticated error model,a novel adaptive and weighted identification method based on generalized cross validation(GCV)is proposed.Specifically,this approach innovatively introduces Gauss-Markov estimation into the GCV algorithm and utilizes prior physical information to construct both a weighted identification model and a weighted cross-validation function,thus eliminating the inaccuracy caused by significant differences in dimensional magnitudes of pose errors and achieving accurate identification with flexible numerical stability.Finally,the kinematic calibration experiment is conducted.The comparative experimental results demonstrate that the presented approach is effective and has enhanced accuracy performance over typical least squares methods,with maximum position and orientation errors reduced from 2.279 mm to 0.028 mm and from 0.206°to 0.017°,respectively.
基金Supported by National Natural Science Foundation of China (Grant No.92148301)。
文摘The world is currently undergoing profound changes which have never happened within the past century.Global competition in the technology and industry fields is becoming increasingly fierce.The strategic competition of the major powers further focuses on the manufacturing industry.Developed countries such as the United States,Germany,and Japan have successively put forward strategic plans such as“re-industrialization”and“return of manufacturing industry”,aiming to seize the commanding heights of a new round of global high-end technology competition and expand international market share.Standing at the historic intersection of a new round of scientific and technological revolution and China's accelerated high-quality development,the“14th Five-Year Plan”clearly pointed out that intelligent manufacturing is the main development trend to promote China's manufacturing to the medium-high end of the global value chain.This reflects the importance of advanced manufacturing for national strategic layout.To better grasp the development direction of advanced manufacturing equipment,the development process and current application status of manufacturing equipment are summarized,and thereafter the characteristics of manufacturing equipment in different development stages of the manufacturing industry are analyzed.Finally,the development trend of advanced milling equipment is prospected.
文摘Positioning and navigation technology is a new trend of research in mobile robot area.Existing researches focus on the indoor industrial problems,while many application fields are in the outdoor environment,which put forward higher requirements for sensor selection and navigation scheme.In this paper,a complete hybrid navigation system for a class of mobile robots with load tasks and docking tasks is presented.The work can realize large-range autonomous positioning and path planning for mobile robots in unstructured scenarios.The autonomous positioning is achieved by adopting suitable guidance methods to meet different application requirements and accuracy requirements in conditions of different distances.Based on the Bezier curve,a path planning scheme is proposed and a motion controller is designed to make the mobile robot follow the target path.The Kalman filter is established to process the guidance signals and control outputs of the motion controller.Finally,the autonomous positioning and docking experiment are carried out.The results of the research verify the effectiveness of the hybrid navigation,which can be used in autonomous warehousing logistics and multi-mobile robot system.
基金Supported by National Key Research and Development Program of China(Grant No.2019YFB1309900)Institute for Guo Qiang,Tsinghua University of China(Grant No.2019GQG0007).
文摘Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure the reliability and determinism of system execution,a flexible real-time control system architecture and interaction algorithm are required.The ROS framework was designed to improve the reusability of robotic software development by providing a distributed structure,hardware abstraction,message-passing mechanism,and application prototypes.Rich ecosystems for robotic development have been built around ROS1 and ROS2 architectures based on the Linux system.However,because of the fairness scheduling principle of the default Linux system design and the complexity of the kernel,the system does not have real-time computing.To achieve a balance between real-time and non-real-time computing,this paper uses the transmission mechanism of ROS2,combines it with the scheduling mechanism of the Linux operating system,and uses Preempt_RT to enhance the real-time computing of ROS1 and ROS2.The real-time performance evaluation of ROS1 and ROS2 is conducted from multiple perspectives,including throughput,transmission mode,QoS service quality,frequency,number of subscription nodes and EtherCAT master.This paper makes two significant contributions:firstly,it employs Preempt_RT to optimize the native ROS2 system,effectively enhancing the real-time performance of native ROS2 message transmission;secondly,it conducts a comprehensive evaluation of the real-time performance of both native and optimized ROS2 systems.This comparison elucidates the benefits of the optimized ROS2 architecture regarding real-time performance,with results vividly demonstrated through illustrative figures.
基金National Key Research and Development Program of China(Grant No.2019YFB1309900)Shandong Provincial Key Research and Development Program of China(Grant No.2019JZZY010432)Institute for Guo Qiang,Tsinghua University,China(Grant No.2019GQG0007).
文摘The teleoperation of a 6 degrees-of-freedom(DOF)manipulator is one of the basic methods to extend people’s capabilities in the wide variety of applications.The master interface based on the force/torque(FT)sensor could provide the full-dimension intuitive teleoperation of a 6-DOF robot since it has the ability to trigger 6-DOF command input.However,due to the force coupling,noise disturbance and unlimited input signals of the FT sensor,this force-sensed interface could not be widely used in practice.In this paper,we present an intuitive teleoperation method based on the FT sensor to overcome these challenges.In this method,the input signals from the force-sensed joystick were filtered and then processed to the force commands by force limit algorithm,with the merits of anti-interference,output limitation,and online velocity adjustment.Furthermore,based on the admittance control and position controller,the manipulator could be teleoperated by the force commands.Three experiments were conducted on our self-designed robotic system.The result of the first experiment shows that the interfered force from the force coupling could be effectively suppressed with the limitation of the input force through force limit algorithm.Then,a parameter was introduced in the other two experiments to adjust the velocity online practically with force limit algorithm.The proposed method could give a practical solution to the intuitive teleoperation based on the FT sensor.
基金National Natural Science Foundation of China(Grant Nos.51922057,91948301).
文摘High-speed parallel robots have been extensively utilized in the light industry.However,the influence of the nonlinear dynamic characteristics of high-speed parallel robots on system’s dynamic response and stable operation cannot be ignored during the high-speed reciprocating motion.Thus,trajectory planning is essential for efficiency and stability from pick-and-place(PAP)actions.This paper presents a method for planning the equal-height pick-and-place trajectory considering velocity constraints to improve the PAP efficiency and stability of high-speed parallel robots.The velocity constraints in the start-and-end points can reduce vibration from picking and placing,making the trajectory more suitable to complex beltline situations.Based on velocity constraints,trajectory optimization includes trajectory smoothness and joint torque to optimize cycle time is carried out.This paper proposes an online trajectory optimization solution.By using back propagation(BP)neural networks,the solution is simplified and can be solved in real-time.Simulation and experiments were carried out on the SR4 parallel robot.The results show that the proposed method improves the efficiency,smoothness,and stability of the robot.This paper proposes an online trajectory planning method which is velocity constraints based and can improve the efficiency and stability of high-speed parallel robots.The work of this research is conducive to finely applying high-speed parallel robots.
文摘The health of people around the world and the global economy are under substantial threat from the outbreak of pandemics[1].Controlling pandemics is extremely challenging,with preventing the spread of pathogens the most important and critical step.Of all preventative actions,body temperature screening is undoubtedly highly necessary and effective[2].
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant No. 51425501）, and by the Beijing Municipal Science ＆ Technology Commission （Grant No. ZI7110000 0817007）. The second author wishes to acknowledge the support provided by the Alexander yon Humboldt （AvH） Foundation.
文摘This paper deals with the conceptual design, kinematic analysis and workspace identification of a novel four degrees-of-freedom （DOFs） high-speed spatial parallel robot for pick-and-place operations. The proposed spatial parallel robot consists of a base, four arms and a 11/2 mobile platform. The mobile platform is a major innova- tion that avoids output singularity and offers the advantages of both single and double platforms. To investigate the characteristics of the robot＇s DOFs, a line graph method based on Grassmann line geometry is adopted in mobility analysis. In addition, the inverse kinematics is derived, and the constraint conditions to identify the correct solution are also provided. On the basis of the proposed concept, the workspace of the robot is identified using a set of presupposed parameters by taking input and output transmission index as the performance evaluation criteria.
基金the National Natural Science Foundation of China under Grant Nos. 51305222 and 51425501, and by the Tsinghua University Initiative Scientific Research Program under Grant No. 2014z22068.
文摘This study introduces a high-speed parallel robot with Schonflies motion. This robot exhibits a promising prospect in realizing high-speed pick-and- place manipulation for packaging production lines. The robot has four identical limbs and a single platform. Its compact structure and single-platform concept provides this robot with good dynamic response potential. A line graph method based on Grassmann line geometry is used to investigate the mobility characteristics of the proposed robot. A generalized Blanding rule is also introduced into this procedure to realize mutual conversion between the line graphs for motions and constraints. Subsequently, the inverse kinematics is derived, and the singularity issue of the robot is investigated using both qualitative and quantitative approaches. Input and output transmission singularity indices are defined based on the reciprocal product in screw theory and the virtual coefficient by considering motion/force transmission performance. Thereafter, the singular loci of the proposed robot with specific geometric parameters are derived. The mobility analysis, inverse kinematics modeling, and singularity analysis conducted in this study are helpful in developing the robot.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant No. 51425501）, and Beijing Municipal Science and Technology Commission （Grant No. Z 171100000817007）. The second author wishes to acknowledge the support of the Alexander von Humboldt Foundation.
文摘An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. After- ward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low- power-consumption workspace is selected for the robot.
