Kinematics and its related issues of a 3-DOF in-parallel compliant mechanism are focused on.The micro manipulation application that requires high accuracy is developed.Design of the developed micromanipulator is based...Kinematics and its related issues of a 3-DOF in-parallel compliant mechanism are focused on.The micro manipulation application that requires high accuracy is developed.Design of the developed micromanipulator is based on the modified Delta mechanism.The main advantages of this manipulator are the use of only revolute flexure hinges and the capability to produce pure translation theoretically.The aim is to develop an efficient kinematic model used for positioning control.For this purpose, the Jacobian matrix relating the end effector position with the actuator displacements is obtained by both theoretical derivation and experiment.Aiming at the abnormality in the motion capabilities of the micromanipulator found in calibration experiment, the mobility of the compliant mechanism on a theoretical level is analyzed by using the matrix method and screw theory.Both the experimental and theoretical results have verified that the compliant mechanism does have rotational motion.展开更多
Singularity analysis is an essential issue for the development and application of parallel manipulators.Most of the existing researches focus on the singularity of parallel manipulators are carried out based on the st...Singularity analysis is an essential issue for the development and application of parallel manipulators.Most of the existing researches focus on the singularity of parallel manipulators are carried out based on the study of Jacobian matrices.A 3-DOF parallel manipulator with symmetrical structure is presented.The novel parallel manipulator employs only revolute joints and consists of four closed-loop subchains connecting to both base and platform via revolute joints.The closed-loop subchain in each chain-leg is a spherical 6R linkage.The motion characteristics of the output link in the spherical 6R linkage with symmetrical structure are analyzed based on the interrelationships between screw systems.The constraints that are exerted on the platform by each chain-leg are investigated applying the concept of generalized kinematic pair in terms of equivalent screw system.Considering the geometric characteristics of the parallel manipulator,the singularity criteria of the parallel manipulator corresponding to different configurations are revealed based on the dependency of screw system and line geometry.The existing conditions of certain configuration that a singularity must occur are determined.This paper presents a new way of singularity analysis based on disposition of constraint forces on the geometrically identified constraint plane and the proposed approach is capable of avoiding the complexity in solving the Jacobian matrices.展开更多
In order to achieve active grinding control,a novel numerical control micropositioning workpiece table with a resolution of 6 nm has been developed.The table is driven by three piezoelectric actuators mounted on the b...In order to achieve active grinding control,a novel numerical control micropositioning workpiece table with a resolution of 6 nm has been developed.The table is driven by three piezoelectric actuators mounted on the base.An elastic structure with three half-notch flexure hinges is designed to apply preload to the piezoelectric actuators.The position of flexure hinges is also elaborately designed with consideration to reduce the bending deformation of the moving part.Three capacitive sensors are used to form close loop control system.Considering the table as a damped 3-DOF mass-spring system,the models of static and dynamic stiffness and error owing to the action of external forces have been established.In order to make the table have high resolution and positioning accuracy,an error compensation algorithm is implemented by using the established models.The experimental testing has been carried out to verify the performance of the workpiece table and the established models of the micropositioning workpieee table.展开更多
The pneumatic muscle actuator(PMA)has many advantages,such as good flexibility,high power/weight ratio,but its nonlinearity makes it difficult to build a static mathematical model with high precision.A new method is p...The pneumatic muscle actuator(PMA)has many advantages,such as good flexibility,high power/weight ratio,but its nonlinearity makes it difficult to build a static mathematical model with high precision.A new method is proposed to establish the model of PMA.The concept of hybrid elastic modulus which is related to the static characteristic of PMA is put forward,and the energy conservation law is used to achieve the expression of the hybrid elastic modulus,which can be fitted out based on experimental data,and the model of PMA can be derived from this expression.At the same time,a 3-DOF parallel mechanism(a new bionic shoulder joint)driven by five PMAs is designed.This bionic shoulder joint adopts the structure of two antagonistic PMAs actualizing a rotation control and three PMAs controlling another two rotations to get better rotation characteristics.The kinematic and dynamic characteristics of the mechanism are analyzed and a new static model of PMA is used to control it.Experimental results demonstrate the effectiveness of this new static model.展开更多
Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one...Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one degree of freedom(DOF), and the power absorption efficiency is not quite satisfactory. In this paper, a 3-DOF WEC is proposed and a simplified frequency-domain dynamic model of the WEC depending on the linear potential theory is conducted. The performances of three geometries of the oscillating body including the cone, the cylinder and the hemisphere have been compared, and the results show that the hemisphere is more suitable for the 3-DOF WEC.Subsequently, the relationship among the parameters of the hemisphere is established based on the equal natural frequencies of the heave and pitch(or roll) motions, and the results show that lowering the center of gravity leads to the better power absorption in the pitch(or roll) motion. In the end, the power matrixes of different sizes of the hemispheres under different irregular waves are obtained, which can give a size design reference for engineers.展开更多
This paper introduces a 3-dof hybrid robotic manipulator which is constructed by combining a parallel mechanism and a pantograph to increase stiffness as well as workspace. And by analyzing its kinematics and dynamics...This paper introduces a 3-dof hybrid robotic manipulator which is constructed by combining a parallel mechanism and a pantograph to increase stiffness as well as workspace. And by analyzing its kinematics and dynamics with Lagrange’s method, the dynamic model is obtained which is essential for feed-forward control of the manipulator. An explicit solution is given out. Finally, a simulation test is carried out on computers.展开更多
Three-degree of freedom(3-DOF) translational parallel manipulators(TPMs) have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on desi...Three-degree of freedom(3-DOF) translational parallel manipulators(TPMs) have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on designers' intuition, empirical knowledge, or associative reasoning and the topology synthesis researches of 3-DOF TPMs are still limited. In order to find out the atlas of designs for 3-DOF TPMs, a topology search is presented for enumeration of 3-DOF TPMs whose limbs can be modeled as 5-DOF serial chains. The proposed topology search of 3-DOF TPMs is aimed to overcome the sensitivities of the design solution of a 3-DOF TPM for a LARM leg mechanism in a biped robot. The topology search, which is based on the concept of generation and specialization in graph theory, is reported as a step-by-step procedure with desired specifications, principle and rules of generalization, design requirements and constraints, and algorithm of number synthesis. In order to obtain new feasible designs for a chosen example and to limit the search domain under general considerations, one topological generalized kinematic chain is chosen to be specialized. An atlas of new feasible designs is obtained and analyzed for a specific solution as leg mechanisms. The proposed methodology provides a topology search for 3-DOF TPMs for leg mechanisms, but it can be also expanded for other applications and tasks.展开更多
基金This project is supported by National Natural Science Foundation of China (No.59775002 and No.50075010).
文摘Kinematics and its related issues of a 3-DOF in-parallel compliant mechanism are focused on.The micro manipulation application that requires high accuracy is developed.Design of the developed micromanipulator is based on the modified Delta mechanism.The main advantages of this manipulator are the use of only revolute flexure hinges and the capability to produce pure translation theoretically.The aim is to develop an efficient kinematic model used for positioning control.For this purpose, the Jacobian matrix relating the end effector position with the actuator displacements is obtained by both theoretical derivation and experiment.Aiming at the abnormality in the motion capabilities of the micromanipulator found in calibration experiment, the mobility of the compliant mechanism on a theoretical level is analyzed by using the matrix method and screw theory.Both the experimental and theoretical results have verified that the compliant mechanism does have rotational motion.
基金supported by National Natural Science Foundation of China (Grant No. 50675016)
文摘Singularity analysis is an essential issue for the development and application of parallel manipulators.Most of the existing researches focus on the singularity of parallel manipulators are carried out based on the study of Jacobian matrices.A 3-DOF parallel manipulator with symmetrical structure is presented.The novel parallel manipulator employs only revolute joints and consists of four closed-loop subchains connecting to both base and platform via revolute joints.The closed-loop subchain in each chain-leg is a spherical 6R linkage.The motion characteristics of the output link in the spherical 6R linkage with symmetrical structure are analyzed based on the interrelationships between screw systems.The constraints that are exerted on the platform by each chain-leg are investigated applying the concept of generalized kinematic pair in terms of equivalent screw system.Considering the geometric characteristics of the parallel manipulator,the singularity criteria of the parallel manipulator corresponding to different configurations are revealed based on the dependency of screw system and line geometry.The existing conditions of certain configuration that a singularity must occur are determined.This paper presents a new way of singularity analysis based on disposition of constraint forces on the geometrically identified constraint plane and the proposed approach is capable of avoiding the complexity in solving the Jacobian matrices.
基金This project is supported by National Natural Science Foundation of China(No.50275104)
文摘In order to achieve active grinding control,a novel numerical control micropositioning workpiece table with a resolution of 6 nm has been developed.The table is driven by three piezoelectric actuators mounted on the base.An elastic structure with three half-notch flexure hinges is designed to apply preload to the piezoelectric actuators.The position of flexure hinges is also elaborately designed with consideration to reduce the bending deformation of the moving part.Three capacitive sensors are used to form close loop control system.Considering the table as a damped 3-DOF mass-spring system,the models of static and dynamic stiffness and error owing to the action of external forces have been established.In order to make the table have high resolution and positioning accuracy,an error compensation algorithm is implemented by using the established models.The experimental testing has been carried out to verify the performance of the workpiece table and the established models of the micropositioning workpieee table.
基金supported by the National Natural Science Foundation of China(No. 51405229)the Natural Science Foundation of Jiangsu Province of China(Nos. BK20151470,BK20171416)
文摘The pneumatic muscle actuator(PMA)has many advantages,such as good flexibility,high power/weight ratio,but its nonlinearity makes it difficult to build a static mathematical model with high precision.A new method is proposed to establish the model of PMA.The concept of hybrid elastic modulus which is related to the static characteristic of PMA is put forward,and the energy conservation law is used to achieve the expression of the hybrid elastic modulus,which can be fitted out based on experimental data,and the model of PMA can be derived from this expression.At the same time,a 3-DOF parallel mechanism(a new bionic shoulder joint)driven by five PMAs is designed.This bionic shoulder joint adopts the structure of two antagonistic PMAs actualizing a rotation control and three PMAs controlling another two rotations to get better rotation characteristics.The kinematic and dynamic characteristics of the mechanism are analyzed and a new static model of PMA is used to control it.Experimental results demonstrate the effectiveness of this new static model.
基金financially supported by China Postdoctoral Science Foundation(Grant No.2017M611554)the National Natural Science Foundation of China(Grant No.51335007)
文摘Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one degree of freedom(DOF), and the power absorption efficiency is not quite satisfactory. In this paper, a 3-DOF WEC is proposed and a simplified frequency-domain dynamic model of the WEC depending on the linear potential theory is conducted. The performances of three geometries of the oscillating body including the cone, the cylinder and the hemisphere have been compared, and the results show that the hemisphere is more suitable for the 3-DOF WEC.Subsequently, the relationship among the parameters of the hemisphere is established based on the equal natural frequencies of the heave and pitch(or roll) motions, and the results show that lowering the center of gravity leads to the better power absorption in the pitch(or roll) motion. In the end, the power matrixes of different sizes of the hemispheres under different irregular waves are obtained, which can give a size design reference for engineers.
文摘This paper introduces a 3-dof hybrid robotic manipulator which is constructed by combining a parallel mechanism and a pantograph to increase stiffness as well as workspace. And by analyzing its kinematics and dynamics with Lagrange’s method, the dynamic model is obtained which is essential for feed-forward control of the manipulator. An explicit solution is given out. Finally, a simulation test is carried out on computers.
基金supported by the Chinese Scholarship Council(CSC)for his Ph D study and research at LARM in the University of Cassino and South Latium,Italy,during 2013-2015
文摘Three-degree of freedom(3-DOF) translational parallel manipulators(TPMs) have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on designers' intuition, empirical knowledge, or associative reasoning and the topology synthesis researches of 3-DOF TPMs are still limited. In order to find out the atlas of designs for 3-DOF TPMs, a topology search is presented for enumeration of 3-DOF TPMs whose limbs can be modeled as 5-DOF serial chains. The proposed topology search of 3-DOF TPMs is aimed to overcome the sensitivities of the design solution of a 3-DOF TPM for a LARM leg mechanism in a biped robot. The topology search, which is based on the concept of generation and specialization in graph theory, is reported as a step-by-step procedure with desired specifications, principle and rules of generalization, design requirements and constraints, and algorithm of number synthesis. In order to obtain new feasible designs for a chosen example and to limit the search domain under general considerations, one topological generalized kinematic chain is chosen to be specialized. An atlas of new feasible designs is obtained and analyzed for a specific solution as leg mechanisms. The proposed methodology provides a topology search for 3-DOF TPMs for leg mechanisms, but it can be also expanded for other applications and tasks.
