In order to overcome the drawbacks of 3RRR non-redundant parallel manipulators,a redundantly actuated planar parallel manipulator,the 4RRR manipulator,was examined.In the current study,three types of workspace were an...In order to overcome the drawbacks of 3RRR non-redundant parallel manipulators,a redundantly actuated planar parallel manipulator,the 4RRR manipulator,was examined.In the current study,three types of workspace were analyzed.In the analysis of the reachable workspace,the shape of the workspace of 4RRR PMs was illustrated,and the relationship between the parameters of parallel mechanisms（PMs） and this kind of workspace was discussed.In the analysis of the m-orientation workspace,a procedure for calculating this type of workspace was presented,and the relationship between this type of workspace and the requirement of rotational displacement was revealed.In the analysis of the nonsingular workspace,the singularity of 4RRR PMs was discussed,the boundary of the singularity was illustrated,and a scheme to maximize the nonsingular workspace was presented.Depicting the properties of 4RRR PMs from different perspectives,the analyses of these three kinds of workspace can serve as helpful references for the structure design and mechanism control of 4RRR PMs.展开更多
Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,the...Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,they cannot adequately support the huge axial downward forces that FSW generates.Available parallel mechanism architectures,particularly redundantly actuated architectures for FSW,are still very limited.In this paper,a redundantly actuated 2 UPR-2 RPU parallel robot for FSW is proposed,where U denotes a universal joint,R denotes a revolute joint and P denotes a prismatic pair.First,its semi-symmetric structure is described.Next,inverse kinematics analysis involving an analytical representation of rotational axes is implemented.Velocity analysis is also conducted,which leads to the formation of a Jacobian matrix.Sensitivity performance is evaluated utilizing level set and convex optimization methods,where the local sensitivity indices are unit consistent,coordinate free,and of definite physical significance.Furthermore,global and hierarchical sensitivity indices are proposed for the design process.Finally,dimension synthesis is conducted based on the sensitivity indices and the optimal link parameters of the parallel robot are obtained.In summary,this paper proposes a dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices.展开更多
This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equa...This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equation is formulated in the task space by using the Lagrangian formalism, and the driving force is optimized by utilizing the minimal 2-norm method. Based on the dynamic model, a synchronized sliding mode control scheme based on contour error is proposed to implement accurate motion tracking control. Additionally, an adaptive method is introduced to approximate the lumped uncertainty of the system and provide a chattering-free control. The simulation results indicate the effectiveness of the proposed approaches and demonstrate the satisfactory tracking performance compared to the conventional controller in the presence of the parameter uncertainties and un-modelled dynamics for the motion control of manipulators.展开更多
A redundantly actuated parallel manipulator(RAPM)with mixed translational and rotational degrees of freedom(DOFs)is challenged for its dimensionally homogeneous Jacobian modeling and optimal design of architecture.In ...A redundantly actuated parallel manipulator(RAPM)with mixed translational and rotational degrees of freedom(DOFs)is challenged for its dimensionally homogeneous Jacobian modeling and optimal design of architecture.In this paper,a means to achieve redundant actuation by adding kinematic constraints is introduced,which reduces the DOFs of the end-effector(EE).A generic dimensionally homogeneous Jacobian is developed for this type of RAPMs,which maps the generalized velocities of three points on the EE to the joint velocities.A new optimization algorithm derived from this dimension-ally homogeneous Jacobian is proposed for the optimal design of this type of RAPMs.As an example,this paper presents a spatial RAPM involving linkages and cam mechanisms.This RAPM has 4 DOFs and 6 translational actuations.The linkage lengths and the position of the universal joints of the RAPM are optimized based on the dimensionally homogeneous Jacobian.展开更多
基金Supported by the National Natural Science Foundation of China(No 50775117)the National Key Basic Research and Development (973) Program of China (No 2004CB318000)
文摘In order to overcome the drawbacks of 3RRR non-redundant parallel manipulators,a redundantly actuated planar parallel manipulator,the 4RRR manipulator,was examined.In the current study,three types of workspace were analyzed.In the analysis of the reachable workspace,the shape of the workspace of 4RRR PMs was illustrated,and the relationship between the parameters of parallel mechanisms（PMs） and this kind of workspace was discussed.In the analysis of the m-orientation workspace,a procedure for calculating this type of workspace was presented,and the relationship between this type of workspace and the requirement of rotational displacement was revealed.In the analysis of the nonsingular workspace,the singularity of 4RRR PMs was discussed,the boundary of the singularity was illustrated,and a scheme to maximize the nonsingular workspace was presented.Depicting the properties of 4RRR PMs from different perspectives,the analyses of these three kinds of workspace can serve as helpful references for the structure design and mechanism control of 4RRR PMs.
基金Supported by National Natural Science Foundation of China(Grant Nos.U1713202,51525504).
文摘Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,they cannot adequately support the huge axial downward forces that FSW generates.Available parallel mechanism architectures,particularly redundantly actuated architectures for FSW,are still very limited.In this paper,a redundantly actuated 2 UPR-2 RPU parallel robot for FSW is proposed,where U denotes a universal joint,R denotes a revolute joint and P denotes a prismatic pair.First,its semi-symmetric structure is described.Next,inverse kinematics analysis involving an analytical representation of rotational axes is implemented.Velocity analysis is also conducted,which leads to the formation of a Jacobian matrix.Sensitivity performance is evaluated utilizing level set and convex optimization methods,where the local sensitivity indices are unit consistent,coordinate free,and of definite physical significance.Furthermore,global and hierarchical sensitivity indices are proposed for the design process.Finally,dimension synthesis is conducted based on the sensitivity indices and the optimal link parameters of the parallel robot are obtained.In summary,this paper proposes a dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices.
基金supported by National Natural Science Foundation of China(Nos.51075222 and E050101)Priority Academic Program Development of Jiangsu Higher Education Institutions(No.6,2011)+1 种基金Zhenjiang Municipal Key Technology R&D Program(No.NY2011013)Postgraduate Research and Innovation Program of Jiangsu Higher Education Institutions(No.1221140046)
文摘This paper deals with the dynamics and control of a novel 3-degrees-of-freedom （DOF） parallel manipulator with actuation redundancy. According to the kinematics of the redundant manipulator, the inverse dynamic equation is formulated in the task space by using the Lagrangian formalism, and the driving force is optimized by utilizing the minimal 2-norm method. Based on the dynamic model, a synchronized sliding mode control scheme based on contour error is proposed to implement accurate motion tracking control. Additionally, an adaptive method is introduced to approximate the lumped uncertainty of the system and provide a chattering-free control. The simulation results indicate the effectiveness of the proposed approaches and demonstrate the satisfactory tracking performance compared to the conventional controller in the presence of the parameter uncertainties and un-modelled dynamics for the motion control of manipulators.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51705063 and 51575078)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20190368).
文摘A redundantly actuated parallel manipulator(RAPM)with mixed translational and rotational degrees of freedom(DOFs)is challenged for its dimensionally homogeneous Jacobian modeling and optimal design of architecture.In this paper,a means to achieve redundant actuation by adding kinematic constraints is introduced,which reduces the DOFs of the end-effector(EE).A generic dimensionally homogeneous Jacobian is developed for this type of RAPMs,which maps the generalized velocities of three points on the EE to the joint velocities.A new optimization algorithm derived from this dimension-ally homogeneous Jacobian is proposed for the optimal design of this type of RAPMs.As an example,this paper presents a spatial RAPM involving linkages and cam mechanisms.This RAPM has 4 DOFs and 6 translational actuations.The linkage lengths and the position of the universal joints of the RAPM are optimized based on the dimensionally homogeneous Jacobian.
