The application of the parallel mechanism is still limited in the humanoid robot fields, and the existing parallel humanoid robot joint has not yet been reflected the characteristics of the parallel mechanism complete...The application of the parallel mechanism is still limited in the humanoid robot fields, and the existing parallel humanoid robot joint has not yet been reflected the characteristics of the parallel mechanism completely, also failed to solve the problem, such as small workspace, effectively. From the structural and functional bionic point of view, a three degrees of freedom（DOFs） spherical parallel mechanism for the shoulder complex of the humanoid robot is presented. According to the structure and kinetic characteristics analysis of the human shoulder complex, 3-PSS/S（P for prismatic pair, S for spherical pair） is chosen as the original configuration for the shouder complex. Using genetic algorithm, the optimization of the 3-PSS/S spherical parallel mechanism is performed, and the orientation workspace of the prototype mechanism is enlarged obviously. Combining the practical structure characteristics of the human shouder complex, an offset output mode, which means the output rod of the mechanism turn to any direction at the point a certain distance from the rotation center of the mechanism, is put forward, which provide possibility for the consistent of the workspace of the mechanism and the actual motion space of the human body shoulder joint. The relationship of the attitude angles between different coordinate system is derived, which establishs the foundation for the motion descriptions under different conditions and control development. The 3-PSS/S spherical parallel mechanism is proposed for the shoulder complex, and the consistence of the workspace of the mechanism and the human shoulder complex is realized by the stuctural parameter optimization and the offset output design.展开更多
The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation.To make mobility calculation simple,considering avoiding virtual constraints,some new formul...The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation.To make mobility calculation simple,considering avoiding virtual constraints,some new formulae have been presented,however these formulae can hardly intuitively reflect general link group's restrictions on output member and its influences on independence of output parameters,which is premise to the judgment of the properties of mobility.Towards the problem to reveal the intrinsic relationship between the degree of freedom(DOF)of a mechanism,the link group,and the dimension of output parameters,also to avoid determination of virtual constraint,based on the new concepts of the"DOF of general link group"and"node parameters",a new formula in the calculation of the mobility of mechanisms is presented that is expressed with DOFs of the general link groups and rank of motion parameters of base point of the output link.It is named GOM(mobility of groups and output parameter)formula.On the basis of new concepts of"effective parameters"and"invalid parameters",a rule is put forward for solving the DOF of mechanisms with invalid parameters by GOM formula,that is,the base point parameters are the subset of effective parameters of link group.Thereafter,several examples are enumerated and the results coincide with the prototype data,which proves the validity of the proposed formula.Meanwhile,it is obtained that the necessary and sufficient condition for the judgment of output parameters independence is that each of the DOF of the link group is not less than zero.The proposed formula which is simple in calculation provides theoretical basis for the judgment of independence of output parameters and provides references for type synthesis of novel parallel mechanisms with independence requirements of their output parameters.展开更多
It is widely used for the rotational parallel mechanism in the field of spatial orientation.While owing to the existence of coupling,the forward kinematic solution and the control of the general rotational parallel me...It is widely used for the rotational parallel mechanism in the field of spatial orientation.While owing to the existence of coupling,the forward kinematic solution and the control of the general rotational parallel mechanism are especially difficult.If decoupling can be realized,the kinematic analysis of the mechanism will be very simple.Presently,the research of the parallel mechanism is focused on the inverse solution and structure optimization,and there is a lack of rotation decoupled parallel mechanisms(DPMs).So this paper proposes a family of 2 degree of freedom(DOF)rotational DPMs based on the four-bar linkage mechanism,and performs a characteristic analysis.This family of DPMs is composed of a moving platform,a fixed base and three limbs.Taking U_RRU SPU DPM as an example,the motion feature of this DPM is analyzed with the constraint screw method,and its mobility is calculated by using the Modified Kutzbach-Grtibler criterion.The inverse and forward displacement problems of the proposed parallel mechanism are solved.The decoupled feature of the proposed parallel mechanism is validated by the deduction of the expression of the Jaeobian matrix.Three kinds of singularity conditions of this DPM are discussed,and the atlases of the output parameter concerning different geometric parameters are plotted with the theory of the physical model of the solution space.The proposition and characteristic analysis of the novel rotational DPMs in this paper should be useful for further research and application of the parallel mechanisms.展开更多
The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on ...The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure,which can be used for the force measurement of the robot wrist,is proposed,and its structural optimal design,finite element analysis and calibration experimentation is presented.The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor.The mathematical expression of the sensor's force mapping matrix is introduced.The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively.The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy.The sensor prototype is fabricated,and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS.The calibration device is manufactured,and the data acquisition and processing system is developed.The theoretical and experimental study of the static calibration of the sensor prototype is carried out.The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure,and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.展开更多
The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modem parallel mechanisms. However its range of ap...The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modem parallel mechanisms. However its range of application needs to further extend to general multi-loop spatial mechanism. This kind of mechanism is not only more complex in structure but also with strong motion coupling among loops, making the mobility analysis even more complicated, and the relevant research has long been ignored. It is focused on how to apply the new principle for general spatial mechanism to those various multi-loop spatial mechanisms, and some new meaningful knowledge is further found. Several typical examples of the genera/multi-loop spatial mechanisms with motion couple even strong motion couple are considered. These spatial mechanisms include different closing way： over-constraint appearing in rigid closure, in movable closure, and in dynamic closure as well; these examples also include two different new methods to solve this kind of issue： the way to recognize over-constraints by analyzing relative movement between two connected links and by constructing a virtual loop to recognize over-constraints. In addition, over-constraint determination tabulation is brought to analyze the motion couple. The researches above are all based upon the screw theory. All these multi-loop spatial mechanisms with different kinds of structures can completely be solved by following the directions and examples, and the new mobility theory based on the screw theory is also proved to be valid. This study not only enriches and develops the theory and makes the theory more universal, but also has a special meaning for innovation in mechanical engineering.展开更多
Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through sever...Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out： the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop Closure in many times and the inevitable motion coupling, two important methods are proposed： ＂recognizing over-constraints by analyzing relative movement＂ and ＂recognizing over-constraints by virtual loop＂. The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.展开更多
The structure design for high ratio of carrying capacity to deadweight is one of the challenges for the bionic mechanism,while the problem concerning high carrying capacity has not yet be solved for the existing shoul...The structure design for high ratio of carrying capacity to deadweight is one of the challenges for the bionic mechanism,while the problem concerning high carrying capacity has not yet be solved for the existing shoulder complex.A new type biomimetic shoulder complex,which adopts 3-PSS/S（P for prismatic pair,S for spherical pair） spherical parallel mechanism（SPM）,is proposed.The static equilibrium equations of each component are established by using the vector method and the equations for constrain forces with certain load are solved.Then the constrain force on the middle limb and that on the side limbs are compared in order to verify the unloading performance of the mechanism.In addition,the prototype mechanism of the shoulder complex is developed,and the force feedback experiment is conducted to verify the static analysis,which indicates that the middle limb suffers most of the external force and the effect of mechanics unloading is achieved.The 3-PSS/S spherical parallel mechanism is presented for the shoulder complex,and the realization of mechanics unloading is benefit for the improvement of the carrying capacity of the shoulder complex.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51275443)Key Project of Ministry of Education of China(Grant No.212012)+2 种基金Hebei Provincial Natural Science Foundation of China(Grant No.E2012203034)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111333120004)Research Fund for Outstanding Youth in Higher Education Institutions of Hebei Province,China(Grant No.Y2011114)
文摘The application of the parallel mechanism is still limited in the humanoid robot fields, and the existing parallel humanoid robot joint has not yet been reflected the characteristics of the parallel mechanism completely, also failed to solve the problem, such as small workspace, effectively. From the structural and functional bionic point of view, a three degrees of freedom（DOFs） spherical parallel mechanism for the shoulder complex of the humanoid robot is presented. According to the structure and kinetic characteristics analysis of the human shoulder complex, 3-PSS/S（P for prismatic pair, S for spherical pair） is chosen as the original configuration for the shouder complex. Using genetic algorithm, the optimization of the 3-PSS/S spherical parallel mechanism is performed, and the orientation workspace of the prototype mechanism is enlarged obviously. Combining the practical structure characteristics of the human shouder complex, an offset output mode, which means the output rod of the mechanism turn to any direction at the point a certain distance from the rotation center of the mechanism, is put forward, which provide possibility for the consistent of the workspace of the mechanism and the actual motion space of the human body shoulder joint. The relationship of the attitude angles between different coordinate system is derived, which establishs the foundation for the motion descriptions under different conditions and control development. The 3-PSS/S spherical parallel mechanism is proposed for the shoulder complex, and the consistence of the workspace of the mechanism and the human shoulder complex is realized by the stuctural parameter optimization and the offset output design.
基金supported by National Natural Science Foundation of China(Grant Nos.51275438,51005195)Hebei Provincial Natural Science Foundation of(Grant No.E2011203214)Development Program of Qinhuangdao City,China(Grant No.201101A069)
文摘The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation.To make mobility calculation simple,considering avoiding virtual constraints,some new formulae have been presented,however these formulae can hardly intuitively reflect general link group's restrictions on output member and its influences on independence of output parameters,which is premise to the judgment of the properties of mobility.Towards the problem to reveal the intrinsic relationship between the degree of freedom(DOF)of a mechanism,the link group,and the dimension of output parameters,also to avoid determination of virtual constraint,based on the new concepts of the"DOF of general link group"and"node parameters",a new formula in the calculation of the mobility of mechanisms is presented that is expressed with DOFs of the general link groups and rank of motion parameters of base point of the output link.It is named GOM(mobility of groups and output parameter)formula.On the basis of new concepts of"effective parameters"and"invalid parameters",a rule is put forward for solving the DOF of mechanisms with invalid parameters by GOM formula,that is,the base point parameters are the subset of effective parameters of link group.Thereafter,several examples are enumerated and the results coincide with the prototype data,which proves the validity of the proposed formula.Meanwhile,it is obtained that the necessary and sufficient condition for the judgment of output parameters independence is that each of the DOF of the link group is not less than zero.The proposed formula which is simple in calculation provides theoretical basis for the judgment of independence of output parameters and provides references for type synthesis of novel parallel mechanisms with independence requirements of their output parameters.
基金supported by National Natural Science Foundation of China(Grant No.50875227)
文摘It is widely used for the rotational parallel mechanism in the field of spatial orientation.While owing to the existence of coupling,the forward kinematic solution and the control of the general rotational parallel mechanism are especially difficult.If decoupling can be realized,the kinematic analysis of the mechanism will be very simple.Presently,the research of the parallel mechanism is focused on the inverse solution and structure optimization,and there is a lack of rotation decoupled parallel mechanisms(DPMs).So this paper proposes a family of 2 degree of freedom(DOF)rotational DPMs based on the four-bar linkage mechanism,and performs a characteristic analysis.This family of DPMs is composed of a moving platform,a fixed base and three limbs.Taking U_RRU SPU DPM as an example,the motion feature of this DPM is analyzed with the constraint screw method,and its mobility is calculated by using the Modified Kutzbach-Grtibler criterion.The inverse and forward displacement problems of the proposed parallel mechanism are solved.The decoupled feature of the proposed parallel mechanism is validated by the deduction of the expression of the Jaeobian matrix.Three kinds of singularity conditions of this DPM are discussed,and the atlases of the output parameter concerning different geometric parameters are plotted with the theory of the physical model of the solution space.The proposition and characteristic analysis of the novel rotational DPMs in this paper should be useful for further research and application of the parallel mechanisms.
基金supported by National Natural Science Foundation of China(Grant No.50575192)Hebei Provincial Natural Science Foundation of China(Grant No.E2007000349)
文摘The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques.A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure,which can be used for the force measurement of the robot wrist,is proposed,and its structural optimal design,finite element analysis and calibration experimentation is presented.The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor.The mathematical expression of the sensor's force mapping matrix is introduced.The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively.The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy.The sensor prototype is fabricated,and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS.The calibration device is manufactured,and the data acquisition and processing system is developed.The theoretical and experimental study of the static calibration of the sensor prototype is carried out.The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure,and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.
基金Supported by National Natural Science Foundation of China(Grant No.51005195)Natural Science Research Fund for Youth in Higher Education Institutions of Hebei Province,China(Grant No.QN2014175)
文摘The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modem parallel mechanisms. However its range of application needs to further extend to general multi-loop spatial mechanism. This kind of mechanism is not only more complex in structure but also with strong motion coupling among loops, making the mobility analysis even more complicated, and the relevant research has long been ignored. It is focused on how to apply the new principle for general spatial mechanism to those various multi-loop spatial mechanisms, and some new meaningful knowledge is further found. Several typical examples of the genera/multi-loop spatial mechanisms with motion couple even strong motion couple are considered. These spatial mechanisms include different closing way： over-constraint appearing in rigid closure, in movable closure, and in dynamic closure as well; these examples also include two different new methods to solve this kind of issue： the way to recognize over-constraints by analyzing relative movement between two connected links and by constructing a virtual loop to recognize over-constraints. In addition, over-constraint determination tabulation is brought to analyze the motion couple. The researches above are all based upon the screw theory. All these multi-loop spatial mechanisms with different kinds of structures can completely be solved by following the directions and examples, and the new mobility theory based on the screw theory is also proved to be valid. This study not only enriches and develops the theory and makes the theory more universal, but also has a special meaning for innovation in mechanical engineering.
基金Supported by National Natural Science Foundation of China(Grant No.51005195)Natural Science Research Fund for Youth in Higher Education Institutions of Hebei Province,China(Grant No.QN2014175)
文摘Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out： the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop Closure in many times and the inevitable motion coupling, two important methods are proposed： ＂recognizing over-constraints by analyzing relative movement＂ and ＂recognizing over-constraints by virtual loop＂. The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.
基金Supported by National Natural Science Foundation of China(Grant No.51275443)Key Project of Ministry of Education of China(Grant No.212012)+2 种基金Hebei Provincial Natural Science Foundation of China(Grant No.E2012203034)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111333120004)Research Fund for Outstanding Youth in Higher Education Institutions of Hebei Province,China(Grant No.Y2011114)
文摘The structure design for high ratio of carrying capacity to deadweight is one of the challenges for the bionic mechanism,while the problem concerning high carrying capacity has not yet be solved for the existing shoulder complex.A new type biomimetic shoulder complex,which adopts 3-PSS/S（P for prismatic pair,S for spherical pair） spherical parallel mechanism（SPM）,is proposed.The static equilibrium equations of each component are established by using the vector method and the equations for constrain forces with certain load are solved.Then the constrain force on the middle limb and that on the side limbs are compared in order to verify the unloading performance of the mechanism.In addition,the prototype mechanism of the shoulder complex is developed,and the force feedback experiment is conducted to verify the static analysis,which indicates that the middle limb suffers most of the external force and the effect of mechanics unloading is achieved.The 3-PSS/S spherical parallel mechanism is presented for the shoulder complex,and the realization of mechanics unloading is benefit for the improvement of the carrying capacity of the shoulder complex.
