The digital orchard is an important trend for the future development of orchards towards intelligentization.The current wide variety of orchard gripping objects with different sizes and material characteristics brings...The digital orchard is an important trend for the future development of orchards towards intelligentization.The current wide variety of orchard gripping objects with different sizes and material characteristics brings challenges for gripping operations.In order to improve the versatility and dexterity of the orchard end-effector,a humanoid 14-degree-of-freedom orchard dexterous hand is designed for agronomic operations.An optimal design scheme of the orchard dexterous hand combining orchard gesture analysis and human hand structure is proposed,and the design of the modular fingers,palm,and overall structure of the orchard dexterous hand is completed.The orthogonal and inverse kinematics model of the dexterous hand is established to analyze the motion space of the fingertips,and the dexterity of the orchard dexterous hand is verified by combining with the Kapandji test.The equivalent distribution model of the contact force is solved according to the Hertz theory,and the grasping matrix is established based on the friction surface contact model to realize force-closure,which describes the relationship between the finger and the object being grasped in the configuration.The experimental platform of dexterous hand in the orchard is built,and the experiments of gesture formation,grasping,and contact force testing are carried out.The results show that the dexterous hand can form all kinds of gestures commonly used in the orchard and can grasp spherical fruit with diameters of 26-90 mm,masses of 11-238 g,and all kinds of orchard-specific working tools;for navel oranges with masses of 234 g,the dexterous hand can realize stable grasping under different gestures.This provides a theoretical basis and technical support for the realization of complex agronomy in orchards.展开更多
This paper deals with the problem of force-closure analysis for soft multi-fingered grasps. The first step is the study of the relationship between the external wrench space and the manipulation force space at any con...This paper deals with the problem of force-closure analysis for soft multi-fingered grasps. The first step is the study of the relationship between the external wrench space and the manipulation force space at any contact. Constraint force set, strictly constraint force set and normal force set are defined in the contact force space, followed by an investigation of their relationships. Based on the convexity of the friction constraints for soft finger contact, the necessary and sufficient conditions for force-closure grasps are derived. Accordingly an efficient algorithm for testing force-closure is presented. Some illustrative examples are given.展开更多
Currently, most efficient algorithms for force-closure analysis and dynamic force distribution utilize linear programming, but friction models are nonlinear. Substituting polyhedral cones for circular cones of Coulomb...Currently, most efficient algorithms for force-closure analysis and dynamic force distribution utilize linear programming, but friction models are nonlinear. Substituting polyhedral cones for circular cones of Coulomb friction realizes the linearization of the frictional point contact constraint. So far, however, there is no approach to soft finger contact. This paper present such an approach. Then the foregoing algorithms can be extended to grasping with soft finger contact. Herein an optimal force distribution algorithm for soft multifingered grasps is developed with an illustrative example.展开更多
基金funded by the Hubei Province Technological Innovation Program Project,China(Grant No.2024BBB060)the 2024 Huazhong Agricultural University Independent Science and Technology Innovation Fund Project,China(Grant No.2662024GXPY006)the National Key Research and Development Program,China(Grant No.2024YFD2300800).
文摘The digital orchard is an important trend for the future development of orchards towards intelligentization.The current wide variety of orchard gripping objects with different sizes and material characteristics brings challenges for gripping operations.In order to improve the versatility and dexterity of the orchard end-effector,a humanoid 14-degree-of-freedom orchard dexterous hand is designed for agronomic operations.An optimal design scheme of the orchard dexterous hand combining orchard gesture analysis and human hand structure is proposed,and the design of the modular fingers,palm,and overall structure of the orchard dexterous hand is completed.The orthogonal and inverse kinematics model of the dexterous hand is established to analyze the motion space of the fingertips,and the dexterity of the orchard dexterous hand is verified by combining with the Kapandji test.The equivalent distribution model of the contact force is solved according to the Hertz theory,and the grasping matrix is established based on the friction surface contact model to realize force-closure,which describes the relationship between the finger and the object being grasped in the configuration.The experimental platform of dexterous hand in the orchard is built,and the experiments of gesture formation,grasping,and contact force testing are carried out.The results show that the dexterous hand can form all kinds of gestures commonly used in the orchard and can grasp spherical fruit with diameters of 26-90 mm,masses of 11-238 g,and all kinds of orchard-specific working tools;for navel oranges with masses of 234 g,the dexterous hand can realize stable grasping under different gestures.This provides a theoretical basis and technical support for the realization of complex agronomy in orchards.
文摘This paper deals with the problem of force-closure analysis for soft multi-fingered grasps. The first step is the study of the relationship between the external wrench space and the manipulation force space at any contact. Constraint force set, strictly constraint force set and normal force set are defined in the contact force space, followed by an investigation of their relationships. Based on the convexity of the friction constraints for soft finger contact, the necessary and sufficient conditions for force-closure grasps are derived. Accordingly an efficient algorithm for testing force-closure is presented. Some illustrative examples are given.
文摘Currently, most efficient algorithms for force-closure analysis and dynamic force distribution utilize linear programming, but friction models are nonlinear. Substituting polyhedral cones for circular cones of Coulomb friction realizes the linearization of the frictional point contact constraint. So far, however, there is no approach to soft finger contact. This paper present such an approach. Then the foregoing algorithms can be extended to grasping with soft finger contact. Herein an optimal force distribution algorithm for soft multifingered grasps is developed with an illustrative example.
