Dexterity Analysis And Structural Optimization Of A Continuum Robot

In recent years,with the fast development of science and technology,the robotics as a multi-interdisciplinary subject has also been developed rapidly.Among them,continuum robots based on bionic principles have attracted more and more attention because of the increasing demand of safety and dexterity of robots.Compared to traditional rigid robots,continuum robots adopt compliant structures similar to biological structures such as octopus tentacles and elephant trunks rather than discrete joints and rigid connecting rods,which are suitable for detecting and grasping in small and complex environments.For continuum robots,high safety and dexterity are two of the most prominent advantages.Among them,the high safety can make continuum robots perform better human-computer interaction.The high dexterity allows continuum robots to replace the traditional rigid robots to perform operations in restricted spaces and improve the environmental adaptability.However,due to the unique compliant structures of continuum robots and the complex kinematic mapping relationships,detailed research on their dexterity is lacking.Therefore,in view of the lack of dexterity for continuum robots,a continuum robot with modular joint design was developed.Based on the kinematic model and the Jacobian matrix,from the two dimensions of manipulability and orientability,the local and global dexterity of the continuum robot were studied in depth and used to guide the joint lengths of the robot.For the manipulability dimension in dexterity,based on the condition number of the Jacobian matrix,through the definition and calculation of the manipulability indices,the local and global manipulability of continuum robots were deeply analyzed,and the impact of joint lengths on manipulability were explored in detail.Then,we obtained its optimal joint length by introducing a particle swarm optimization(PSO)algorithm,which enables the continuum robot to achieve the best global manipulability.Finally,we present a sensitivity index for simulated and experimental verifications of the intuitive manipulability of the continuum robot with optimal joint lengths.Also,the relationship between the sensitivity and manipulability indices is investigated,that is,end points with higher manipulability show more uniform distributions of sensitivity.For the orientability dimension in dexterity,combined with the actual operational requirements,the accessible ratio and angle indices were proposed to comprehensively reflect the orientability of the continuum robot in the task space.And the effects of joint lengths on the two orientability indices were analyzed in detail.After that,based on the improved PSO,the joint length that optimizes the overall orientability in the task space was obtained.Finally,the simulated and experimental results verify that the design of the continuum robot with optimal joint length can effectively improve the orientability in the task space.In this paper,based on the two dimensions of manipulability and orientability,the quantitative calculations and visual analysis of the dexterity of continuum robots were deeply studied,and the experimental verifications of dexterity were carried out subtly.These laid a solid foundation for the application of dexterity to guide the structural designs and the further development of relevant theories in the field of continuum robots.