Research On Dynamics Characteristics Of Helical Cable-Driven Soft Manipulator Based On ANCF

In recent years,soft manipulators made of flexible materials have shown great advantages in medical,industrial and other fields.Inspired by creatures in nature,many soft manipulators are used to imitate the complex three-dimensional motion of animals.At present,there are many theories and methods to study the bending motion of the soft manipulator,but there is a lack of theoretical research on the torsional motion and spiral motion of the manipulator.Due to the wide application of torsional motion and spiral motion in soft manipulators such as octopus and elephant trunk,it is of great theoretical significance to construct the dynamic model and analyze the characteristics of soft manipulators that can realize torsional and spiral motion.In this paper,the beam element based on the absolute nodal coordinate method(ANCF)is used to study the forward and inverse dynamics modeling methods and dynamic characteristics of single-segment and two-segments soft manipulators driven by cable.The main work is as follows:Firstly,the basic theory of three-dimensional two-node low-order beam element based on ANCF is introduced.The position vector,mass matrix,generalized external force,generalized elastic force and Jacobian matrix of any point on the beam element section are derived.Secondly,the dynamic model of a single-section soft manipulator driven by cable is established by using the beam element based on ANCF,and its dynamic characteristics are analyzed.The generalized cable force and its Jacobian matrix of the driving cable are derived,and the forward dynamic model of the manipulator is established.The simulation results of the example are compared with the simulation results of ABAQUS,and the influence of gravity,driving cable radius and pitch on the torsional deformation of the manipulator is obtained.On this basis,the constraint equation of the end point target trajectory is introduced,and the inverse dynamics model of the manipulator is established.The torsional motion curve and the spiral motion curve of the end of the manipulator are taken as the target trajectory respectively.The simulation results are compared with the AB AQUS results to verify the correctness of the model.Finally,the dynamic model of a two-section soft manipulator driven by cable with fixed joint connection is established by using the beam element based on ANCF,and its dynamic characteristics are analyzed.The forward dynamic model of the manipulator is established by introducing the fixed joint constraint equation.The simulation results of the example are compared with the ABAQUS results,and the influence of load application mode,gravity,radius and pitch of driving cable in different segment on the torsional deformation of the manipulator is obtained.On this basis,the inverse dynamics model of the manipulator is established by introducing the constraint equation of the end point target trajectory and the load distribution coefficient.The torsional motion curve and the spiral motion curve of the end of the manipulator are taken as the target trajectory respectively.The simulation results are compared with the ABAQUS results to verify the correctness of the model.