Kinematic Model And Experimental Study Of Soft Manipulator Under Contact Constraints

Traditional rigid robots have high stiffness,poor adaptability in unstructured environments,low flexibility,low degrees of freedom,complex design structures,and limited working space.Researchers get inspiration from nature's creatures and design a new mechanical device-soft robot.Soft robots have made major technological breakthroughs in technological innovation.Due to their great deformability,the structural body can be continuously deformed in a limited space,imitating creatures for continuous movement,and changing its shape according to the characteristics of the environment.The soft manipulator is a typical continuum robot made of soft materials.Its bionic principle is derived from soft biological tissues or organs such as octopus tentacles,elephant trunks and mammal tongues.It is mainly made of flexible materials and has flexible structure and greater degrees of freedom,and can be used to explore uneven terrain.Compared with rigid manipulators,soft manipulators have many potential advantages,such as being able to interact with the environment while maintaining stability.Although the soft manipulator has the characteristics of multiple degrees of freedom and good environmental adaptability,there are still many difficulties in the modeling of the soft manipulator,so that it cannot be used in high-precision operations on a large scale.Two prominent problems are kinematics modeling and load characteristic analysis.This paper proposes a variable curvature kinematics modeling method based on the Neo-Hookean superelastic model for the nonlinear mechanical characteristics of the silicone matrix of the soft manipulator.Combined with the related knowledge of material mechanics,the static analysis of the soft manipulator is carried out,and the posture of the soft manipulator is obtained by the D-H modeling method in the global coordinate system.A soft manipulator prototype is designed,and the corresponding experimental platform is built.The motion degree and posture are obtained by image processing,and the effectiveness of the model is verified by simulation and experiment.The main contents and innovations of this article are as follows:1.Considering the contact constraints of the soft manipulator's environment,this paper proposes a soft manipulator kinematics modeling method based on the curvature division of the contact point.The modeling method is mainly to regard the soft manipulator as the arc of many discrete segments,and to get the posture relationship of the whole soft manipulator through the D-H modeling method.2.Calculate the characteristic parameters of the soft manipulator in different states through static equations,which mainly include the soft manipulator's posture and the force of each discrete segment,that is,the magnitude and direction of the contact force can be obtained without the sensor,and the static model can correctly predict the grasping and load characteristics of the manipulator.3.The test system of the soft manipulator is built,and the soft manipulator can be driven accurately and in real time by hydraulic pressure.During the experiment,the posture of the soft manipulator is extracted to obtain the changes of the soft manipulator under different motion states.Through the six-axis force sensor,the contact force received by the soft manipulator under the contact environment is collected,and the contact experiment and the grab load experiment are completed to verify the correctness of the model.