Motion Analysis And Trajectory Planning Of A Continuum Manipulator Based On NiTi Alloy Rods

Continuum manipulator is a new kind of bionic robot inspired by soft biological organs such as elephant trunk and octopus tentacle.Because it has no rigid connecting rod and discrete joints,the manipulator with good flexibility and compliant has a very broad application prospect in minimally invasive surgery,detection and maintenance of narrow space,etc.,which has attracted more and more researchers’ attention.The design of a “series-parallel hybrid” continuum manipulator made of super-elastic Ni Ti alloy rods was introduced.The manipulator consisted of three sub-arms with a total of 9 degrees of freedom,and each sub-arm has 3 degrees of freedom,driven by the push and pull force of the Ni Ti rods,and the drive system adopted stepping linear screw sliders.After the structure was determined and compared the bending resistance of the manipulator under various rod configurations,a new type of “co-radial”rod configuration and rotationally symmetrical base layout were finally adopted to make the structure of the entire manipulator more compact,which also made it have better scalability and model applicability.Under the assumption of piecewise constant curvature bending,the homogenous transformation matrix method was proposed for analyzing the multi-segment forward kinematics for the “serial-parallel” hybrid manipulator based the Jones single-segment kinematics model.Then a closed-form solution of homogeneous transformation was proposed to investigate the multi-segment inverse kinematics model of the manipulator.In order to solve the problem of bending coupling between the proximal and the distal,the inverse kinematics model was then improved by using displacement compensation strategy to express the spatial position of the end more efficiently and accurately.Moreover,the force of each manipulator was analyzed briefly based on the lumped mass method,this condensed parameter method greatly simplified the calculation in the process of dynamics analysis and laid a foundation for the design of the closed-loop control system in the future.Based on kinematics,the end position of the manipulator was obtained by numerical simulation of forward kinematics,then the workspace of each segment was obtained by Monte-Carlo method,while a point selection planning algorithm for circular trajectory was proposed based on the inverse kinematics,and further analysis and discussion were carried out in combination with the displacement compensation strategy above.Finally,a series of experiments were conducted using the manipulator to verify the effectiveness of the proposed model.The experimental results for the space posture and the trajectory planning were consistent with the simulation results,which demonstrated that the designed continuum manipulator has good motion performance.This work provides ideas and methodologies for the application of continuum manipulators in practical operations.There are 45 full-text pictures,4 tables,and 96 references.