Design And Control Of Deployable Manipulator Driven By Nylon Fiber And Motor

With the development of aerospace technology and the continuous exploration of space,many space tasks require the participation of large space robotic arms.The contradiction between the traditional large-scale large-mass manipulator and the relatively small storage space of the launch vehicle has become increasingly prominent.This paper proposed a new type of nylon fiber-motor driven truss extendable robotic arm,which can not only be folded and deployed for storage and transportation,but also more lightweight than the traditional pure motor-driven truss extendable robotic arm.The mechanical system of the manipulator was analyzed and designed,including the configuration design of the manipulator and the design of the actuator.Among them,the configuration of the manipulator adopts a series and parallel truss mechanism,which has a high stiffness mass ratio.The modular design of the manipulator was adopted.Each joint unit has two degrees of freedom,one translation and one rotation,respectively.The translation can be used for the folding and unfolding movement of the manipulator,and the rotation was used for the operation task.In order to further reduce the mass of extendable manipulator,the combined driving mode of nylon fiber actuator and motor was studied,and the parallel driving mode of nylon fiber actuator was designed and analyzed.The kinematics of the manipulator was analyzed,and the relationship between the manipulator operating space,joint space and driving space was established.Through the method of kinematics decoupling,the complex kinematics model of extendable manipulator was transformed into kinematics model of joint element and kinematics model of equivalent extendable manipulator.The forward and inverse kinematics model of the joint element of the manipulator was established by geometric method.The forward kinematics model of the equivalent extendable manipulator was established by DH modeling method,and the inverse kinematics model of the equivalent extendable manipulator was established by the improved weighted minimum norm method,so that the inverse solution of the equivalent extendable manipulator is more accurate.The s-shaped curve was adopted to plan the trajectory of the operating space and driving space of the extendable manipulator respectively,so as to ensure the continuity of acceleration in the operation process of the manipulator and realize the smoother trajectory control of the manipulator.At the same time,a two-stage motion control system of upper computer plus embedded controller(lower computer)of the extendable manipulator was built,which enabled the manipulator to complete the functions of folding and expanding motion and track tracking.The upper computer was mainly responsible for trajectory planning of the mechanical arm,sending control instructions and monitoring the running state of the mechanical arm,while the lower computer was mainly responsible for processing the upper computer instructions,control of nylon fiber actuator and motor,sensor data acquisition,etc.In order to verify the functions of the manipulator and the related work in the paper,an experiment platform for the stretch-able manipulator and a gravity compensation platform for simulating the microgravity working environment of the manipulator were built respectively,and the experiments on the manipulator's expansion motion,linear tracking and grasping were carried out.The experimental results show that the manipulator can fulfill the design requirements and functions.