Design And Realization Of The Control System Of A Cable-driven Manipulator

The cable-driven manipulator is a new type of structure that adopts the cable drive and all the servo units such as motors can be arranged on the base.Compared with traditional manipulators,cable-driven manipulators have smaller mass and inertia,stronger load capacity,easier to achieve lightweight and miniaturization,and because of the use of cable transmission,the cable-driven manipulator has a certain degree of flexibility.Based on the above characteristics,the use of the cable-driven structure is particularly suitable for use in human-oriented robots and scenes that interact with people.The cable-driven structure will provide a new solution in the field of robotics,and the research on cable-driven manipulators will play an important role in these directions.This article first analyzes and summarizes the basic problems of the cable drive such as the contraction and release of the cable and the tension of the cable,and designs a cable winding and cable tensioning mechanism.Subsequently,the realization of the cable-driven joint was analyzed,and a new type of cable-driven joint structure was designed.Based on the geometric relationship between the cable length and the joint angle in the cable-driven joint,the kinematics model of the cable-driven manipulator is analyzed and established.In the process of kinematics modeling,the influence of factors such as cable shifting angle from the pulley,the change of cable release point,cable force deformation and other factors are analyzed,and the upper bounds of the above three factors on kinematics are given through numerical simulation experiments.The dynamic model of the cable-driven manipulator is also analyzed and established,and the simplest expression form of the differential equation of the cable-driven manipulator dynamic model is derived.The difficulty in the modeling of the cable-driven manipulator system is the modeling of the cable.In this article,two different processing methods are listed and the corresponding conclusions are given.Aiming at the simplest form of the dynamic model of the cable-driven manipulator,PID control,nonlinear and linear active disturbance rejection controllers are designed,and several sets of controller parameters are obtained through many rounds of parameter adjustments.The performance of these three kinds of controls are compared through numerical simulation experiments.Through comparison and simulation,the effects of the tracking-differentiator and the extended state observer in the ADRC are analyzed,which has guiding significance for the understanding of the parameter adjustment process of the ADRC.Finally,in view of the motor driver signal requirements,motor angle measurement,joint angle measurement,cable tension measurement and other issues in the cable-driven manipulator system,a cable-driven manipulator control system is designed.Through experiments on the physical platform,the correctness of the kinematics and dynamics model is verified.The performance of the cable-driven manipulator system is analyzed through two sets of experiments given by a constant value command and a dynamic command.Due to the limitation of the experimental platform,the closed loop of the motor position can only be realized,and the closed loop control of the joint angle cannot be realized.After adding the speed plan,the experimental platform can achieve a response speed of 2Hz.Only the closed-loop control of the motor position is performed.The maximum error of the joint angle commanded by a given constant value is about 6°,and the joint angle error under the dynamic response is within ±10°.