Control Design And Analysis Of Cable-Driven Multi-Link Robot

Cable-Driven Parallel Robots(CDPRs)have many benefits over traditional manipulators due to their unique characteristics of utilizing cables rather than rigid links,such as a high payload-to-weight ratio,lightweight transmission,reconfigurability,and large workspace.With these benefits,there is considerable potential to use CDPRs in a wide variety of applications.The research on the theory of CDPRs mainly includes the study of kinematics,dynamics,workspace,cable tension solutions,and control methods.In this study,a planar multi-link cable-driven robot(MLCDR)is designed and investigated based on its theoretical research in conjunction with prior studies.It can be applied in various practical applications,including in the field of rehabilitation systems.This paper mainly concentrates on developing a robust controller for a planar three-link robot driven by four cables,analyzing the proposed control method,and building a virtual prototype to verify the theoretical analysis of the proposed mechanism.The main research work in this paper is as follows:Based on the condition of cable distribution,the configuration of the planar MLCDR is deduced.The inverse kinematics in cable-driven robots determines the length of the cables for a given desired posture,while the forward kinematics solves the robot’s rotational angle with a given initial cable length.Thus,the lengths of the cables of the multi-body mechanism driven by four cables are calculated through the Denavit–Hartenberg method,and the rotation angles of the robot are solved using the Newton-Raphson algorithm.The dynamic model of the planar robot is established based on the Lagrange approach.The tension of cables and the torque of joints are then calculated and simulated through MATLAB,which is considered the theoretical part of the model.Under the limitation of cable tension output,the null-space conditions are utilized to analyze the boundary of the wrenchclosure workspace.Then,the wrench-feasible workspace of the MLCDR is solved.The overall control system scheme of the robot is introduced.The differential PID controller,traditional sliding mode controller,and a robust adaptive sliding mode controller are adopted to control the motion of the robot in order to track the desired trajectory with high performance and accuracy.The stability of the whole system is investigated according to the Lyapunov theorem.Finally,SolidWorks and ADAMS software are used to design and assemble the planar MLCDR prototype.After the model is constructed,the inverse kinematics and the dynamics of the robot are verified.Then,the co-simulation MATLAB/ ADAMS is carried out to verify the proposed controller.The outcomes of the co-simulation show that the suggested robust ASMC controller exhibited the best trajectory tracking performance when compared to the PID controller and traditional SMC.Additionally,the proposed controller has less chattering impact than a conventional sliding mode controller,which verifies the effectiveness and feasibility of the developed control.