Development Of Four-Cable-Driven Parallel Robot Control System Based On Linux

As a member of the robot family,cable-driven parallel manipulator(CDPM)is widely used in aerospace,disaster relief,photography and video,medical rehabilitation and other fields.However,compared with the traditional robots,the motion control of CDPM is more challenging.For example,the cable can only bear the axial tension,and the parallel mechanism has strong coupling,etc.Therefore,a 4-CDPM with 3-DOF in a vertical plane is studied in this paper.A control scheme based on ARM + FPGA is proposed,and the design and experiment of the CDPM system are completed.Control system design: Firstly,fully considering the problem of the pulley wrap angle,the analysis model of cable-pulley system is established.In addition,the inverse kinematics solution of the CDPM is completed.Then,the dynamic simulation analysis of the CDPM is completed by means of ADAMS software,and the variation of cable force is obtained.Finally,based on the above analysis and combined with the characteristics of different control schemes,the control system scheme of ARM main control module + FPGA driver module is proposed.Trajectory planning: As the core of the whole control system,motion control and planning have a direct impact on the control accuracy and efficiency of the manipulator.The following four parts of work are completed for trajectory planning:(1)Under finite tension condition,the workspace of the end effector is solved by using static wrench balance equations.(2)The interpolation of the motion trajectory is completed by means of the cubic B-spline curve.(3)An acceleration-deceleration algorithm based on improved SCCA cam curve is proposed.(4)Based on the above work,the planning of the motion trajectory of the end effector is realized based on the continuous small line segment interpolation method.Control system software development: On the one hand,the development environment of the ARM main control board is configured,and the Linux system is transplanted as the software foundation.The development,transplantation and testing of the control system application software are completed based on Qt Creator.On the other hand,the data communication between the FPGA module,the ARM module and the acquisition module is established.The control instructions are cached,checked,serial-parallel converted in the FPGA driver module,and the parallel driving of four-way motors is realized.Experimental verification: A prototype of the CDPM is made and various trajectory motions are executed to verify the basic functions and control effects of the system.During the experiment,the cable tension sensor is used to measure the position and posture,and the three pulley tension sensor is used to measure the cable tension.The results show:(1)The position error of the end effector is about 2%.(2)The rotation angle error is within 2°.(3)The results of cable force by measurement and simulation are basically consistent.Finally,the experimental error is analyzed and the corresponding improvement measures are proposed.