Modeling And Motion Control Of A Three-degree-of-freedom Cable-driven Camera-stabilized Parallel Platform

With the development of underwater scientific exploration,underwater photography has become an indispensable work.In order to stably track and shoot the image of the underwater target,it is required that the camera device can adjust the shooting angle with the movement of the target point while resisting external interference.The camera stabilized platform is a device that can carry a camera device to maintain stability under external interference and move according to the desired trajectory.It can enable the camera device to complete the three-degree-of-freedom movements of space roll,pitch and yaw under its action,and ensures that the camera device can adjust the shooting angle at any time,so as to achieve the purpose of stably shooting moving targets.The cable-driven parallel robot is a parallel mechanism that uses the cables as the driving unit to realize the movement of the end-effector in space.According to the above background and research requirements of the subject,as well as the current research status of cable-driven parallel robots,this paper proposes a three-degree-of-freedom cable-driven underwater camera stabilized parallel robot platform.The main research contents are as follows:Firstly,according to the literature review and research,a novel type of three-degree-of-freedom cable-driven underwater camera stabilized platform is designed,and its structural characteristics and mechanical theoretical model are analyzed.According to the coordinate transformation method,the kinematic position,velocity and acceleration of the platform are analyzed.Based on the kinematics modeling,the forward and inverse solution algorithm of the platform are researched and designed,and verified by Matlab simulation.Secondly,the dynamic analysis of the robot platform is carried out,and the dynamic model of the system is established by the Newton-Euler method in the non-inertial frame.In addition,in order to obtain the tension of the four cables in real time and keep the tension of the cables within a reasonable range,an algorithm for solving the cable tension was studied and verified in the controller simulation experiment.Then,on the basis of the above kinematics and dynamics modeling,in order to deal with modeling uncertainty and external disturbance,this paper proposes a double-loop integral-type global fast terminal sliding mode control strategy.And in the Simulink environment of Matlab software,it is compared with the other two sliding mode controllers.Simulation results show that among the three control schemes,the control strategy proposed in this paper has better control performance in attitude tracking response and tracking error,and has the advantages of fast finite time convergence,high tracking accuracy,fast transient response,and strong robustness.Finally,the hardware structure of the robot platform is selected and processed,and a physical prototype of the three-degree-of-freedom parallel robot platform is built.Under the two control strategies,the attitude tracking performance of the robot motion platform is experimentally compared and verified.The experimental results verify that the mobile platform has good attitude tracking performance under the two control strategies,which proves the correctness of the design of the three-degree-of-freedom parallel robot platform and the rationality of the control strategy.