Driver System Design And Trajectory Optimization Of Cable-Driven Parallel Grasping Mechanism

This paper takes a cable-driven parallel multi-body robot developed by Tsinghua University as the research object,and conducts in-depth theoretical research on the key issues of its dynamic modeling,transmission system selection,and trajectory planning?The goal is to achieve high speed performance and low energy consumption of Cabledriven Parallel Mechanism,and the resulting related theory applied to the prototype.The specific research content is as follows:Firstly,an inverse kinematics model of the mechanism is established based on the vector loop method,and the numerical solution of the positive kinematics is obtained using the Maple numerical analysis software.By analyzing the velocity and acceleration of the middle spring element,a dynamic model of matrix form is established based on the Lagrangian energy method,and then the inertia matrix of the mechanism is obtained;The simulation of the dynamic model under a given trajectory by the mechanism is validated using Matlab software.This part lays the foundation for the drive system design and trajectory optimization.Secondly,because the servo motor and reduction ratio parameters of the mechanism have a great influence on the kinematics and dynamics of the mechanism,in order to achieve the goal of high-speed gripping,the servo motor and the reduction ratio parameters are designed.A flow method for quickly determining the servo motor and speed ratio parameters of a cable-driven parallel mechanism is proposed.Taking the cable-driven parallel robot studied as an example,the rated speed,torque,power,rotor inertia and other parameters of the servo motor are reduced.The specific parameters were designed and selected,and the matching drum radius and rope parameters were optimized.According to the characteristic curve of the speed and torque of the servo motor,the selected servo system is checked and adjusted so that the cost of the mechanism can be reduced without losing the capture speed.Based on the institutional inertia matrix,the CVI index is used to analyze the overall inertia distribution of the organization,providing guidance for the determination of high-quality work space.Finally,according to the actual high-speed crawling requirements,based on the genetic algorithm,the crawling trajectory of the mechanism under the two conditions of minimum time and energy consumption are planned.Firstly,the classic point-to-point crawling trajectory is improved.The speed and acceleration of the control mechanism in the start-stop phase is 0,and the curve is smooth and continuous.The Deboor recurrence formula is used to establish the time series model of the curve based non-uniform 5 rational B-spline interpolation in the joint space.By establishing speed,torque and power constraints in the joint space,and using the minimum time as the mechanism's optimization index,a trajectory that minimizes the time for one-way crawling by the organization is planned.In order to reduce the energy consumption of the system,a genetic algorithm is used to plan the optimal energy time series under the condition of a single crawling time limit of 0.25 s.In addition,the results of comparing the trajectories at different positions in the workspace under the two constraints are compared.Based on the parametric design results of this paper,a prototype of the cable parallel mechanism was built,and the theoretical research results above were experimentally studied,and good practical results were obtained.The parallel robot prototype realized high-speed grasping motion of 120 times per minute under horizontal movement of 300 mm.