| The table feed system is a key component of the CNC machine tool,and its control precision directly affects the working performance of the CNC machine tool.Most of the traditional worktables use a single motor to drive a single ball screw,but this structure is prone to torsion tendency under heavy load and high speed,which affects the motion accuracy.Although the driving method of using double motors to drive double ball screws to jointly drive a worktable can obtain a large load capacity,there is a synchronization error between the two screws,which affects the synchronization accuracy of the worktable.It is of great significance to study the factors affecting the synchronization error of the system and the method of synchronization control.This thesis takes the double-screw feed system as the research object,establishes the electromechanical coupling model of the double-screw feed system,analyzes the influencing factors of the synchronization error of the feed system,designs different control algorithms,and compares and analyzes different synchronization methods.The influence of the control algorithm on the synchronous tracking error of the system is investigated.Finally,the experimental verification of the synchronous control strategy is carried out.The main research work done in this thesis is as follows:(1)The control part and the mechanical part of the double-screw feed system are analyzed respectively,and the electromechanical coupling model of the double-screw feed system is established;the three-ring parameters of the double-screw feed system are designed and analyzed,using MATLAB /Simulink simulates the electromechanical coupling model,which provides a basis for the analysis of the influencing factors of the synchronization error and the design of the synchronization control strategy.(2)Based on the electromechanical coupling model of the double lead screw feed system,the model is simulated with MATLAB/Simulink software,and the effects of internal factors(axial stiffness,damping and lead of the lead screw)and external factors(feed speed,load position and friction)on the synchronization error are analyzed.(3)Based on the theory of fuzzy control and sliding mode control,a single-axis fuzzy sliding mode controller is designed,which improves the single-axis tracking accuracy and response speed;at the same time,a fuzzy adaptive PID cross-coupling control algorithm is designed to control the connection between the two screws.In order to improve its synchronization performance,and compared with the traditional PID control algorithm,the results show that the designed control method has better tracking accuracy and synchronization performance.(4)The experimental platform of the synchronous control system of the double-screw feed system is designed and built.First,the tracking error experiment of the double-screw feed system is completed on the experimental platform,which verifies the effectiveness and feasibility of the control strategy designed in this thesis.The laser interferometer has completed the single-axis positioning accuracy detection experiment of the double-screw feed system.The results show that the single-axis fuzzy sliding mode control has better tracking accuracy and positioning accuracy than the single-axis PID control;the fuzzy adaptive PID cross-coupling control can Reduce the synchronization error between the two axes. |
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