| Servo press has the advantages of flexible processing,high precision,high efficiency,green manufacturing,etc.,and is widely used in the precision forming industry.The multilink servo press uses a servo motor as the driving source,and the transmission mechanism realizes deceleration and torque increase.It can be used for high-precision forming processing with large loads.However,due to the existence of factors such as clearance motion pair and flexible rod in the transmission mechanism,The forming motion accuracy is unstable,and the long-term wear of the motion pair will also affect the motion execution accuracy.Therefore,this thesis will conduct theoretical modeling and analysis on the transmission error of the multi-link servo press,aiming to grasp the cause and influence mechanism of the error.At the same time,it will research the motion control strategy of the servo press to accurately track the motion trajectory of the main slider.The purpose of improving forming accuracy.The main research contents of this thesis are as follows:1.In terms of transmission error analysis of multi-link mechanism,the constraint equation of multi-body mechanism is established based on the Cartesian coordinate system,and the inevitable motion pair clearance and flexible rod factors in the transmission system are introduced,and the ideal mechanism dynamic model and the motion pair with clearance are established respectively.also include Mechanism dynamics model and multi-body mechanism rigid-flexible coupling dynamics model,laying the foundation for subsequent research on mechanism dynamic response and motion pair wear;2.In order to accurately describe the contact and collision behavior at the clearance of the motion pair,several typical contact collision force models and friction force models are selected,and they are improved and applied to the contact and collision analysis at the clearance of the motion pair,aiming to establish more accurate dynamics Model;In addition,quantitative analysis of the initial collision speed,material restitute coefficient and surface roughness of different contact collision force models is aimed at studying the influence of various parameters on the degree of contact collision at the clearance of the motion pair;3.In view of the current lack of research on the wear of servo press mechanism at domestic and abroad,this thesis establishes a dynamic wear model of servo press multi-link mechanism,uses Archard wear model and interval discretization idea to track the movement trajectory of the motion pairs clearance,wear depth prediction and surface profile reconstruction.The periodic behavior of the motion pair wear is studied,and the influence of the long-term wear of the motion pair on the dynamic response and motion accuracy of the mechanism is analyzed.The results show that long-term wear increases the irregularity of the surface profile of the motion pair,and causes the instability of the dynamic response of the mechanism to increase,thereby reducing the motion accuracy;4.An experimental platform for the motion control system of the servo press is built,and various control algorithms are used to improve the dynamic motion tracking performance under no-load drawing conditions,and based on the forming force and position information of the main slider under the drawing load conditions,The mapping relationship between the two establishes the equivalent stiffness of the comprehensive error.The experimental results show that the motion control system based on the feedforward-switching PID feedback controller is effectively improved in displacement,velocity and acceleration response,and the maximum displacement error of the main slider is reduced by 43.31% compared with the motion control system using only the feedback controller,thus verifying that the motion control strategy established in this thesis can effectively improve the accuracy of the forming trajectory. |
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