Modeling And Simulation Analysis Of Feed System For Ball Screw Wear

CNC machine tools are common equipments for modern production.Ball screw is one of the important transmission components in feed system and has a great influence on the performance of the machine tool.After the screw is worn,the performance of the feed system is reduced,which leads to the low-quality production if servo parameters are not adjusted accordingly.Thus,the dynamic characteristics caused by wear screw are studied in the paper,which provides the support for parameters' adjustment of sevro control system.It is of great siginificance for CNC machine to stay a good working condition.The specific work is as follows:Aiming at the influence of wear screw on the movement of the feed system,a dynamic model of the feed system is established,and the influence brought by screw wear for the feed system movement is analyzied theoretically,and the single-axis feed experiment is built to carry out related research on wear screw.Aiming at the problem of non-linear friction caused by wear screw,the problem that Stribeck friction model can't describe the change of measured friction at the macro-sliding stage is pointed out,and viscous friction correction coefficient is proposed accordingly,which improves the accuracy of the friction model.The new friction model is verified on other machine tools.It is found that wear screw has a significant effect on friction characteristic of feed system at the low speed stages throught comparing the difference between the friction model when the screw is on weared state and on unweared state.For the influence of mechanical inertia on the model parameter accuracy,Based on rotational inertia identification algorithm by using model reference adaptive technology,the method of signal splicing and zero-phase filtering is used to eliminate the direction mutation and phase deviation caused by the signal filtering.The shortcomings of fixed gain parameter algorithm are pointed out,then,the parameter adaptation algorithm is used to improve the convergence speed and robustness of the algorithm.The results show that the accuracy of identification is higher when the acceleration is greater.Finally,in order to obtain the influence of wear screw on the dynamic characteristics,some relevant experiments are designed on the single-axis feed bench.Through that,the axial vibration characteristics of the table are analyzed.Then,the 55-65 Hz frequency of signal is selected to indentify the parameters of dynamic model,and it is showed that screw wear reduces the axial stiffnes of feed system and intensifies the axial vibration of table by comparing the models.Finally,the correctness of models established in this paper are verified through experiments.