| Stiffness is the important performance index of the ball screw.For the slender shaft parts that bear torque,the torsional stiffness cannot be ignored.At present,there has been a lack of effective testing methods and equipment for the torsional stiffness of the ball screw.To this end,based on the major national science and technology project,this article conducts theoretical analysis on the torsional stiffness of the ball screw,develops a torsional stiffness test system,and conducts experimental research to improve the ball screw's comprehensive stiffness theory and detection system,laying the foundation for the high rigidity design and improvement of the ball screw.The specific research content is as follows:(1)The theoretical model of the torsional stiffness of the ball screw is established.The torsional stiffness of the ball screw is divided into the torsional stiffness of the screw shaft and the torsional contact stiffness of the contact area between the ball and the raceway.Considering the geometric parameters of the screw raceway,the calculation formula of the torsional stiffness of the screw shaft is deduced,and considering the weakening effect of the screw raceway on the torsional stiffness,the theoretical calculation formula is modified with coefficients.Then the concept of torsional contact stiffness is introduced.Based on the rolling contact theory,the theoretical models of the torsional contact stiffness of single-nut and double-nut ball screws are established respectively.Based on the theoretical analysis,the influencing factors of the torsional stiffness of the ball screw are analyzed.(2)The torsional stiffness test system of the ball screw is built.According to the working principle of the ball screw torsional stiffness test system,two loading schemes of the test system are proposed and the overall structure design is completed.On this basis,the hardware is selected and the circuit is connected.Then the measurement and control software is developed using VB,and the program of each function module is written to realize the automatic measurement of the test system.(3)The test method for the torsional stiffness of the ball screw is proposed and the test is carried out.Based on the test system,torsional stiffness test plan is formulated.Carry out initial tests to compare the two proposed loading methods.Based on the test results,the repeatability and reproducibility of the test system are analyzed,and the uncertainty is evaluated.Carry out actual tests,analyze and verify the correctness of the theoretical model,and analyze the factors affecting the torsional stiffness of the ball screw.(4)The comprehensive stiffness theory of the ball screw considering torsional stiffness is studied.The axial transformation model of torsional stiffness is proposed,and the comprehensive stiffness of the ball screw is calculated based on this.Combined with the test,the role of torsional stiffness in the comprehensive stiffness of the ball screw is analyzed.Aiming at the effect of the comprehensive stiffness of the ball screw in the actual application process,the influence of the comprehensive stiffness on the positioning accuracy and dynamic response characteristics is qualitatively analyzed,and it is proved that the torsional stiffness of the ball screw cannot be ignored. |
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