| The CNC crankshaft comprehensive measuring machine is the most effective equipment to realize the efficient and high-precision measurement of crankshaft multi-parameters,and the follow-up system is one of the most important functional components of the crankshaft comprehensive measuring machine,and its accuracy level is the most critical factor affecting the entire crankshaft measuring system.Therefore,it is necessary to carry out the research work of the follow-up measurement system,including the principle,structural form and method of improving the follow-up accuracy of the follow-up system,so as to create conditions for the further design and development of the crankshaft comprehensive measuring machine.Firstly,according to the measurement method of crankshaft radial following,the measurement principle of servo tracking measurement method and follow-up measurement method is studied,and the geometric error of follow-up guide rail,displacement sensor error,and probe device that cause the measurement accuracy of the follow-up system are analyzed.Based on the main factors such as the error and the change of contact force,and according to the uncertainty components generated by various influencing factors,the system measurement uncertainty models under the two measurement methods were established respectively.Through the calculation of the example,it is determined that the design research should be carried out with a better follow-up measurement method.The actual radial displacement of the measurement point is obtained by using dual displacement transducer measurements,which can effectively eliminate the influence of the Abbe error of the follower on the radial displacement measurement and improve the measurement accuracy of the follow-up system.Secondly,based on the follow-up measurement method,a follow-up system measurement scheme is designed in which the linear spring exerts the pre-tightening force and the counterweight exerts the pre-tightening force.According to the measurement principles of the two schemes of applying preload,the dynamic models of the system are established respectively,and the structural parameters of the system are optimized with the goal of minimizing the fluctuation of the contact force.The simulation results of the two force application methods show that for different masses of the follower device,the overall degree of the average fluctuation of the contact force when the linear spring applies the preload force is small,and there is an optimal Structural parameters.Applying it to the experimental structural parameters can ensure the stability of the contact force during the measurement process,thereby improving the measurement accuracy of the entire follow-up system.Thirdly,the mechanical structure of the follow-up system for crankshaft measurement is designed based on the follow-up measurement method in which the linear spring exerts the preload force.According to the functional requirements of crankshaft measurement,the moving mechanism,displacement detection device and feed and recovery device of the measuring plate are designed,the basic parameters of the spring are designed and calculated.The threedimensional overall structure model of the follow-up system is established,and each component is processed and assembled to complete the physical assembly.Finally,a crankshaft measurement follow-up system experimental platform was built for measurement experiments.By measuring different connecting rod journals and different cross sections of the crankshaft under test,the measurement error is calculated using the theoretical values as a standard to check the measurement accuracy of the crankshaft measurement followup system designed in this paper.The measurement results show that this crankshaft measurement follow-up system has a maximum measurement error of 10.2μm at the unit shift transducer,which is less than 3.7μm after compensation by both displacement transducers,and the repeatability accuracy is within the range of 0.7μm. |
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