Characteristic Analysis Of Table Dynamometer Based On FBG Sensor

In the cutting process,the tool wear and fracture and other machining conditions will lead to lower accuracy of the workpiece or the interrupt of the processing process,affecting product quality and production efficiency,so we need to monitor the mechanical properties of the tool in real time to determine its working condition,prevent the tool damage and extended tool life.Cutting force is the most direct variable in the machining process,which is most sensitive to the change of machining state.Its accurate and reliable measurement is an important means to understand and evaluate the state and performance of the machining process.It is also an important guarantee to judge the state of the tool.Through consulting a large number of cutting force measurement related literature,this paper put forward a milling dynamometer which use octagonal ring as the conversion elastomer and the fiber grating as the sensing element,then analyze the strain transfer law of the octagonal ring and the milling force sensing principle of the dynamometer,determine the size and material parameters of the octagonal ring according to material mechanics knowledge.Then,the stiffness characteristics of the dynamometer are analyzed theoretically to obtain the theoretical stiffness values of the dynamometer,and the actual stiffness value of the dynamometer is obtained through experiments.The simulation analysis and experimental study of the dynamometer is carried out to obtain its natural frequency in three directions and working frequency band.The static performance indexes such as sensitivity,linearity and repeatability of the dynamometer are studied experimentally and then obtained.Aiming at the problem that the load in three directions will influence each other in the multimeter milling force measurement,the multidimensional force coupling characteristic of the dynamometer is analyzed,and the decoupled formula of the milling force is obtained.Then,the simulation analysis of the coupling performance of single octagonal ring and the whole dynamometer is carried out to prove the correctness of the theoretical analysis.Finally,we compare the measurement error before decoupling with after by the the coupling experiment,which proves that the decoupling method can greatly improve the measurement accuracy.In addition,thelight-thermal coupling characteristics of the fiber grating sensor and the force-thermal coupling characteristics of the octagonal ring composite sensing structure are analyzed for the problem that the temperature change caused by the cutting process affects the cutting force measurement accuracy.And the actual temperature characteristics curve of FBG sensor and octagonal ring composite sensing structure are obtained by experiment to achieve the the temperature compensation in cutting force measurement process,greatly improving the precision of the cutting force measurement.