Development Of High Frequency Cutting Force Sensor Based On PVDF Pizeoelectirc Film

Cutting force is an important parameter in machining.Cutting force dynamometers are widely used in cutting force measurement.The use of piezoelectric material sensors can improve the dynamometer performance.PVDF(Polyvinylidene Fluoride)piezoelectric film,because of its good dynamic characteristics,wide frequency response range,high sensitivity,large flexible,low cost advantages,are increasingly widely used in dynamic monitoring of the cutting force.This research object is the design of a new high performance economical piezoelectric force sensor,which is based on the high speed micro milling,by using PVDF piezoelectric film.First of all,a simple one-dimensional parallel sensor is designed according to the strain concentration structure,and do simple milling experiments to verifying the rationality of structure.According to the kinetics of elastomer,the relationships between free vibration natural frequency and various parameters of the piezoelectric force platform are derived,which are pivotal to select the size range of piezoelectric force platform.High stiffness elastomer parallel middle low stiffness elastic sheet structure is used in the design of x and y direction milling force load sensitive element in the milling force load platform,while section mutation structure is used in the design of z direction's.The load platform measuring range can be got through modal analysis and static analysis by finite element software.Secondly,according to the using conditions and PVDF piezoelectric film properties,the piezoelectric equation can be determined.Thin film sensors and the piezoelectric force measuring platform are fabricated.By using the finite element software,the relationship between the applied load and output electric field can be got through mechanical-piezoelectric joint simulation of piezoelectric force platform.Then,the decoupled algorithm of the dynamo platform can be derived according to the nature of PVDF piezoelectric film in the polarization direction and relationship between the load,strain and charge.Two decoupled matrixes including simulation and theory are deviced.Finally,with the assist of DASYLab(Data Acquisition system Laboratory)multifunctional configuration software,the upper computer is designed,completing the dynamic monitoring system design and realizing the cutting force signal acquisition,processing,real-time display and storage,and other functions.By building a test system and choosing different per tooth feeding,milling experiment is carried out,which comes to relationships between cutting force and each tooth feeding.Choosing appropriate parameters,contrast examination is carried between load platform and Kistler dynamometer,and the cutting force signal will be decoupled after the experiment.The experiment proved that the cutting force sensor can well reflect the milling cutting force dynamic change,and the decoupling matrix is able to reduce interference in all directions to some extent,and improve measurement accuracy of the monitoring system.