Development Of Shearing Piezoelectric Four-dimensional Dynamometer

With the development of science and technology,the traditional manufacturing industry is also developing in the direction of high-end,segmentation,automation and intelligence.Intelligent machine tools are the core of the manufacturing industry in the new century,the monitoring and measurement of intelligent machine tools which are parts of its intelligent technologies need to be realized by sensors / dynamometers.The accurate acquisition of cutting force is very crucial to the monitoring accuracy of machine tools.During the cutting processes,the frequency of cutting force is high and the range of the force amplitude is large,and there are lots of disturbing factors in the measurement environment and so many kinds of cutting methods used,which bring great challenges to the design of the dynamometers.Aiming at the design requirements of high precision,strong anti-interference ability and wide application range of the dynamometers,this paper analyzes the traditional piezoelectric measurement method,puts forward a new measurement method,designs two novel sensors and a dynamometer,and analyzes and verifies the performance of the sensors and dynamometer by experiments.In this paper,the characteristic of the commonly used x0-cut and y0-cut quartz wafers is compared,the load sharing relationship between the sensors and the wafers is analyzed,the force loss model of the wafers is obtained,and then the law of sensitivity changes is obtained.The piezoelectric coefficient matrix of the quartz crystal is established,the number of interference force that makes the two types of wafers produce interdimensional interference is obtained.The output of the three-dimensional piezoelectric force links and sensors under high temperature environment is analyzed,and the relationship between the sensitive direction of interference and the measurement direction of the two wafers is obtained.Based on the above analysis,it is concluded that the test performance of the y0-cut wafers is theoretically better than that of the x0-cut wafers.A new method for measuring four-dimensional cutting force using only y0-cut wafers is proposed.A certain number of y0-cut wafers with shear effect are arranged around the dynamometer,the arrangement of the wafers in each direction is selected,and the theoretical output model of the new method is established.It is proved theoretically that the method can measure the four-dimensional force.According to the layout of y0-cut wafers in the new method,two novel shear type two-dimensional force sensors are designed.The relationship between the assembly errors between wafers and wafer groups and the cross-talks of sensors is traced,and the error range is obtained according to the cross-talk requirements.The structure of the shear type four-dimensional dynamometer with shear type sensors as the core component is designed.The size of the key components of the dynamometer is optimized.The preload method selection and the calculation of the preload value are carried out to ensure that the dynamometer can be in the best measurement state.According to the theoretical output model,the measuring ranges of the dynamometer in four directions are calculated,which provides the basis for the use of the dynamometer.The overall performance of the designed shear type dynamometer is analyzed.The reason for the output loss under lateral force is traced,and the law of force loss caused by only shear type wafers are used in the measurement of lateral force is obtained.The mapping relationship between output and input of the dynamometer is obtained through the deformation acquisition experiment and finite element simulation analysis of the force links.According to the theoretical output model,the matching relationship between the external force applied on the dynamometer and the point of force application is obtained.The relationship between the assembly errors of the sensors which occur at assembly of the dynamometer and cross-talks of the dynamometer is analyzed,and the relationship model between the installation deviation angle of the sensors and the cross-talks is established.According to the cross-talk requirements of the dynamometer,the assembly tolerance range is proposed to realize the high-precision assembly of the dynamometer and improve the measurement accuracy of the dynamometer.Perform performance verification experiments for the shear type sensors and dynamometer.The static performance calibration experiment of the sensors is carried out,apply standard forces on the sensors in two directions to obtain its linearity and repeatability in each direction.Apply standard forces and moments on the dynamometer in four directions to obtain its static performance.Dynamic percussion experiment of the dynamometer is carried out to obtain its natural frequency in each direction.Finally,an anti-environmental interference experiment is carried out on the dynamometer,which mainly aims at the effect of environmental temperature changes on the performance of the dynamometer.The above experiments prove that the dynamometer is suitable for accurate measurement of cutting force in different environments and different working conditions.By comparing x0 type wafers with y0 type wafers,this paper proposes a new method for four-dimensional force measurement using only y0 wafers.Applying theoretical analysis and experimental verification and other means,corresponding to the shear sensor and dynamometer used in the new method are designed and analyzed.The dynamometer can measure fourdimensional force.The linearity and repeatability are both less than 1%,and the crosstalk is less than 5%.It is verified that the new four-dimensional force measurement method can achieve high-precision and strong anti-interference ability measurement.