Design Of The Cutting Force Self-sensing Smart Turning Tool And Error Compensation Study

With the rapid development of new energy,new materials and new technologies,the upgrade of new industrialization is subverting the traditional manufacturing mode.Cutting is a widely applied method of mechanical processing in modern manufacturing industry.The real-time state of cutting tool directly affects the accuracy,efficiency and surface quality of parts.Therefore,the new method,technology and system of tool condition parameter monitoring developed by modern sensing technology,computer technology and signal processing technology have great theoretical significance and practical value.Aiming at the requirement of real-time monitoring and monitoring accuracy of tool state in intelligent machining,a cutting force self-sensing smart tool integrating piezoelectric ceramic sensing system is designed.Through the research on the system design and error compensation of smart tool,tool are endowed with the ability to perceive cutting force while executing machining.This research can realize real-time on-line monitoring of cutting force reflecting tool state.The relevant research results have important reference value for the rapid development of adaptive intelligent processing technology.The main contents of this paper are as follows:A new structural design scheme of cutting force self-sensing smart turning tool is proposed.A new cutting force sensing element is designed and its static performance is tested.By analyzing the performance of different types of piezoelectric ceramics,the type of piezoelectric ceramics embedded in tool pad was determined.The shape of piezoelectric ceramic sheet was determined by stress analysis.The size parameters of piezoelectric ceramic sheet are determined by theoretical calculation.After that,the size design of tool pad,the welding of signal transmission wire and insulation are studied.Finally,the corresponding fabrication and assembly of cutting force sensing element are completed.In order to test and evaluate the performance of the designed cutting force sensing element,the measuring principle of piezoelectric ceramic sensor is analyzed,and a signal acquisition system is established.The static performances such as linearity,sensitivity,repeatability and hysteresis of the cutting force sensing element are calibrated.Based on the micro-polarization mechanism of ferroelectric effect of piezoelectric ceramics,the reason of hysteresis nonlinearity of cutting force sensing element under external force is analyzed and explained.In order to test and evaluate the comprehensive performance of the cutting force sensing smart turning tool,the mechanical and thermal characteristics of the smart turning tool are analyzed.A dynamic calibration test system is built,and the experimental modal analysis of the designed tool is carried out by the method of hammering excitation.The natural frequency of the smart tool is obtained by the integration simulation and test results.The sensitivity of the designed tool is calibrated by direct coupling method,and the linear response relationship between the output voltage and the main cutting force is obtained.Finally,a comparative test experiment of smart cutting tool is carried out to verify the working reliability and cutting force perception ability.Through the above research,the following conclusions can be drawn: 1)The mechanical properties research shows that the maximum stress of each part of the smart turning tool increases compared with that of the ordinary turning tool,but the maximum stress of each part is lower than the compressive strength of the material under the cutting force satisfying the design goal.So the stress intensity meets the requirements.2)The thermal performance study shows that the maximum temperature of the piezoelectric ceramic sheet embedded in the pad will not exceed its Curie temperature when the maximum cutting temperature is below 400℃.3)The first natural frequency of the smart turning tool is far more than 4 times of the system frequency.The tool will not be damaged by resonance in the process of machining.The smart turning tool meets the application requirements.4)The designed cutting force self-sensing smart turning tool has good cutting force perception ability.When the cutting force is relatively small,the working performance of the smart turning tool is stable.With the increase of cutting force,the cutting heat has a certain impact on the performance of the tool.In order to compensate for the hysteresis nonlinearity error of cutting force sensing elements and improve the detection accuracy,an improved Bouc-Wen model is proposed,which can reflect the asymmetric hysteresis characteristics of cutting force sensing elements.The influence of model parameters and the amplitude and frequency of input signal on the size,shape and stationarity of hysteresis curve is discussed.The inverse model and the identification method of model parameters are given.The improved Bouc-Wen inverse model is used as compensator to compensate the hysteresis nonlinearity of cutting force sensing element of smart turning tool.The effectiveness of error control is verified by comparative experiments.The relevant conclusions provide a new way to control the asymmetric hysteresis error.In order to compensate the sensitivity temperature drift error of cutting force sensing element,a temperature drift compensation method based on improved Elman neural network is proposed.The results of comparative test show that the predictive force of the compensation model is in good agreement with the actual load force of the cutting force sensing element,and the error is obviously reduced after compensation with the sensitivity temperature drift compensation model established in this paper,which effectively guarantees the detection accuracy.This study provides an effective compensation method for sensitivity temperature drift of designed smart tool,and has important reference value for the research of other devices with sensitivity temperature drift characteristics.