Design Of Thin Film Strain Sensor And Cutting Force Data Acquisition System For Suspended Structure

In the context of intelligent manufacturing and Industry 4.0,high-speed and high-precision have become prominent features of modern cutting technology.Researching methods and technologies to obtain real-time and accurate cutting force and other information during the cutting process has important theoretical significance and practical application value for indepth understanding of the cutting process,mastering the cutting mechanism,and improving the surface processing quality of workpieces.Embedding thin film strain sensors into cutting tools for cutting force measurement has the characteristics of accuracy and high reliability.The rapid development of technologies such as microelectronics,sputtering deposition,and semiconductor etching has provided effective means for the miniaturization,intelligence,and integration of devices.Based on the preliminary work of our research group,this paper proposes a thin film strain sensor with a suspended structure,and designs a corresponding cutting force data acquisition system for the thin film strain sensor based on the STM32 microcontroller.The main tasks include the design and preparation of the thin film sensor,characterization of mechanical and electrical performance,design of the hardware circuit and PCB card of the data acquisition system,and software design of the data acquisition system,The main research content and innovative achievements are as follows.Based on the analysis of the cutting force measurement principle of the film strain sensor,a film strain sensor with suspended structure composed of substrate,transition layer,insulation layer and sensitive layer is designed.The technology method of preparing part of the cavity structure on the surface of the insulation layer is used to make the film resistance grid deposited on the insulation layer have suspended structure,which increases the strain sensitivity of the sensor.By means of stainless steel elastic substrate polishing,magnetron sputtering coating,photoetching and ion beam etching,the preparation process of the membrane strain sensor with suspended structure was designed.The electrical properties of the prepared sensor samples were studied.The test results show that the membrane has good anti-plastic deformation ability.The calculated strain coefficient of the membrane sensor with suspended structure is 1.62.According to the output signal characteristics of the sensor,the overall scheme of data acquisition system based on STM32 microcontroller is designed.By analyzing the hardware composition and design index of the acquisition system,according to the modular design idea,the high precision instrument amplifier AD620 chip and integrated operational amplifier TL082 chip are selected to amplify and filter the voltage signal output of the suspended thin film strain sensor,and the signal conditioning circuit is designed.A/D conversion circuit is designed with 16 bit high precision AD7606 chip which is convenient for the main control chip to receive digital signal.With STM32 chip as the control core,the main control unit circuit is designed,including the system clock circuit,reset circuit,start configuration circuit,serial communication circuit,program download and debugging circuit.On the basis of the hardware circuit design,the design of PCB file is completed and the PCB data acquisition card is made.The integration of all hardware functions on the PCB card is realized.The software design is divided into two parts: the lower computer software for direct control of hardware devices and the upper computer software for debugging and analysis of hardware devices.The lower computer software is designed and written the main control program in the Keil μVision5 development platform,which mainly analyzes and describes the clock configuration program,A/D conversion program and serial communication program in detail.The serial port configuration and signal analysis of STM32 microcontroller are completed.Based on Lab VIEW of virtual instrument technology,the upper computer user interface and data acquisition program block diagram are designed,and the information reading and data processing of the lower computer are completed.The cutting force measurement system model of embedded suspended thin film strain sensor was established,and the static force sensitivity calibration test was carried out by embedding the prepared suspended thin film strain sensor into the tool handle.The strain values and output voltage values of the sensor were measured under unidirectional load,and the loadstrain and load-voltage fitting curves were obtained.The static force sensitivity of the suspended thin film strain sensor is 1.24 m V/N.The same load as the sensitivity calibration test was applied to the sensor sample on the unidirectional tension meter,and the output voltage of the sensor was simulated by using the designed data acquisition card and software program,and the output voltage curve under the corresponding load was obtained.The voltage value in the curve was compared with the voltage value in the static calibration test,and the effectiveness of the data acquisition system was verified.