Development Of Metal Foreign Body Detection System In Harvesting Machine

During the green fodder harvesting process,the metal foreign body damages the cutting table cutter,which affects the service life of the machine and reduces the harvesting efficiency.Moreover,the metal foreign matter often caught in the harvested green storage feed is easy to damage the cow's stomach.Foreign advanced green harvesting machines are generally equipped with metal detection devices,and the price is relatively expensive.The country is in its infancy and there are no mature commercial products at present.In view of the above problems,based on the analysis and comparison of the common methods of metal detection,the metal detection system of the green feeding machine was designed and the bench test was carried out.The main research contents are as follows:1.Metal detection principle and detection circuit design research.According to the principles of electromagnetic induction and eddy current effect,the advantages and disadvantages of the four detection schemes of differential beat,self-excited oscillation,energy-consuming and balanced are analyzed,and the improved self-excited oscillation metal detection scheme is finally determined.Using the modular design method,the detection coil module,LDC detection module,control and transmission module,and power module are designed.The STM32F103 series chip is selected as the main control chip,the VP230 is used as the CAN transmission module transceiver,and the inductance detection chip LDC 1000 is used as the coil data acquisition chip.The data detected by the LDC detection module is sent to the upper computer through the CAN transceiver under the coordination of the main control unit.2.Metal sensor device structure design.Based on the requirements of the roller structure of the green feeding machine and the safety detection distance,the position,quantity,size,winding method and mechanical structure of the detecting coil are designed.Among them,a strong magnetic core is added inside the detecting coil,which effectively improves the detection distance and detection.Precision.3.Software system design.The lower computer software realizes the digital signal conversion of the LDC detection module,the digital filtering processing of the main control unit and the real-time data transmission of the CAN communication.The digital filtering uses the Kalman filter algorithm with anti-external vibration interference and no delay,which improves the Sensitivity and accuracy of the metal detector of the green feeder.Based on Lab VIEW,the upper computer software of the metal detection system is designed,and the driver can perform metal foreign object processing according to the real-time alarm information.4.Metal test system simulation test bench construction and test verification.A metal test system simulation test bench for simulating straw feeding was built,including a frame,a stainless steel feed roller,a conveyor and a speed control device.A large number of verification tests,such as detection sensitivity,early warning accuracy,and reaction time,were carried out on the test bench.The experimental results show that the detection limit of the metal wire is the maximum safety detection distance of 100mm(safe transmission time is 0.23s).The diameter is 0.6mm,the length is 12mm,the alarm accuracy rate is 90%,the system reaction time is 0.16s,which is shorter than the safe transmission time,which meets the requirements of metal detection and warning of the green feeding machine.