| Front-end drive system is an important component of the circular scanningultrasonic endoscopic imaging equipment which detect the characteristics of the faulthistology features of digestive organs through the ultrasonic probe, use ultrasonicecho receiving amplifying circuit and digital processing circuit to implement thefunction of receiving，conditioning and conversion of the ultrasonic echo, eventuallyforming ultrasonic tomography image organization. The Front-end drive system is akey component for driving ultrasonic transducer to complete the circular scanningimaging; its performance has important influence on the quality of endoscopicultrasound imaging. To develop circular scanning ultrasonic endoscopic imagingequipment with independent intellectual property right for break the monopoly offoreign companies in this field, in this paper, we design the Front-end drive system ofthe circular scanning ultrasonic endoscopic imaging equipment based on theendoscopic ultrasound product functional requirements.The main work of this paper is shown as the following:1、According to function and task requirements of Front-end drive system, completethe task division and the design proposal development of each function module.2、Implement the design of motor drive. Design a hardware feedback circuit withStep-Down Voltage Regulator chip, which has the function to adjust the output byitself, and a D/A module offered by MCU to regulate the real-time rotate speed.Experiment result shows that we can precisely control the PMW (Pulse WidthModulation) signal excitation. The motor drive system has high accuracy, fastresponse, excellent reliability, and good versatility and portability. The feedbackresponse time is20μs in theory. And the maximum error is±1r/min under thenormal running environment (300-1500r/min) and varying load conditions,which means the average instability is reduced to0.11%compared with the simplespeed control by MCU which is0.94%error range. This drive system canguarantee the smooth movement of a load-changing motor, so as to ensure theimaging quality, and effectively improve the efficiency and accuracy of thediagnosis.3、Implement the design of high voltage drive with the high voltage generatemodulator. Design a feedback control system with the DAC and ADC of MCU.Realize the high precision output of high voltage to drive the transducer. The high voltage drive has the advantages of high precision, high reliability. It can output0-200V accurately; the maximum voltage error is0.2V. The high voltage driveincreases the drive voltage of transducer, enhances the ultrasonic transmittingpower. It also can keep the output voltage stable and help to improve thesignal-to-noise ratio of the ultrasonic image.4、Achieve the purpose to automatic recognition the probe frequency and impedanceinformation with I2C communication.5、Complete the information transfer between host computer and front-end drivesystem with RS-485communication.6、Implement the design of the system monitoring modulator, drive system canautomatically detect and recognize fault and take corresponding measures. It canguarantee the reliable operation and safe of whole system and guarantee the safetyof the users and equipment in greatest degree. |
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