The Research And Development Of Output Power Controllable Low-Power Ultrasonic Generator

Soil quality, output, soil anti-erosion energy and the ability of anti-degradation determined by the stability of soil aggregate.There are many differences in the existed soil aggregate stability assessment methods. And these methods can only qualitative assessment the stability of soil aggregates.Ultrasonic dispersion method can quantitatively assess the stability of soil aggregates.However existed ultrasound equipment output power is high, when it used to measuring the stability of soil aggregates, the soil was dispersed completely in a short time, cannot be measured for different soil’s suitable ultrasonic dispersing power. Based on the above background, an output power controllable low-power ultrasonic generator was developed in this paper. Then the ultrasonic generator was using to assessing the stability of soil aggregate,and different soil’s suitable ultrasonic dispersion power was explored. The main contents and conclusions include:(1) According to the demand of low output power, an output power less than 10 W ultrasonic transducers was customized. The admittance of ultrasonic transducer equivalent circuit was analyzed. Thus, based on current and the phase difference of current and voltage in the transducer circuit, a frequency auto-tracing solution was proposed. In addition, based on the relationship between RMS current of the transducer circuit and the amplitude(power)of transducer vibration, a constant power control solution have been designed to keep the power constant.(2) The main circuit structure of ultrasonic generator was designed. Rectifier and power adjustment circuit, an inverter circuit, a driver circuit, a matching circuit, a feedback circuit and the main control circuit was analyzed and discussed. A rectifier with Buck chopper accomplished adjustable output power. PWM wave generator based on DDS technique, and IR2110 driver chip together to drive the full-bridge inverter to realized high-power supersonic AC output with adjustable frequency.(3) According to the configuration of hardware circuit, the control software program has been programmed, including frequency auto-tracing and constant power control program. In order to achieve fast and accurate control, variable step size control strategy was used.Operation simple and convenient interactive interface was designed.(4) A soil aggregate stability assessment experiment platform was built, based on ultrasonic dispersing method. Then low and constant of output power performance of the ultrasonic generator was verified. The results show that when the ultrasonic generator output power is set to 30% to 70%, the transducer output power can be considered constant and is less than 10 W. Low output power and constant power goals are achieved. The stability of five soils aggregate were assessed, and traditional Yoder wet sieving was used to as a comparison.The results show the ultrasonic generator can be used to assessing the stability of the soil, but not to Dark brown soil from Heilongjiang province and Loam from Hebei. Under the conditions of different power setting, five typical soil was dispersed by the ultrasonic generator. The results show due to their different characteristics, different soil should applies different ultrasonic dispersing power. Loam from Hebei and dark brown soil from Heilongjiang suitable ultrasonic dispersing power are 8.86 W. Yellow loam from Chongqing city and red soil from Jiangxi suitable ultrasonic dispersing power are 9.16 W. Fluvo-aquic soil from Zhejiang suitable ultrasonic dispersing power more than 9.52 W.