在功率超声的应用中,精确的振幅控制是决定加工质量的重要因素.传统的检测控制结构需要复杂的外部仪器或检测电路,可能存在灵活性差及非线性等问题.针对此问题,提出了一种轻量级振幅检测与控制方案.该方案采用高速AD转换器采样换能器的工作电流和电压,实时计算可以反映振幅的动态支路电流.采用现场可编程逻辑门阵列(field-programmable gate array,简称FPGA)作为超声电源控制器,同时对换能器工作频率和动态支路电流进行闭环控制.在本设计中,超声电源工作在反谐振点以获取较高的能量传输效率.实验结果表明,该方案能够准确地控制振幅,并能在负载变化较大时稳定振幅.

超声红外热成像以超声作为激励源,能够用于检测多种工件,但是由于热传导效应及空气的散射,检测结果中缺陷边缘较为模糊,成像对比度不高,并且会有温度分布不均引起的"散斑噪声".为解决以上问题,提出了一种对超声红外热成像结果进行缺陷检测和定位的方法,使用限制对比度自适应直方图均衡(contrast limited adaptive histo-gram equalization,简称CLAHE)方法对图像进行对比度增强,用巴特沃斯滤波器进行降噪,根据图像的局部方差特征判断是否有缺陷,并通过形态学处理对缺陷中心进行定位.实验表明,根据局部方差可以对图像进行有效判断,经过形态学处理之后能够准确定位.该研究为通过超声红外热成像实现缺陷检测及定位提供了一种便捷有效的方法.

This paper presents the design and realization of intelligent upgrade based on temperature control of electric heating cooker. The cooker is supplied by segmented PID algorithm which helps to realize precise temperature control. By fully utilizing STM32 MCU, intelligent upgrade including smart-friendly interaction as well as pre-stored menu information is achieved, which means automatic temperature control and operation reminding are available. More importantly, the cooker allows manual adjustment during automatic control and can record this information via Flash. In that way, it can implement real-time menu information update, thus making it more human-friendly.