Author：An-Pan Cherng¹, Yang-Huang Fan², Wen-Hang Chen², Gang-Jhy Wu³

¹ Professor, Department of Biomechatronic Engineering, National Ilan University
² Graduate Student, Department of Biomechatronic Engineering, National Ilan University
³ Associate Professor, Department of Biomechatronic Engineering, National Ilan University

Abstract：

    This research is aimed at developing a fruits as well as vegetables volume sorting system, which is based on a Helmholtz resonator. This system is a dry type and non-contact measurement system. In addition, it can be used to measure the volume of water-soaking-forbidden objects. The principle of Helmholtz resonator is based on the fact that its acoustic resonant frequency is a function of cavity volume. When an alien object is inserted into the cavity, the total air volume inside the cavity decreases. As a result, its acoustic resonant frequency increases. An automatic striking mechanism composed of three hammers was designed to induce the acoustic impulse responses, and a Singular Values Decomposition (SVD) algorithm was applied to extract these resonant frequencies consecutively. The averaged resonant frequency was then used as the measured resonant frequency. An air-sealed conveyor system was fabricated to transport each fruit for measuring its resonant frequency. For grading purposes, a mechanical-electrical system with air-cylinder, wood-slider, and a Programmable Logic Controller (PLC) was also integrated. The averaged successful rate of sorting fruits reaches 85% for both regular-shape fruits (guava and apple) and irregular-shape fruits (yam and custard apple), very close to the requirement of 90% successful rate for a commercial fruit grading system. The top speed of the developed system is 35 fruits per minute.

Keywords: Helmholtz resonator, Volume sorting machine, Singular value decomposition