Fast weighing of pistachio nuts by vibration sensor array

Abstract

Impact acoustic sound signal is previously used to discriminate open-shell pistachios from closed ones and for crack detection purposes. Weight of the pistachio samples can be utilized as a feature vector for sorting and grading processes. Nevertheless, traditional weighing procedure is time consuming. Moreover, efficient fast weighing system based on impact acoustic signals for pistachio nuts has not been studied yet. This study aims to discuss the design and evaluation of a real time fast weighing system for pistachio nuts. Proposed system can be extended to other agricultural or industrial products where weight information is critical as well. In order to eliminate the sensor noise and improve the signal quality, piezoelectric sensor arrays containing 15 piezoelectric vibration sensors are employed. Final impact acoustic signal energy is determined by averaging the sensor array signals.10 pistachio samples with incremented weights ranging from 0.56 to 1.64 gr are utilized for calibration process of the sensor array. Extra two heavy objects (4.05 and 5.65 gr) are participated to the calibration set also. In order to improve accuracy and achieve consistent measurements repetitive trials approach is adopted. Excessive repetition of experiments theoretically yields more accurate and consistent measurements with minimum standard deviation. Consequently it is observed that 10 times repetition scheme produces satisfactory results with 3% coefficient of variation and 5ms of computational cost indicates that proposed system can be applicable for fast weighing of pistachio nuts.