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Received Apr 23, 2017; Revised Jun 23, 2017; Accepted Jul 12, 2017
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
The conveyor belt is widely used, for sensing application, to measure continuously the physical parameters of an object in many fields [1]. The vision sensors are used for tracking and identifying an object moving on a conveyor belt [2–4], and range sensors are used for volume measurement [5]. The automatic weighing and sorting system is used in food and pharmaceutical industry where continuous and precise mass measurement of small objects is required [6, 7]. The belt conveyor is used for automatic weighing to continuously feed products under measurement [8–12]. However the horizontal and rotational movements of belt conveyor eventually cause vibration [13], and these behave as noise source to the output of load cell sensor [14, 15]. High signal-to-noise ratio (SNR) is needed to improve accuracy and resolution of weighing machine; thus noise reduction is essential process [16–19]. The electric motor, AC induction or BLDC motor, is used to actuate belt conveyor [20–22], which has different vibration characteristics. Also other individual components of belt conveyor, such as bearing, belt, and roller, with accompanying vibration, transfer noise to load cell sensor [23]. The way to reduce the vibration noise of belt conveyor has been investigated [24, 25], and the method to locate the fault point in belt conveyor has been attempted by analyzing audible signal from belt conveyor [26, 27]. Also the investigation to driving motor to reduce the noise was conducted [28]. The work to improve accuracy through modeling has been performed for weighing machine adapting belt conveyor [29]. Further efforts to enhance continuous measurement accuracy for high speed mass measurement have been performed [30, 31]. In respect of analysis method, the algorithm adapting frequency analysis [32, 33] or digital filter [34] was attempted. In this paper, the noise in load cell signal in an automatic weighing system based on a belt conveyor is analyzed, and the method...