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標題: | 水果運輸過程中振動與損傷之研究 Study on Vibration and Injury of Fruits during Transportation |
作者: | Chih-Kai Yang 楊智凱 |
指導教授: | 葉仲基 |
關鍵字: | 振動分析,機率密度函數,功率頻譜密度,運輸,隨機控制曲線,楊桃, vibration analysis,probability density function (PDF),power spectral density (PSD),transportation,random profile,carambola, |
出版年 : | 2005 |
學位: | 博士 |
摘要: | 水果於採收後因為人為或機械因素,會造成損傷導致品質降低,其中部分外力是導因於運輸時的振動。國內水果自果園搬運至集貨場所作初步處理,多以小型農用搬運車為主要運輸工具,此階段之運輸過程,稱之第一運輸階段。裝箱後的水果經貨運卡車載送至大型批發市場或是大盤水果商,此為第二運輸階段。最後轉由零售商拆箱零售給一般消費者。
為探討國內水果產銷過程有關運輸方面的問題,本研究建立一套田間振動資料蒐集系統,量測與記錄第一與第二運輸階段之振動資料,並分析其功率頻譜密度(PSD)曲線。結果搬運車底盤後側之振動最大、中間位置次之,再來是駕駛座位下方之底盤位置,貨台前緣位置則最小;同時發現輪胎胎壓在0.77~1.12 kg/cm2範圍內之變化,對行進之小型農用搬運車振動並無明顯影響。期間也探討對於隨機振動理論中機率密度函數(PDF),應用在實際量測時,透過統計方法,可得到小型農用搬運車的速度、胎壓、載重與道路種類對振動的影響,同時也驗證,以機率密度函數之變異數施行複因子變方分析與功率頻譜密度分析,兩者是可行的、並行的分析方法,而且是相輔相成的關係。 接著發展多段式變動樣本數二次多項式迴歸技術,求取應用於振動控制器之最適隨機振動控制曲線,經過頻譜圖的比對,田間試驗量測之振動功率頻譜密度曲線形狀以及峰值發生之頻率值皆與振動平台模擬之振動資料相符;惟位於較高頻率範圍內模擬振動之峰值稍有不足。 本研究在第二運輸階段中結合全球衛星定位系統與振動資料蒐集系統,發展出一套有效整合調查第二階段之運輸路線以及記錄農產品受振情形之系統及其運作模式。且以台南縣楠西鄉密枝村至台北果菜公司第一市場為例,以馬來西亞種裝箱楊桃進行模擬運輸過程之隨機振動,先經20分鐘的第一運輸階段(小型農用搬運車,正常胎壓、農路、2/3最大負載、速度8.5 km/h)進行模擬,接著20分鐘山區道路,再以四個半小時的高速公路的路程,最後半個小時以市區與一般道路的隨機控制曲線進行隨機振動。由模擬運輸振動過後楊桃之損傷試驗結果,二氧化碳生成率在處理組與對照組有差異存在,應可作為短時間檢測損傷之指標。而乙烯生成率因為乙烯量幾乎量測不出來,並不適合作為檢測楊桃損傷之指標。 相信本研究結果,可用以探討分析水果在運輸過程中之振動特性與損傷情形,提供作為減少水果運銷過程品質與產值損耗之參考。 The injuries of fruits after harvest result in considerable degradation in quality. Injuries are caused by manhandling or mechanical operations in general. One of these causes is the vibration during transportation. Fruits are transported from orchard farms to an assembly yard of production-marketing groups by a maneuverable small-type agricultural transporter, and this is called the first stage of transportation. Well-packaged fruits are consigned to the distribution center by trucks and package dealt to retailers. Consumers then buy fruits from a retail market or outlet. This is the second stage of transportation. To investigate the transportation of domestic fruits after harvest, this study tried to build up the field data acquisition system. The vibration data of the first and second stage transportation were measured and recorded and the curves of the power spectral density (PSD) were analyzed. In all of the tests, the magnitudes of PSD’s were found to be in descending order: the rear part of the main chassis beneath the truck-bed, the middle part of the main chassis, the frame beneath the driver’s seat and the front part of the main chassis. Besides, the inflation pressure had no significant influence on the vibration of the transporter. Meanwhile, the probability density function (PDF) and the power density function analysis’s were both feasible and consistent with each other in this research. A “multi-segments 2-degree polynomial regression with increasing sampling variability” technique was developed and carried out by MATLAB program in this study. Comparing the field data and the results of simulation, it showed that satisfactory coincidence existed in the shapes of the average PSDs and the frequency of peak signals. However, the peak values in higher frequency range showed some differences. To combine the GPS and the field data acquisition system was a way to develop an effective working model of investigating the second stage of transportation and of recording the working process of horticultural produce by vibration. In order to evaluate the injury caused by vibration, the packaged Malaysian carambola was vibrated by the electro-dynamic shaker as the trip from Tainan county to Taipei city. The simulation of random vibration controlled by random profile of a small-type agricultural transporter in the conditions of regular tire pressure, farm road, 400 kg loading and velocity at 8.5 km/h ran for 20 minutes. The following procedure was a 20-minute mountain road trip and a 4.5 hr-trip on high way. Finally, a 30-minute trip was on the urban road. The result of the injured carambola by transport vibration revealed that the rage of carbon dioxide was different between the sets of treatment and the check. It could be an index of injured carambola. It was almost impossible to measure the ethylene quantity of samples after the simulation vibration. Therefore, the measurement of ethylene may not be suitable for a prompt indication. The study could be a contribution of the investigation of the characteristic of vibration and the injury of fruits during transportation and can offer a way to reduce the damage and value loss of fruit. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/35889 |
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顯示於系所單位: | 生物機電工程學系 |
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