Performance Evaluation of Hand-Held Olive Harvesters
Keywords:Olive, Harvester, Natural Frequency, Shaking Stroke, overall evaluation criterion
The aim of this research was to evaluate three types of commonly used hand-held olive harvesters in small olive farms (pulsed motion double head olive harvester, hook type hand-held olive harvester and pneumatic comb olive harvester) in the Kingdom of Saudi Arabia. The specific objectives were to (a) determine the values of some olive plant parameters including physical-mechanical properties of fruit-stem system, natural frequency of the olive fruit-stem system and suitable shaking stroke), (b) establish and determine the values of the evaluation criteria which included machine productivity, fruit removal percentage, fruit damage, specific consumed energy and olive harvesting cost, (c) determine the quality characteristic for each criterion, (d) assign the evaluating criteria their relative weights, (e ) perform field experiments to assess the performance of the three harvesters and (f) calculate the value of overall evaluation criterion. The study was carried out during the period of 2017-2018. The average values of natural frequency were 30.1, 28.1 and 24.0 Hz for full mature stage, half-ripe and full-ripe fruits, respectively. The estimated values of damping ratio were 0.103, 0.103 and 0.106 for full mature stage, half-ripe and full-ripe fruits respectively. The estimated shaking stroke was about 70 mm. The highest values of machine productivity (88.4 kg.h-1) and fruit removal percentage (98.0%) were found with the pulsed motion double head olive harvester at the speed of 1500 rpm while the lowest value of machine productivity (55.6 kg.h-1) and fruit removal percentage (62.4%) were found with the hook type olive harvester at the 24 Hz frequency and 70 mm stroke. The highest fruit damage (5.5-6.6) was observed with the pulse motion double head harvester while the lowest fruit damage (2.0-2.5%) was observed with the hook type harvester. The specific consumed energy values ranged from 17.0 to 27.0 W.h.kg-1. The total harvesting costs were 3.62, 3.65 and 3.69 $.h-1 for the pulse motion double head harvester, the hook type harvester and the pneumatic comb harvester, respectively. The results showed that the highest value of overall evaluation criterion (OEC) was 84.9 for the pulsed motion double head olive harvester at speed of 1500 rpm). Also, the values of OEC of the pulsed motion double head olive harvester for the other two speeds (1100 and 1300 rpm) outperformed the other harvesters (at all treatments). The higher OEC of the pulse motion double head olive harvester was due to the low operating costs and increased fruit removal percentage. Based on OEC, the pulsed motion double head olive harvester came first (OEC in the range of 70.2.5-84.9 %), followed by the pneumatic comb olive harvester (OEC in the range of 42.8-70.2 %) and the hook type olive harvester olive harvesters (OEC in the range of 13.9-54.3%).