Shaker Head Research Articles

Estimation of proper shaking parameters for pistachio trees based on their trunk size

Trunk shaking is the most common mechanical harvesting system for harvesting pistachio. Harvesting machine operators often subjectively decide how to set the shaking parameters such as frequency and duration and this requires experience. The main objectives of this study were to evaluate the effect of tree morphology and shaking parameters such as trunk size and shaking pattern on the energy distribution through the branches and to optimise the shaking intensity of individual pistachio trees based on a tree-specific feedback loop. Wireless 3D accelerometer sensors were built and used to measure vibration transmission through the tree canopy at different locations and to monitor the energy transmission between the machine shaker head and the tree trunk. Thirty trees were selected for this study and were divided into three groups based on the trunk circumference size. To study the effect of a shaking pattern on the vibration transmission through the tree, four shaking patterns were selected and tested. Shaking duration was measured and it showed an average of 30% longer time compared to the shaking pattern duration. The effect of all four shaking patterns was analysed using continuous wavelet transform. The responses of trees were analysed and the optimum shaking intensity for each tree was determined. A model was developed to estimate the optimum shaking intensity for pistachio trees based on their trunk size. The model showed that 37, 57, and 65% are the optimum shaking intensity percentages for small, medium, and large trees, respectively. • Mechanical harvesting systems for pistachio trees were studied. • Vibration transmission through the pistachio tree canopy was measured and analysed. • Wavelet analysis was used to find proper shaking intensity for each tree. • A model for optimum shaking intensity based on trunk size was developed.

An Experimental Study and Mathematical Modeling of Vibration Transfer in Pistachio Trees Using an Inertia-Type Trunk Shaker and Field-Adapted Wireless Sensors

Trunk shakers are the most widely used mechanical harvesting machines for harvesting nut trees, including pistachio in California. Improvement of these machines requires a better understanding of the shaking dynamics of the existing trunk shakers during harvest. In this study, the effects of four different shaking patterns on three sizes of pistachio trees of different ages, shapes, and sizes were investigated under field conditions. The vibration acceleration of the real pistachio tree was measured using a wireless network of 3-axis accelerometers installed on the shaker head and different parts of the trees during the shaking harvest. Changes in acceleration and the effect of tree morphology on the magnitude of acceleration in each pattern are presented and discussed. A new location index λ, which is based on the distance of the sensor from the shaking point and diameter of the branch at each sensor location, is introduced. This study focused on mathematical modeling of the variation and distribution of the acceleration throughout the tree canopy. The sensor location index, relative force ratio (RFR), and relative kinetic energy ratio (RKER) were defined to better understand the energy damping in each part of the tree. The results showed that the relationship between the acceleration peaks and the sensor location index could be expressed by a third-degree polynomial function with an acceptable coefficient of determination. Under different shaking patterns, similar changes in the RFR of the tree at different locations and for different trees were observed. This finding indicates that the vibration force is significantly damped as the distance from the shaker clamps increases. However, the RKER values at the same shaking pattern result in different effects at different points on the branches according to tree morphology.

Field Evaluation of Targeted Shake-and-Catch Harvesting Technologies for Fresh Market Apple

HighlightsThree shaking methods and vibratory harvesting systems were evaluated and compared.Multi-year field evaluations were performed with up to six cultivars trained to formal architectures.The updated semi-automated system achieved the highest fruit removal efficiency and the best fruit quality.Abstract. Apple is the most economically important agricultural crop in Washington State. In 2018, Washington State produced ~3.3 billion kg of apple, accounting for approximately 63% of U.S. production. Fresh-market apple is currently harvested manually, requiring large numbers seasonal semi-skilled workers for a small harvest window. To overcome the increasing challenges of uncertain labor availability and raising labor costs, a promising mechanical harvesting system, using a targeted shake-and-catch approach, is under development at Washington State University. This study evaluated the system by analyzing its fruit harvest efficiency and fruit quality with three shaking methods, i.e., continuous non-linear, continuous linear, and intermittent linear shaking, on up to six apple cultivars trained to formal tree architectures. Results showed that intermittent linear shaking achieved 90% fruit removal efficiency for ‘Scifresh’ cultivar, while continuous linear shaking achieved only 63% removal efficiency for ‘Gala’. This study also compared three vibratory systems: a hand-held system, a hydraulically driven system, and a semi-automated hydraulic system. The semi-automated system achieved the highest fruit removal efficiency (90%), followed by the hand-held (87%) and hydraulic (84%) systems, mainly due to the different shaking methods employed. However, the differences were statistically insignificant. Fruit catching efficiency varied among the harvesting systems, with the hand-held system achieving the highest efficiency (97%), followed by the hydraulic (91%) and semi-automated (88%) systems. Among the three tested technologies, the prototype semi-automated system achieved the highest level of mechanization, as well as high fruit removal efficiency and the best fruit quality. Because the semi-automated system did not include an auto-positioning function, positioning its shaker head took about eight times longer (~103 s) than the actual shaking time (~13 s), which suggests that a fully automated system is desirable to further increase productivity. This study showed that the shake-and-catch approach has great potential for practical adoption in harvesting of fresh-market apple and therefore can have a positive economic impact on the U.S. apple industry. Keywords: Automation in apple production, Bulk mechanical harvest, Semi-automated system, Shaking method, Time efficiency.

Development of the method of the large scale spacecraft dynamic environment test

Spacecraft must undergo such phase as lift-off, inter-stage separation, fairing jettisoning and spacecraft/launch vehicle separation during the launch. And the dynamic environments of these phases can be divided into vibration, acoustics, shock, etc. To assure its reliability in launch and in-orbit phases, many ground dynamic tests must be carried out in the process of development of the spacecraft, such as vibration test, acoustic test, shock test and so on. In the past few decades, with the successful launch of many spacecrafts and satellites, China has accumulated a lot of test experience and established an effective dynamic environment test specification and standard. But, the dimension and the mass of the Chinese space station have greatly increased compared to the previous satellites. The customary test methods and test facilities cannot satisfy the requirements of the ground dynamic test verification of the large scale spacecraft. For example, the force of vibration table required for vibration test is estimated to far more than the capacity of the largest single electrodynamic vibration shaker. So how to carry out the ground dynamic test for these large scale spacecrafts and ensure their validity is the key technical problem should be solved. This paper mainly introduces the development of the dynamic test verification technology of large scale spacecraft such as “Tianzhou” cargo spacecraft and space station. Firstly, the methods of the vibration test and the acoustic test are presented. Secondly, the static load compensation technology in vibration test, the method of the section test, and the extrapolation technique based on the test data are discussed detailedly, and their merit and shortcoming are summarized respectively. Moreover, the technical difficulties research in the large scale vibration shaker and the reverberation chamber are analyzed, especially in the shaker head expander table and the slip table. The development of VTS-1400 vibration test system and RATF-4000 reverberation chamber at Tianjing AIT Test Center are presented in following. Finally, the prospect of the development of the large scale spacecraft dynamic environment test is proposed.

An automatic trunk-detection system for intensive olive harvesting with trunk shaker

Trunk shakers are widely used for olive harvesting, being the main detachment system for fruit harvesting. In recent decades, the components of trunk shakers have evolved at mechanical, hydraulic and control levels. However, machine accuracy depends on the operator, whose expertise is a key factor for issues such as trunk debarking caused by grabbing systems, shaking parameters, or on-foot operator safety. The objective of this work was to develop an automatic trunk-detection system to reduce operator influence on the process. Thus, the automatic system via infrared sensor was implemented on a trunk shaker head hitched to a tractor. A control algorithm, control logic and display for trunk grabbing automation were developed. The automatic system was tested under laboratory and field conditions to assess the influence of some variables on trunk detection. The evaluated variables were colour, material, diameter, and target location within the sensor field of vision. The success rate of the automatic system was 91% for trunk grabbing. In the field phase, the efficacy of the automatic system was compared to an operator performing the tasks manually, obtaining times of 16.05 ± 2.8 s tree−1 and 21.54 ± 5.29 s tree−1 respectively, and a percentage of success in trunk grabbing of 92.9%. Automatic mode improved manual mode by saving 27.3% of time, improving effective field capacity. The automatic mode developed here provided a high ratio of success and it showed highly reliable and efficient performance compared with manual mode.

Assessment of aerial and underground vibration transmission in mechanically trunk shaken olive trees

The present study analyses the transmission of vibrations generated from a multidirectional trunk shaker to olive tree structure considering both the aerial zone (trunk and branches) and the underground zone (the coarse root). The vibration characterization was conducted by measuring acceleration on several points of the tree during harvesting operations. The influence of two different heights of shaker head clamping was analysed. In addition, a dynamic probing was performed in order to evaluate soil compaction. The results showed that the vibration performed by the trunk shaker head, corresponding to an acceleration resultant of approximately 77 ms–2 with a dominant vibration frequency of 18 Hz, increased up to 106% in branches and decreased up to 90% in trunks. At root level, where the analysis was carried out at 1/3 and 2/3 of the coarse root length, the acceleration values diminished significantly to 17 ms–2 and 12 ms–2, respectively. Soil dynamic resistance was lower (36 kg cm–2) near the trees than between the trees (53 kg cm–2). The vibration transmission to the aerial and the underground parts diversely influences the dynamic behaviour of the olive tree, considering an operational frequency of a commercial trunk shaker. The assessment of vibration transmission to the aerial part could contribute to improve fruit detachment and reduce branch breaking and leaf detachment. While vibration transmission to the underground part rises new challenges considering soil compaction in olive groves.

A new shaker head design for reducing bark injuries on fruit trees

A new shaker head design for reducing bark injuries on fruit trees

Optimal design of head expander for a lightweight and high frequency vibration shaker

Vibration testing requires the head expander to interface with both the test component and vibration shaker. At times, head expanders have resonant frequencies over the frequency range of interest. The moving mass will also have an influence on the shakers thrust ability during vibration testing. In order to ensure a successful vibration test, it is necessary to observe the resonant frequency and mass of the head expander. The aim of this study is to optimize the shape and size of the head expander with a lightweight and an improved resonant frequency. This was achieved using a FE modal analysis and design of experiments (DOE). Firstly, the vibration characteristics, such as the resonant frequencies and mode shapes of the baseline model were estimated using a FE modal analysis. In order to validate the FE modal analysis, a modal test was performed and the test results were then compared with those from the FE analysis. Secondly, three shapes of head expander were suggested to select the geometry with the best vibration characteristics, and the design variables of the head expander were defined. The vibration characteristics of the three geometries and their design variables were assessed in terms of their weights and resonant frequencies. Finally, optimization process was performed to find a minimum mass within the target frequency and diameter of platform plate. The coefficients from the regression equation for the objective function were calculated to provide optimized data for the vibration shaker head expander.

Coupled moment analysis of stacked counter-rotating eccentric-mass tree shaker energy-wheel system

This paper expands the historical “Planar model” equation for inertial tree shakers using stacked counter-rotating eccentric-mass energy-wheels and accounts for coupled moments using a “Planar Force and Moment Model”. The energy-wheel configuration utilised by many tree shakers creates planar forces and coupled moment maxima and minima. When the centrifugal acceleration force vectors of each energy-wheel are aligned, this creates a force maximum, acting radially about the tree. The stacked energy-wheels assembly produces a coupled moment due to the centrifugal acceleration force vectors acting on a lever arm. The lever arm vectors extend from a coordinate system coincident with the shaft centre line, and between the upper and lower energy-wheels centre of gravity. A coupled moment maximum occurs when the energy-wheel force vectors are opposing, the planar force is a minimum. The shaker head will roll, pitch, and yaw about the tree trunk due to the instantaneous coupled moment. The rotational and non-normal planar forces are more likely to cause tree trunk bark injury. Subsystems, such as lubricated pads and slings, are required to mitigate transmission of damaging forces. The Planar Force and Coupled Moment Model identifies the force causing vertical tree displacement. Though the Planar model shows that the timing of the energy-wheels produces the observed bi-directional pattern of force maxima, addition of the Coupled Moment shows that timing cannot eliminate non-normal forces. The new model provides a more complete representation of forces applied to the tree and could be used to optimise design for reduced tree damage.

Application of the Abscission Agent 5-Chloro-3-methyl-4-nitro-1H-pyrazole Does Not Affect Peel Integrity or Postharvest Decay of Mechanically Harvested Late-season Fruit of ‘Valencia’ Orange during the Normal Commercial Harvest-to-processing Period

In Florida, the combined use of mechanical harvesters and the abscission agent 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) for late-season harvesting (May to June) of fruit of ‘Valencia’ orange is effective at removing mature fruit with minimal adverse effects on the subsequent season's crop. However, CMNP can cause fruit peel scarring, and no data were available on how this affects peel integrity and potential losses resulting from fruit crushing and/or decay before processing. In this study, two late-season harvest dates were tested in commercial orchards during 2009 and 2010. Harvesting treatments consisted of combinations of two mechanical harvester ground speeds (0.8 and 1.6 km·h−1), two harvester shaker head frequencies (185 and 220 cycles/min), and CMNP foliar applications (4 days before harvesting) at 250 and 300 mg·L−1 in a spray volume of 2810 L·ha−1 plus mechanically-harvested and hand-picked controls. After harvesting, fruit samples were randomly collected from each block for peel resistance and postharvest decay evaluations. Peel resistance was determined by measuring both peel puncture force and fruit crush force. Fruit used to study postharvest decay were stored at 27 °C and 50% relative humidity or ambient conditions and evaluated daily for 8 days. Peel resistance was unaffected by mechanical harvesting combinations or CMNP application. No significant effects on postharvest decay were found among treatments for at least 3 days after harvest. However, a significant increase in postharvest decay between CMNP-treated and untreated fruit began between 4 and 6 days after harvest such that by 8 days after harvest, decay was as high as 25% in CMNP-treated fruit. The results indicate that CMNP can be safely used in combination with late-season mechanical harvesting under the conditions described in this study without losses resulting from fruit crushing or decay for at least 3 days, a time period well within the normal commercial harvest-to-processing time of ≈36 h.

Late-season `Valencia' Orange Mechanical Harvesting with an Abscission Agent and Low-frequency Harvesting

An abscission agent (5-chloro-3-methyl-4-nitro-1H-pyrazole [CMNP]) at 300 mg·L–1 in a volume of 2810 L·ha–1 was applied to Valencia orange trees [Citrus sinensis (L.) Osb.] on 22 May 2004. At this time, immature and mature fruit were present on the tree simultaneously. Three days after application, fruit were mechanically harvested using a trunk-shake-and-catch system. The power to the shaker head was operated at full- or half-throttle (FT or HT, respectively), and the duration of trunk shaking was 2 seconds at FT or 4 seconds at FT and HT. Mature fruit removal percentage and number of immature fruit removed, and fruitlet weight and diameter were determined. Mature fruit removal percentage with 2 seconds at FT or 4 seconds at FT harvesting ±CMNP, or 4 seconds at HT + CMNP was not significantly different and ranged between 89% to 97%. Harvesting at 4 seconds HT without CMNP removed significantly less mature fruit than any treatment. CMNP did not affect immature fruit removal by the trunk shaker. Harvesting at 4 seconds at HT removed significantly less immature fruit than 2 seconds at FT or 4 seconds at FT. No significant difference in fruitlet weight or diameter was measured between any trunk shaker harvest operation and CMNP treatment. Trunk shaking frequency was estimated to be 4.8 and 8.0 Hz at HT and FT, respectively. Yield in 2005 was determined on the same trees used for harvest treatments in 2004. CMNP did not impact yield. No significant difference in yield was seen between the hand-picked control and 4 seconds at HT, whereas yield in the remaining treatments was lower. The results demonstrate that CMNP application combined with low frequency trunk shaker harvesting can achieve high percentage of mature fruit removal with no significant impact on return yield of the following crop.

Development of a Commercial Fruit Firmness Sorter

Sorting of fruits and vegetables by firmness and maturity is essential for marketing uniform high quality produce. In the US and in Europe, supermarkets increasingly demand high quality and uniform produce. Although machines for sorting fruits by size and external appearance are commercially available, a machine for sorting fruits by firmness and maturity does not exist.This paper describes the development of a firmness sorting machine which was successfully tested in a commercial packinghouse. The machine comprises a unique conveying system which allows physical contact of the inspected items by a sensor finger ‘on-the-go’, thereby enabling sorting fruits into ‘firm’ - ‘soft’ grades at 2·5 to 7·5 fruits/s per lane, without any damage to the fruit. The firmness sensors of the machine comprise a small electrodynamic shaker, for vibrationally exciting the bottom part of the inspected fruit. The root mean square (r.m.s.) level of the fruit-type-specific input signalXiis measured in the shaker head. The r.m.s. level of the output signalXois measured by a miniature accelerometer attached to the sensor finger contacting the top part of the fruit. A firmness indexPFT(Peleg firmness test) is defined as:PFT=Xo/(Xo−Xi). Relatively firmer fruits pass a larger portion of the input vibration signal than softer fruits because the latter attenuate the input vibration energy more. Thus, largerPFTvalues indicate firmer fruits. Examples of firmness sorting of apples, nectarines and kiwifruit are presented.

Vibration test bearing table apparatus affording a single degree of freedom test piece path

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