Progress 09/01/13 to 08/31/18
Outputs
Target Audience:The primary audience was Florida Citrus Industry growers and representatives who have interest in high density citrus production and harvesting. We also participated in Florida Horticultural Society meetings, field days and workshops were outcomes of this research were discussed. Changes/Problems:The status of the phase II prototype rebuid was not completed. We accomplished the results that we desired in testing,design and modeling analysis. However, the continued assault from Citrus Greening (HLB) has forced supplemental funding sources to shift resources toward disease and pest related projects. As a result, in our third and fourth year (with no-cost extension), we were forced to cut back on fabrication labor and design support. This resulted in delays in design and fabrication that eventually lead to significant cutbacks in development efforts. We continue to work toward completion, but without funds to do many functions in a timely manner. Consequently, it may still be another year or so before the 2nd prototype is completed, but weare committed to pressing forward. What opportunities for training and professional development has the project provided?During this project, pre-professional MS engineering graduates worked on significant aspects of the design, fabrication and testing. In addition, graduate students participated in design, analysis and testing. How have the results been disseminated to communities of interest?Yes, the outcomes of this work has been demonstrated to growers during field days and workshops. In addition, program outcomes have been presented and published in conference proceedings. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
In Phase I, our initial goals were to fabricate a self-propelled prototype of the proposed shaking mechanism. This system would then be tested under research field conditions to insure that the concept will effectively harvest fruit on Advanced Citrus Production Systems (ACPS) trees with in the space constraints. Our primary design requirements were the following; 1) Tree clearance of up to 10 ft tall by 8 feet wide, 2) Overall platform dimensions less than 10 ft wide by 12 ft tall in transport mode , 3) Adjustable wheel base/shaker base to accommodate trees as they mature from 3 years to fully mature dwarf trees, 4) Narrow between row clearance for high density, 5) Potential for adding automatic load leveling to accommodate grove field conditions, 6) Under belly clearance to accommodate a catch frame or other various implements. Our primary focus in 2014 was devoted to improving the harvesting mechanism performance and stability. We rebuilt the shaker systems drive shaft and crank throw mechanism to reduce excessive vibration and enhance performance at high shaker RPM. We also improved the shaker/tree interface by adding another layer of shaker fingers to each side. Effectively we doubled the shaker finger count and improved the shaker action in the center of the tree. Plus, we insured that the trees were hedged and skirted to favorable conditions for mechanical harvesting. We conducted field harvest trials on grapefruit at the high density citrus block at PSREU in January 2014, replicating the trials from May 2013, but with the new harvesting mechanism improvements. Statistically significant trials were conducted to examine the harvesting efficiency as a function of various harvesting machine parameters; such as, 1) ground speed, 2) shaker frequency, 3) wheel base setting, 4) beater penetration setting, and 5) beater finger length. It was found that the interactions were significant on harvesting efficiencies and we achieved harvesting rates of up to 94%, which was a significant improvement over 2013 trial results. We later conducted field trials at a commercial Valencia site of GFC in Indiantown, FL in May of 2014. In the first trial we obtained an approximate 70% removal. However, we conducted a second trial on Valencia/Flying dragon at the SWFREC in Immokalee later in May 2014, where we installed longer shaker rods on the interior shakers, resulting in a 97% harvesting efficiency. In 2015 and 2016, we conducted harvesting trials near Immokalee, FL at a Hickory Branch grove managed by CPI. These trees were oversized for the machine, unskirted, and located on difficult terrain for our phase I prototype. In an attempt to monitor tree stress, we decided to attempt harvesting under less than ideal conditions and experienced reduced harvesting efficiencies less than 70% in some cases. We also observed that the trees, which were HLB positive, demonstrated yield loss between year one and year two, although the trees response in sap flow recovered within a few weeks. It should be noted that the second trial each year was held in early May, and there was some fruit set loss. In the Phase I design, the harvesting head was statically positioned at a width using the wheel base adjustment cylinders. This means that the width has to be set at the largest tree requirement to minimize tree damage while sacrificing harvesting efficiency on the smaller trees. In 2014 we began working on the designs and eventually the fabrication of the Phase II prototype that would incorporate a number of enhancements to the harvesting system and the vehicle platform as a whole. The primary enhancements have been increased mobility, power and terrain capabilities provided by larger motors, individual leg leveling with automated control, wheel base adjustment, 4-wheel drive and steer, and the potential for adding a catch frame and material handling system to cross convey into trailing transport vehicles. In regard to the harvesting system, we had determined that the head should be modified to provide a means for moving the head in and out as the tree size varies. The basic design of the beaters and driveshaft will remain conceptually the same, while being mounted into a hydraulically actuated box frame design. We sought to create a sliding mechanism with the ability for the shaker system to move in and out to conform to the shape of the canopy. The linkage between the driveshaft and the beaters was modified to achieve a smoother acting and more robust functional design. Other aspects that were incorporated were increased maximum height for the beaters and a variable beater angle to adapt to the general curved shape of a tree canopy. The concept was modeled using a structural/mechanical design tool named SolidWorks 2013, while MSC Adams was used for dynamic analysis. In order to optimize the design, alternatives were tested to accommodate the maximum height of the beaters using the 'Flexible Multibody dynamics with FEA' approach in MSC Adams. This analysis was used to help size the shaker components. The next challenge that we faced was improving the drive shaft performance. There were resonant frequency in the original shaft around 300 to 325 RPM, which was really too close to our desired operarting frequency. Through the use of MSC ADAMS, we were able to redesign and strengthen the shaft to ultimately achieve a more stable design with less vibration. The design improvements were achieved through the use of strategically placed gussets and couterbalance weights. Strain energy plots were used to optimize the material selection and placement of counterweights. From these designs, we developed fabrication drawings and built the new shaking systems. The stability and performance of this design was then tested during 2016 using a laboratory test set up. The purpose for these trials were to insure that we didn't have any danerous resonate frequencies in the operating range and to insure that the shaker was delivering ample energy to the tree. This was accomplished by instrumenting the shaker and a mockup tree (structural members and spring damping cylinders to resist shaker motion) with accelerometers to measure the accelerations imparted to the tree by the shaker. To accomplish this accelerometers are mounted at strategic locations to monitor the applied forces. In addition, we have also been working on sensors that will be mounted on the front of the harvester to profile the citrus canopy. This data can be geo-referenced to provide growers with historical data on tree canopy volume and tree size, but also will be used for controlling the automated harvesting head in real time, which will follow the canopy profile to insure that optimal pressure is applied to the tree canopy to maximize the harvesting efficiency while minimizing tree damage. We have run test comparison between LEDDAR (an LED based radar) and ultrasonics to see which systems provide more robust canopy measurements. Laboratory tests were conducted to establish feasibility and develop sensor integration, while the field tests validated performance. These tests demonstrated that both sensors can do the head control job with different pros and cons. The LEDDAR is more precise and gives a better visualization of the canopy profile, while the Ultrasonic device is more cost effective and does an adequate job for simple head control. In 2017 and 2018, we completed fabrication of the new harvesting mechanism which was mounted on the new over the top platform. The completion of the second prototype continues even now, as the systems hydraulics and controls are designed and implemented on the machine platform. Once all fabrication and assembly tasks are completed, the new prototype will be tested in field conditions.
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2015
Citation:
Burks, T.F., K. Morgan, F.M. Roka. 2015. Evaluation of Impacts of Mechanically Harvesting High-density Semi-dwarf Citrus on Tree Health and Yield, Florida State Horticultural Society Annual Meeting. Paper No. C-01.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2014
Citation:
Burks, T.F., N. Aldisory, W.S. Castle, F.M. Roka. 2014. Development of Harvesting Equipment for Higher Density Citrus Grove Architectures, Florida State Horticultural Society Annual Meeting. Paper No. C-16.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2013
Citation:
Burks, T.F., N. Aldisory, W.S. Castle, F.M. Roka. 2013. Future Prospects of Advanced Citrus Production and Harvesting Equipment for High Density Grove Architectures, Florida State Horticultural Society Annual Meeting. Paper No. C-9.
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Progress 09/01/13 to 08/31/14
Outputs
Target Audience:In 2016, we continued to run field trials with our prototype harvester, and were active with growers to demonstrate potential. This year we have continued to reach out to growers to talk about our program through an extension activity held at Florida's Natural Grove House in Lake Wales, FL. Approximately, 20 growers attended the event, and were introduced to our system development efforts. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Two graduate students (1 MS and 1 PhD) have been working through UF on aspects of this development project. How have the results been disseminated to communities of interest?This year we have continued to reach out to growers to talk about our program through an extension activity held at Florida's Natural Grove House in Lake Wales, FL. Approximately, 20 growers attended the event, and were introduced to our system development efforts. What do you plan to do during the next reporting period to accomplish the goals?We will continue to work on individual job tasks necessary to complete the overall objectives, and finish the second prototype harvesting machine. We will then conduct field trials to varify performance and then conduct product introduction demonstrations to growers to inform them of the new equipment capabilities.
Impacts
What was accomplished under these goals?
There were two primary areas of focus during this reporting period. 1) Enhancement and completion of the second prototype chassis, power plant and hydraulics. Significant progress has been made in both of these areas such that the physical chassis, drive legs with steering, and harvesting heads are nearly all completed. 2) We have been working on implementing the controls concepts for the dynamic harvesting head control, which included the harvesting mechanisms, their actuators and the feedback sensing system that will profile the tree canopy and provide insight into the tree configuration so that harvesting performance can be achieved. In both of these topic ares we have made significant progress, but there is more work to do.
Publications
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