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Mass Harvesters :: Yield Monitoring

Annual Progress Report:


    Development of yield monitoring systems for citrus mechanical harvesters.

Current Work:

Compare three concepts for measuring mass/volume flow rate of citrus on the fruit delivery conveyor belt. These include (I) load cell-based mass flow sensing, (II) an image-based volume sensing yield monitor, and (III) an optical mass flow rate measuring yield monitoring system. These systems are being developed and studied to find the best yield monitoring system for canopy shake and catch harvesters. The details for these techniques are discussed below. In addition, dynamic accuracy of several commonly used GPS receivers was evaluated to understand their performance under grove conditions and to choose the right class of GPS receivers for the yield monitoring system.

(I) Load cell-based mass flow sensing for citrus mechanical harvester machines

A) Yield monitoring system for canopy shake and catch harvesters

Currently, there is no yield monitoring system commercially available for citrus mechanical harvesters. A test rig was built to evaluate the accuracy of the mass or volume sensing system of three yield monitoring concepts. This test rig allows a series of repeatable tests with different flow rates. The direct weighing system used in this study consisted of four load cells, a summing box, belt speed sensor, and a display unit. Farmscan’s canlink 3000 monitor system was modified and used for direct weighing of citrus mass flow over the fruit conveyor belt of an Oxbo canopy shake and catch mechanical harvesting system. The Farmscan system provides the yield rate, load area harvested (total and trip), speed, time, and GPS information. The load cells are hermetically sealed sheer beams, are suitable for outside mounting, and operate in wet and dusty conditions. The preliminary test showed encouraging results with as low as 2.2% error under test conditions.

Figure 1 | Figure 2

B) Yield monitoring system for citrus harvested by trunk shaking system

A low-cost yield monitoring system is being developed for the Coe-Collier trunk shaker. The Coe-Collier trunk shaker mechanical harvesting machine utilizes two self-propelled units on either side of the tree. One unit consists of a shaker and fruit deflector. After shaking, the fruit is deflected to the unit at the opposite side which receives the fruit and conveys it to a trailing cart with a wagon of rectangular base. This wagon holds approximately 75 boxes (6750 lb) of fruit. Four load cells were placed on the four corners under the wagon so the entire weight of the wagon is exerted on the load cells which will continuously record the total weight of the wagon and fruit. A GPS is connected to record the position of each shaken tree and movement of the harvester. The data acquisition system records the incremental weight of the wagon with fruit each second along with the GPS location information. Software is being developed to use this information and create a yield map. This yield monitoring system would not only provide information of the mass loaded into the goat cart but also provide fruit yield of the area and approximate individual tree yield. This information would also help the grower to reduce the overload fine in on-road transportation of fruit from the grove to the processing plants as well as under-utilization of the transportation truck.

Figure 3 | Figure 4

(II) Image-based volume sensing yield monitoring for continuous canopy shaker harvesting machines

The Image-based volume sensing yield monitor consists of hardware and software to record the count and measure the size of each citrus fruit that passes over the fruit conveyor belt. The hardware system consists of a color camera and four halogen lamps. A 3CCD progressive scan digital color camera (HV-F31, Hitachi Kokusai Electric Inc.) was used for the imaging system. Four halogen lamps (Master Line Plus 50W GU5.3 12V 38D, Phillips Electronics) are used for illumination with special filters to remove glare. A housing was built with a ¼-inch thick aluminum sheet to hold the lamps and the camera for image acquisition. The housing is used to keep the sunlight from going in the conveyor belt. Appropriate heights of the camera and lamps were determined such that high quality images could be acquired with uniform illumination. For optical, time-of-flight based counting/sizing arrangement for citrus fruits, we have developed a sensing arrangement consisting of a measurement frame with a halogen lighting unit and sensor arrays. Currently we are developing an algorithm to count and measure the size of citrus from their image taken by the camera as the fruit is passing over the conveyor belt.

Figure 5

(III) An optical mass flow rate measuring yield monitoring system

A mass flow sensing system is being developed to count the amount of fruit harvested by a continuous canopy shaker with catch frame. This is completed by counting the fruit in random confined flow using laser beams. The fruit can be counted by the interrupting laser beams. Figure 7 shows the laboratory testing of the system with tennis balls.

In this concept each fruit is considered as a particle that can be detected with very small laser beams because the particles are spherical. Overlapping fruits can be detected using timing information to distinguish between singles and doubles etc. Multiple laser beams are used for redundancy and lenses are used to deal with vibrating laser beams. The laboratory experiment with tennis balls showed encouraging results. The system needs to address the issues of vibration of the canopy shaker, mounting of the laser sensor, bouncing of the fruit and non-spherical shape of the fruit.

Figure 6 | Figure 7

GPS Dynamic Accuracy Test

The Global Positioning System (GPS) is one of the key technologies that have made precision agriculture possible. By using GPS you can proceed: yield mapping, parallel tracking, vehicle guidance, plant-specific application and variable-rate application. However, having several commercially available GPS systems with prices varying from $100 to $3,000, which one will be the best choice for owning, renting, or purchasing? This project tells the dynamic accuracy of different GPS systems.

Six GPS systems: Garmin GPS18 1Hz with Wide Area Augementation System (WAAS), Garmin GPS 18 5Hz with WAAS, Trimble AgGPS 132 with WAAS, Trimble AgGPS 132 with Beacon, Trimble 106 Atamans, and Trimble 106 with WAAS, will be compared in this project.

The preliminary result shows that Garmin 1Hz, Garmin 5Hz, Trimble 132 with WAAS, and Trimble 132 with Beacon work fine in each situation. Trimble 106 Atamans and Trimble 106 with WAAS easily lost signal in the citrus grove. Results also show:

  • Driving in east-west direction has better accuracy than in north-south direction.
  • Garmin 18 5Hz has better accuracy than Garmin 1Hz when mounted at a middle and high height.
  • Trimble 132 with Beacon signal has more accuracy than Trimble 132 with WAAS.
  • Mounting height affects the accuracy of the Garmin GPS receiver but does not affect the Trimble GPS receiver.

Figure 8 | Figure 9

For more information

Reza Ehsani

Visits since 05/21/2014