Location: Quality and Safety Assessment Research Unit
2018 Annual Report
Objectives
1. Enable new commercial sensor-in-system flowing-grain microwave moisture and density meters for precision farming and yield monitoring.
2. Enable a portable, commercial microwave meter to create capacity for rapid grading in-shell almond and peanut by determining moisture content, meat content, and foreign material contents.
3. Enable new commercial microwave sensors for monitoring controlled drying of grain, peanuts and other seeds.
Approach
I: To enable a new commercial sensor for flowing grain microwave moisture and density, dielectric-based algorithms for bulk density and moisture content determination at microwave frequencies will be tested in flowing situations. In designing a flowing-grain system, the frequency must be higher than 3 GHz, free-space transmission techniques will be used for on-line applications, and measurements will be performed in the near field to keep the system compact. At least three cultivars each of wheat, corn, and soybeans will be obtained from certified seed with some geographic and seasonal diversity. Moisture, density, and temperature will be varied for model development and then validated on flowing grain. Next, a prototype sensor made with off-the-shelf components will be assembled and tested. Then a user-friendly, step-by-step software programs will be developed to control the measurements with moisture predictions within 0.2% to 0.5%, and bulk density will be within less than 2% relative error.
II: The above system will next be developed for rapid grading of in-shell almond and peanut by determining moisture content, meat content, and foreign material contents. First dielectric properties data will be collected with laboratory grade instrumentation on un-cleaned and cleaned in-shell almonds and peanuts of different varieties and from different locations and compared to oven-drying moisture and meat content. Measurements will also be collected on almond and peanut kernels alone. The data will comprise of dielectric properties corresponding to frequency, temperature, moisture content, bulk density, meat content, and foreign material content. The next step is to develop a microwave prototype for moisture content, meat content, and foreign material content in in-shell almonds and peanuts which will be externally controlled with a laptop computer and ultimately packaged to satisfy grading requirements and withstand working conditions at buying stations.
III: The last approach is to use the microwave moisture sensors developed above to monitor and record moisture content of grain, peanuts and other seeds in real-time during drying while improving efficiency through control of drying and minimizing energy consumption when compared to existing drying controls. To accomplish this, a microwave moisture meter will be combined with three temperature sensors and a relative humidity sensor to monitor peanut drying in a quarter scale-model drying wagon to optimize the drying process by determining real time in-shell kernel moisture content in different zones of the trailer. Similar work will be performed with cereal grains and oilseeds stored and dried in large, farm storage bins. Varying temperature and moisture profiles will be evaluated during the drying process. Through feedback control, the system will optimize the drying process to better ensure even drying throughout the trailer (for peanuts) and bin (for grains). Once successful, the microwave moisture meter(s) will then be integrated with all other sensors in one single unit including a microcontroller, an LCD, and mass storage device.
Progress Report
This is the final report for this project as it has been terminated and merged with project 6040-44140-002-00D, "Assessment and Improvement of Poultry Meat, Egg, and Feed Quality."
In many situations, moisture content and bulk density sensing of grain and seed are needed while they are flowing such as on combine during harvest or during postharvest processing operations. Both moisture content and bulk density can be used for yield monitoring, determine grain and seed quality, and conditions for safe storage. Microwave sensors can be used for real-time determination of moisture content and bulk density from measurement of the dielectric properties at a single microwave frequency. Free-space type microwave sensors have the advantages of being nondestructive, do not require physical contact with the material, and can be mounted without disturbing any given process. Declining microwave components prices have also made them inexpensive compared to other indirect methods. For optimum use of this technology, effect of several parameters including frequency, distance between the antennas and the sample, and sample thickness were investigated numerically through microwave modeling simulations and experimentally by using a vector network analyzer for measurements on different varieties of wheat, corn, and soybeans over a broad range of microwave frequencies between 2 GHz and 18 GHz. Results of these investigations indicated that accurate measurements of the dielectric properties can be achieved at a single frequency (above 3 GHz to avoid effect of ionic conduction) and in the near field with the sample placed at one wavelength of the transmitting and receiving antennas for samples with a thickness allowing a minimum attenuation of 8 decibels. Because the cost and availability of microwave components at 5.8 GHz (developed for telecommunications), this frequency was selected for the development of a low-cost microwave sensing system for flowing material. To simulate dynamic situations in the laboratory, a flowing system was designed, assembled and tested for wheat, corn and soybeans. It consisted of a conical stainless-steel hopper that was connected to a rectangular cross-section polycarbonate chute through a PVC pipe. At the bottom of the polycarbonate chute, was a rectangular-to-circular stainless steel transition to an iris diaphragm-type valve that could be manually adjusted to provide different flow rates. Two patch antennas operating at 5.8 GHz were placed on opposite sides of the polycarbonate chute at one wavelength (5.17 cm) from the chute. The antennas were connected to a Hewlett-Packard 8510C vector network analyzer. Samples of different varieties of wheat, corn, and soybeans were conditioned to moisture ranges of practical interest. The calibration of the system was performed with static samples for temperatures ranging from 0 to 50 degree Celsius and bulk densities ranging from loosely packed to compacted. The calibration coefficients were then used to predict moisture content and bulk density of flowing samples of wheat, corn and soybeans with flowing rates ranging from 74 grams per second to 2928 grams per second. The highest flowing rate was obtained when the iris diaphragm-type valve was opened to its maximum diameter. Several density-independent algorithms for moisture determination were used. The standard errors of performance on flowing wheat, corn, and seed samples were between 0.29% and 0.94%, wet basis with the oven moisture taken as a reference. The bulk density was predicted with a standard error of performance of less than 0.05 grams per cubic centimeter. These values are comparable to those obtained for measurement on static samples. To further demonstrate the feasibility of the measurements with a low-cost system, the vector network analyzer was replaced with a microwave circuit made with off-the-shelf components. Initial results indicate that a level of accuracy comparable to that obtained with expensive vector network analyzer can be achieved.
Grading of peanuts and almonds is tedious, time consuming, and prone to human errors. Developing a low-cost portable microwave meter for peanuts and almonds would provide a means for rapid assessment of several quality-related parameters for their grading. A novel portable microwave meter operating at a single microwave frequency of 10 GHz was assembled, tested, and calibrated for use on both uncleaned and cleaned unshelled peanuts and almonds. The meter consists of a microwave circuit, made with off-the-shelf components, for attenuation and phase measurement which are used for the computation of the dielectric properties. These properties are then used to determine the quality parameters of interest. The microwave circuit is connected through a switch to two separate arrays of microstrip antennas. One array of antennas was used for measurement on cleaned unshelled peanuts/almonds. From these measurements on a given sample, the unshelled peanut/almond moisture content and kernel moisture content are determined. The second array of antennas is used for measurement on uncleaned unshelled peanuts/almonds. The measurements provide the bulk density and moisture content of the unshelled peanuts/almonds-foreign materials mixture. The measurements were automated (laptop controlled) and the data were store for each sample. A novel algorithm was developed for instantaneous determination of moisture content (in-shell and kernels), bulk density and foreign material content from a single microwave measurement on uncleaned unshelled peanuts/almonds. Knowledge of moisture content and foreign materials content at the front end will provide a means for decision making concerning completing the whole grading process or sending the peanut trailer for further cleaning and/or drying. Therefore, the proposed meter will simplify the current grading process and will result in significant time and energy savings.
Peanut and grain and seed drying are large-scale operations involving considerable amounts of energy and are often subject to human interaction for monitoring and controlling the drying process. Microwave sensing technology was used to monitor the drying process with the objectives of obtaining real-time information to optimize the energy consumption and to minimize human interaction. A microwave moisture sensor was integrated with multiple humidity and temperature sensors to effectively monitor the drying parameters as grain, seed, and peanuts were dried in a quarter-scale peanut drying system and eighth-scale grain bin drying system. For the peanut drying system, two relative humidity sensors were used to monitor humidity of the air blown into the peanuts and the exhaust air from the peanuts. Three temperature sensors were used to monitor the temperature of the air blown in the peanuts, the exhaust air, and peanut bed temperature. For the grain and seed drying system, four relative humidity sensors were used to monitor humidity of the air blown into the grain/seed, exhaust air, and within the grain/seed bed. A total of eight temperature sensors were used to monitor the temperature of the air blown into the grain/seed, exhaust air, and within the bed of grain/seed at different heights. User-friendly software, to control and monitor both drying systems, was developed to run the measurements. The drying parameters were measured every 12 seconds. Field testing of a unit integrating the microwave moisture meter and humidity and temperature sensors for monitoring peanut drying revealed that under certain ambient temperature and humidity conditions moisture actually increased during drying which provides the operator with crucial information to shut off the drier resulting in significant energy savings.
Accomplishments
1. Automated system for controlling and monitoring the drying process of peanuts, grains and seeds. ARS researchers at Athens, Georgia integrated a microwave moisture meter with multiple relative humidity and temperature sensors for real-time monitoring and control of the drying process of peanuts, grains, and seeds. Also, user-friendly software was developed to run the measurements and collect and store the data for further analysis. The low-cost system will be instrumental in optimizing the drying process, improving quality, and minimizing cost by avoiding non-beneficial drying.
Review Publications
Julrat, S., Trabelsi, S., Nelson, S.O. 2018. Open-ended half-mode substrate integrated waveguide sensor with ground flange for complex permittivity measurement. IEEE Sensors Journal. doi:10.1109/JSEN.2018.2801316.
Ellison, C., Mckeown, M.S., Trabelsi, S., Marculescu, C., Boldor, D. 2018. Dielectric characterization of Bentonite clay at various moisture contents and with mixtures of biomass in the microwave spectrum. Journal of Microwave Power and Electromagnetic Energy. doi:10.1080/08327823.2017.1421407.
Trabelsi, S. 2017. New calibration algorithms for dielectric-based microwave moisture sensors. IEEE Sensors Letters. 1(6):1-4.
Trabelsi, S. 2018. Measuring changes of radio-frequency dielectric properties of chicken meat during storage. Journal of Food Measurement and Characterization. 12(2):683-690.
Lewis, M.A., Trabelsi, S., Nelson, S.O. 2018. Estimating costs of nonbeneficial dryer operation by using a peanut drying monitoring system. Applied Engineering in Agriculture. 34(3):491-496.
