Design and control of precision drop-on-demand herbicide application in agricultural robotics

Drop-on-demand weed control is a field of research within Precision Agriculture, where the herbicide application is controlled down to individual droplets. This paper focuses on the fluid dynamics and electronics design of the droplet dispensing. The droplets are formed through an array of nozzles, controlled by two-way solenoid valves. A much used control circuit for opening and closing a solenoid valve is a spike and hold circuit, where the solenoid current finally is discharged over a Schottky diode on closing. This paper presents a PWM design, where the discharge is done by reversing the polarity of the voltage. This demands an accurate timing of the reverse spike not to recharge and reopen the valve. The PWM design gives flexibility in choosing the spike and hold voltage arbitrarily, and may use fewer components. Calculations combined with laboratory experiments verify this valve control strategy. In early flight the stability of the tail, or filament, is described in theory by the Ohnesorge number. In later flight, when a droplet shape has formed, the droplet stability is governed by the Weber number. These two considerations have opposite implications on the desired surface tension of the fluid. The Weber number is more important for longer distances, as the filament satelites normally catch up and join the main droplet in flight

Leaf-specific weed control for vegetable crops in the UK

Weed control in field vegetables in the UK is becoming increasingly challenging due to the loss of herbicide actives and demands by policy makers and consumers for lower pesticide use. Research at University of Reading in conjunction with Concurrent Solutions LLC in the USA, is developing a robotic weeder for field vegetables using image analysis to locate weed leaves and a novel Drop-on-Demand (DoD) applicator to apply droplets of herbicides to these leaves. No chemical is applied to the crop and none directly to the soil. Leaf-specific application of herbicide droplets is an alternative to selective chemistry or biotechnology while potentially reducing herbicide use. Although targeted micro-rates of herbicides have been studied, little is known about the exact rates needed to control weeds when microdoses are applied as one droplet to a single leaf or plant. In glasshouse trials, individual weed seedlings were controlled by applying a single droplet of herbicide and dose-response relationships were quantified. As a general recommendation, weeds that are up to the 4-leaf stage can be controlled with a dose of 32 μg of glyphosate and 28 μg of glufosinate-ammonium when they are applied as a single droplet per seedling. In order to answer the question if the efficacy is reproducible in the field, manually applied droplets of glyphosate and glufosinateammonium were made to the naturally occurring weed population in transplanted cabbage and leek crop. Droplet applications made on three and ten occasions after transplanting the cabbages and leeks, respectively reduced residual weed biomass at harvest by over 90% compared to the weedy control. Also, droplet treatments gave a crop yield, which did not differ significantly from the weed-free control. At the same time, the total amount of herbicide active ingredient applied was up to 82% and 94% lower than currents spraying methods for the leeks and cabbages, respectively. Because of the high value of the crop and the higher yields associated with ultraprecise droplet application, it would appear to be economical to apply these droplets using a robotic weeder. The applicator which was developed by Concurrent Solutions LLC in the USA for Drop-on-Demand droplet applications was tested under indoor conditions. The effect of pressure, distance from the target, wind direction and motion of the applicator was tested on the targeting accuracy of the applicator. Recommendations for future field applications suggested that the applicator should operate at 138 kPa pressure and set at 15 cm height from weeds

Design and control of precision drop-on-demand herbicide application in agricultural robotics

This is the author’s final, accepted and refereed manuscript to the article.Drop-on-demand weed control is a field of research within Precision Agriculture, where the herbicide application is controlled down to individual droplets. This paper focuses on the fluid dynamics and electronics design of the droplet dispensing. The droplets are formed through an array of nozzles, controlled by two-way solenoid valves. A much used control circuit for opening and closing a solenoid valve is a spike and hold circuit, where the solenoid current finally is discharged over a Schottky diode on closing. This paper presents a PWM design, where the discharge is done by reversing the polarity of the voltage. This demands an accurate timing of the reverse spike not to recharge and reopen the valve. The PWM design gives flexibility in choosing the spike and hold voltage arbitrarily, and may use fewer components. Calculations combined with laboratory experiments verify this valve control strategy. In early flight the stability of the tail, or filament, is described in theory by the Ohnesorge number. In later flight, when a droplet shape has formed, the droplet stability is governed by the Weber number. These two considerations have opposite implications on the desired surface tension of the fluid. The Weber number is more important for longer distances, as the filament satelites normally catch up and join the main droplet in flight.Akseptert fagfellevurdert versjon/postprint. “© © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

High-throughput in vitro analysis of the extracellular matrix cancer environment modelled using 3D bioprinting

Thousands of drugs that passed the two-dimensional (2D) cell culture models and animal studies often failed when entering human clinical trials. This has led to a global effort to develop three-dimensional (3D) in vitro models to better reflect the cellular responses in vivo. One remaining challenge is creating 3D cell culture models that closely mimic native tissues in a high throughput manner. Herein, an electrostatically crosslinked PEG-based hydrogels system was developed to create high-throughput 3D in vitro models using a drop-on-demand 3D bioprinter. A 3-arm PEG-based polymer backbones were modified with either permanent cationic or anionic charged moieties and investigated the scalability for printing purposes. The resulting charged polymers can be conjugated further with various degrees of cell adhesive RGD motifs to study the influences of cell adhesive motifs on the spheroid formation of breast cancer cells (MCF-7). The formation, stability and mechanical properties of hydrogels with and without RGD were examined to evaluate cytotoxicity and cellular response to materials in a 3D environment. The spheroids of MCF-7 cells could be released with high viability by exposing them to a 2 M NaCl solution for 5 min and analysed with flow cytometry to characterise cellular responses and behaviours in detail. The printability of inks was evaluated through a series of experiments including viscosity, surface tension, density, droplet formation, cell sedimentation and homogeneity of inks. Fluids with the Z numbers within the printable region (4 £ Z £ 20) were used as rapid screening for potential inks compatible with DoD printing. Cell sedimentation and homogeneity of cell-laden suspensions were explored to ensure consist number of printed cells during 90 min printing process. Optimised ink formulations and printing parameters were used to print well-defined 3D hydrogel structures and precise cell deposition to achieve single spheroid formation with controllable spheroid diameter to evaluate chemotherapy drug responses. Taken together, this hydrogel system shows great promise as a 3D ECM mimic of cancer microenvironments with controllable biophysical and biochemical properties. Reliable printing and precise cell deposition show potential for high-throughput drug screening and toxicity testing. The ease of gelation and dissolution through salt concentration provides a way to quickly harvest the cells for analysis at any time of interest

The contribution of precision agriculture technologies to farm productivity and the mitigation of greenhouse gas emissions in the EU

EU Agriculture hast to cope with global challenges such as climate change mitigation or making farming more efficient. The active management of agriculture practices using appropriate technologies and practices, as Precision Agriculture, could reduce greenhouse gas (GHG) emissions while increasing agriculture productivity and income. However, information on the uptake and impacts of the use of precision agriculture technologies in EU is so far sparse and site specific. This technical report assesses the impact of Precision agriculture technology (PAT) on GHG emissions and farm economics. To this end, a typology of PAT was created in order to identify those that had the greatest potential to reduce GHG emissions. Secondly, five case studies were selected with the aim of identifying a combination of EU countries, precision agriculture techniques and arable crop types that could realise the maximum potential economic and environmental benefits of adopting PATs. A survey was applied to 971 adopters and non-adopters on the selected study cases with the aim of assessing the reasons behind uptake and the economic and environmental impacts of different. Finally economic and environmental impacts were investigated though a partial budgeting analysis and Miterra-Europe model respectively. Results indicate that although most farmers were aware of PAT, uptake rates are low among surveyed farmers. High investment costs, farm size and age were identified has fundamental hampering adoption. The survey reveals that adoption barriers might be overcome by boosting economic incentives aiming at improving economic performance both directly and indirectly. However, nonmonetary incentives such as technical advice or training also seemed to be interesting for surveyed farmers. The results of the survey also showed that information points such as peer-to-peer learning, visit to trade fairs, researchers and industry dealers had a positive effect on enhancing PAT uptake. The results of the partial budget analysis, where capital costs of the technologies are not included, indicate that impacts are highly variable by country, farm type and size and by technology. The results of the environmental impact analysis showed that the introduction of PAT might have positive effects on the environment, with reductions in GHG emissions from the fertiliser application, fertiliser production and fuel use.JRC.D.4-Economics of Agricultur