Test Drive: Raven's Hawkeye System

Raven's Hawkeye system takes spray quality to a higher level by ensuring constant pressure when applying pesticides with homogeneous drops and equal rates in all areas of application.

Most of the time, in the tests we carried out for Revista Cultivar Máquinas, we evaluated conventional machines such as tractors, seeders, harvesters, sprayers, etc. There are few opportunities we have to test technology products, which are added to other machines, with the aim of increasing the quality of work. For this edition of Revista Cultivar, we present a product that, when added to a sprayer, can transform it into cutting-edge technology equipment, even if the machine is conventional.
For this edition, the equipment on which we bring technical information obtained in the field is the application control system, Raven's Hawkeye model. The model, which in a free translation into Portuguese could be “hawk's eye” and which in our language the phonetic transcription is “rocai”, is a kit that, when placed in any sprayer, can precisely control the application.

Raven has been working on rate control systems for sprayers since the 70s, but pulsed application technologies, which control pressure, arrived in the USA 4 years ago and have been available on the Brazilian market for a few months.
The application of chemical products, in liquid form, is one of the most important operations in almost all agricultural production cycles and major crops, appearing in all work routine schedules. However, alongside this importance, it is known that it is one of those that requires the most dedication and care, due to the great possibility of environmental contamination, intoxication of the people involved and, from an economic aspect, the great possibility of financial and agronomic losses, when badly carried out. 
To test Hawkeye, we traveled to the municipality of Ribeirão Preto, specifically a production farm for a large sugar cane factory. There we verified that the care and control carried out at the plant are quite great and the quality check diagnoses in the application are constant. However, it is known that the more important and higher the costs involved in the operation, the higher the quality requirements. This is the point where the equipment we tested is inserted. Equipment is used that guarantees an increase in the level of quality in equipment used in this complex operation. 
On the other hand, using equipment with these characteristics has a positive effect on the entire control chain, as it is not possible to invest in systems that do not take care in periodic maintenance, such as cleaning the equipment, checking for leaks, defects due to wear, etc. 

HAWKEYE SYSTEM
The Hawkeye system consists of a kit, made up of a central control module, two communication cables (harnesses), one primary, which controls and sends information to the middle of the boom, and the other secondary, which controls the extreme portions. of the spray bar. Also components of the system are PWM control valves, which are placed in the nozzle holder anti-drip (as many as there are nozzles) and an Isobus standard monitoring panel.
It should be noted that the kit is fully compatible with the Isobus protocol, which allows full compatibility with other equipment that uses this standard. In a visual analysis, the quality of the harnesses is noticeable and impressive, which present excellent sealing and protection against the environmental factors of the application.
The standard Isobus control panel was located inside the cabin, on the console positioned to the operator's right. The flexibility of use is total, being compatible with all commercial brands that comply with this protocol, making it possible to use this monitor with any machine. 
It is also possible to use monitors from other brands to work with this system. This attribute, which at first seems natural, is actually a differentiator, as the customer can keep their original panel or even control their machine with the Raven panel, according to their wishes. In this case, the operator who accompanied us in the test expressed his preference for the Hawkeye system monitor, due to the quality of the information, the look of the screen and the ease of use. At the time of purchase, the customer simply needs to inform the brand and model of their application machine and the kit will come in accordance with the equipment. 

The operating principle of the equipment is based on precise control of the working pressure, always keeping it in a position to provide the ideal droplet size, sustaining the flow of the product, in accordance with the machine's travel speed. The priority is not to do what other machines do, which is control opening and closing nozzle by nozzle, but to control the quality of the application, using the droplet size parameter for this. 
As a principle, it is emphasized that the equipment acts on the working pressure that arrives at the application tip, therefore when the equipment varies, for operational reasons, its displacement speed, the flow rate will be changed, maintaining the droplet size. In this way, the application rate per hectare will be maintained. Of course, the user must choose the correct tip for the job, which allows the ideal agronomic conditions for the application, and the Hawkeye system will maintain constant pressure without changing the droplet size, which is ideal for a good application.

As mentioned and reinforcing the theme of quality of application, the kit replaces the anti-drip membrane with a PWM valve that also performs this function. The PWM valves (acronym, in English, for Pulse Width Modulation and which in Portuguese would be “Modulation by Pulse Width”) adopt as a way of functioning a scale of a signal of electrical origin, to control the proportional opening and closing of a flow, in this case of the spray liquid. The valve consists of a piston and an electric coil, which

controls proportional opening and closing at a frequency of 10Hz. During its flow and interval control work, it controls the pressure by opening and closing the valve. Although the system is called pulsed spraying, as the frequency is high, ten pulses per second, the time interval between one pulse and another is 0,1 second. And to further increase the desired quality, the manufacturer configured the equipment so that this pulsation is alternated per nozzle, which improves the operating condition. The system, as we said, provides a visualization of the application through the monitor and can even, if the user wishes, create georeferenced maps of application rate and working pressure. As previously mentioned, the equipment is not just for control opens and closes, nozzle-to-nozzle, but also proportional opening/closing. For this reason it is possible to control the system pressure and the flow rate of each nozzle. This ability of the system allows it to advance in quality, in order to carry out precise tasks, such as compensating the flow in the curve, where the nozzles on the part of the bar that is inside the curve travel a smaller arc than those on the outside of the curve, varying the distance, by the largest arc. Without this system, the application volume would be lower in the outer part of the curve and greater in the area covered by the nozzles in the inner part of the curve. The equipment uses accelerometers, which are in the control module, “perceives” the curve and its magnitude, correcting the flow rate in the nozzle. This correction does not require any external interference, as it does not depend on the quality of the GPS signal, without mandatory correction and signal accuracy. For the

Using this system advantage does not require unlocking, and is standard for all Hawkeye equipment.

TEST
After learning about the characteristics and operating details of the equipment, we set off for field testing. To test this equipment, we traveled to the municipality of Ribeirão Preto, specifically a production farm of a large sugar cane factory, in a plot of approximately 22 hectares that had been established in 2014, therefore entering the fourth year of production. The operation involved an application of pre-emergent herbicide in an amount of 200 liters per hectare. The manager informed us that this same equipment is used to apply fungicides, insecticides (leafhoppers) and foliar fertilization.

On site, with the help of technicians from the company Raven and the plant itself, we tested the equipment that was coupled to a self-propelled sprayer, used in the application of liquid products, brand Case model Patriot 350, with a 30 meter boom and 60 nozzles, with spacing of 50 centimeters, assisted by a tank truck with a capacity of 16 thousand liters and which covers one shift of the machine with this volume. From inside the cabin we monitor the travel speed, varying between 14km/h and 15km/h, with 300kPa (3 Bar) of average pressure and an average flow per nozzle of 500 milliliters per minute. The Hawkeye equipment was neither a demonstration nor a development product, being the property of the company in full use, acquired at the end of 2017.
Due to the characteristics of the terrain, the chemical application operation is carried out at speeds close to, but not exceeding, 15km/h. The terrain has a certain slope and some undulations resulting from the existence of wide-based terraces still remain apparent in the area. In the past, sugarcane was planted along contour lines and currently planting is done towards the longest length of the plot. 
From this mechanized set, an operational field capacity of approximately 100 hectares per shift or 300 hectares per day is achieved, even without the use of automatic pilot, which is an option on the farm, depending on operational conditions. 24-hour shifts are carried out, in three eight-hour shifts per operator. We checked the operator's ability to control the height of the bar and execute border passes in areas with slopes and terraces still visible. When configuring the equipment, the operator must enter the rate information (liters per hectare) and working pressure.

The production manager explained to us that the plant uses application maps and then builds land application reports. For him, the introduction of the Hawkeye system caused a positive change in the quality of application, as currently with the system it is difficult to find application problems that previously appeared on maps, with equipment that does not use the system. To present this experience and seek this perception, we reproduced this in the field, turning off the system and comparing the areas on the application map.
We carried out tests with water-sensitive papers to visually evaluate the droplet size distribution, with the system running and switched off and with a variation in travel speed between 14km/h and 20km/h. We were able to verify that the system presented a more uniform droplet profile, even with speed variations. When we turned off the system, the application control map clearly showed the variations that this system aims to reduce, easily visualized on the map displayed on the monitor screen.
It was also possible to evaluate the quality of the work by comparing data sheets from the 2017 harvest, when the Hawkeye system was not yet used, and from 2018, with the equipment already in use. Raven's technical team that monitors customers and works on market development has carried out various applied research, aiming to prove the efficiency of the equipment and the economic gains for customers in different situations. Various data processed and transformed into applied knowledge indicate technical and economic advantages. 
For the test, we counted on the assistance, in addition to the farm operator, who was willing to assist with stops, returns and maneuvers to enable us to evaluate the equipment, and also from agricultural engineers Alberto Maza, Raven Sales Manager for Latin America; Felipe Oliveros, originally from Colombia, who works in the commercial area for other countries in America, and Vitor Higa, who is a specialist in Precision Agriculture at Raven.

CONCLUSIONS
In general terms and seeking to consider the viability of the investment in contrast to the quality provided by the equipment, it appears that several aspects have a positive impact on Hawkeye's work proposal.
Firstly, it can be seen, even through user experience, that one of the ways to evaluate quality is through clear evidence of uniformity in droplet size and applied dose, with variations in operational speed. Quality can also be assessed by the fact that it is not necessary to carry out rework, when application efficiency is better. This is combined with other agronomic values, such as less persistence of invasive plants, control of the amount of product applied, predictability of prepared volumes and better organization of the agricultural operation. It should not be forgotten that the equipment prioritizes droplet size by controlling the working pressure and, consequently, the applied volume.  

It is also important to mention that with Raven's equipment, the self-propelled spray bar, which originally has ten sections, now has 60 sections, as with the equipment, each nozzle can be controlled individually.
The return on investment seems clear, based on customer data in the area where we carried out the test, for which a saving in financial resources of 5,5% is estimated, which, on the scale that is practiced in a medium-sized plant and large size, it is quite representative. 
Finally, there is a very significant advantage, even with the difficulties in measuring the so-called quality of the operation, as it is possible to maintain the working pressure and, therefore, control the size of drops, improving the application and reducing the much feared product drift.