Wayne Woldt, John Nowatzki, Randy Price, Dharmendra Saraswat, Paul Weckler 2016-02-26 23:59:37
Special Series on Unmanned Aircraft, Part 1 Unmanned aircraft. The mere mention evokes many reactions. No matter what your reaction is, one thing is for sure: unmanned aircraft are a disruptive technology that brings an array of new opportunities to agriculture. Is ASABE ready to embrace this emerging technology that has roots in remote sensing, information systems, robotics, engineering, and aviation? This article, the first in a three-part series, explores unmanned aircraft and the enticing possibilities they offer agriculture, as well as the many challenges that need to be addressed. Let’s begin looking forward by first looking back. A look back and a look forward Unmanned aircraft have a long history in military aviation. One of the earliest examples was the development of the Curtiss N-9 Aerial Torpedo in March 1918. This was followed closely by the Kettering Bug, with a memorable test flight in October 1918, and the development of target drones in the interwar years (1919- 1939). There were significant advances during World War II, particularly the V-1 “Buzz Bomb,” and more recent development of modern military systems, such as the General Atomics MQ-1 Predator and MQ-9 Reaper. These sophisticated military systems have motivated development of civilian unmanned aircraft for both recreational and commercial purposes. Looking to the future, imagine an agricultural operation that hosts an array of unmanned aircraft of different types and configurations, ready on their launch pads, awaiting the command to rise into the sky, even at night, to fly autonomous missions and update the dense matrix of information needed for maximizing production while minimizing economic risks and adverse environmental impacts. With such a system, the producer will have constant, detailed information on the entire farming operation, synthesized into easy-to-understand metrics, combined with adaptive management tools to drive the decision support system?in other words, the farm of the future. Back to reality In addition to military advances, innovations in remote control model airplanes also contributed to the development of unmanned aircraft for civilian applications. For example, deriving their inspiration from military technology, hobby aviators extracted the positional sensors from Nintendo Wii gaming devices and integrated them into model aircraft control systems. Those early equipment hackers had a vision of integrated microcontrollers that would allow unmanned aircraft to fly without human intervention. As the recreational and hobby grades of unmanned aircraft continue to evolve into commercial- grade equipment, the impact will be profound. In recognition of this far-reaching potential, note that “unmanned aircraft system” (or UAS) is the official terminology used by the U.S. Federal Aviation Administration (FAA). This terminology encompasses all the various systems that comprise unmanned aircraft, including the aircraft, autopilot, ground control station, communication network, and human pilot, among others. The viability of unmanned aircraft (UA) for commercial purposes became a reality with the FAA’s Modernization and Reform Act (FMRA) of 2012. A key element of this legislation was a mandate that the FAA integrate UA into the national airspace system, with the implication that use of UA for commercial purposes would eventually be legal under federal aviation regulations. The rule-making process was to be completed by September 30, 2015. However, the reality is that the U.S. national airspace system is very complex, and the current projected completion date is now June 2016. In the meantime, while it is not yet legal to fly UA for commercial purposes, including production agriculture, the FAA can grant special exemptions that allow highly managed UA flights. These exemptions are complex. They are discussed below and will be further explored in an upcoming article. When the FAA finalizes the rules for civilian use of UA, the path to using UA for production agriculture will be clear. The regulatory environment In the meantime, there is considerable confusion about the legal use of UA and the FAA’s authority to regulate UA. Most people do not routinely interact with the FAA or encounter FAA regulations. The public is not aware of the complex body of rules, regulations, and case law associated with aviation. In fact, the U.S. has the most complex, but also the safest, airspace in the world, and the FAA has broad authority to ensure safety within the national airspace system. Some of the common myths about UA include: • UA are not real aircraft. • UA are not subject to FAA regulation. • The FAA doesn’t control the airspace below 400 feet. • UA operation for commercial or business purposes is okay if the vehicle is small, operated over private property, and below 400 feet. • It’s okay to fly UA beyond the pilot’s line of sight as long as the vehicle comes back. In reality, the FAA is responsible for air safety from the ground up. The FAA has authority to create and enforce regulations to protect individuals and property on the ground and to prevent collisions between aircraft, between aircraft and land or water vehicles, and between aircraft and airborne objects. Consistent with its authority, the FAA has regulations that apply to all aircraft, whether manned or unmanned, and irrespective of the altitude at which the aircraft is operating. For example, FAA regulations prohibit any person from operating any aircraft in a careless or reckless manner so as to endanger the life or property of others. According to federal regulations, there are three operational categories of UA: The recreational hobby category for model aircraft has existed since the 1930s. This category is based on intent and is covered under Section 336 of the FMRA of 2012, which codified the hobby rules for the first time. The recreational hobby group has mostly policed itself through the Academy of Model Aeronautics. Since 1981, the hobby community has operated under FAA Advisory Circular AC 91-57a. The public use category includes government use of UA, such as for law enforcement, as well as public university research (mainly “aeronautical research” as defined by the FAA), with all flights taking place under the authority of an FAA-issued certificate of authorization (COA). The civilian category (including commercial use) encompasses UA flights for hire, for education and training at universities, for industrial use, and for anything not classified as hobby or public use. On March 24, 2015, the FAA announced a streamlined COA process for commercial UA operations. The new policy allows commercial operators, who are permitted to fly under Section 333 of the FMRA, to fly without coordination with air traffic control facilities. Commercial UA operators will receive a streamlined COA to fly if they adhere to certain limitations, including: flights must remain at or below 200 feet during daylight visual conditions, flights must be at least two miles from airports and five miles from airports with an operational control tower, and the pilot must have a pilot certificate. Without a Section 333 exemption, the FAA requirements for commercial UA operation are quite strict. In general, the FAA requires a type-certificated aircraft, an FAA-certificated pilot, qualified ground observers, and formal processes and documentation for maintenance, training, and operations. While new FAA rules have been proposed for small UA that will greatly simplify commercial use, they are not expected to take effect until mid-2016 or maybe even 2017. Virtually all aircraft that fly in the national airspace system must be registered, just as all cars must be registered and display license plates for operation on public roads. On manned aircraft, the registration is indicated by the “N” number prominently displayed on the fuselage. For UA, the FAA has released a new registration process. Any UA that weighs less than 250 g (0.55 lb) at takeoff is exempt from registration. For hobby flying, the owner of the aircraft is assigned a registration number upon completion of the registration process, and that number must be affixed to all aircraft that weigh more than 250 g and less than 25 kg (55 lb). For commercial UA, each aircraft must be registered using the traditional aircraft registration process until March 31, 2016. After that, the aircraft can be registered using a new web-based process. Infractions of FAA regulations can result in significant fines, on the order of $10,000 per violation. An overview of the technology Several technologies have made UA possible, including small-scale electronics, microcontrollers, the global positioning system (GPS), inertial measurement unit (IMU) sensors, sensor fusion, brushless motors, and high-energy, low-density batteries. Perhaps the largest contributor to UA feasibility is GPS, which consists of two satellite constellations (GPS and GLONASS) that can provide positional accuracy down to a few meters using an electronic receiver not much larger than a quarter. In addition, sensor fusion combines accelerometers and IMU sensors to provide accurate vehicle attitude information with very small components. Furthermore, high-energy, low-weight batteries (such as lithium polymer, or LiPo) provide the energy storage density and high amperage needed to allow the entire vehicle weight to be carried by propeller power for an extended period. An additional development that has contributed to UA success is the brushless motor that uses frame-mounted coils (versus traditional spinning coils, which need brushes) surrounded by a rotating magnet field. These high-speed motors have virtually no wear (except for the bearings) and an extended speed range. When this motor technology is combined with high-speed electronics, a multirotor UA has a sufficient thrust-to-weight ratio to fly without needing wing aerodynamics. All these developments have come together to create UA that are compact and able to carry useful payloads with automated guidance and attitude holding features that even beginning pilots can fly with ease. For agricultural purposes, UA systems currently exist in two forms: multi-rotors and fixed-wing aircraft. Multi-rotors lift the entire weight of the vehicle with propeller power and allow vertical takeoff and landing. Multi-rotors typically have four, six, or eight motor units, termed quad-, hex-, and octocopter, but singlerotor systems are available, and older gas-powered single-rotor (swash plate) helicopter designs have also been used. Fixed-wing aircraft are based on remote control model airplanes and come in two main types: delta wing and the traditional long aspect ratio. These aircraft can be electric or gas powered, although electric versions are more common because of the low cost of LiPo batteries, elimination of the liquid fuel, and reduced vibration. The advantages of multi-rotors are their vertical takeoff and landing, which can be helpful for inexperienced pilots and in situations where open areas are not available for horizontal takeoff or landing. In addition, multi-rotors usually have a small frame, low weight, and a user-friendly interface. For example, if control is lost, the user can simply release the controls, and the vehicle will automatically stop, right itself, and hold position or land. This allows student pilots to oper- ate a multi-rotor with little flight experience. The disadvantages of multi-rotors (compared to fixed-wing aircraft) are their increased power consumption, slower airspeeds of typically 15 to 40 kph (9 to 25 mph), and limited flight times of typically 10 to 30 minutes. These flight characteristics typically allow a multi-rotor to cover 16 to 32 ha (40 to 80 acres) per flight. In addition, multi-rotors have no glide path. If the battery loses power or some other system failure occurs, the aircraft will drop from the sky. The advantages of fixed-wing aircraft are their increased flight times (roughly three times that of multi-rotors), potential lower cost relative to a multi-rotor, and faster airspeeds of typically 30 to 100 kph (18 to 62 mph), which translates to more area covered per flight. Fixed-wing aircraft can also glide to a safe landing in the event of a system failure, thereby protecting the sensors and other components. The disadvantages of fixed-wing aircraft are in takeoff and landing, which usually require an open area free of obstacles. In addition, fixed-wing aircraft typically require a pilot experienced with remote control aircraft, who can assume control in case the autonomous control system fails. Finally, a fixedwing airframe is typically larger than that of a multirotor and can require extra cargo room in transport. Typical flight times for fixedwing UA are 30 minutes to more than an hour, and while most can cover an area of 32 to 130 ha (80 to 320 acres), current regulatory limits, which require keeping the UA within the pilot’s line of sight, restrict the coverage area to about 64 ha (160 acres). Efforts are underway to develop hybrid UA that can take off vertically and then transition to a fixed-wing configuration to allow longer flight times. Research is also ongoing in “sense and avoid” technology to allow autonomous UA to safely transit the national airspace system. Other researchers are looking at ways to combine the data provided by UA with data from other sources to create useful, multi-scale information. There is also active research on deploying swarms of UA with collective control and data analysis. Others are exploring the use of midsize and large UA for applications in agriculture. Rapid phenotyping is one such area of agricultural research that will benefit from UA. There is also interest in developing UA that can interact with their environment, such as extracting soil or water samples for later analysis. And some multi-rotors, using fuel cells and other advanced energy technologies, have flown for more than 3.5 hours on a single charge. Virtually all the UA currently used in the U.S. and internationally can be characterized as small UA, with a gross takeoff weight of less than 55 lb (25 kg). While there are many uses for small UA in crop and livestock production, it is important to note that mid-size and large UA will also find uses in agriculture, particularly in the U.S. Great Plains and Midwest. The opportunities for UA in agriculture Most growth in the UA industry will be in the commercial and civilian market, as the shift away from the military market gains momentum. Projections for the commercial and civilian UA market vary widely, depending on the particular aviation analyst and their assumptions. However, there is general consensus that the market is expected to grow, with one estimate indicating a compound annual rate of 19% between 2015 and 2020, compared with 5% growth in the military market. While estimates vary, in general, UA spending is expected to nearly double over the next decade, from $6.6 billion to $11.4 billion on an annual basis, and the segment is expected to generate $89 billion in revenue during the next ten years. Most market projections indicate that agriculture will constitute the largest share of the civilian UA market, often estimated to be 70% of the UA industry’s capacity. This makes sense from a couple of perspectives. The agricultural market is primarily in rural areas, thereby minimizing the social and privacy concerns that arise in urban areas. At the same time, UA can greatly enhance a producer’s ability to monitor and manage large parcels of land, which is otherwise quite challenging. Current estimates by the United Nations point to more than 9.6 billion people on Earth by 2050. Our ability to produce the food and fiber required to sustain the growing world population will be severely tested. Projections indicate that the world will face a 70% gap between the crop calories that were produced in 2015 and the calories likely required in 2050. The magnitude and difficulty of meeting this challenge, along with the risks of not meeting it in terms of global instability, make it the grand challenge of the 21st century. A well-recognized strategy for meeting this grand challenge is to close the yield gap through agricultural intensification using new management practices and technologies that increase food production per unit of land area. Unfortunately, intensification of agriculture can also have adverse impacts on environmental sustainability. Research and development are underway to advance agricultural technologies, leading to practices that minimize adverse impacts while maximizing yields. One promising approach is precision agriculture, which is based on observing, measuring, and responding to the spatial and temporal variability of natural systems, such as topography, soil, and weather, integrated with the variability in crop and livestock production systems. Large crop production systems are complex and require timely data across multiple space and time scales to produce optimal management strategies for improved production. With precision agriculture, agriculture is embracing Big Data, and UA can help feed the data engine. Major challenges for crop production include managing large parcels of land, as well as managing water, nutrients, pests, disease, weeds, and plant and animal genetics, and making timely decisions. Problems can arise rapidly and unexpectedly and, if not dealt with promptly, can result in significant yield loss. UA technology provides an unprecedented ability to place crop and soil sensors, robotic treatment systems, and information technology at diverse and precise locations as an integral part of an overall management system. This will lead to precise application of inputs, efficient water and resource management, and increased sustainability and security of food production?in other words, precision agriculture. The next steps Sensor technology for UA is developing quickly. Sensors are becoming smaller and lighter while performing better and delivering higher resolution across greater ranges. Today, most agricultural applications use color and near-infrared sensors. Both are useful for field scouting, and the nearinfrared band can be used to determine vegetative indices of growing crops. Multispectral sensors are poised to become more common on UA because they can capture the red, green, blue, and infrared bands in a single flight. However, there is still a great need for research on the effective use of UA in agriculture. Using remote sensing to identify and quantify crop nutrient deficiencies, water shortages, disease symptoms, and weed infestations is not simple. Most nutrient deficiencies and disease symptoms can be masked by other factors. For example, nitrogen and sulfur deficiencies and excess moisture can all cause chlorosis in corn plants. For now, aerial imagery of field conditions still needs to be correlated with ground-truth data to ensure a high level of reliability. This may change with additional research and the integration of additional sensor systems, such as thermal infrared and hyperspectral, that seek to increase information and our ability to resolve production challenges. There are many potential uses of UA in crop management, and some crop management applications are already fairly well developed. Row crop emergence and stand count, nitrogen deficiency in corn, and identification of weed infestations are feasible. Other issues are more difficult and need more research. These include detection of most crop diseases and insect damage, early detection of moisture stress, as well as specific weed identification. Research is also in progress on the use of UA for livestock inventory and location determination, as well as identifying animal body temperatures and collecting sensory information through active radio frequency tags. Small UA are ideal for a wide array of applications in agriculture, including: • Natural resource management, using UA as hydrologic observatories. • Agricultural resilience to climate variability, using UA data for adaptive management. • Crop scouting, using UA to identify and eradicate weeds. • Livestock management, using UA for animal tracking and monitoring animal health. • Water management, using UA for irrigation control and flood assessment. • Crop health and growth, using UA to monitor soil moisture, vegetation type, and vegetation index. • Management and application of pesticides, using UA for crop dusting. • Control of runoff and soil loss, using UA to monitor sediment loads to streams and rivers. • Security of agricultural operations, using UA for aerosol sampling and as persistent sentries. Other opportunities for agricultural UA include management of specialty crops, nurseries, and orchards. Automated inventory control in nurseries is a particularly good application for UA. Counting plants is labor-intensive, and maintaining an accurate count is a challenge because the plants are constantly being moved around due to mortality or shipping. Research has shown that plant count accuracy using UA depends on plant spacing, plant type, and flight altitude, and the overall results were reported as “very accurate.” There is also research on using mid-sized UA to improve the quality of cherry crops. Citrus, apple, other tree crops are likely to benefit from UA for addressing inventory and crop quality issues. Much of this research involves collaboration with producers to correlate aerial imagery, soil analyses, and field observations with in-field sensor data and yield data. The long-term economic impact for crop and livestock production still needs to be determined, and current research seeks to compare the utility and economics of UA to other methods of agricultural management. Ultimately, data analysis companies, agricultural producers, and agricultural retailers will be able to use these comparisons to build efficient business models. In the meantime, image transfer, data processing, and data analysis need further research and development. Because UA altitude is currently limited to 400 feet by FAA regulations, a single image provides limited coverage of the area of interest. Typically, several images are combined to create a mosaic. For example, images of flat terrain acquired with UA-mounted cameras using a frontal overlap of 70% to 80% (parallel to the flight direction) and a side overlap of 60% to 70% (between flight tracks) provide higher quality data. However, the flight time and computational time both increase with greater image overlaps. The user must find a trade-off between computational time and the ability to provide timely, highquality images. A number of software options, including cloud-based solutions, are available to automate the process of mosaicking images. This research builds on photogrammetry, and it often involves developing an interface between the autopilot and the sensor system. Transferring gigabytes of data over wireless or cellular networks is another obstacle to widespread UA adoption. Data transfer will be improved by data compression techniques and selection methods that can strip out the image data not needed for a specific application and transfer only the data needed, thereby reducing the data-processing time. Producers are more interested in the information derived from remote sensing imagery than in the imagery itself, and they will be more willing to pay for a map that shows, for example, where their crops are nitrogen deficient than for the original image. Timeliness, accuracy, and reliability will be the mark of successful UA applications. ASABE’s Unmanned Aerial Systems Committee Recognizing the potential of UA for agriculture, an ad hoc group of 19 ASABE members met at the 2013 Annual International Meeting (AIM) in Kansas City to discuss the topic. The group decided that the topic should be pursued and that the Society’s support would be critical. In a follow-up meeting at the 2014 AIM in Montreal, the group decided to petition ASABE to become a formal committee under the auspices of the Machinery Systems technical community. The group also decided on a name, “Unmanned Aerial Systems,” to facilitate communication and to create an identity as part of the petition process. A petition was developed with the involvement of all the group members and presented to ASABE. The initial vote was positive. The petition was modified based on recommendations from Machinery Systems leadership, and after a final review, the petition to form the new Unmanned Aerial Systems committee (MS-60) was approved. The new committee met for the first time at the 2015 AIM in New Orleans. Current membership is set at 59 members, with both national and international representation. A portion of the petition to establish the new committee is included in the sidebar. An invitation to you Research and development are underway to advance agricultural technologies, leading to practices that minimize adverse impacts while maximizing yields. At the same time, the recent move toward opening the national air space to UA will be a game changer for agriculture. UA technology offers an unprecedented opportunity to place crop and soil sensors, livestock information systems, robotic treatment systems, and advanced information systems at diverse and precise locations as integral parts of a multiscale approach to agricultural management, increasing production and improving the efficiency of agricultural operations. Furthermore, UA will continue to evolve into active crop protection methods, such as automated sample collection and treatment application. UA will lead to increased sustainability and security of food production, efficient management of resources (water, nutrients, energy, etc.), deployment of new information systems based on aerial imaging and integrated sensor networks, and real-time crop and livestock management. However, there are also significant knowledge gaps that may prevent producers from understanding how UA can benefit their operations. At a fundamental level, producers need to know what technologies are available, understand the operating principles, and determine the economic advantages before they can make informed decisions about selecting and implementing this new technology. A few areas of interest have been noted in this article, and there are many more. Your imagination is the only limit. Resource will be highlighting UA in future articles, and we extend an invitation to share your UA-related work. Please consider sharing your research, commercial efforts, and educational activities so that others may benefit from your experience. If you are interested in contributing, contact Wayne Woldt at email@example.com. Author guidelines for Resource are available at www.asabe.org/publications/resourcemagazine.aspx. ASABE member Wayne Woldt, P.E., Associate Professor, Department of Biological Systems Engineering and School of Natural Resources, University of Nebraska-Lincoln, and Director, NU-AIRE Laboratory, Lincoln, Neb., USA, firstname.lastname@example.org. ASABE member John Nowatzki, Agricultural Machine Systems Specialist, Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, USA, email@example.com. ASABE member Randy Price, Assistant Professor, Dean Lee Research and Extension Center, Louisiana State University, Alexandria, USA, firstname.lastname@example.org. ASABE member Dharmendra Saraswat, Associate Professor, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Ind., USA, email@example.com. ASABE member Paul Weckler, P.E., Associate Professor, Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, USA, firstname.lastname@example.org.
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