agronomy Review Field Robots for Intelligent Farms—Inhering Features from Industry Pablo Gonzalez-de-Santos * , Roemi Fernández , Delia Sepúlveda, Eduardo Navas , Luis Emmi and Manuel Armada Centre for Automation and Robotics (UPM-CSIC), Arganda del Rey, 28500 Madrid, Spain; [email protected] (R.F.); [email protected] (D.S.); [email protected] (E.N.); [email protected] (L.E.); [email protected] (M.A.) * Correspondence: [email protected] Received: 1 September 2020; Accepted: 22 October 2020; Published: 24 October 2020 Abstract: Estimations of world population growth urgently require improving the efficiency of agricultural processes, as well as improving safety for people and environmental sustainability, which can be opposing characteristics. Industry is pursuing these objectives by developing the concept of the “intelligent factory” (also referred to as the “smart factory”) and, by studying the similarities between industry and agriculture, we can exploit the achievements attained in industry for agriculture. This article focuses on studying those similarities regarding robotics to advance agriculture toward the concept of “intelligent farms” (smart farms). Thus, this article presents some characteristics that agricultural robots should gain from industrial robots to attain the intelligent farm concept regarding robot morphologies and features as well as communication, computing, and data management techniques. The study, restricted to robotics for outdoor farms due to the fact that robotics for greenhouse farms deserves a specific study, reviews different structures for robot manipulators and mobile robots along with the latest techniques used in intelligent factories to advance the characteristics of robotics for future intelligent farms. This article determines similarities, contrasts, and differences between industrial and field robots and identifies some techniques proven in the industry with an extraordinary potential to be used in outdoor farms such as those derived from methods based on artificial intelligence, cyber-physical systems, Internet of Things, Big Data techniques, and cloud computing procedures. Moreover, different types of robots already in use in industry and services are analyzed and their advantages in agriculture reported (parallel, soft, redundant, and dual manipulators) as well as ground and aerial unmanned robots and multi-robot systems. Keywords: agricultural manipulator; autonomous mobile robot; multirobot system; precision agriculture; intelligent farms; smart farm 1. Introduction According to the Food and Agriculture Organization (FAO), the world’s human inhabitants are expected to reach 9.6 billion people by 2050. Feeding this huge population is largely considered one of the greatest outstanding challenges in terms of human initiatives. Cultivated land is close to its maximum in developed countries, and as predicted by the European Agricultural Machinery Association (CEMA) [1]—the association representing the European agricultural machinery industry—food production must increase by 70% to successfully feed the human population circa 2050. This mission demands more efficient infrastructure, farms, and production devices capable of preserving resources in a sustainable, environmentally friendly, and cost-effective manner. The precision farming concept, which consists of assembling different methods and techniques to manage variations in the field to increase crop productivity, improve business profitability, and ensure Agronomy 2020, 10, 1638; doi:10.3390/agronomy10111638 www.mdpi.com/journal/agronomy Agronomy 2020, 10, x FOR PEER REVIEW 2 of 24 Agronomy 2020, 10, 1638 2 of 24 The precision farming concept, which consists of assembling different methods and techniques to manage variations in the field to increase crop productivity, improve business profitability, and eco-environmentalensure eco-environmental sustainability, sustainabi haslity, provided has provided some significant some significant solutions. solutions. After moreAfter thanmorethree than decadesthree decades of development, of development, the basic the basic technologies technologies on which on which precision precision farming farming was was constructed constructed are becomingare becoming mature mature enough enough to aidto aid in accomplishingin accomplishing this this mission. mission. Figure Figure1 illustrates1 illustrates some some of of these these techniquestechniques alongalong with with their their connections, connections, distinguishing distinguishing those based those on information based on and information communication and technologiescommunication (ICT) technologies from those (ICT) that rely from on thos fielde that robotics rely [on2– 7field]. robotics [2–7]. Figure 1. Technologies involved inin precisionprecision agriculture.agriculture. Currently,Currently, agriculturalagricultural activitiesactivities involvinginvolving roboticsrobotics exhibitexhibit aa highhigh degreedegree ofof technologytechnology andand areare capablecapable ofof performingperforming autonomousautonomous tasks.tasks. Most of these tasks are re relatedlated to harvesting and weeding, followedfollowed byby the the disease disease detection detection and seeding,and seeding, according according to a recent to a study recent on researchstudy on and research commercial and agriculturalcommercial robotsagricultural for field robots operations for field [8 operations]. For example, [8]. For fertilization-spreading example, fertilization-spreading tasks can be executedtasks can autonomouslybe executed autonomously if the appropriate if the implement appropriate tanks implem have beenent tanks filled withhave fertilizerbeen fill anded with attached fertilizer to fueled and autonomousattached to fueled vehicles, autonomous but only until vehi thecles, system but only hasrun until out the of fertilizersystem ha ors fuel.run out Then, of humanfertilizer operators or fuel. haveThen, to human participate operators in refilling have to and participate refueling in/recharging. refilling and The refueling/recharging. same concept is applicable The same to concept planting is andapplicable spraying. to planting and spraying. Furthermore,Furthermore, harvestingharvesting systems systems must must o ffloffloadoad the th yielde yield when when their their collecting collecting tanks tanks are full,are full, and thisand operationthis operation is mostly is mostly performed performed by by operators. operators. Similarly, Similarly, the the attachment attachment of of agricultural agricultural tools—andtools—and tooltool interchanging—requiresinterchanging—requires thethe involvementinvolvement ofof operators.operators. However, these manualmanual operationsoperations areare susceptiblesusceptible toto automation,automation, asas similarsimilar operationsoperations havehave been automated in industry. Thus, another step forwardforward forfor agricultureagriculture isis toto relegaterelegate operatorsoperators toto meremere supervisorssupervisors byby combiningcombining thesethese typestypes ofof activitiesactivities withwith otherother alreadyalready automatedautomated farmfarm managementmanagement activitiesactivities toto organizeorganize aa fullyfully automatedautomated systemsystem approachingapproaching thethe modelmodel ofof the fully automate automatedd factory, wherewhere rawraw materials enterenter and finishedfinished productsproducts leaveleave with with no no human human intervention. intervention. Thus, Thus a fully, a automated fully automated farm can farm be seen can as be an agriculturalseen as an fieldagricultural where materialsfield where (seeds, materials fertilizers, (seeds, herbicides,fertilizers, herbicides, etc.) enter etc.) and enter crops and leave crops with leave no with human no intervention.human intervention. Moreover, Moreover, this parallelism this parallelism can be extrapolated can be extrapolated for farms tofor closely farms resembleto closely the resemble intelligent the factoryintelligent model. factory This model. idea is This the intelligentidea is the farm intellig concept,ent farm which concept, is a fully which automated is a fully farm automated upper layerfarm thatupper builds layer a completelythat builds connected a completely and flexible connected system and that flexible [9] optimizes system system that [9] performance optimizes throughsystem aperformance wider network, through learns a wider from network, new conditions learns from in real- new or conditions quasi-real-time, in real- adaptsor quasi-real-time, the system toadapts new workingthe system conditions, to new working and performs conditions, whole and production performs processeswhole production autonomously. processes autonomously. AnAn intelligentintelligent farm farm is foundedis founded on autonomouson autonomous decision decision making making [10] to guarantee[10] to guarantee asset efficiency; asset improveefficiency; product improve quality, product product quality, safety, product and environmental safety, and sustainability;environmental decrease sustainability; production decrease costs; minimizeproduction delivery costs; minimize time to consumers; delivery time increase to consum marketers; share; increase enhance market profitability; share; enhance and maintainprofitability; the laborand maintain force. To the achieve labor theforce. intelligent To achieve farm, the many intelligent of the farm, systems many and of components the systems that and are components currently beingthat are used currently in agriculture