Controller Area Network Based Distributed Control for Autonomous Vehicles Matthew .J Darr the Ohio State University
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University of Kentucky UKnowledge Biosystems and Agricultural Engineering Faculty Biosystems and Agricultural Engineering Publications 3-2005 Controller Area Network Based Distributed Control for Autonomous Vehicles Matthew .J Darr The Ohio State University Timothy S. Stombaugh University of Kentucky, [email protected] Scott A. Shearer University of Kentucky Right click to open a feedback form in a new tab to let us know how this document benefits oy u. Follow this and additional works at: https://uknowledge.uky.edu/bae_facpub Part of the Agriculture Commons, Bioresource and Agricultural Engineering Commons, and the Technology and Innovation Commons Repository Citation Darr, Matthew J.; Stombaugh, Timothy S.; and Shearer, Scott A., "Controller Area Network Based Distributed Control for Autonomous Vehicles" (2005). Biosystems and Agricultural Engineering Faculty Publications. 150. https://uknowledge.uky.edu/bae_facpub/150 This Article is brought to you for free and open access by the Biosystems and Agricultural Engineering at UKnowledge. It has been accepted for inclusion in Biosystems and Agricultural Engineering Faculty Publications by an authorized administrator of UKnowledge. For more information, please contact [email protected]. Controller Area Network Based Distributed Control for Autonomous Vehicles Notes/Citation Information Published in Transactions of the ASAE, v. 48, issue 2, p. 479-490. © 2005 American Society of Agricultural Engineers The opc yright holder has granted the permission for posting the article here. Digital Object Identifier (DOI) https://doi.org/10.13031/2013.18312 This article is available at UKnowledge: https://uknowledge.uky.edu/bae_facpub/150 CONTROLLER AREA NETWORK BASED DISTRIBUTED CONTROL FOR AUTONOMOUS VEHICLES M. J. Darr, T. S. Stombaugh, S. A. Shearer ABSTRACT. The goal of this project was to evaluate the potential of a controller area network (CAN bus) to be used as the communication network for a distributed control system on an autonomous agricultural vehicle. The prototype system utilized microcontroller-driven nodes to act as control points along a CAN bus. Messages were transferred to the steering, transmission, and hitch control nodes via a task computer. The task computer utilized global positioning system data to generate appropriate control commands. Laboratory and field testing demonstrated that each of the control nodes could function simultaneously over the CAN bus. Results showed that the task computer adequately applied a feedback control model to the system and achieved guidance accuracy levels well within the desired range. Testing also demonstrated the system’s ability to complete normal field operations, such as headland turning and implement control. Keywords. Autonomous vehicle, Controller area network, Distributed control systems, Microcontrollers, Precision agriculture. ver the past several years, technology has contin- ideology for a worldwide equipment communication proto- ued to play an increasing role in agriculture. The col is the International Organization for Standardization industry has recently seen the advent and develop- 11783 standard (ISO, 1998), which was designed for ment of many types of automated vehicles ranging agricultural and construction equipment. This standard fromO planters to sprayers to harvesters. These vehicles have utilizes the controller area network (CAN) 2.0B protocol to all sustained different levels of automation. Some were capa- transmit serial data between networked control system ble of fully autonomous field operations, while others were components (Stone et al., 1999b). The CAN system was developed for specific control operations such as autosteer- designed to link multiple electronic control units (ECU) over ing (Reid et al., 2000). Commercialization of these technolo- a single data bus and inherently lends itself to becoming the gies has come at a substantial cost to the farmer. Autosteer backbone of a distributed control system for autonomous systems range in cost from $10,000 to $50,000 depending on vehicle operations because of its high data transmission rate, their accuracy and functionality. The largest component of expandability, and reliability (CAN-CIA, 2002). the system price is the level of global positioning system Robert Bosch GmbH designed the controller area network (GPS) accuracy desired. in 1986 upon request by Daimler Benz to develop a system There has also been a recent increase in the number of that would allow for communication between three electron- electronic components on agricultural equipment. During ic control units. It was noted that standard UART commu- normal field situations, operators must interact with spray nication could not complete this task because it only allowed rate controllers, variable rate controllers, and implement for point-to-point communication. Although the CAN bus system controllers, as well as controls for normal vehicle was originally designed for automotive applications, it has operation. Attempts have been made to create a standard been applied to many areas of automation and control communication link within all agricultural equipment but (CAN-CIA, 2002). The unique aspects of a CAN network are have thus far failed within the U.S. The most common that each message is preceded by an identifier that is unique to the transmitting controller, and that multiple controllers can communicate over a single two-wire bus. If two messages are transmitted simultaneously, an automatic arbitration Article was submitted for review in September 2004; approved for process ensures that the highest priority message is trans- publication by the Power & Machinery Division of ASAE in February mitted first. The lower priority message then has the 2005. Presented at the 2004 ASAE Annual Meeting as Paper No. 041155. Mention of trade name, proprietary product, or specific equipment does opportunity to retransmit upon completion of the first not constitute a guarantee or warranty by The Ohio State University or the message (Bosch, 1991). University of Kentucky and does not imply the approval of the named The International Standards Organization (ISO, 1998) product or the exclusion of other products that may be suitable. 11783 standard was created to standardize electronic com- The authors are Matthew J. Darr, ASAE Student Member, Research Associate, Department of Food, Agricultural, and Biological Engineering, munication on agricultural tractors and equipment. The ISO The Ohio State University, Columbus, Ohio; and Timothy S. Stombaugh, 11783 standard comprises 13 documents outlining specifica- ASAE Member Engineer, Assistant Professor, and Scott A. Shearer, tions for the physical communication layer, network layout, ASAE Member Engineer, Professor, Department of Biosystems and and message prioritization, among others. CAN 2.0B was Agricultural Engineering, University of Kentucky, Lexington, Kentucky. chosen for the communication protocol because of its Corresponding author: Matthew J. Darr, 590 Woody Hayes Drive Room 212, Columbus, OH 43210; phone: 614-292-1406; fax: 614-292-9448; growing use in mobile equipment. The ISO 11783 standard e-mail: [email protected]. extends the definition of the CAN 2.0B protocol and specifies Transactions of the ASAE Vol. 48(2): 479−490 E 2005 American Society of Agricultural Engineers ISSN 0001−2351 479 many parameters concerning the serial communication and OBJECTIVES hardware connections. Much of ISO 11783 follows the exact The goal of this project was to evaluate the potential of a specifications of the Society of Automotive Engineers CAN bus to be used as the communication network for a standard J1939 (SAE, 1998) in an attempt to make the two distributed control system on an autonomous agricultural standards compatible (Stone et al., 1999b). vehicle. This project also evaluated an inexpensive compass Several manufacturers have implemented partial net- as a feedback tool for in-field turning operations. Whenever works or CAN-based systems on their equipment in the past applicable, the ISO 11783 standard was followed during this several years. The Genesis series tractor from New Holland project. These project goals were accomplished through (New Holland, Pa.) incorporated a CAN-based network in implementation of the following sub-objectives: 1994 (Young, 1993). Ag-Chem Equipment Company (Du- S Design a modular distributed control system. luth, Ga.) patented the use of network-based control systems S Interface the electronic control units on the CAN bus for multi-product applications, which have been used in their with sensors and controls specific to the autonomous Falcon control systems (Monson and Dahlen, 1995). Deere operation of a prime mover vehicle. and Company (Moline, Ill.) has implemented ECU-based S Develop a digital steering control system for the auton- control networks since the introduction of the 7000 series omous test vehicle. tractor in 1992 (Stone et al., 1999b). S Demonstrate the ability of the vehicle to complete a Computer simulations have shown that normal agricultur- typical field operation. al machinery configured with an ISO 11783 based CAN bus will produce average message latency of less than 6 ms with proper prioritization. When bus loads increase to 80% DESIGN OF A MODULAR DISTRIBUTED capacity, messages with low priorities could see latency times approaching 70 ms (Hofstee and Goense, 1999). CONTROL SYSTEM Hofstee and Goense (1999) also showed that average The requirements for the distributed control system on the message