applied sciences Article Topological Navigation and Localization in Tunnels—Application to Autonomous Load-Haul-Dump Vehicles Operating in Underground Mines Mauricio Mascaró, Isao Parra-Tsunekawa, Carlos Tampier and Javier Ruiz-del-Solar * Advanced Mining Technology Center, Department of Electrical Engineering, Universidad de Chile, Santiago 8370451, Chile; [email protected] (M.M.); [email protected] (I.P.-T.); [email protected] (C.T.) * Correspondence: [email protected] Abstract: Mobile robots are no longer used exclusively in research laboratories and indoor controlled environments, but are now also used in dynamic industrial environments, including outdoor sites. Mining is one industry where robots and autonomous vehicles are increasingly used to increase the safety of the workers, as well as to augment the productivity, efficiency, and predictability of the processes. Since autonomous vehicles navigate inside tunnels in underground mines, this kind of navigation has different precision requirements than navigating in an open environment. When driving inside tunnels, it is not relevant to have accurate self-localization, but it is necessary for autonomous vehicles to be able to move safely through the tunnel and to make appropriate decisions Citation: Mascaró, M.; at its intersections and access points in the tunnel. To address these needs, a topological navigation Parra-Tsunekawa, I.; Tampier, C.; system for mining vehicles operating in tunnels is proposed and validated in this paper. This system Ruiz-del-Solar, J. Topological was specially designed to be used by Load-Haul-Dump (LHD) vehicles, also known as scoop trams, Navigation and Localization in operating in underground mines. In addition, a localization system, specifically designed to be Tunnels—Application to used with the topological navigation system and its associated topological map, is also proposed. Autonomous Load-Haul-Dump Vehicles Operating in Underground The proposed topological navigation and localization systems were validated using a commercial Mines. Appl. Sci. 2021, 11, 6547. LHD during several months at a copper sub-level stoping mine located in the Coquimbo Region in https://doi.org/10.3390/ the northern part of Chile. An important aspect to be addressed when working with heavy-duty app11146547 machinery, such as LHDs, is the way in which automation systems are developed and tested. For this reason, the development and testing methodology, which includes the use of simulators, scale-models Academic Editors: Luis Gracia and of LHDs, validation, and testing using a commercial LHD in test-fields, and its final validation in a Carlos Perez-Vidal mine, are described. Received: 1 June 2021 Keywords: autonomous navigation; topological mapping; field robotics; mining automation Accepted: 13 July 2021 Published: 16 July 2021 Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in published maps and institutional affil- The development of robotic applications has increased significantly in the last decade, iations. and currently, robotic systems are being utilized for many purposes, in various environ- ments. Mobile robots are no longer used exclusively in research laboratories and indoor controlled environments, but are now also used in dynamic industrial environments and outdoor sites. Moreover, the efforts for developing autonomous cars and drones have had the effect of strengthening the development and use of other autonomous machines and Copyright: © 2021 by the authors. vehicles in various industries. Licensee MDPI, Basel, Switzerland. This article is an open access article Mining is one industry in which autonomous vehicles have been in use for at least distributed under the terms and 13 years. Industrial use of autonomous hauling trucks started in 2008 in the Gabriela Mistral conditions of the Creative Commons copper open-pit mine, located in the north of Chile. Currently, the use of autonomous Attribution (CC BY) license (https:// mining equipment, mainly vehicles, is an important requirement in the whole mining creativecommons.org/licenses/by/ industry. This is because mining operations need to increase the safety of the workers, as 4.0/). well as to augment the productivity, efficiency, and predictability of the processes. Safety is, Appl. Sci. 2021, 11, 6547. https://doi.org/10.3390/app11146547 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, x FOR PEER REVIEW 2 of 26 Appl. Sci. 2021, 11, 6547 2 of 27 is, without doubt, a key factor, and has been the top priority of mining companies in recent withoutyears. This doubt, is true, a key especially, factor, and in has underground been the top mining priority operations of mining with companies their hazardous in recent years.environments This is true,in which especially, workers in undergroundare constantly mining exposed operations to the risks with of their rock hazardous falls, rock environmentsbursts, and mud in rushes, which workersand where are the constantly presence exposedof dust in to the the air risks can ofresult rock in falls, a number rock bursts,of associated and mud occupational rushes, and diseases where the in the presence workers of dust[1]. in the air can result in a number of associatedIn an occupationalundergrounddiseases mine, autonomous in the workers vehicles [1]. navigate inside tunnels. This kind of navigationIn an underground has different mine,precision autonomous requirements vehicles from navigatethose where inside they tunnels. are navigating This kind in ofan navigation open environment. has different First, precision tunnels requirements are GNSS-denied from thoseenvironments where they and are thus navigating vehicles incannot an open use environment. any GNSSs (Global First, tunnels Navigation are GNSS-denied Satellite Systems) environments to self-localize. and thus Secondly, vehicles cannotwhen driving use any inside GNSSs tunnels, (Global it is Navigation not relevant Satellite to have Systems) an accurate to self-localize.localization system, Secondly, but whenit is essential driving to inside be able tunnels, to move it safely is not through relevant the to havetunnel, an and accurate to make localization appropriate system, deci- butsions it isat essentialits intersections to be able and to access move points. safely throughThis is completely the tunnel, different and tomake from appropriatemost robotic decisionsapplications, at its where intersections safe navigation and access requires points. an accurate This is completelydetermination different of the fromrobot’s most po- robotic applications, where safe navigation requires an accurate determination of the sition and orientation at every moment. robot’s position and orientation at every moment. To address this need, a topological navigation system for mining vehicles operating To address this need, a topological navigation system for mining vehicles operating in tunnels is proposed and validated in this paper. This system was specially designed to in tunnels is proposed and validated in this paper. This system was specially designed be used by Load-Haul-Dump (LHD) vehicles, also known as scoop trams, operating in to be used by Load-Haul-Dump (LHD) vehicles, also known as scoop trams, operating underground mines. An LHD is a four-wheeled, center-articulated vehicle with a frontal in underground mines. An LHD is a four-wheeled, center-articulated vehicle with a bucket used to load and transport ore on the production levels of an underground mine frontal bucket used to load and transport ore on the production levels of an underground (See Figure 1). These machines are a key component in the extraction of ore from under- mine (See Figure1). These machines are a key component in the extraction of ore from ground mines because the ore extraction rate from the mine depends directly on the effi- underground mines because the ore extraction rate from the mine depends directly on the ciency of the LHD. The proposed system permits a commercial LHD, which is a very large efficiency of the LHD. The proposed system permits a commercial LHD, which is a very vehicle, to navigate inside tunnels that are just a couple of meters wider than the LHD. In large vehicle, to navigate inside tunnels that are just a couple of meters wider than the LHD.addition, In addition, it allows itbi-directional allows bi-directional navigation navigation and so-called and so-called inversioninversion maneuvers,maneuvers, both re- bothquired required in standard in standard LHD operations LHD operations inside inside productive productive sectors sectors of underground of underground mines. mines. (See (Seean example an example in Figure in Figure 2). In2 addition,). In addition, a localization a localization system, system, specifically specifically designed designed to be used to bewith used the with topological the topological navigation navigation system system and its and associated its associated topological topological map, map,is also is alsopro- proposed.posed. FigureFigure 1.1. LHDLHD andand sensorssensors forfor thethe AutonomousAutonomous NavigationNavigation System.System. An important aspect to be addressed when working with heavy-duty machinery, such as the LHDs, is the way in which automation systems are developed and tested. In order to address this important issue, we use a development process for autonomous systems for mining equipment, which is comprised of the following four-stages: (i) development using specific simulation tools, which are fed with real data from