{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,25]],"date-time":"2026-06-25T16:34:22Z","timestamp":1782405262758,"version":"3.54.5"},"reference-count":23,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2018,11,23]],"date-time":"2018-11-23T00:00:00Z","timestamp":1542931200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010661","name":"Horizon 2020 Framework Programme","doi-asserted-by":"publisher","award":["731667"],"award-info":[{"award-number":["731667"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The use of multiple aerial vehicles for autonomous missions is turning into commonplace. In many of these applications, the Unmanned Aerial Vehicles (UAVs) have to cooperate and navigate in a shared airspace, becoming 3D collision avoidance a relevant issue. Outdoor scenarios impose additional challenges: (i) accurate positioning systems are costly; (ii) communication can be unreliable or delayed; and (iii) external conditions like wind gusts affect UAVs\u2019 maneuverability. In this paper, we present 3D-SWAP, a decentralized algorithm for 3D collision avoidance with multiple UAVs. 3D-SWAP operates reactively without high computational requirements and allows UAVs to integrate measurements from their local sensors with positions of other teammates within communication range. We tested 3D-SWAP with our team of custom-designed UAVs. First, we used a Software-In-The-Loop simulator for system integration and evaluation. Second, we run field experiments with up to three UAVs in an outdoor scenario with uncontrolled conditions (i.e., noisy positioning systems, wind gusts, etc). We report our results and our procedures for this field experimentation.<\/jats:p>","DOI":"10.3390\/s18124101","type":"journal-article","created":{"date-parts":[[2018,11,23]],"date-time":"2018-11-23T12:20:28Z","timestamp":1542975628000},"page":"4101","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":36,"title":["Decentralized 3D Collision Avoidance for Multiple UAVs in Outdoor Environments"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5850-1137","authenticated-orcid":false,"given":"Eduardo","family":"Ferrera","sequence":"first","affiliation":[{"name":"Networked Embedded Systems Group, University of Duisburg-Essen, 45127 Essen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alfonso","family":"Alc\u00e1ntara","sequence":"additional","affiliation":[{"name":"Group of Robotics, Vision and Control, University of Seville, 41092 Seville, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7534-0187","authenticated-orcid":false,"given":"Jes\u00fas","family":"Capit\u00e1n","sequence":"additional","affiliation":[{"name":"Group of Robotics, Vision and Control, University of Seville, 41092 Seville, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6235-9524","authenticated-orcid":false,"given":"Angel R.","family":"Casta\u00f1o","sequence":"additional","affiliation":[{"name":"Group of Robotics, Vision and Control, University of Seville, 41092 Seville, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pedro J.","family":"Marr\u00f3n","sequence":"additional","affiliation":[{"name":"Networked Embedded Systems Group, University of Duisburg-Essen, 45127 Essen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"An\u00edbal","family":"Ollero","sequence":"additional","affiliation":[{"name":"Group of Robotics, Vision and Control, University of Seville, 41092 Seville, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,11,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Martinoli, A., Mondada, F., Correll, N., Mermoud, G., Egerstedt, M., Hsieh, M.A., Parker, L.E., and St\u00f8y, K. 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