{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,31]],"date-time":"2025-12-31T14:56:05Z","timestamp":1767192965847,"version":"build-2065373602"},"reference-count":32,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2021,6,13]],"date-time":"2021-06-13T00:00:00Z","timestamp":1623542400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007273","name":"Comisi\u00f3n Interministerial de Ciencia y Tecnolog\u00eda","doi-asserted-by":"publisher","award":["PID2020-119522RB-I00"],"award-info":[{"award-number":["PID2020-119522RB-I00"]}],"id":[{"id":"10.13039\/501100007273","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The high accuracy and dynamic performance of parallel robots (PRs) make them suitable to ensure safe operation in human\u2013robot interaction. However, these advantages come at the expense of a reduced workspace and the possible appearance of type II singularities. The latter is due to the loss of control of the PR and requires further analysis to keep the stiffness of the PR even after a singular configuration is reached. All or a subset of the limbs could be responsible for a type II singularity, and they can be detected by using the angle between two output twist screws (OTSs). However, this angle has not been applied in control because it requires an accurate measure of the pose of the PR. This paper proposes a new hybrid controller to release a 4-DOF PR from a type II singularity based on a real time vision system. The vision system data are used to automatically readapt the configuration of the PR by moving the limbs identified by the angle between two OTSs. This controller is intended for a knee rehabilitation PR, and the results show how this release is accomplished with smooth controlled movements where the patient\u2019s safety is not compromised.<\/jats:p>","DOI":"10.3390\/s21124080","type":"journal-article","created":{"date-parts":[[2021,6,14]],"date-time":"2021-06-14T22:25:46Z","timestamp":1623709546000},"page":"4080","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Vision-Based Hybrid Controller to Release a 4-DOF Parallel Robot from a Type II Singularity"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0403-4593","authenticated-orcid":false,"given":"Jos\u00e9 L.","family":"Pulloquinga","sequence":"first","affiliation":[{"name":"Departamento de Ingenier\u00eda de Sistemas y Autom\u00e1tica, Instituto de Autom\u00e1tica e Inform\u00e1tica Industrial, Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rafael J.","family":"Escarabajal","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda de Sistemas y Autom\u00e1tica, Instituto de Autom\u00e1tica e Inform\u00e1tica Industrial, Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jes\u00fas","family":"Ferr\u00e1ndiz","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda de Sistemas y Autom\u00e1tica, Instituto de Autom\u00e1tica e Inform\u00e1tica Industrial, Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marina","family":"Vall\u00e9s","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda de Sistemas y Autom\u00e1tica, Instituto de Autom\u00e1tica e Inform\u00e1tica Industrial, Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vicente","family":"Mata","sequence":"additional","affiliation":[{"name":"Departamento de Ingenier\u00eda Mec\u00e1nica y de Materiales, Instituto Universitario de Investigaci\u00f3n Concertado de Ingenier\u00eda Mec\u00e1nica y Biomec\u00e1nica, Universitat Polit\u00e8cnica de Val\u00e8ncia, 46022 Valencia, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8931-6401","authenticated-orcid":false,"given":"M\u00f3nica","family":"Ur\u00edzar","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Faculty of Engineering in Bilbao, University of the Basque Country, 48013 Bilbao, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,6,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Briot, S., and Khalil, W. 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