{"id":"https://openalex.org/W3035390057","doi":"https://doi.org/10.1109/lra.2020.3001541","title":"Extremum Seeking Control for Stiffness Auto-Tuning of a Quasi-Passive Ankle Exoskeleton","display_name":"Extremum Seeking Control for Stiffness Auto-Tuning of a Quasi-Passive Ankle Exoskeleton","publication_year":2020,"publication_date":"2020-01-01","ids":{"openalex":"https://openalex.org/W3035390057","doi":"https://doi.org/10.1109/lra.2020.3001541","mag":"3035390057"},"language":"en","primary_location":{"id":"doi:10.1109/lra.2020.3001541","is_oa":false,"landing_page_url":"https://doi.org/10.1109/lra.2020.3001541","pdf_url":null,"source":{"id":"https://openalex.org/S4210169774","display_name":"IEEE Robotics and Automation Letters","issn_l":"2377-3766","issn":["2377-3766"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310319808","host_organization_name":"Institute of Electrical and Electronics Engineers","host_organization_lineage":["https://openalex.org/P4310319808"],"host_organization_lineage_names":["Institute of Electrical and Electronics Engineers"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"IEEE Robotics and Automation Letters","raw_type":"journal-article"},"type":"article","indexed_in":["crossref"],"open_access":{"is_oa":false,"oa_status":"closed","oa_url":null,"any_repository_has_fulltext":false},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5030652380","display_name":"Saurav Kumar","orcid":"https://orcid.org/0000-0002-2253-0462"},"institutions":[{"id":"https://openalex.org/I162577319","display_name":"The University of Texas at Dallas","ror":"https://ror.org/049emcs32","country_code":"US","type":"education","lineage":["https://openalex.org/I162577319"]}],"countries":["US"],"is_corresponding":true,"raw_author_name":"Saurav Kumar","raw_affiliation_strings":["Department of Electrical Engineering and the Department of Bioengineering, The University of Texas at Dallas, Richardson, USA"],"affiliations":[{"raw_affiliation_string":"Department of Electrical Engineering and the Department of Bioengineering, The University of Texas at Dallas, Richardson, USA","institution_ids":["https://openalex.org/I162577319"]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5098481131","display_name":"Matthew Zwall","orcid":null},"institutions":[{"id":"https://openalex.org/I162577319","display_name":"The University of Texas at Dallas","ror":"https://ror.org/049emcs32","country_code":"US","type":"education","lineage":["https://openalex.org/I162577319"]}],"countries":["US"],"is_corresponding":false,"raw_author_name":"Matthew Zwall","raw_affiliation_strings":["Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, USA"],"affiliations":[{"raw_affiliation_string":"Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, USA","institution_ids":["https://openalex.org/I162577319"]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5076214359","display_name":"Edgar Bol\u00edvar-Nieto","orcid":"https://orcid.org/0000-0001-7697-4387"},"institutions":[{"id":"https://openalex.org/I162577319","display_name":"The University of Texas at Dallas","ror":"https://ror.org/049emcs32","country_code":"US","type":"education","lineage":["https://openalex.org/I162577319"]}],"countries":["US"],"is_corresponding":false,"raw_author_name":"Edgar Bolivar-Nieto","raw_affiliation_strings":["Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, USA"],"affiliations":[{"raw_affiliation_string":"Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, USA","institution_ids":["https://openalex.org/I162577319"]}]},{"author_position":"middle","author":{"id":"https://openalex.org/A5051369788","display_name":"Robert D. Gregg","orcid":"https://orcid.org/0000-0002-0729-2857"},"institutions":[{"id":"https://openalex.org/I27837315","display_name":"University of Michigan\u2013Ann Arbor","ror":"https://ror.org/00jmfr291","country_code":"US","type":"education","lineage":["https://openalex.org/I27837315"]}],"countries":["US"],"is_corresponding":false,"raw_author_name":"Robert D. Gregg","raw_affiliation_strings":["Department of Electrical and Computer Engineering, The University of Michigan, Ann Arbor, USA"],"affiliations":[{"raw_affiliation_string":"Department of Electrical and Computer Engineering, The University of Michigan, Ann Arbor, USA","institution_ids":["https://openalex.org/I27837315"]}]},{"author_position":"last","author":{"id":"https://openalex.org/A5061986744","display_name":"Nicholas Gans","orcid":"https://orcid.org/0000-0003-3462-4199"},"institutions":[{"id":"https://openalex.org/I189196454","display_name":"The University of Texas at Arlington","ror":"https://ror.org/019kgqr73","country_code":"US","type":"education","lineage":["https://openalex.org/I189196454"]}],"countries":["US"],"is_corresponding":false,"raw_author_name":"Nicholas Gans","raw_affiliation_strings":["The University of Texas at Arlington Research Institute, University of Texas at Arlington, Arlington, USA"],"affiliations":[{"raw_affiliation_string":"The University of Texas at Arlington Research Institute, University of Texas at Arlington, Arlington, USA","institution_ids":["https://openalex.org/I189196454"]}]}],"institutions":[],"countries_distinct_count":1,"institutions_distinct_count":5,"corresponding_author_ids":["https://openalex.org/A5030652380"],"corresponding_institution_ids":["https://openalex.org/I162577319"],"apc_list":null,"apc_paid":null,"fwci":2.2719,"has_fulltext":false,"cited_by_count":36,"citation_normalized_percentile":{"value":0.88125629,"is_in_top_1_percent":false,"is_in_top_10_percent":false},"cited_by_percentile_year":{"min":97,"max":99},"biblio":{"volume":null,"issue":null,"first_page":"1","last_page":"1"},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T11601","display_name":"Neuroscience and Neural Engineering","score":0.9941999912261963,"subfield":{"id":"https://openalex.org/subfields/2804","display_name":"Cellular and Molecular Neuroscience"},"field":{"id":"https://openalex.org/fields/28","display_name":"Neuroscience"},"domain":{"id":"https://openalex.org/domains/1","display_name":"Life Sciences"}},"topics":[{"id":"https://openalex.org/T11601","display_name":"Neuroscience and Neural Engineering","score":0.9941999912261963,"subfield":{"id":"https://openalex.org/subfields/2804","display_name":"Cellular and Molecular Neuroscience"},"field":{"id":"https://openalex.org/fields/28","display_name":"Neuroscience"},"domain":{"id":"https://openalex.org/domains/1","display_name":"Life Sciences"}},{"id":"https://openalex.org/T10784","display_name":"Muscle activation and electromyography studies","score":0.9735999703407288,"subfield":{"id":"https://openalex.org/subfields/2204","display_name":"Biomedical Engineering"},"field":{"id":"https://openalex.org/fields/22","display_name":"Engineering"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11023","display_name":"Prosthetics and Rehabilitation Robotics","score":0.9372000098228455,"subfield":{"id":"https://openalex.org/subfields/2204","display_name":"Biomedical Engineering"},"field":{"id":"https://openalex.org/fields/22","display_name":"Engineering"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/exoskeleton","display_name":"Exoskeleton","score":0.949653148651123},{"id":"https://openalex.org/keywords/stiffness","display_name":"Stiffness","score":0.7425569891929626},{"id":"https://openalex.org/keywords/ankle","display_name":"Ankle","score":0.7134042978286743},{"id":"https://openalex.org/keywords/preferred-walking-speed","display_name":"Preferred walking speed","score":0.5306839942932129},{"id":"https://openalex.org/keywords/gait","display_name":"Gait","score":0.5299932360649109},{"id":"https://openalex.org/keywords/control-theory","display_name":"Control theory (sociology)","score":0.506112277507782},{"id":"https://openalex.org/keywords/joint-stiffness","display_name":"Joint stiffness","score":0.48175501823425293},{"id":"https://openalex.org/keywords/computer-science","display_name":"Computer science","score":0.44456806778907776},{"id":"https://openalex.org/keywords/simulation","display_name":"Simulation","score":0.42564696073532104},{"id":"https://openalex.org/keywords/spring","display_name":"Spring (device)","score":0.4226458966732025},{"id":"https://openalex.org/keywords/physical-medicine-and-rehabilitation","display_name":"Physical medicine and rehabilitation","score":0.42070674896240234},{"id":"https://openalex.org/keywords/engineering","display_name":"Engineering","score":0.31263166666030884},{"id":"https://openalex.org/keywords/structural-engineering","display_name":"Structural engineering","score":0.2590663433074951},{"id":"https://openalex.org/keywords/control","display_name":"Control (management)","score":0.1922016739845276},{"id":"https://openalex.org/keywords/medicine","display_name":"Medicine","score":0.14776739478111267},{"id":"https://openalex.org/keywords/artificial-intelligence","display_name":"Artificial intelligence","score":0.08738914132118225},{"id":"https://openalex.org/keywords/surgery","display_name":"Surgery","score":0.06879967451095581}],"concepts":[{"id":"https://openalex.org/C146549078","wikidata":"https://www.wikidata.org/wiki/Q191944","display_name":"Exoskeleton","level":2,"score":0.949653148651123},{"id":"https://openalex.org/C2779372316","wikidata":"https://www.wikidata.org/wiki/Q569057","display_name":"Stiffness","level":2,"score":0.7425569891929626},{"id":"https://openalex.org/C2778640784","wikidata":"https://www.wikidata.org/wiki/Q168002","display_name":"Ankle","level":2,"score":0.7134042978286743},{"id":"https://openalex.org/C70770792","wikidata":"https://www.wikidata.org/wiki/Q7239848","display_name":"Preferred walking speed","level":2,"score":0.5306839942932129},{"id":"https://openalex.org/C151800584","wikidata":"https://www.wikidata.org/wiki/Q2370000","display_name":"Gait","level":2,"score":0.5299932360649109},{"id":"https://openalex.org/C47446073","wikidata":"https://www.wikidata.org/wiki/Q5165890","display_name":"Control theory (sociology)","level":3,"score":0.506112277507782},{"id":"https://openalex.org/C2781415944","wikidata":"https://www.wikidata.org/wiki/Q559210","display_name":"Joint stiffness","level":3,"score":0.48175501823425293},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.44456806778907776},{"id":"https://openalex.org/C44154836","wikidata":"https://www.wikidata.org/wiki/Q45045","display_name":"Simulation","level":1,"score":0.42564696073532104},{"id":"https://openalex.org/C2778712887","wikidata":"https://www.wikidata.org/wiki/Q102836","display_name":"Spring (device)","level":2,"score":0.4226458966732025},{"id":"https://openalex.org/C99508421","wikidata":"https://www.wikidata.org/wiki/Q2678675","display_name":"Physical medicine and rehabilitation","level":1,"score":0.42070674896240234},{"id":"https://openalex.org/C127413603","wikidata":"https://www.wikidata.org/wiki/Q11023","display_name":"Engineering","level":0,"score":0.31263166666030884},{"id":"https://openalex.org/C66938386","wikidata":"https://www.wikidata.org/wiki/Q633538","display_name":"Structural engineering","level":1,"score":0.2590663433074951},{"id":"https://openalex.org/C2775924081","wikidata":"https://www.wikidata.org/wiki/Q55608371","display_name":"Control (management)","level":2,"score":0.1922016739845276},{"id":"https://openalex.org/C71924100","wikidata":"https://www.wikidata.org/wiki/Q11190","display_name":"Medicine","level":0,"score":0.14776739478111267},{"id":"https://openalex.org/C154945302","wikidata":"https://www.wikidata.org/wiki/Q11660","display_name":"Artificial intelligence","level":1,"score":0.08738914132118225},{"id":"https://openalex.org/C141071460","wikidata":"https://www.wikidata.org/wiki/Q40821","display_name":"Surgery","level":1,"score":0.06879967451095581}],"mesh":[],"locations_count":1,"locations":[{"id":"doi:10.1109/lra.2020.3001541","is_oa":false,"landing_page_url":"https://doi.org/10.1109/lra.2020.3001541","pdf_url":null,"source":{"id":"https://openalex.org/S4210169774","display_name":"IEEE Robotics and Automation Letters","issn_l":"2377-3766","issn":["2377-3766"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310319808","host_organization_name":"Institute of Electrical and Electronics Engineers","host_organization_lineage":["https://openalex.org/P4310319808"],"host_organization_lineage_names":["Institute of Electrical and Electronics Engineers"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"IEEE Robotics and Automation Letters","raw_type":"journal-article"}],"best_oa_location":null,"sustainable_development_goals":[{"score":0.8899999856948853,"display_name":"Affordable and clean energy","id":"https://metadata.un.org/sdg/7"}],"awards":[],"funders":[],"has_content":{"grobid_xml":false,"pdf":false},"content_urls":null,"referenced_works_count":33,"referenced_works":["https://openalex.org/W1540560684","https://openalex.org/W1975175976","https://openalex.org/W2015244452","https://openalex.org/W2015977498","https://openalex.org/W2018771588","https://openalex.org/W2028383950","https://openalex.org/W2053628882","https://openalex.org/W2054930183","https://openalex.org/W2058074226","https://openalex.org/W2073136132","https://openalex.org/W2082806606","https://openalex.org/W2095062552","https://openalex.org/W2096003909","https://openalex.org/W2097370531","https://openalex.org/W2100030191","https://openalex.org/W2149646777","https://openalex.org/W2153409886","https://openalex.org/W2163424852","https://openalex.org/W2166003201","https://openalex.org/W2170477928","https://openalex.org/W2374703312","https://openalex.org/W2471234362","https://openalex.org/W2700163520","https://openalex.org/W2763589635","https://openalex.org/W2883265178","https://openalex.org/W2922515478","https://openalex.org/W2946778909","https://openalex.org/W2968028487","https://openalex.org/W2969549923","https://openalex.org/W2972787835","https://openalex.org/W4285719527","https://openalex.org/W4300443332","https://openalex.org/W6709258235"],"related_works":["https://openalex.org/W2076010016","https://openalex.org/W2106701171","https://openalex.org/W4319872523","https://openalex.org/W4291274560","https://openalex.org/W2088250640","https://openalex.org/W3175516278","https://openalex.org/W1989142914","https://openalex.org/W2051161423","https://openalex.org/W2488929535","https://openalex.org/W4308735990"],"abstract_inverted_index":{"Recently,":[0],"it":[1,74],"has":[2],"been":[3],"shown":[4],"that":[5,93,169],"light-weight,":[6],"passive,":[7],"ankle":[8,116,186],"exoskeletons":[9,66],"with":[10,118,164],"spring-based":[11],"energy":[12],"store-and-release":[13],"mechanisms":[14],"can":[15],"reduce":[16],"the":[17,26,40,56,95,104,127,130,134,171,175,181,185],"muscular":[18,41,45,96,131],"effort":[19,46,97,132],"of":[20,25,87,106,124,160,174,193],"human":[21],"walking.":[22],"The":[23,188],"stiffness":[24,59,70,121,137,183],"spring":[27,58,136,161],"in":[28,36,79],"such":[29],"a":[30,68,85,88,114,119,145,147],"device":[31,89],"must":[32],"be":[33],"properly":[34],"tuned":[35],"order":[37],"to":[38,60,77],"minimize":[39],"effort.":[42],"However,":[43],"this":[44,110],"changes":[47,78],"for":[48,157],"different":[49,99,139],"locomotion":[50],"conditions":[51],"(e.g.,":[52],"walking":[53,80,100,140,172,201],"speed),":[54],"causing":[55],"optimal":[57,135],"vary":[61],"as":[62,170],"well.":[63],"Existing":[64],"passive":[65,107],"have":[67],"fixed":[69],"during":[71],"operation,":[72],"preventing":[73],"from":[75],"responding":[76],"conditions.":[81],"Thus,":[82],"there":[83],"is":[84,142],"need":[86],"and":[90,133,196,206],"auto-tuning":[91],"algorithm":[92,154],"minimizes":[94],"across":[98,138],"conditions,":[101],"while":[102],"preserving":[103],"advantages":[105],"exoskeletons.":[108],"In":[109],"letter,":[111],"we":[112],"developed":[113],"quasi-passive":[115],"exoskeleton":[117],"variable":[120],"mechanism":[122],"capable":[123],"self-tuning.":[125],"As":[126],"relationship":[128],"between":[129],"speeds":[141],"not":[143],"known":[144],"priori,":[146],"model-free,":[148],"discrete-time":[149],"extremum":[150],"seeking":[151],"control":[152],"(ESC)":[153],"was":[155],"implemented":[156],"real-time":[158],"optimization":[159],"stiffness.":[162],"Experiments":[163],"an":[165],"able-bodied":[166],"subject":[167],"demonstrate":[168],"speed":[173,202],"user":[176],"changes,":[177],"ESC":[178],"automatically":[179],"tunes":[180],"torsional":[182],"about":[184],"joint.":[187],"average":[189],"RMS":[190],"EMG":[191],"readings":[192],"tibialis":[194],"anterior":[195],"soleus":[197],"muscles":[198],"at":[199],"slow":[200],"decreased":[203],"by":[204],"26.48%":[205],"7.42%,":[207],"respectively.":[208]},"counts_by_year":[{"year":2025,"cited_by_count":7},{"year":2024,"cited_by_count":7},{"year":2023,"cited_by_count":6},{"year":2022,"cited_by_count":11},{"year":2021,"cited_by_count":5}],"updated_date":"2025-11-06T03:46:38.306776","created_date":"2025-10-10T00:00:00"}
