{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,15]],"date-time":"2026-01-15T10:18:57Z","timestamp":1768472337195,"version":"3.49.0"},"reference-count":42,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2022,6,1]],"date-time":"2022-06-01T00:00:00Z","timestamp":1654041600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Graz University of Technology"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>An optimal control of the combustion process of an engine ensures lower emissions and fuel consumption plus high efficiencies. Combustion parameters such as the peak firing pressure (PFP) and the crank angle (CA) corresponding to 50% of mass fraction burned (MFB50) are essential for a closed-loop control strategy. These parameters are based on the measured in-cylinder pressure that is typically gained by intrusive pressure sensors (PSs). These are costly and their durability is uncertain. To overcome these issues, the potential of using a virtual sensor based on the vibration signals acquired by a knock sensor (KS) for control of the combustion process is investigated. The present work introduces a data-driven approach where a signal-processing technique, designated as discrete wavelet transform (DWT), will be used as the preprocessing step for extracting informative features to perform regression tasks of the selected combustion parameters with extreme gradient boosting (XGBoost) regression models. The presented methodology will be applied to data from two different spark-ignited, single cylinder gas engines. Finally, an analysis is obtained where the important features based on the model\u2019s decisions are identified.<\/jats:p>","DOI":"10.3390\/s22114235","type":"journal-article","created":{"date-parts":[[2022,6,1]],"date-time":"2022-06-01T21:43:42Z","timestamp":1654119822000},"page":"4235","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Estimation of Combustion Parameters from Engine Vibrations Based on Discrete Wavelet Transform and Gradient Boosting"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9040-2860","authenticated-orcid":false,"given":"Achilles","family":"Kefalas","sequence":"first","affiliation":[{"name":"Institute of Thermodynamics and Sustainable Propulsion Systems, Graz University of Technology, 8010 Graz, Austria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8645-7973","authenticated-orcid":false,"given":"Andreas B.","family":"Ofner","sequence":"additional","affiliation":[{"name":"Know-Center GmbH, Research Center for Data-Driven Business & Big Data Analytics, 8010 Graz, Austria"}]},{"given":"Gerhard","family":"Pirker","sequence":"additional","affiliation":[{"name":"LEC GmbH, Large Engine Competence Center, 8010 Graz, Austria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2688-8701","authenticated-orcid":false,"given":"Stefan","family":"Posch","sequence":"additional","affiliation":[{"name":"LEC GmbH, Large Engine Competence Center, 8010 Graz, Austria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3257-743X","authenticated-orcid":false,"given":"Bernhard C.","family":"Geiger","sequence":"additional","affiliation":[{"name":"Know-Center GmbH, Research Center for Data-Driven Business & Big Data Analytics, 8010 Graz, Austria"}]},{"given":"Andreas","family":"Wimmer","sequence":"additional","affiliation":[{"name":"Institute of Thermodynamics and Sustainable Propulsion Systems, Graz University of Technology, 8010 Graz, Austria"},{"name":"LEC GmbH, Large Engine Competence Center, 8010 Graz, Austria"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Maurya, R.K. 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