{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T09:18:11Z","timestamp":1776763091420,"version":"3.51.2"},"reference-count":74,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2019,6,26]],"date-time":"2019-06-26T00:00:00Z","timestamp":1561507200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Funda\u00e7\u00e3o Estadual de Amparo \u00e0 Pesquisa do Estado do Esp\u00edrito Santo","award":["72982608"],"award-info":[{"award-number":["72982608"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Child-Robot Interaction (CRI) has become increasingly addressed in research and applications. This work proposes a system for emotion recognition in children, recording facial images by both visual (RGB\u2014red, green and blue) and Infrared Thermal Imaging (IRTI) cameras. For this purpose, the Viola-Jones algorithm is used on color images to detect facial regions of interest (ROIs), which are transferred to the thermal camera plane by multiplying a homography matrix obtained through the calibration process of the camera system. As a novelty, we propose to compute the error probability for each ROI located over thermal images, using a reference frame manually marked by a trained expert, in order to choose that ROI better placed according to the expert criteria. Then, this selected ROI is used to relocate the other ROIs, increasing the concordance with respect to the reference manual annotations. Afterwards, other methods for feature extraction, dimensionality reduction through Principal Component Analysis (PCA) and pattern classification by Linear Discriminant Analysis (LDA) are applied to infer emotions. The results show that our approach for ROI locations may track facial landmarks with significant low errors with respect to the traditional Viola-Jones algorithm. These ROIs have shown to be relevant for recognition of five emotions, specifically disgust, fear, happiness, sadness, and surprise, with our recognition system based on PCA and LDA achieving mean accuracy (ACC) and Kappa values of 85.75% and 81.84%, respectively. As a second stage, the proposed recognition system was trained with a dataset of thermal images, collected on 28 typically developing children, in order to infer one of five basic emotions (disgust, fear, happiness, sadness, and surprise) during a child-robot interaction. The results show that our system can be integrated to a social robot to infer child emotions during a child-robot interaction.<\/jats:p>","DOI":"10.3390\/s19132844","type":"journal-article","created":{"date-parts":[[2019,6,27]],"date-time":"2019-06-27T02:43:41Z","timestamp":1561603421000},"page":"2844","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":50,"title":["Visual and Thermal Image Processing for Facial Specific Landmark Detection to Infer Emotions in a Child-Robot Interaction"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2500-9709","authenticated-orcid":false,"given":"Christiane","family":"Goulart","sequence":"first","affiliation":[{"name":"Northeast Network of Biotechnology (RENORBIO), Postgraduate Program in Biotechnology, Health Sciences Center, Federal University of Espirito Santo (UFES), Av. Marechal Campos, 1468, Vitoria-ES 29043-900, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0765-7094","authenticated-orcid":false,"given":"Carlos","family":"Valad\u00e3o","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Electrical Engineering, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8937-031X","authenticated-orcid":false,"given":"Denis","family":"Delisle-Rodriguez","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Electrical Engineering, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"},{"name":"Center of Medical Biophysics, University of Oriente, Patricio Lumumba s\/n, Santiago de Cuba 90500, Cuba"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Douglas","family":"Funayama","sequence":"additional","affiliation":[{"name":"Computer Engineering Department, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alvaro","family":"Favarato","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guilherme","family":"Baldo","sequence":"additional","affiliation":[{"name":"Electrical Engineering Department, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vin\u00edcius","family":"Binotte","sequence":"additional","affiliation":[{"name":"Postgraduate Program in Electrical Engineering, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3742-0952","authenticated-orcid":false,"given":"Eliete","family":"Caldeira","sequence":"additional","affiliation":[{"name":"Electrical Engineering Department, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1185-2773","authenticated-orcid":false,"given":"Teodiano","family":"Bastos-Filho","sequence":"additional","affiliation":[{"name":"Northeast Network of Biotechnology (RENORBIO), Postgraduate Program in Biotechnology, Health Sciences Center, Federal University of Espirito Santo (UFES), Av. Marechal Campos, 1468, Vitoria-ES 29043-900, Brazil"},{"name":"Postgraduate Program in Electrical Engineering, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"},{"name":"Electrical Engineering Department, UFES, Av. Fernando Ferrari, 514, Vitoria-ES 29075-910, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,6,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"20180026","DOI":"10.1098\/rstb.2018.0026","article-title":"Live human\u2013robot interactive public demonstrations with automatic emotion and personality prediction","volume":"374","author":"Gunes","year":"2019","journal-title":"Philos. Trans. R. Soc. B"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1038","DOI":"10.1007\/s10803-012-1645-2","article-title":"Social Robots as Embedded Reinforcers of Social Behavior in Children with Autism","volume":"43","author":"Kim","year":"2012","journal-title":"J. Autism Dev. Disord."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Valadao, C., Caldeira, E., Bastos-Filho, T., Frizera-Neto, A., and Carelli, R. (2016). A New Controller for a Smart Walker Based on Human-Robot Formation. Sensors, 16.","DOI":"10.3390\/s16071116"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1175","DOI":"10.1109\/34.954607","article-title":"Toward machine emotional intelligence: analysis of affective physiological state","volume":"23","author":"Picard","year":"2001","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Conn, K., Liu, C., Sarkar, N., Stone, W., and Warren, Z. (2008, January 1\u20133). Affect-sensitive assistive intervention technologies for children with autism: An individual-specific approach. Proceedings of the RO-MAN 2008\u2014The 17th IEEE International Symposium on Robot and Human Interactive Communication, Munich, Germany.","DOI":"10.1109\/ROMAN.2008.4600706"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Shier, W.A., and Yanushkevich, S.N. (2015, January 7\u20139). Biometrics in human-machine interaction. Proceedings of the 2015 International Conference on Information and Digital Technologies, Zilina, Slovakia.","DOI":"10.1109\/DT.2015.7222989"},{"key":"ref_7","unstructured":"Goulart, C., Valadao, C., Caldeira, E., and Bastos, T. (2018). Brain signal evaluation of children with Autism Spectrum Disorder in the interaction with a social robot. Biotechnol. Res. Innov."},{"key":"ref_8","first-page":"345","article-title":"Emotion Detection from Thermal Facial Imprint based on GLCM Features","volume":"11","author":"Latif","year":"2016","journal-title":"ARPN J. Eng. Appl. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1109\/TPAMI.2014.2366127","article-title":"Automatic analysis of facial affect: A survey of registration, representation, and recognition","volume":"37","author":"Sariyanidi","year":"2014","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Ko, B. (2018). A brief review of facial emotion recognition based on visual information. Sensors, 18.","DOI":"10.3390\/s18020401"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Rusli, N., Sidek, S.N., Yusof, H.M., and Latif, M.H.A. (2015). Non-Invasive Assessment of Affective States on Individual with Autism Spectrum Disorder: A Review. IFMBE Proceedings, Springer.","DOI":"10.1007\/978-981-10-0266-3_47"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1109\/TITB.2009.2034649","article-title":"Emotion recognition from EEG using higher order crossings","volume":"14","author":"Petrantonakis","year":"2009","journal-title":"IEEE Trans. Inf. Technol. Biomed."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Basu, A., Routray, A., Shit, S., and Deb, A.K. (2015, January 17\u201320). Human emotion recognition from facial thermal image based on fused statistical feature and multi-class SVM. Proceedings of the 2015 Annual IEEE India Conference (INDICON), New Delhi, India.","DOI":"10.1109\/INDICON.2015.7443712"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"7803","DOI":"10.1007\/s11042-016-3418-y","article-title":"Facial expression recognition based on local region specific features and support vector machines","volume":"76","author":"Ghimire","year":"2017","journal-title":"Multimed. Tools Appl."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Perikos, I., Paraskevas, M., and Hatzilygeroudis, I. (2018, January 6\u20138). Facial Expression Recognition Using Adaptive Neuro-fuzzy Inference Systems. Proceedings of the 2018 IEEE\/ACIS 17th International Conference on Computer and Information Science (ICIS), Singapore.","DOI":"10.1109\/ICIS.2018.8466438"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TAFFC.2014.2386334","article-title":"Automatic facial expression recognition using features of salient facial patches","volume":"6","author":"Happy","year":"2014","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Goulart, C., Valadao, C., Delisle-Rodriguez, D., Caldeira, E., and Bastos, T. (2019). Emotion analysis in children through facial emissivity of infrared thermal imaging. PLoS ONE, 14.","DOI":"10.1371\/journal.pone.0212928"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"250","DOI":"10.1016\/j.infrared.2017.01.002","article-title":"Human emotions detection based on a smart-thermal system of thermographic images","volume":"81","year":"2017","journal-title":"Infrared Phys. Technol."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Wang, S., Shen, P., and Liu, Z. (November, January 30). Facial expression recognition from infrared thermal images using temperature difference by voting. Proceedings of the 2012 IEEE 2nd International Conference on Cloud Computing and Intelligence Systems, Hangzhou, China.","DOI":"10.1109\/CCIS.2012.6664375"},{"key":"ref_20","unstructured":"Pop, F.M., Gordan, M., Florea, C., and Vlaicu, A. (2010, January 24\u201326). Fusion based approach for thermal and visible face recognition under pose and expresivity variation. Proceedings of the 9th RoEduNet IEEE International Conference, Sibiu, Romania."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"951","DOI":"10.1111\/psyp.12243","article-title":"Thermal infrared imaging in psychophysiology: Potentialities and limits","volume":"51","author":"Ioannou","year":"2014","journal-title":"Psychophysiology"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"83000C","DOI":"10.1117\/12.907123","article-title":"Face detection and eyeglasses detection for thermal face recognition","volume":"8300","author":"Zheng","year":"2012","journal-title":"SPIE Proc."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"682","DOI":"10.1109\/TMM.2010.2060716","article-title":"A Natural Visible and Infrared Facial Expression Database for Expression Recognition and Emotion Inference","volume":"12","author":"Wang","year":"2010","journal-title":"IEEE Trans. Multimed."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"17507","DOI":"10.3390\/s150717507","article-title":"Evaluation of fear using nonintrusive measurement of multimodal sensors","volume":"15","author":"Choi","year":"2015","journal-title":"Sensors"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1007\/s11760-010-0177-5","article-title":"Automatic facial expression recognition: Feature extraction and selection","volume":"6","author":"Lajevardi","year":"2012","journal-title":"Signal Image Video Process."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"784","DOI":"10.4218\/etrij.10.1510.0132","article-title":"Robust facial expression recognition based on local directional pattern","volume":"32","author":"Jabid","year":"2010","journal-title":"ETRI J."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Kabir, M.H., Jabid, T., and Chae, O. (September, January 29). A local directional pattern variance (LDPv) based face descriptor for human facial expression recognition. Proceedings of the 2010 7th IEEE International Conference on Advanced Video and Signal Based Surveillance, Boston, MA, USA.","DOI":"10.1109\/AVSS.2010.9"},{"key":"ref_28","unstructured":"Shan, C., Gong, S., and McOwan, P.W. (2005, January 14). Robust facial expression recognition using local binary patterns. Proceedings of the IEEE International Conference on Image Processing 2005, Genova, Italy."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Shan, C., and Gritti, T. (2008, January 1\u20134). Learning Discriminative LBP-Histogram Bins for Facial Expression Recognition. Proceedings of the British Machine Vision Conference 2008, Leeds, UK.","DOI":"10.5244\/C.22.27"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"779","DOI":"10.1109\/TSMCB.2009.2029076","article-title":"Image ratio features for facial expression recognition application","volume":"40","author":"Song","year":"2009","journal-title":"IEEE Trans. Syst. Man Cybern. Part B Cybern."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1109\/T-AFFC.2011.13","article-title":"Facial expression recognition using facial movement features","volume":"2","author":"Zhang","year":"2011","journal-title":"IEEE Trans. Affect. Comput."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1023\/B:VISI.0000013087.49260.fb","article-title":"Robust Real-Time Face Detection","volume":"57","author":"Viola","year":"2004","journal-title":"Int. J. Comput. Vis."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Jiang, B., Martinez, B., Valstar, M.F., and Pantic, M. (2014, January 24\u201328). Decision level fusion of domain specific regions for facial action recognition. Proceedings of the 2014 22nd International Conference on Pattern Recognition, Stockholm, Sweden.","DOI":"10.1109\/ICPR.2014.312"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"803","DOI":"10.1016\/j.imavis.2008.08.005","article-title":"Facial expression recognition based on local binary patterns: A comprehensive study","volume":"27","author":"Shan","year":"2009","journal-title":"Image Vis. Comput."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Kazemi, V., and Sullivan, J. (2014, January 24\u201327). One millisecond face alignment with an ensemble of regression trees. Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition, Columbus, OH, USA.","DOI":"10.1109\/CVPR.2014.241"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"9573","DOI":"10.3390\/s111009573","article-title":"Facial expression recognition based on local binary patterns and kernel discriminant isomap","volume":"11","author":"Zhao","year":"2011","journal-title":"Sensors"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Yang, J., Wang, X., Han, S., Wang, J., Park, D.S., and Wang, Y. (2019). Improved Real-Time Facial Expression Recognition Based on a Novel Balanced and Symmetric Local Gradient Coding. Sensors, 19.","DOI":"10.3390\/s19081899"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1016\/j.neuroscience.2014.02.009","article-title":"Thermal signature of fear conditioning in mild post traumatic stress disorder","volume":"266","author":"Giacinto","year":"2014","journal-title":"Neuroscience"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"138","DOI":"10.1016\/j.bbe.2014.09.001","article-title":"Methods of face localization in thermograms","volume":"35","author":"Marzec","year":"2015","journal-title":"Biocybern. Biomed. Eng."},{"key":"ref_40","unstructured":"Trujillo, L., Olague, G., Hammoud, R., and Hernandez, B. (2005, January 21\u201323). Automatic Feature Localization in Thermal Images for Facial Expression Recognition. Proceedings of the 2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR\u201905)\u2014Workshops, San Diego, CA, USA."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"979","DOI":"10.1109\/TBME.2009.2035926","article-title":"Classifying Affective States Using Thermal Infrared Imaging of the Human Face","volume":"57","author":"Nhan","year":"2010","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_42","first-page":"120","article-title":"The OpenCV library","volume":"25","author":"Bradski","year":"2000","journal-title":"Dr Dobb\u2019s J. Softw. Tools"},{"key":"ref_43","unstructured":"Malis, E., and Vargas, M. (2007). Deeper Understanding of the Homography Decomposition for Vision-Based Control. [Ph.D. Thesis, INRIA]."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"187","DOI":"10.5194\/jsss-4-187-2015","article-title":"Calibration of uncooled thermal infrared cameras","volume":"4","author":"Budzier","year":"2015","journal-title":"J. Sens. Sens. Syst."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1109\/34.908974","article-title":"Pca versus lda","volume":"23","author":"Kak","year":"2001","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1080\/01621459.1989.10478752","article-title":"Regularized discriminant analysis","volume":"84","author":"Friedman","year":"1989","journal-title":"J. Am. Stat. Assoc."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Kwon, O.W., Chan, K., Hao, J., and Lee, T.W. (2003, January 1\u20134). Emotion recognition by speech signals. Proceedings of the Eighth European Conference on Speech Communication and Technology, Geneva, Switzerland.","DOI":"10.21437\/Eurospeech.2003-80"},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Bamidis, P.D., Frantzidis, C.A., Konstantinidis, E.I., Luneski, A., Lithari, C., Klados, M.A., Bratsas, C., Papadelis, C.L., and Pappas, C. (2009). An integrated approach to emotion recognition for advanced emotional intelligence. International Conference on Human-Computer Interaction, Springer.","DOI":"10.1007\/978-3-642-02580-8_62"},{"key":"ref_49","unstructured":"Ververidis, D., Kotropoulos, C., and Pitas, I. (2004, January 17\u201321). Automatic emotional speech classification. Proceedings of the 2004 IEEE International Conference on Acoustics, Speech, and Signal Processing, Montreal, QC, Canada."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"415","DOI":"10.1109\/72.991427","article-title":"A comparison of methods for multiclass support vector machines","volume":"13","author":"Hsu","year":"2002","journal-title":"IEEE Trans. Neural Netw."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Japkowicz, N., and Shah, M. (2011). Evaluating Learning Algorithms: A Classification Perspective, Cambridge University Press.","DOI":"10.1017\/CBO9780511921803"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1007\/s12369-014-0245-z","article-title":"A robot learns the facial expressions recognition and face\/non-face discrimination through an imitation game","volume":"6","author":"Boucenna","year":"2014","journal-title":"Int. J. Soc. Robot."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Busso, C., Deng, Z., Yildirim, S., Bulut, M., Lee, C.M., Kazemzadeh, A., Lee, S., Neumann, U., and Narayanan, S. (2004, January 13\u201315). Analysis of emotion recognition using facial expressions, speech and multimodal information. Proceedings of the 6th International Conference on Multimodal Interfaces, State College, PA, USA.","DOI":"10.1145\/1027933.1027968"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1370","DOI":"10.1109\/JPROC.2003.817122","article-title":"Toward an affect-sensitive multimodal human-computer interaction","volume":"91","author":"Pantic","year":"2003","journal-title":"Proc. IEEE"},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1109\/79.911197","article-title":"Emotion recognition in human-computer interaction","volume":"18","author":"Cowie","year":"2001","journal-title":"IEEE Signal Process. Mag."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"757","DOI":"10.1109\/34.598232","article-title":"Coding, analysis, interpretation, and recognition of facial expressions","volume":"19","author":"Essa","year":"1997","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_57","first-page":"3474","article-title":"Recognition of facial expression from optical flow","volume":"74","author":"Mase","year":"1991","journal-title":"IEICE Trans. Inf. Syst."},{"key":"ref_58","doi-asserted-by":"crossref","unstructured":"Yacoob, Y., and Davis, L. (1994). Computing Spatio-Temporal Representations of Human Faces. [Ph.D. Thesis, Department of Computer Science, University of Maryland].","DOI":"10.1109\/CVPR.1994.323812"},{"key":"ref_59","doi-asserted-by":"crossref","unstructured":"Lee, C.M., Yildirim, S., Bulut, M., Kazemzadeh, A., Busso, C., Deng, Z., Lee, S., and Narayanan, S. (2004, January 4\u20138). Emotion recognition based on phoneme classes. Proceedings of the Eighth International Conference on Spoken Language Processing, Jeju Island, Korea.","DOI":"10.21437\/Interspeech.2004-322"},{"key":"ref_60","unstructured":"Nwe, T.L., Wei, F.S., and De Silva, L.C. (2001, January 19\u201322). Speech based emotion classification. Proceedings of the IEEE Region 10 International Conference on Electrical and Electronic Technology, TENCON 2001 (Cat. No. 01CH37239), Singapore."},{"key":"ref_61","doi-asserted-by":"crossref","unstructured":"Mehta, D., Siddiqui, M.F.H., and Javaid, A.Y. (2018). Facial emotion recognition: A survey and real-world user experiences in mixed reality. Sensors, 18.","DOI":"10.3390\/s18020416"},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"Bharatharaj, J., Huang, L., Mohan, R., Al-Jumaily, A., and Kr\u00e4geloh, C. (2017). Robot-Assisted Therapy for Learning and Social Interaction of Children with Autism Spectrum Disorder. Robotics, 6.","DOI":"10.3390\/robotics6010004"},{"key":"ref_63","doi-asserted-by":"crossref","unstructured":"Kosonogov, V., Zorzi, L.D., Honor\u00e9, J., Mart\u00ednez-Vel\u00e1zquez, E.S., Nandrino, J.L., Martinez-Selva, J.M., and Sequeira, H. (2017). Facial thermal variations: A new marker of emotional arousal. PLoS ONE, 12.","DOI":"10.1371\/journal.pone.0183592"},{"key":"ref_64","unstructured":"Yoshitomi, Y., Miyaura, T., Tomita, S., and Kimura, S. (October, January 29). Face identification using thermal image processing. Proceedings of the 6th IEEE International Workshop on Robot and Human Communication, RO-MAN\u201997 SENDAI, Sendai, Japan."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1007\/s11704-014-3295-3","article-title":"Emotion recognition from thermal infrared images using deep Boltzmann machine","volume":"8","author":"Wang","year":"2014","journal-title":"Front. Comput. Sci."},{"key":"ref_66","first-page":"34","article-title":"Human emotion recognition using thermal image processing and eigenfaces","volume":"5","author":"Bijalwan","year":"2015","journal-title":"Int. J. Eng. Sci. Res."},{"key":"ref_67","unstructured":"Yoshitomi, Y., Miyawaki, N., Tomita, S., and Kimura, S. (October, January 29). Facial expression recognition using thermal image processing and neural network. Proceedings of the 6th IEEE International Workshop on Robot and Human Communication, RO-MAN\u201997 SENDAI, Sendai, Japan."},{"key":"ref_68","unstructured":"Vukadinovic, D., and Pantic, M. (2005, January 12). Fully Automatic Facial Feature Point Detection Using Gabor Feature Based Boosted Classifiers. Proceedings of the 2005 IEEE International Conference on Systems, Man and Cybernetics, Waikoloa, HI, USA."},{"key":"ref_69","doi-asserted-by":"crossref","unstructured":"Di Nuovo, A., Conti, D., Trubia, G., Buono, S., and Di Nuovo, S. (2018). Deep Learning Systems for Estimating Visual Attention in Robot-Assisted Therapy of Children with Autism and Intellectual Disability. Robotics, 7.","DOI":"10.3390\/robotics7020025"},{"key":"ref_70","doi-asserted-by":"crossref","unstructured":"Suk, M., and Prabhakaran, B. (2014, January 23\u201328). Real-time mobile facial expression recognition system\u2014A case study. Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition Workshops, Columbus, OH, USA.","DOI":"10.1109\/CVPRW.2014.25"},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1049\/iet-bmt.2014.0104","article-title":"Survey on real-time facial expression recognition techniques","volume":"5","author":"Deshmukh","year":"2016","journal-title":"IET Biom."},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1016\/j.patcog.2011.05.006","article-title":"Facial expression recognition using radial encoding of local Gabor features and classifier synthesis","volume":"45","author":"Gu","year":"2012","journal-title":"Pattern Recognit."},{"key":"ref_73","doi-asserted-by":"crossref","first-page":"467","DOI":"10.1109\/TIP.2002.999679","article-title":"Gabor feature based classification using the enhanced fisher linear discriminant model for face recognition","volume":"11","author":"Liu","year":"2002","journal-title":"IEEE Trans. Image Process."},{"key":"ref_74","first-page":"13472","article-title":"Face detection and tracking using KLT and Viola Jones","volume":"11","author":"Boda","year":"2016","journal-title":"ARPN J. Eng. Appl. Sci."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/13\/2844\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:01:27Z","timestamp":1760187687000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/13\/2844"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,6,26]]},"references-count":74,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2019,7]]}},"alternative-id":["s19132844"],"URL":"https:\/\/doi.org\/10.3390\/s19132844","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,6,26]]}}}