{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,13]],"date-time":"2025-12-13T23:05:46Z","timestamp":1765667146875,"version":"build-2065373602"},"reference-count":55,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2016,2,27]],"date-time":"2016-02-27T00:00:00Z","timestamp":1456531200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This article studies the suitability of smartphones with built-in inertial sensors for biofeedback applications. Biofeedback systems use various sensors to measure body functions and parameters. These sensor data are analyzed, and the results are communicated back to the user, who then tries to act on the feedback signals. Smartphone inertial sensors can be used to capture body movements in biomechanical biofeedback systems. These sensors exhibit various inaccuracies that induce significant angular and positional errors. We studied deterministic and random errors of smartphone accelerometers and gyroscopes, primarily focusing on their biases. Based on extensive measurements, we determined accelerometer and gyroscope noise models and bias variation ranges. Then, we compiled a table of predicted positional and angular errors under various biofeedback system operation conditions. We suggest several bias compensation options that are suitable for various examples of use in real-time biofeedback applications. Measurements within the developed experimental biofeedback application show that under certain conditions, even uncompensated sensors can be used for real-time biofeedback. For general use, especially for more demanding biofeedback applications, sensor biases should be compensated. We are convinced that real-time biofeedback systems based on smartphone inertial sensors are applicable to many similar examples in sports, healthcare, and other areas.<\/jats:p>","DOI":"10.3390\/s16030301","type":"journal-article","created":{"date-parts":[[2016,2,29]],"date-time":"2016-02-29T10:55:59Z","timestamp":1456743359000},"page":"301","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":43,"title":["Suitability of Smartphone Inertial Sensors for Real-Time Biofeedback Applications"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6234-8561","authenticated-orcid":false,"given":"Anton","family":"Kos","sequence":"first","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Ljubljana 1000, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sa\u0161o","family":"Toma\u017ei\u010d","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Ljubljana 1000, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4408-327X","authenticated-orcid":false,"given":"Anton","family":"Umek","sequence":"additional","affiliation":[{"name":"Faculty of Electrical Engineering, University of Ljubljana, Ljubljana 1000, Slovenia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"435","DOI":"10.1007\/BF00998946","article-title":"Biofeedback in physical medicine and rehabilitation","volume":"3","author":"Fernando","year":"1978","journal-title":"Biofeedback Self Regul."},{"key":"ref_2","unstructured":"Basmajian, J.V. (1989). Biofeedback: Principles and Practice for Clinicians, Williams & Wilkins. [2nd Ed.]."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Sandweiss, J.H. (1985). Biofeedback and Sports Science, Springer US.","DOI":"10.1007\/978-1-4757-9465-6"},{"key":"ref_4","unstructured":"Blumenstein, B., Bar-Eli, M., and Tenenbaum, G. (2002). Brain and Body in Sport and Exercise: Biofeedback Applications in Performance Enhancement, John Wiley & Sons."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Giggins, O.M., Persson, U.M., and Caulfield, B. (2013). Biofeedback in rehabilitation. J. Neuroeng. Rehabil., 10.","DOI":"10.1186\/1743-0003-10-60"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Huang, H., Wolf, S.L., and He, J. (2006). Recent developments in biofeedback for neuromotor rehabilitation. J. Neuroeng. Rehabil., 3.","DOI":"10.1186\/1743-0003-3-11"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1109\/TBME.2012.2222640","article-title":"iBalance-ABF: A smartphone-based audio-biofeedback balance system","volume":"60","author":"Franco","year":"2013","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Alahakone, A.U., and Arosha Senanayake, S.M.N. (2009, January 4\u20137). A real time vibrotactile biofeedback system for improving lower extremity kinematic motion during sports training. Proceedings of the International Conference of Soft Computing and Pattern Recognition, Malacca, Malaysia.","DOI":"10.1109\/SoCPaR.2009.120"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"206","DOI":"10.2519\/jospt.2010.3166","article-title":"Reducing impact loading during running with the use of real-time visual feedback","volume":"40","author":"Crowell","year":"2010","journal-title":"J. Orthop. Sport Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"919","DOI":"10.1109\/TRO.2007.907481","article-title":"TIKL: Development of a wearable vibrotactile feedback suit for improved human motor learning","volume":"23","author":"Lieberman","year":"2007","journal-title":"IEEE Trans. Robot."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"21","DOI":"10.3758\/s13423-012-0333-8","article-title":"Augmented visual, auditory, haptic, and multimodal feedback in motor learning: A review","volume":"20","author":"Sigrist","year":"2013","journal-title":"Psychon. Bull. Rev."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"909","DOI":"10.1007\/s00221-014-4167-7","article-title":"Sonification and haptic feedback in addition to visual feedback enhances complex motor task learning","volume":"233","author":"Sigrist","year":"2015","journal-title":"Exp. Brain Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"4097","DOI":"10.3390\/s150204097","article-title":"Augmenting the senses: A review on sensor-based learning support","volume":"15","author":"Schneider","year":"2015","journal-title":"Sensors"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1007\/s40279-015-0332-9","article-title":"The use of wearable microsensors to quantify sport-specific movements","volume":"45","author":"Chambers","year":"2015","journal-title":"Sports Med."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2776","DOI":"10.1016\/j.jbiomech.2008.06.024","article-title":"Systematic accuracy and precision analysis of video motion capturing systems\u2014Exemplified on the Vicon-460 system","volume":"41","author":"Windolf","year":"2008","journal-title":"J. Biomech."},{"key":"ref_16","unstructured":"Josefsson, T. (2002). Motion Analysis System. (6,437,820), U.S. Patent."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1007\/s00779-015-0886-4","article-title":"Wearable training system with real-time biofeedback and gesture user interface","volume":"19","author":"Umek","year":"2015","journal-title":"Pers. Ubiquitous Comput."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1007\/s00779-010-0292-x","article-title":"Mobile phone-based pervasive fall detection","volume":"14","author":"Dai","year":"2010","journal-title":"Pers. Ubiquitous Comput."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"6229","DOI":"10.3390\/s140406229","article-title":"A wearable system for gait training in subjects with Parkinson\u2019s disease","volume":"14","author":"Casamassima","year":"2014","journal-title":"Sensors"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Giggins, O.M., Sweeney, K.T., and Caulfield, B. (2014). Rehabilitation exercise assessment using inertial sensors: A cross-sectional analytical study. J. Neuroeng. Rehabil., 11.","DOI":"10.1186\/1743-0003-11-158"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1929","DOI":"10.1007\/s00779-014-0799-7","article-title":"Performance monitoring and evaluation in dance teaching with mobile sensing technology","volume":"18","author":"Wei","year":"2014","journal-title":"Pers. Ubiquitous Comput."},{"key":"ref_22","unstructured":"Smartphone-penetration. Available online: http:\/\/en.wikipedia.org\/wiki\/List_of_countries_by_smartphone_penetration."},{"key":"ref_23","unstructured":"Number of smartphones. Available online: http:\/\/www.emarketer.com\/Article\/2-Billion-Consumers-Worldwide-Smartphones-by-2016\/1011694."},{"key":"ref_24","unstructured":"Trackman Golf (2009). We need to define industry standards for accuracy. Trackman News, Available online: http:\/\/trackmangolf.com."},{"key":"ref_25","unstructured":"Fitzgerald, A.M. A practical Guide to MEMS inertial sensors. Available online: http:\/\/www.amfitzgerald.com\/papers\/131114_AMFitzgerald_MEMS_Inertial_Sensors.pdf."},{"key":"ref_26","unstructured":"Looney, M. A Simple Calibration for MEMS Gyroscopes. Available online: http:\/\/www.edn.com\/design\/sensors\/4363439\/A-simple-calibration-for-MEMS-gyroscopes."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1109\/MCS.2009.935122","article-title":"How good is your gyro: Ask the experts","volume":"30","author":"Grewal","year":"2010","journal-title":"IEEE Control Syst."},{"key":"ref_28","unstructured":"Motion Sensing in the iPhone 4: MEMS Accelerometer. Available online: http:\/\/www.memsjournal.com\/2010\/12\/motion-sensing-in-the-iphone-4-mems-accelerometer.html."},{"key":"ref_29","unstructured":"ST Microelectronics, M.E.M.S. Digital Output Motion Sensor Ultra Low-Power High. Performance 3-Axes \u201cNano\u201d Accelerometer, LIS331DLH Specifications. ST Microelectronics. Available online: http:\/\/www.st.com\/web\/en\/resource\/technical\/document\/datasheet\/CD00213470.pdf."},{"key":"ref_30","unstructured":"Motion Sensing in the iPhone 4: MEMS Gyroscope. Available online: http:\/\/www.memsjournal.com\/2011\/01\/motion-sensing-in-the-iphone-4-mems-gyroscope.html."},{"key":"ref_31","unstructured":"ST Microelectronics, M.E.M.S. Motion Sensor: Ultra-Stable Three-Axis Digital Output Gyroscope, L3G4200D Specifications. ST Microelectronics. Available online: http:\/\/www.st.com\/web\/en\/resource\/technical\/document\/datasheet\/CD00265057.pdf."},{"key":"ref_32","unstructured":"ST Microelectronics Everything about STMicroelectronics\u2019 3-Axis Digital MEMS Gyroscopes, TA0343, Technical article. ST Microelectronics. Available online: http:\/\/www.st.com\/web\/en\/resource\/technical\/document\/technical_article\/DM00034730.pdf."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"140","DOI":"10.1109\/TIM.2007.908635","article-title":"Analysis and modeling of inertial sensors using Allan variance","volume":"57","author":"Hou","year":"2008","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_34","unstructured":"Stockwell, W. Bias Stability Measurement: Allan Variance. Available online: http:\/\/www.moog-crossbow.com\/Literature\/Application_Notes_Papers\/Gyro_Bias_Stability_Measurement_using_Allan_Variance.pdf."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1109\/MCOM.2013.6495768","article-title":"MEMS inertial sensors: A tutorial overview","volume":"51","author":"Shaeffer","year":"2013","journal-title":"IEEE Commun. Mag."},{"key":"ref_36","first-page":"1","article-title":"A study of mobile sensing using smartphones","volume":"2013","author":"Liu","year":"2013","journal-title":"Int. J. Distrib. Sens. Netw."},{"key":"ref_37","unstructured":"Ortiz, J.L.R. (2015). Smartphone-Based Human Activity Recognition, Springer."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"170","DOI":"10.5081\/jgps.7.2.170","article-title":"Calibration and stochastic modelling of inertial navigation sensor errors","volume":"7","author":"Pagiatakis","year":"2008","journal-title":"J. GPS"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1017\/S0373463307004560","article-title":"A standard testing and calibration procedure for low cost MEMS inertial sensors and units","volume":"61","author":"Aggarwal","year":"2008","journal-title":"J. Navig."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1720","DOI":"10.3390\/s120201720","article-title":"Signal processing of MEMS gyroscope arrays to improve accuracy using a 1st order markov for rate signal modeling","volume":"12","author":"Jiang","year":"2012","journal-title":"Sensors"},{"key":"ref_41","unstructured":"Aggarwal, P., Syed, Z., Niu, X., and El-Sheimy, N. (2006, January 8\u201313). Cost-effective testing and calibration of low cost MEMS sensors for integrated positioning, navigation and mapping systems. Proceedings of the XIII Fig Conference, Munich, Germany."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"517","DOI":"10.1016\/j.sna.2012.12.024","article-title":"Compensation of drifts in high-Q MEMS gyroscopes using temperature self-sensing","volume":"201","author":"Prikhodko","year":"2013","journal-title":"Sens. Actuators A Phys."},{"key":"ref_43","unstructured":"Weinberg, H. (2011). Analog Devices. Technical Article MS-2158."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1109\/PROC.1966.4634","article-title":"Statistics of atomic frequency standards","volume":"54","author":"Allan","year":"1966","journal-title":"IEEE Proc."},{"key":"ref_45","unstructured":"IEEE Standard Specification Format Guide and Test Procedure for Single-Axis Laser Gyros. Available online: http:\/\/ieeexplore.ieee.org\/xpl\/articleDetails.jsp?arnumber=494457&filter=AND%28p_Publication_Number:3601%29."},{"key":"ref_46","unstructured":"Allan Variance. Available online: http:\/\/www.allanstime.com\/AllanVariance\/."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1917","DOI":"10.1088\/0957-0233\/18\/7\/018","article-title":"The use of the Allan deviation for the measurement of the noise and drift performance of microwave radiometers","volume":"18","author":"Land","year":"2007","journal-title":"Meas. Sci. Technol."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Hongwei, S., Yuli, L., and Guangfeng, C. (2010, January 17\u201319). Relations between the Standard variance and the Allan variance. Proceedings of the 2010 International Conference on Computational and Information Sciences, Chengdu, China.","DOI":"10.1109\/ICCIS.2010.23"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"493","DOI":"10.1109\/JSEN.2005.844538","article-title":"Mechanical-thermal noise in MEMS gyroscopes","volume":"5","author":"Leland","year":"2005","journal-title":"IEEE Sens. J."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1016\/S0038-1101(02)00220-4","article-title":"Measurement of noise characteristics of MEMS accelerometers","volume":"47","author":"Korman","year":"2003","journal-title":"Solid. State. Electron."},{"key":"ref_51","unstructured":"Woodman, O.J. (2007). An Introduction to Inertial Navigation, University of Cambridge, Computer Laboratory. Techical Report UCAMCL-TR-696 14."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"14885","DOI":"10.3390\/s140814885","article-title":"Time-and Computation-Efficient Calibration of MEMS 3D Accelerometers and Gyroscopes","volume":"14","year":"2014","journal-title":"Sensors"},{"key":"ref_53","unstructured":"Woods, T. Maintain A Quiet Head. Available online: http:\/\/www.golfdigest.com\/golf-instruction\/2009-10\/tiger_woods_keep_quiet_head."},{"key":"ref_54","unstructured":"Doyle, B. Experts Weigh in on Head Movement during the Golf Swing. Available online: https:\/\/foreverbettergolf.com\/articles\/experts-weigh-in-on-head-movement-during-the-golf-swing\/."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Karantonis, D.M., Narayanan, M.R., Mathie, M., Lovell, N.H., and Celler, B.G. (2006). Implementation of a real-time human movement classifier using a triaxial accelerometer for ambulatory monitoring. IEEE Trans. Inf. Technol. Biomed., 10.","DOI":"10.1109\/TITB.2005.856864"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/3\/301\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:19:50Z","timestamp":1760210390000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/3\/301"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2016,2,27]]},"references-count":55,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2016,3]]}},"alternative-id":["s16030301"],"URL":"https:\/\/doi.org\/10.3390\/s16030301","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2016,2,27]]}}}