{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,5]],"date-time":"2026-09-05T01:42:44Z","timestamp":1788572564784,"version":"build-2803163510"},"reference-count":57,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2025,4,9]],"date-time":"2025-04-09T00:00:00Z","timestamp":1744156800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Carl Zeiss Foundation for the HeiAge Project","award":["P2017-01-002"],"award-info":[{"award-number":["P2017-01-002"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>With rapid advancements in lower-limb exoskeleton hardware, two key challenges persist: the accurate assessment of user biomechanics and the reliable control of device behavior in real-world settings. This study presents a modular, sensor-based system designed to enhance both biomechanical evaluation and control of lower-limb exoskeletons, leveraging advanced sensor technologies and fuzzy logic. The system addresses the limitations of traditional lab-bound, high-cost methods by integrating inertial measurement units, force-sensitive resistors, and load cells into instrumented crutches and 3D-printed insoles. These components work independently or in unison to capture critical biomechanical metrics, including the anteroposterior center of pressure and crutch ground reaction forces. Data are processed in real time by a central unit using fuzzy logic algorithms to estimate gait phases and support exoskeleton control. Validation experiments with three participants, benchmarked against motion capture and force plate systems, demonstrate the system\u2019s ability to reliably detect gait phases and accurately measure biomechanical parameters. By offering an open-source, cost-effective design, this work contributes to the advancement of wearable robotics and promotes broader innovation and accessibility in exoskeleton research.<\/jats:p>","DOI":"10.3390\/s25082379","type":"journal-article","created":{"date-parts":[[2025,4,9]],"date-time":"2025-04-09T07:49:02Z","timestamp":1744184942000},"page":"2379","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Development and Validation of a Modular Sensor-Based System for Gait Analysis and Control in Lower-Limb Exoskeletons"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7871-778X","authenticated-orcid":false,"given":"Giorgos","family":"Marinou","sequence":"first","affiliation":[{"name":"Institute of Computer Engineering (ZITI), Heidelberg University, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ibrahima","family":"Kourouma","sequence":"additional","affiliation":[{"name":"Institute of Computer Engineering (ZITI), Heidelberg University, 69120 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1353-0943","authenticated-orcid":false,"given":"Katja","family":"Mombaur","sequence":"additional","affiliation":[{"name":"Institute for Anthropomatics and Robotics, Optimization and Biomechanics for Human-Centred Robotics, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany"},{"name":"Department of Systems Design Engineering, CERC Human-Centred Robotics and Machine Intelligence, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,4,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"du Plessis, T., Djouani, K., and Oosthuizen, C. (2021). A review of active hand exoskeletons for rehabilitation and assistance. Robotics, 10.","DOI":"10.3390\/robotics10010040"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"283","DOI":"10.1007\/s41315-018-0064-8","article-title":"Upper limb rehabilitation using robotic exoskeleton systems: A systematic review","volume":"2","author":"Rehmat","year":"2018","journal-title":"Int. J. Intell. Robot. Appl."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Wang, T., Zhang, B., Liu, C., Liu, T., Han, Y., Wang, S., Ferreira, J.P., Dong, W., and Zhang, X. (2022). A Review on the Rehabilitation Exoskeletons for the Lower Limbs of the Elderly and the Disabled. Electronics, 11.","DOI":"10.3390\/electronics11030388"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Smith, A.J., Fournier, B.N., Nantel, J., and Lemaire, E.D. (2020). Estimating upper extremity joint loads of persons with spinal cord injury walking with a lower extremity powered exoskeleton and forearm crutches. J. Biomech., 107.","DOI":"10.1016\/j.jbiomech.2020.109835"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Marinou, G., Sloot, L., and Mombaur, K. (2022, January 21\u201324). Towards efficient lower-limb exoskeleton evaluation: Defining biomechanical metrics to quantify assisted gait familiarization. Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics, Seoul, Republic of Korea.","DOI":"10.1109\/BioRob52689.2022.9925360"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"123040","DOI":"10.1109\/ACCESS.2021.3110595","article-title":"Review on Control Strategies for Lower Limb Rehabilitation Exoskeletons","volume":"9","author":"Li","year":"2021","journal-title":"IEEE Access"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Barbareschi, G., Richards, R., Thornton, M., Carlson, T., and Holloway, C. (2015, January 25\u201329). Statically vs dynamically balanced gait: Analysis of a robotic exoskeleton compared with a human. Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, Milan, Italy.","DOI":"10.1109\/EMBC.2015.7319937"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1179\/2045772313Y.0000000126","article-title":"Vertical ground reaction force-based analysis of powered exoskeleton-assisted walking in persons with motor-complete paraplegia","volume":"36","author":"Fineberg","year":"2013","journal-title":"J. Spinal Cord Med."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Kanko, R.M., Laende, E.K., Davis, E.M., Selbie, W.S., and Deluzio, K.J. (2021). Concurrent assessment of gait kinematics using marker-based and markerless motion capture. J. Biomech., 127.","DOI":"10.1016\/j.jbiomech.2021.110665"},{"key":"ref_10","unstructured":"Ribeiro, N.F., and Santos, C.P. (2017, January 16\u201318). Inertial measurement units: A brief state of the art on gait analysis. Proceedings of the ENBENG 2017\u20145th Portuguese Meeting on Bioengineering, Proceedings, Coimbra, Portugal."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Park, S., and Yoon, S. (2021). Validity Evaluation of an Inertial Measurement Unit (IMU) in Gait Analysis Using Statistical Parametric Mapping (SPM). Sensors, 21.","DOI":"10.3390\/s21113667"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"6891","DOI":"10.3390\/s140406891","article-title":"IMU-Based Joint Angle Measurement for Gait Analysis","volume":"14","author":"Seel","year":"2014","journal-title":"Sensors"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"De Miguel-Fern\u00e1ndez, J., Salazar-Del Rio, M., Rey-Prieto, M., Bay\u00f3n, C., Guirao-Cano, L., Font-Llagunes, J.M., and Lobo-Prat, J. (2023). Inertial sensors for gait monitoring and design of adaptive controllers for exoskeletons after stroke: A feasibility study. Front. Bioeng. Biotechnol., 11.","DOI":"10.3389\/fbioe.2023.1208561"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"16-00595","DOI":"10.1299\/jbse.16-00595","article-title":"Performance estimation of the lower limb exoskeleton for plantarflexion using surface electromyography (sEMG) signals","volume":"12","author":"Park","year":"2017","journal-title":"J. Biomech. Sci. Eng."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Kong, Y.K., Choi, K.H., Cho, M.U., Kim, S.Y., Kim, M.J., Shim, J.W., Park, S.S., Kim, K.R., Seo, M.T., and Chae, H.S. (2022). Ergonomic Assessment of a Lower-Limb Exoskeleton through Electromyography and Anybody Modeling System. Int. J. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph19138088"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"908","DOI":"10.1016\/j.jelekin.2012.04.009","article-title":"The effect of perspiration on the sEMG amplitude and power spectrum","volume":"22","author":"Damecour","year":"2012","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.arcontrol.2022.04.003","article-title":"From sensing to control of lower limb exoskeleton: A systematic review","volume":"53","author":"Sun","year":"2022","journal-title":"Annu. Rev. Control"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Ne\u0165ukov\u00e1, S., Bejtic, M., Mal\u00e1, C., Hor\u00e1kov\u00e1, L., Kut\u00edlek, P., Kauler, J., and Krupi\u010dka, R. (2022). Lower Limb Exoskeleton Sensors: State-of-the-Art. Sensors, 22.","DOI":"10.3390\/s22239091"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Moon, D.H., Kim, D., and Hong, Y.D. (2019). Intention Detection Using Physical Sensors and Electromyogram for a Single Leg Knee Exoskeleton. Sensors, 19.","DOI":"10.3390\/s19204447"},{"key":"ref_20","unstructured":"Kawamoto, H., Lee, S., Kanbe, S., and Sankai, Y. (2003, January 8). Power assist method for HAL-3 using EMG-based feedback controller. Proceedings of the SMC\u201903 Conference Proceedings. 2003 IEEE International Conference on Systems, Man and Cybernetics. Conference Theme\u2014System Security and Assurance (Cat. No.03CH37483), Washington, DC, USA."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1109\/MSPEC.2005.1515961","article-title":"The rise of the body bots [robotic exoskeletons]","volume":"42","author":"Guizzo","year":"2005","journal-title":"IEEE Spectr."},{"key":"ref_22","unstructured":"Kawamoto, H., Kanbe, S., and Sankai, Y. (2003, January 2). Power assist method for HAL-3 estimating operator\u2019s intention based on motion information. Proceedings of the 12th IEEE International Workshop on Robot and Human Interactive Communication, 2003. Proceedings. ROMAN 2003, Millbrae, CA, USA."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"16213","DOI":"10.1109\/JSEN.2021.3076114","article-title":"Neuromechanical Signal-Based Parallel and Scalable Model for Lower Limb Movement Recognition","volume":"21","author":"Iqbal","year":"2021","journal-title":"IEEE Sens. J."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Zhang, P., Gao, X., Miao, M., and Zhao, P. (2022). Design and Control of a Lower Limb Rehabilitation Robot Based on Human Motion Intention Recognition with Multi-Source Sensor Information. Machines, 10.","DOI":"10.3390\/machines10121125"},{"key":"ref_25","unstructured":"Gil, I.C. (2021). Development of an Instrumented Crutch for Quantitative Gait Monitoring and Diagnosis of Patients with Multiple Sclerosis. [Ph.D. Thesis, University of the Basque Country]."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Khandakar, A., Mahmud, S., Chowdhury, M.E.H., Reaz, M.B.I., Kiranyaz, S., Mahbub, Z.B., Ali, S.H.M., Bakar, A.A.A., Ayari, M.A., and Alhatou, M. (2022). Design and Implementation of a Smart Insole System to Measure Plantar Pressure and Temperature. Sensors, 22.","DOI":"10.3390\/s22197599"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Manupibul, U., Charoensuk, W., and Kaimuk, P. (2014, January 26\u201328). Design and development of SMART insole system for plantar pressure measurement in imbalance human body and heavy activities. Proceedings of the 7th 2014 Biomedical Engineering International Conference, Fukuoka, Japan.","DOI":"10.1109\/BMEiCON.2014.7017420"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Nascimento, D.H.A., Magalh\u00e3es, F.A., Sabino, G.S., Resende, R.A., Duarte, M.L.M., and Vimieiro, C.B.S. (2022). Development of a Human Motion Analysis System Based on Sensorized Insoles and Machine Learning Algorithms for Gait Evaluation. Inventions, 7.","DOI":"10.3390\/inventions7040098"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"16589","DOI":"10.3390\/s150716589","article-title":"An Ambulatory System for Gait Monitoring Based on Wireless Sensorized Insoles","volume":"15","author":"Fontecha","year":"2015","journal-title":"Sensors"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Silva, P.M.M., Holanda, L.J., Granados, E.E., and Morya, E. (2017, January 6\u201311). Building Pressure-Sensitive Foot Insoles for Public Health Evaluation in Smart Cities. Proceedings of the 2017 IEEE First Summer School on Smart Cities (S3C), Natal, Brazil.","DOI":"10.1109\/S3C.2017.8501375"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"72221","DOI":"10.1109\/ACCESS.2019.2920134","article-title":"Personalised Control of Robotic Ankle Exoskeleton Through Experience-Based Adaptive Fuzzy Inference","volume":"7","author":"Yin","year":"2019","journal-title":"IEEE Access"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1177\/0018720819883500","article-title":"Assessing the Involvement of Users During Development of Lower Limb Wearable Robotic Exoskeletons: A Survey Study","volume":"62","author":"Beckerle","year":"2020","journal-title":"Hum. Factors"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1173","DOI":"10.1109\/TITB.2010.2058813","article-title":"Computational Intelligent Gait-Phase Detection System to Identify Pathological Gait","volume":"14","author":"Senanayake","year":"2010","journal-title":"IEEE Trans. Inf. Technol. Biomed."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"3369","DOI":"10.1109\/TIM.2015.2465751","article-title":"Wireless Instrumented Crutches for Force and Movement Measurements for Gait Monitoring","volume":"64","author":"Sardini","year":"2015","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1308","DOI":"10.1109\/TIM.2018.2799019","article-title":"Estimation of ground reaction forces using low-cost instrumented forearm crutches","volume":"67","author":"Seylan","year":"2018","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Chen, Y.F., Napoli, D., Agrawal, S.K., and Zanotto, D. (2018, January 26\u201329). Smart Crutches: Towards Instrumented Crutches for Rehabilitation and Exoskeletons-Assisted Walking. Proceedings of the 2018 7th IEEE International Conference on Biomedical Robotics and Biomechatronics (Biorob), Enschede, The Netherlands.","DOI":"10.1109\/BIOROB.2018.8487662"},{"key":"ref_37","unstructured":"Kong, K., and Tomizuka, M. (2008, January 19\u201323). Smooth and continuous human gait phase detection based on foot pressure patterns. Proceedings of the 2008 IEEE International Conference on Robotics and Automation, Pasadena, CA, USA."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"338","DOI":"10.1016\/S0019-9958(65)90241-X","article-title":"Fuzzy sets","volume":"8","author":"Zadeh","year":"1965","journal-title":"Inf. Control"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Laffranchi, M., D\u2019Angella, S., Vassallo, C., Piezzo, C., Canepa, M., De Giuseppe, S., Di Salvo, M., Succi, A., Cappa, S., and Cerruti, G. (2021). User-Centered Design and Development of the Modular TWIN Lower Limb Exoskeleton. Front. Neurorobotics, 15.","DOI":"10.3389\/fnbot.2021.709731"},{"key":"ref_40","unstructured":"Marinou, G., and Kourouma, I. (2025, April 08). MoSeS-LLEx: A Modular Sensor System for Lower-Limb Exoskeletons. Available online: https:\/\/github.com\/ibokou\/MoSeS-LLEx."},{"key":"ref_41","unstructured":"FUTEK Advanced Sensor Technology (2025, April 08). Miniature Threaded In Line Load Cell. Available online: https:\/\/www.futek.com\/store\/load-cells\/threaded-in-line-load-cells\/miniature-threaded-in-line-LCM200\/FSH03903."},{"key":"ref_42","unstructured":"Avia Semiconductor (2016). 24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales, Avia Semiconductor. Available online: http:\/\/en.aviaic.com\/detail\/730856.html."},{"key":"ref_43","unstructured":"Adafruit Industries (2025, April 08). Adafruit ESP32-S3 Feather. Available online: https:\/\/learn.adafruit.com\/adafruit-esp32-s3-feather\/overview."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"530","DOI":"10.1016\/j.clinbiomech.2012.12.003","article-title":"In vivo hip joint loads during three methods of walking with forearm crutches","volume":"28","author":"Damm","year":"2013","journal-title":"Clin. Biomech."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1016\/j.sna.2018.10.019","article-title":"Proportion-based fuzzy gait phase detection using the smart insole","volume":"284","author":"Ding","year":"2018","journal-title":"Sens. Actuators A Phys."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"191","DOI":"10.15446\/dyna.v85n205.66432","article-title":"Experimental characterization, modeling and compensation of hysteresis in force sensing resistors","volume":"85","author":"Matute","year":"2018","journal-title":"Rev. DYNA"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"9002","DOI":"10.4081\/ejtm.2020.9002","article-title":"Validation of a portable system for spatial-temporal gait parameters based on a single inertial measurement unit and a mobile application","volume":"30","author":"Aqueveque","year":"2020","journal-title":"Eur. J. Transl. Myol."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Coviello, G., Avitabile, G., Florio, A., and Talarico, C. (2020, January 9\u201312). A Study on IMU Sampling Rate Mismatch for a Wireless Synchronized Platform. Proceedings of the 2020 IEEE 63rd International Midwest Symposium on Circuits and Systems, Springfield, MA, USA.","DOI":"10.1109\/MWSCAS48704.2020.9184531"},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Coviello, G., Avitabile, G., and Florio, A. (2020, January 16\u201318). The Importance of Data Synchronization in Multiboard Acquisition Systems. Proceedings of the 20th IEEE Mediterranean Electrotechnical Conference, MELECON 2020\u2014Proceedings, Palermo, Italy.","DOI":"10.1109\/MELECON48756.2020.9140622"},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Coviello, G., Avitabile, G., and Florio, A. (2020). A Synchronized Multi-Unit Wireless Platform for Long-Term Activity Monitoring. Electronics, 9.","DOI":"10.3390\/electronics9071118"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"169107","DOI":"10.1109\/ACCESS.2019.2953302","article-title":"Development and hybrid control of an electrically actuated lower limb exoskeleton for motion assistance","volume":"7","author":"Chen","year":"2019","journal-title":"IEEE Access"},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Terrazas-Rodas, D., Rocca-Huaman, L., Ramirez-Amaya, C., and Alvarez-Rodriguez, A.E. (2022, January 1\u20134). Lower-Limb Exoskeleton Systems for Rehabilitation and\/or Assistance: A Review. Proceedings of the 2022 IEEE International IOT, Electronics and Mechatronics Conference, IEMTRONICS 2022, Toronto, ON, Canada.","DOI":"10.1109\/IEMTRONICS55184.2022.9795739"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1016\/j.jbiomech.2019.03.004","article-title":"Foot centre of pressure and ground reaction force during quadriceps resistance exercises; a comparison between force plates and a pressure insole system","volume":"87","author":"Munkhammar","year":"2019","journal-title":"J. Biomech."},{"key":"ref_54","unstructured":"Ugurlu, B., Oshima, H., and Narikiyo, T. (June, January 31). Lower body exoskeleton-supported compliant bipedal walking for paraplegics: How to reduce upper body effort?. Proceedings of the IEEE International Conference on Robotics and Automation, Hong Kong, China."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1016\/j.gaitpost.2017.07.044","article-title":"Biomechanical parameters for gait analysis: A systematic review of healthy human gait","volume":"58","author":"Roberts","year":"2017","journal-title":"Gait Posture"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"46","DOI":"10.4218\/etrij.2018-0639","article-title":"Gait event detection algorithm based on smart insoles","volume":"42","author":"Kim","year":"2020","journal-title":"ETRI J."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1073","DOI":"10.3390\/s140101073","article-title":"A Wireless Flexible Sensorized Insole for Gait Analysis","volume":"14","author":"Crea","year":"2014","journal-title":"Sensors"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/8\/2379\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:13:17Z","timestamp":1760029997000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/8\/2379"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,4,9]]},"references-count":57,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2025,4]]}},"alternative-id":["s25082379"],"URL":"https:\/\/doi.org\/10.3390\/s25082379","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,4,9]]}}}