{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T02:25:46Z","timestamp":1773714346538,"version":"3.50.1"},"reference-count":47,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2023,7,6]],"date-time":"2023-07-06T00:00:00Z","timestamp":1688601600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Guangdong Science and Technology Research Council","award":["2020B1515120064"],"award-info":[{"award-number":["2020B1515120064"]}]},{"name":"Guangdong Science and Technology Research Council","award":["ITS\/156\/20FP"],"award-info":[{"award-number":["ITS\/156\/20FP"]}]},{"name":"Innovation and Technology Fund, HKSAR","award":["2020B1515120064"],"award-info":[{"award-number":["2020B1515120064"]}]},{"name":"Innovation and Technology Fund, HKSAR","award":["ITS\/156\/20FP"],"award-info":[{"award-number":["ITS\/156\/20FP"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper proposes a method for accurate 3D posture sensing of the soft actuators, which could be applied to the closed-loop control of soft robots. To achieve this, the method employs an array of miniaturized sponge resistive materials along the soft actuator, which uses long short-term memory (LSTM) neural networks to solve the end-to-end 3D posture for the soft actuators. The method takes into account the hysteresis of the soft robot and non-linear sensing signals from the flexible bending sensors. The proposed approach uses a flexible bending sensor made from a thin layer of conductive sponge material designed for posture sensing. The LSTM network is used to model the posture of the soft actuator. The effectiveness of the method has been demonstrated on a finger-size 3 degree of freedom (DOF) pneumatic bellow-shaped actuator, with nine flexible sponge resistive sensors placed on the soft actuator\u2019s outer surface. The sensor-characterizing results show that the maximum bending torque of the sensor installed on the actuator is 4.7 Nm, which has an insignificant impact on the actuator motion based on the working space test of the actuator. Moreover, the sensors exhibit a relatively low error rate in predicting the actuator tip position, with error percentages of 0.37%, 2.38%, and 1.58% along the x-, y-, and z-axes, respectively. This work is expected to contribute to the advancement of soft robot dynamic posture perception by using thin sponge sensors and LSTM or other machine learning methods for control.<\/jats:p>","DOI":"10.3390\/s23136189","type":"journal-article","created":{"date-parts":[[2023,7,7]],"date-time":"2023-07-07T01:57:09Z","timestamp":1688695029000},"page":"6189","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["An End-to-End Dynamic Posture Perception Method for Soft Actuators Based on Distributed Thin Flexible Porous Piezoresistive Sensors"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9475-8677","authenticated-orcid":false,"given":"Jing","family":"Shu","sequence":"first","affiliation":[{"name":"Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8835-7896","authenticated-orcid":false,"given":"Junming","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"}]},{"given":"Kenneth Chik-Chi","family":"Cheng","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR 999077, China"},{"name":"Research Institute for Sports Science and Technology, The Hong Kong Polytechnic University, Hong Kong SAR 999077, China"}]},{"given":"Ling-Fung","family":"Yeung","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"}]},{"given":"Zheng","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"},{"name":"Department of Surgery, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4375-653X","authenticated-orcid":false,"given":"Raymond Kai-yu","family":"Tong","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong SAR 999077, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,7,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"467","DOI":"10.1038\/nature14543","article-title":"Design, fabrication and control of soft robots","volume":"521","author":"Rus","year":"2015","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2100140","DOI":"10.1002\/aisy.202100140","article-title":"Soft actuators and robotic devices for rehabilitation and assistance","volume":"4","author":"Pan","year":"2022","journal-title":"Adv. Intell. Syst."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1177\/0278364919873379","article-title":"Model-based online learning and adaptive control for a \u201chuman-wearable soft robot\u201d integrated system","volume":"40","author":"Tang","year":"2021","journal-title":"Int. J. Robot. Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"338","DOI":"10.1089\/soro.2016.0060","article-title":"Novel variable-stiffness robotic fingers with built-in position feedback","volume":"4","author":"Yang","year":"2017","journal-title":"Soft Robot."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Yuen, M.C., Tonoyan, H., White, E.L., Telleria, M., and Kramer, R.K. (June, January 29). Fabric sensory sleeves for soft robot state estimation. Proceedings of the 2017 IEEE international conference on robotics and automation (ICRA), Singapore.","DOI":"10.1109\/ICRA.2017.7989649"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Gillespie, M.T., Best, C.M., and Killpack, M.D. (2016, January 16\u201321). Simultaneous position and stiffness control for an inflatable soft robot. Proceedings of the 2016 IEEE international conference on robotics and automation (ICRA), Stockholm, Sweden.","DOI":"10.1109\/ICRA.2016.7487240"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1071","DOI":"10.1126\/science.aac5082","article-title":"Highly stretchable electroluminescent skin for optical signaling and tactile sensing","volume":"351","author":"Larson","year":"2016","journal-title":"Science"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"eaai7529","DOI":"10.1126\/scirobotics.aai7529","article-title":"Optoelectronically innervated soft prosthetic hand via stretchable optical waveguides","volume":"1","author":"Zhao","year":"2016","journal-title":"Sci. Robot."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Wall, V., Z\u00f6ller, G., and Brock, O. (June, January 29). A method for sensorizing soft actuators and its application to the RBO hand 2. Proceedings of the 2017 IEEE International Conference on Robotics and Automation (ICRA), Singapore.","DOI":"10.1109\/ICRA.2017.7989577"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Truby, R.L., Katzschmann, R.K., Lewis, J.A., and Rus, D. (2019, January 14\u201318). Soft robotic fingers with embedded ionogel sensors and discrete actuation modes for somatosensitive manipulation. Proceedings of the 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft), Seoul, Republic of Korea.","DOI":"10.1109\/ROBOSOFT.2019.8722722"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1109\/TMRB.2021.3063844","article-title":"Design and Preliminary Evaluation of an Electromagnetically Actuated Soft-Tethered Colonoscope","volume":"2","author":"Li","year":"2021","journal-title":"IEEE Trans. Med. Robot. Bionics"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Elkeran, M., and Fanni, M. (2018, January 5\u20138). A transient FEA-based methodology for designing soft surgical manipulators. Proceedings of the 2018 IEEE International Conference on Mechatronics and Automation (ICMA), Changchun, China.","DOI":"10.1109\/ICMA.2018.8484508"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Katzschmann, R.K., Della Santina, C., Toshimitsu, Y., Bicchi, A., and Rus, D. (2019, January 14\u201318). Dynamic motion control of multi-segment soft robots using piecewise constant curvature matched with an augmented rigid body model. Proceedings of the 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft), Seoul, Republic of Korea.","DOI":"10.1109\/ROBOSOFT.2019.8722799"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Bajo, A., Goldman, R.E., and Simaan, N. (2011, January 9\u201313). Configuration and joint feedback for enhanced performance of multi-segment continuum robots. Proceedings of the 2011 IEEE International Conference on Robotics and Automation (ICRA), Shanghai, China.","DOI":"10.1109\/ICRA.2011.5980005"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1089\/soro.2018.0088","article-title":"Worm-like soft robot for complicated tubular environments","volume":"6","author":"Zhang","year":"2019","journal-title":"Soft Robot."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/j.robot.2014.08.014","article-title":"Soft robotic glove for combined assistance and at-home rehabilitation","volume":"73","author":"Polygerinos","year":"2015","journal-title":"Robot. Auton. Syst."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"8001","DOI":"10.1039\/C9SM01046G","article-title":"Carbon fibre based flexible piezoresistive composites to empower inherent sensing capabilities for soft actuators","volume":"15","author":"Yan","year":"2019","journal-title":"Soft Matter"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Pan, M., Yuan, C., Anpalagan, H., Plummer, A., Zou, J., Zhang, J., and Bowen, C. (2020). Soft Controllable Carbon Fibre-based Piezoresistive Self-Sensing Actuators. Actuators, 9.","DOI":"10.3390\/act9030079"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3299","DOI":"10.1109\/LRA.2020.2976320","article-title":"Distributed Proprioception of 3D Configuration in Soft, Sensorized Robots via Deep Learning","volume":"5","author":"Truby","year":"2020","journal-title":"IEEE Robot. Autom. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Ye, Z., Pang, G., Liang, Y., Lv, H., Xu, K., Wu, H., and Yang, G. (2023). Highly Stretchable and Sensitive Strain Sensor Based on Porous Materials and Rhombic-Mesh Structures for Robot Teleoperation. Adv. Sens. Res., 2300044.","DOI":"10.1002\/adsr.202300044"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2007436","DOI":"10.1002\/adfm.202007436","article-title":"Flexible hybrid sensor systems with feedback functions","volume":"31","author":"Xu","year":"2021","journal-title":"Adv. Funct. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2200050","DOI":"10.1002\/aisy.202200050","article-title":"Bioinspired Co-Design of Tactile Sensor and Deep Learning Algorithm for Human\u2013Robot Interaction","volume":"4","author":"Kong","year":"2022","journal-title":"Adv. Intell. Syst."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2008701","DOI":"10.1002\/adma.202008701","article-title":"A wearable body condition sensor system with wireless feedback alarm functions","volume":"33","author":"Xu","year":"2021","journal-title":"Adv. Mater."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1007\/s42242-021-00171-2","article-title":"Emerging wearable flexible sensors for sweat analysis","volume":"5","author":"Heng","year":"2022","journal-title":"Bio-Des. Manuf."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"9609","DOI":"10.1039\/C9TC01874C","article-title":"Highly stable kirigami-structured stretchable strain sensors for perdurable wearable electronics","volume":"7","author":"Xu","year":"2019","journal-title":"J. Mater. Chem. C"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1038\/s42254-019-0063-1","article-title":"Buffering by buckling as a route for elastic deformation","volume":"1","author":"Vella","year":"2019","journal-title":"Nat. Rev. Phys."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"9570","DOI":"10.1021\/acsami.1c21003","article-title":"A soft sponge sensor for multimodal sensing and distinguishing of pressure, strain, and temperature","volume":"14","author":"Lo","year":"2022","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"46848","DOI":"10.1021\/acsami.1c09975","article-title":"Wearable, washable, and highly sensitive piezoresistive pressure sensor based on a 3D sponge network for real-time monitoring human body activities","volume":"13","author":"Li","year":"2021","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2101051","DOI":"10.1002\/smtd.202101051","article-title":"MXene-sponge based high-performance piezoresistive sensor for wearable biomonitoring and real-time tactile sensing","volume":"6","author":"Wei","year":"2022","journal-title":"Small Methods"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2817","DOI":"10.1021\/acs.nanolett.1c04976","article-title":"Ultrasensitive pressure sensor sponge using liquid metal modulated nitrogen-doped graphene nanosheets","volume":"22","author":"Li","year":"2022","journal-title":"Nano Lett."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"55756","DOI":"10.1021\/acsami.1c17923","article-title":"Multifunctional soft robotic finger based on a nanoscale flexible temperature\u2013pressure tactile sensor for material recognition","volume":"13","author":"Yang","year":"2021","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1604434","DOI":"10.1002\/adfm.201604434","article-title":"Omnidirectional bending and pressure sensor based on stretchable CNT-PU sponge","volume":"27","author":"Chen","year":"2017","journal-title":"Adv. Funct. Mater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"10033","DOI":"10.1039\/C8NR02813C","article-title":"A flexible pressure sensor based on rGO\/polyaniline wrapped sponge with tunable sensitivity for human motion detection","volume":"10","author":"Ge","year":"2018","journal-title":"Nanoscale"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"5127","DOI":"10.1109\/LRA.2022.3155225","article-title":"Soft robot skin with conformal adaptability for on-body tactile perception of collaborative robots","volume":"7","author":"Ye","year":"2022","journal-title":"IEEE Robot. Autom. Lett."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"670","DOI":"10.1109\/TMRB.2020.3020320","article-title":"Design and implementation of robot skin using highly sensitive sponge sensor","volume":"2","author":"Ye","year":"2020","journal-title":"IEEE Trans. Med. Robot. Bionics"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Shu, J., Wang, J., Lau, S.C.Y., Su, Y., Heung, K.H.L., Shi, X., Li, Z., and Tong, R.K.y. (2022). Soft Robots\u2019 Dynamic Posture Perception Using Kirigami-Inspired Flexible Sensors with Porous Structures and Long Short-Term Memory (LSTM) Neural Networks. Sensors, 22.","DOI":"10.3390\/s22207705"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"234","DOI":"10.1016\/j.mechatronics.2017.10.005","article-title":"Bending angle prediction and control of soft pneumatic actuators with embedded flex sensors\u2014A data-driven approach","volume":"50","author":"Elgeneidy","year":"2018","journal-title":"Mechatronics"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"eaav1488","DOI":"10.1126\/scirobotics.aav1488","article-title":"Soft robot perception using embedded soft sensors and recurrent neural networks","volume":"4","author":"Thuruthel","year":"2019","journal-title":"Sci. Robot."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Shu, J., Wang, J., Su, Y., Liu, H., Li, Z., and Tong, R.K.Y. (2022, January 27\u201330). An End-to-end Posture Perception Method for Soft Bending Actuators Based on Kirigami-inspired Piezoresistive Sensors. Proceedings of the 2022 IEEE-EMBS International Conference on Wearable and Implantable Body Sensor Networks (BSN), Ioannina, Greece.","DOI":"10.1109\/BSN56160.2022.9928494"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1735","DOI":"10.1162\/neco.1997.9.8.1735","article-title":"Long short-term memory","volume":"9","author":"Hochreiter","year":"1997","journal-title":"Neural Comput."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Shih, B., Drotman, D., Christianson, C., Huo, Z., White, R., Christensen, H.I., and Tolley, M.T. (2017, January 24\u201328). Custom soft robotic gripper sensor skins for haptic object visualization. Proceedings of the 2017 IEEE\/RSJ international conference on intelligent robots and systems (IROS), Vancouver, BC, Canada.","DOI":"10.1109\/IROS.2017.8202199"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"671","DOI":"10.1089\/soro.2018.0131","article-title":"Fiber optic shape sensing for soft robotics","volume":"6","author":"Galloway","year":"2019","journal-title":"Soft Robot."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"3820","DOI":"10.1109\/LRA.2019.2929978","article-title":"A quadrotor with an origami-inspired protective mechanism","volume":"4","author":"Shu","year":"2019","journal-title":"IEEE Robot. Autom. Lett."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1661","DOI":"10.1177\/0278364910368147","article-title":"Design and kinematic modeling of constant curvature continuum robots: A review","volume":"29","author":"Webster","year":"2010","journal-title":"Int. J. Robot. Res."},{"key":"ref_45","unstructured":"Kingma, D.P., and Ba, J. (2014). Adam: A method for stochastic optimization. arXiv."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"eabq4385","DOI":"10.1126\/sciadv.abq4385","article-title":"Fluidic innervation sensorizes structures from a single build material","volume":"8","author":"Truby","year":"2022","journal-title":"Sci. Adv."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1144","DOI":"10.1089\/soro.2020.0172","article-title":"A learning-based approach to sensorize soft robots","volume":"9","author":"Ang","year":"2022","journal-title":"Soft Robot."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/13\/6189\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:07:10Z","timestamp":1760126830000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/13\/6189"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,7,6]]},"references-count":47,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2023,7]]}},"alternative-id":["s23136189"],"URL":"https:\/\/doi.org\/10.3390\/s23136189","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,7,6]]}}}