Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement

Soft actuators have garnered significant attention for applications in medical and wearable devices owing to their lightweight properties and inherent safety. Nevertheless, standardized performance charts for such actuators remain scarce, complicating the selection of suitable actuators for specific...

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Main Authors: Soya SATO, Makoto ASAI, Hidetoshi TAKAHASHI
Format: Article
Language:English
Published: The Japan Society of Mechanical Engineers 2025-06-01
Series:Mechanical Engineering Journal
Subjects:
Online Access:https://www.jstage.jst.go.jp/article/mej/12/4/12_25-00104/_pdf/-char/en
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author Soya SATO
Makoto ASAI
Hidetoshi TAKAHASHI
author_facet Soya SATO
Makoto ASAI
Hidetoshi TAKAHASHI
author_sort Soya SATO
collection DOAJ
description Soft actuators have garnered significant attention for applications in medical and wearable devices owing to their lightweight properties and inherent safety. Nevertheless, standardized performance charts for such actuators remain scarce, complicating the selection of suitable actuators for specific applications. One of the fundamental characteristics of soft actuators is that the force–displacement relationship is influenced by the stiffness of the object with which they interact. To evaluate the sensor characteristics, conventional methods employ rigid load cells, which hinders the simultaneous measurement of force and displacement under varying stiffness conditions. Here, we propose a force sensor consisting of a seesaw-type beam embedded with an internal magnet and a laser displacement meter. External magnets are installed above and below the internal magnet, enabling modulation of the beam’s effective spring constant by varying the distance to the external magnets and their magnetic polarity. This configuration enables both repulsive and attractive magnetic forces, facilitating continuous and wide-range stiffness adjustment. The sensor structure was fabricated using a 3D printer. Experimental validation confirmed that the spring constant was tunable within the range of 5.9 to 20 N/m. Furthermore, the sensitivity of the laser displacement meter remained consistent, with a standard deviation corresponding to an error of approximately 2.2% across varying stiffness conditions. These results suggest that the proposed sensor can measure force while adjusting its stiffness, making it useful for evaluating the performance of soft actuators under different mechanical stiffness conditions.
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spelling doaj-art-e528d58e8a1345c5aeecfeee62f4ca702025-08-20T01:59:35ZengThe Japan Society of Mechanical EngineersMechanical Engineering Journal2187-97452025-06-0112425-0010425-0010410.1299/mej.25-00104mejSeesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurementSoya SATO0Makoto ASAI1Hidetoshi TAKAHASHI2School of Integrated Design Engineering, Graduate School of Science and Technology, Keio UniversityKeio University Global Research Institute, Keio UniversitySchool of Integrated Design Engineering, Graduate School of Science and Technology, Keio UniversitySoft actuators have garnered significant attention for applications in medical and wearable devices owing to their lightweight properties and inherent safety. Nevertheless, standardized performance charts for such actuators remain scarce, complicating the selection of suitable actuators for specific applications. One of the fundamental characteristics of soft actuators is that the force–displacement relationship is influenced by the stiffness of the object with which they interact. To evaluate the sensor characteristics, conventional methods employ rigid load cells, which hinders the simultaneous measurement of force and displacement under varying stiffness conditions. Here, we propose a force sensor consisting of a seesaw-type beam embedded with an internal magnet and a laser displacement meter. External magnets are installed above and below the internal magnet, enabling modulation of the beam’s effective spring constant by varying the distance to the external magnets and their magnetic polarity. This configuration enables both repulsive and attractive magnetic forces, facilitating continuous and wide-range stiffness adjustment. The sensor structure was fabricated using a 3D printer. Experimental validation confirmed that the spring constant was tunable within the range of 5.9 to 20 N/m. Furthermore, the sensitivity of the laser displacement meter remained consistent, with a standard deviation corresponding to an error of approximately 2.2% across varying stiffness conditions. These results suggest that the proposed sensor can measure force while adjusting its stiffness, making it useful for evaluating the performance of soft actuators under different mechanical stiffness conditions.https://www.jstage.jst.go.jp/article/mej/12/4/12_25-00104/_pdf/-char/enforce sensorsvariable spring constantspiral seesaw beammagnetic restoring force
spellingShingle Soya SATO
Makoto ASAI
Hidetoshi TAKAHASHI
Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
Mechanical Engineering Journal
force sensors
variable spring constant
spiral seesaw beam
magnetic restoring force
title Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
title_full Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
title_fullStr Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
title_full_unstemmed Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
title_short Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
title_sort seesaw type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement
topic force sensors
variable spring constant
spiral seesaw beam
magnetic restoring force
url https://www.jstage.jst.go.jp/article/mej/12/4/12_25-00104/_pdf/-char/en
work_keys_str_mv AT soyasato seesawtypeforcesensorwithvariablespringconstantutilizingmagneticrestoringforceandexternallaserdisplacementmeasurement
AT makotoasai seesawtypeforcesensorwithvariablespringconstantutilizingmagneticrestoringforceandexternallaserdisplacementmeasurement
AT hidetoshitakahashi seesawtypeforcesensorwithvariablespringconstantutilizingmagneticrestoringforceandexternallaserdisplacementmeasurement