Design and experimental testing of a tactile sensor for self-compensation of contact error in soft tissue stiffness measurement

Frank Efe Erukainure*, Victor Parque, Mohsen A. Hassan, Ahmed M.R. FathEl-Bab

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The measurement of viscoelastic properties of soft tissues has become a research interest with applications in the stiffness estimation of soft tissues, sorting and quality control of postharvest fruit, and fruit ripeness estimation. This paper presents a tactile sensor configuration to estimate the stiffness properties of soft tissues, using fruit as case study. Previous stiffness-measuring tactile sensor models suffer from unstable and infinite sensor outputs due to irregularities and inclination angles of soft tissue surfaces. The proposed configuration introduces two low stiffness springs at the extreme ends of the sensor with one high stiffness spring in-between. This study also presents a closed form mathematical model that considers the maximum inclination angle of the tissue’s (fruit) surface, and a finite element analysis to verify the mathematical model, which yielded stable sensor outputs. A prototype of the proposed configuration was fabricated and tested on kiwifruit samples. The experimental tests revealed that the sensor’s output remained stable, finite, and independent on both the inclination angle of the fruit surface and applied displacement of the sensor. The sensor distinguished between kiwifruit at various stiffness and ripeness levels with an output error ranging between 0.18 % and 3.50 %, and a maximum accuracy of 99.81 %, which is reasonable and competitive compared to previous design concepts.

Original languageEnglish
Pages (from-to)5309-5324
Number of pages16
JournalJournal of Mechanical Science and Technology
Issue number10
Publication statusPublished - 2022 Oct


  • ANSYS Mechanical APDL
  • Fruit quality and sorting
  • Kiwifruit elastic modulus
  • Kiwifruit tissue stiffness
  • Surface roughness
  • Tactile sensing

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering


Dive into the research topics of 'Design and experimental testing of a tactile sensor for self-compensation of contact error in soft tissue stiffness measurement'. Together they form a unique fingerprint.

Cite this