Computational Vibration Patterns of a Haptic Thimble for Different Placements of Embedded Piezoelectric Actuators
R.O. Ketwaru (TU Delft - Mechanical Engineering)
Yasemin Vardar – Mentor (TU Delft - Human-Robot Interaction)
A. Hunt – Mentor (TU Delft - Micro and Nano Engineering)
Gokhan Serhat – Mentor (Katholieke Universiteit Leuven)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
This study
investigates how the placement and excitation frequency of piezoelectric
actuators embedded in a soft silicone haptic thimble influence displacement
patterns on the human fingertip. A finite element model (HapThimb) was
developed in COMSOL Multiphysics by extending the DigiTip (Serhat &
Kuchenbecker, 2021) model with a 4 mm thick Ecoflex 30 layer and four
tangentially acting actuators positioned on the bottom, front, and both sides
of the fingertip. The model simulates both free and forced vibrations to
identify resonance modes and actuator-specific deformation patterns.
Free vibration analysis revealed that the addition of the thimble significantly
reduced natural frequencies, with the first eigenmode shifting from 103.5 Hz
(bare finger) to 45 Hz (with thimble).
Moreover, the number of observed modes increased, reflecting the thimble’s
contribution to the complex dynamic behaviour of the system. Forced vibration
analysis across the frequency range of 1–260 Hz revealed that actuator location
has a strong effect on both the amplitude and spatial distribution of
displacements. The bottom actuator yielded the highest local response (53.8 μm at 185 Hz), while the front
actuator produced weaker, and localised responses. The side actuators,
activated in-phase, resulted in the broadest and most versatile vibrational
patterns, exciting multiple finger regions with peaks up to 41.4 μm. These findings highlight the
importance of actuator placement in achieving desired tactile effects. The
results inform design strategies for wearable haptic devices by identifying
configurations that maximise vibrational efficiency and spatial selectivity.