ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

APPLICATION OF A MODIFIED ELASTIC FOUNDATION CONTACT
MODEL FOR SIMULATING HAND-OBJECT INTERACTION IN
GRASPING TASKS
1. ABSTRACT
A. Pérez-González 1 , J.L. Sancho-Bru 2 , M. Jurado-Tovar 3 ,
M. C. Mora 2
The present work proposes the use of a modified elastic foundation model (mEFM),
previously developed in our group [1], for modelling soft contact in human hand-object
interaction. The model introduces three additional parameters to the classical Kalker’s
elastic foundation model for non-Hertzian contact [2]. A method is proposed to adjust
the parameters of this mEFM through an optimization process to fit in vivomeasurements
of the force-displacement and force-contact area responses. The process
is illustrated in the present work for the index fingertip. The effect in the results of
spatial discretisation of the model is also analysed.
2. INTRODUCTION
Human grasp modelling is a challenging goal in biomechanics. The hand is a complex
system, with more than twenty degrees of freedom actuated by a considerable number
of muscles throughout the tendons, and controlled by the central nervous system.
Furthermore, large deformations of the soft tissues of the hand appear as a result of the
hand-object contact in human grasping. Research advances in the last decades in three
different areas might be combined to move towards a realistic and self-contained
biomechanical model of the hand in the next future [3]: hand biomechanics, hand
ergonomics and robotic grasping. In this context, grasp contact modelling is essential to
evaluate the stability of the object being grasped or to rate the performance of a grasp.
Point contact with and without friction and soft-finger contact models have been used in
the past to model hand-object interaction in robotic applications. Point contact models,
also named rigid-body contact models, assume rigid-body models for the hand and the
grasped object while the soft-finger contact models, also called compliant or regularised
models, assume that the hand is a deformable element grasping a rigid body [4]. The
point contact models do not represent real contact situations and thus different
researchers have moved toward more realistic soft contact models [5, 6, 7].
Some researchers have analysed in recent years the deformation of the fingertip against
a flat surface, proposing different models to account for the deformation of the fingertip
[8, 9, 10]. Serina et al. [8] proposed the use of a “waterbed” model, although this model
1
Professor and Head, Department of Mechanical Engineering and Construction, Universitat Jaume I,
Avda. Sos Baynat s/n, Castellón, SPAIN.
2
Professor, Department of Mechanical Engineering and Construction, Universitat Jaume I, Avda. Sos
Baynat s/n, Castellón, SPAIN.
3
PreDoctoral Student, Department of Mechanical Engineering and Construction, Universitat Jaume I,
Avda. Sos Baynat s/n, Castellón, SPAIN.