Due to the complexity of the human hand and the immense variability in tasks that
we use our hands for on a day-to-day basis, there has long been a desire for classification schemes to categorize these activities and the hand postures/movements utilized in executing them. Initially, this interest was primarily centered in fields such
as biomechanics, hand surgery, and rehabilitation [1–4]. With the advent of robotics
into manufacturing tasks, the study of hand function received new life as researchers
began to investigate human hands in order to shed light on the design and control of
robotic end effectors.
In this chapter, I describe a few classification schemes related to hand use in
everyday environments and tasks that should be useful to researchers interested in
human manipulation, hand biomechanics, prosthesis and robotic end-effector
design, and rehabilitation. In Sect. 2, I present a simple sub-classification of the
Activities of Daily Living (ADLs) [5, 6] for the application of robotics in human
environments, putting forth a standard categorization that allows robotic tasks to
be discussed in terms of the analogous human tasks and their hierarchal classifications. While this is by no means an exhaustive classification, it does provide
some structure to terminology that is primarily used in an ad hoc manner.
In Sect. 3, I briefly review the fairly deep literature related to grasp classification, with sub-categorizations according to the static placement of the fingers
during power and precision grasps (instead of the movements of the fingers and
hand during manipulation movements). This short section is followed by a
description of a preliminary experimental examination (Sect. 4) of the frequency
with which various grasp types are used in daily tasks, focusing on two subjects: a
housemaid and a machinist. For each of these subjects, 4 h of video from a headmounted camera is analyzed to determine how frequent each grasp type is used
and for how long. For each subject, on the order of three thousand distinct grasp
changes are observed over the 4 h period, a statistic indicative of the variability
and frequency of hand use in human living.
Finally, in Sect. 5, I present a classification of hand and finger motions during
in-hand manipulation tasks, focusing on the nature of the motion of the hand/
fingers as well as contact with external objects. This taxonomy is hand- and
movement-centric in nature (as opposed to object- and force-centric, for instance),
and is some of the first extensive work on a topic that is sure to receive more
attention as robotic and prosthetic hands become more dexterous.
In order to keep the tone of this chapter as an overview of hand classification,
many of the details are not presented in substantial depth. Instead, the reader is
asked to refer to the original publications [7–9] for a more extensive description of
related work, details on experimental methodology, or in-depth description of the
classifications presented here.
Classification of different movements, activities, and positions is useful in laying a foundation of understanding and consistency in the study of hand functionality. This study not only describes classifications of the different Activities of Daily Living (ADLs), but also describes a thorough categorization of different hand gripping motions. I have found this article particularly helpful due to the flowchart that clearly displays the differences between specific gripping needs in multiple situations. This chart can be used in further research to clarify aspects to focus on.