The human hand is highly versatile and easily adaptable to a variety of manipulation tasks, exposing flexible solutions to the needs of control. In daily life, humans beings are, apparently without effort, able to generate complex and elegant movements of the hand and fingers, such as typing on keyboards, playing a musical instrument, or writing.
In this paper we focus on the analysis of human hand movements during handwriting tasks, a subject which has been studied for many decades.
We present for the first time, at the best of our knowledge, a methodological approach based on the biomechanics of the human hand to compare two different input methods, i.e., the finger and the stylus, in digital handwriting tasks.
Performance of two input methods is evaluated and compared in terms of manipulability indexes in the task space, i.e., the ratio between a measure of performance (displacement, velocity, force in the task space) and a measure of effort in the input/joint space.
Beside the mathematical analysis based on a biomechanical model of the hand, two experiments are presented, in which subjects were asked to write on a touchscreen using either their index finger, or a stylus.
The results (both analytical and experimental) assess that writing with the finger is more suitable for performing large, but not very accurate motions, while writing with the stylus leads to a higher precision and more isotropic motion performance.
D. Prattichizzo, L. Meli, and M. Malvezzi.
“Digital Handwriting with a Finger or a Stylus: a Biomechanical Comparison.”
IEEE Transactions on Haptics, 2015.