Tutorial on Embodiment
3.3. Grasping Case Studies*
At first sight, grasping and locomotion do not seem to have much in common. However, as we will show in this section, the implications of embodiment illustrated thus far in locomotion can be equally well demonstrated in case studies that involve grasping. In essence, the rich and dynamic interactions of walking or running bodies with the ground will be replaced by equally complex interactions of hand morphologies and objects being grasped.
Morphology and materials contribute to grasping behavior. Hand joint structure, muscle mechanics, and the distribution and density of bone to joint movements and muscle recruitment during manipulative behavior are all important variables, as investigated by Marzke and Marzke (2000). It has also been reported that ridged structure of human skin offers better grip due to increased friction (Cartmill, 1979). However, we will use two robotic case studies for our illustration of ‘cheap grasping', i.e. grasping that is stable and reliable, yet requires little control. First, we will demonstrate a robotic hand, in which the attention paid to the mechanical construction leads to self-adaptation of the grasp to different objects. Second, we will present a recent universal robotic gripper, where the morphological approach was taken to its extreme.
*This section has been adapted from Hoffmann and Pfeifer (2011).
Cartmill, M. (1979), 'The volar skin of primates: its frictional characteristics and their functional significance', Amer. J. Physical Anthropology 50, 497-510.
Hoffmann, M. & Pfeifer, R. (2011), The implications of embodiment for behavior and cognition: animal and robotic case studies, in W. Tschacher & C. Bergomi, ed., The Implications of Embodiment: Cognition and Communication, Exeter: Imprint Academic, pp. 31-58.
Marzke, M. & Marzke, R. (2000), 'Evolution of the human hand: approaches to acquiring, analysing and interpreting the anatomical evidence', J. Anat. 197, 121-140.