Thermodynamic Techniques: A Literature Review

This article showcases the ingenious approach for comparing hand postures using well accepted method (PCA). Our method exploits use a ratio of variances in eigen directions generated by PCA for comparison of two hand postures. Posture similarity index (PSI) is a novel measure of similarity of two postures in the synergy space. The index gives an idea of the kinematic effort required for generating a posture from other postures. We took this idea further for identifying representative postures from the large pool of various postures including common postures (activities of daily living; ADL) and special postures. Our approach which involved combining the inherent structure of hand postures allows relative comparison of kinematic efforts from

1998; Mason et al. 2001; Ciocarlie et al. 2007; Feix et al. 2013). According to theory, CNS try to minimize the efforts by combining multiple DoFs and actuating multi-joint movement together (Santello et al. 2013). However, it is shown in novel task CNS prefers task accomplishment as the first preference over minimization of efforts [30, 39] (Todorov et al., 2002;2004). We can argue that the approach of handling multiple degrees of freedom is task dependent. Our study comprises of two different task, one is performing common postures such as grabbing a hammer or picking up a glass, another task involves making aesthetic postures (i.e. ASL, Bharatanatyam). Statistical analysis shows that first three synergy components of common postures combined together covers the significantly large amount of variance in comparison with special postures. In addition to that from our definition of representative postures, common posture occupies lesser space whereas special postures are spread across the synergy space. Both findings suggest that CNS does not always try to minimize the effort. Rather approach is task specific in which performing well-learnt task such as holding a glass, picking up a pen uses dimensionality reduction approach which results in minimum kinematic efforts. On the contrary, performing a new task such as Bharatanatyam or ASL will result in synergy learning problem [39] (Todorov et al. 2004) but not dimensionality reduction