Posture similarity index: A method to compare hand postures in synergy space
A peer-reviewed article of this Preprint also exists.
Author and article information
Abstract
Background
The Human hand can perform a range of manipulation tasks, from holding a pen to holding a hammer. Central Nervous System (CNS) uses different strategies in different manipulation tasks based on task requirements. Several attempts to compare postures of the hand have been made. Some of these have been developed for use in Robotics and animation industries. In this study, we develop an index to quantify the similarity between two human hand postures, the posture similarity index.
Methods
Twelve right-handed volunteers performed 70 postures and lifted and held 30 objects (total of 100 different postures, each performed 5 times). Kinematics of individual finger phalanges (segments) were captured by using a 16-sensor electromagnetic tracking sensor system. The hand was modelled as a 21-DoF system and the corresponding joint angles were computed. We used principal component analysis to extract kinematic synergies from this 21-DoF data. We developed a posture similarity index (PSI), that represents similarity between posture in the synergy (Principal component) space. First, performance of this index was tested using a synthetic dataset. After confirming that it performs well with synthetic dataset, we used it to analyse experimental data. Further, we used PSI to identify postures that are representative in the sense that they have a greater overlap (in synergy space) with a large number of postures.
Results
Using synthetic data and real experimental data, it was found that PSI was a relatively accurate index of similarity in synergy space. Also, it was found that more special postures than common postures were found among “representative” postures.
Conclusion
An index for comparing posture similarity in synergy space has been developed and its use has been demonstrated using synthetic dataset and experimental dataset. In addition, we found that special postures are actually special in the sense that there are more of them in the “representative” postures as identified by our posture similarity index.
Cite this as
2018. Posture similarity index: A method to compare hand postures in synergy space. PeerJ Preprints 6:e3080v2 https://doi.org/10.7287/peerj.preprints.3080v2note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
Author comment
We got one round of peer review from PeerJ. This is the final revised version.
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Additional Information
Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Nayan Bhatt conceived and designed the experiments, performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Varadhan SKM conceived and designed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.
Human Ethics
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
Institutional Ethics Committee at IIT Madras.
Data Deposition
The following information was supplied regarding data availability:
We plan on submitting the raw data in case we end up submitting the article to PeerJ. At this time, we are unable to submit the raw data and code since we are not sure where we will submit this work.
Funding
This work was funded Department of Science and Technology, India's Cognitive Science research initaitive. Grant number: SR/CSRI/97/2014(G). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
