Abstract
We show that all self-motions of pentapods with linear platform of Type 1 and Type 2 can be generated by line-symmetric motions . Thus this paper closes a gap between the more than 100 year old works of Duporcq and Borel and the extensive study of line-symmetric motions done by Krames in the 1930s. As a consequence we also get a new solution set for the Borel Bricard problem. Moreover we discuss the reality of self-motions and give a sufficient condition for the design of linear pentapods of Type 1 and Type 2, which have a self-motion free workspace.
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Notes
- 1.
These are the only non-trivial motions where every point of the moving space has a spherical trajectory (cf. [3, Chap. VI]).
- 2.
The corresponding sphere centers of lines belonging to the other regulus are again located on lines (cf. [9, p. 24]), which imply linear pentapods with an architecturally singular design.
- 3.
- 4.
These are the parameters a, c, g, k used in [9, Sect. 2.3].
- 5.
This angle condition can be seen as the limit of the sphere condition (cf. [12, Sect. 4.1]).
- 6.
A self-motion is dangerous as it is uncontrollable and thus a hazard to man and machine.
- 7.
Note that all basic surfaces and trajectories can be parametrized due to Remark 2.
References
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Acknowledgements
This research is funded by Grant No. P 24927-N25 of the Austrian Science Fund FWF within the project “Stewart Gough platforms with self-motions”.
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Nawratil, G. (2018). On the Line-Symmetry of Self-motions of Linear Pentapods. In: Lenarčič, J., Merlet, JP. (eds) Advances in Robot Kinematics 2016. Springer Proceedings in Advanced Robotics, vol 4. Springer, Cham. https://doi.org/10.1007/978-3-319-56802-7_16
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DOI: https://doi.org/10.1007/978-3-319-56802-7_16
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