Abstract Based on observations from nature, tails are believed to help animals achieve highly agile motions. Traditional single-link robotic tails serve as a good simplification for both modeling and implementation purposes. However, this approach cannot explain the complicated tail behaviors exhibited in nature where multi-link structures are more commonly observed. Unlike its single-link counterpart, articulated multi-link tails essentially belong to the serial manipulator family which possesses special motion transmission design challenges. To address this challenge, a cable-driven hyper-redundant design becomes the most used approach. Limited by cable strength and elastic components, this approach suffers from low-frequency response, inadequate generated inertial loading, and fragile hardware, which are all critical drawbacks for robotic tails design. To solve these structure-related shortcomings, a multi-link robotic tail made up of rigid links is proposed in this paper. The new structure takes advantage of the traditional hybrid mechanism architecture, but utilizes rigid mechanisms to couple the motions between the ith link and the (i + 1)th link rather than using cable actuation. By doing so, the overall tail becomes a rigid mechanism that achieves quasi-uniform spatial bending for each segment and allows performing highly dynamic motions. The mechanism and detailed design of this new robotic tail are presented. The kinematic model was developed and an optimization process was conducted to reduce the bending non-uniformity for the rigid tail. Based on this special optimization design, the dynamic model of the new mechanism is significantly simplified. A small-scale three-segment prototype was integrated to verify the proposed mechanism's unique mobility.
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A Cable Length Invariant Robotic Tail Using a Circular Shape Universal Joint Mechanism
This paper presents the development of a new robotic tail based on a novel cable-driven universal joint mechanism. The novel joint mechanism is synthesized by geometric reasoning to achieve the desired cable length invariance property, wherein the mechanism maintains a constant length for the driving cables under universal rotation. This feature is preferable because it allows for the bidirectional pulling of the cables which reduces the requisite number of actuators. After obtaining this new joint mechanism, a serpentine robotic tail with fewer actuators, simpler controls, and a more robust structure is designed and integrated. The new tail includes two independent macro segments (2 degrees of freedom each) to generate more complex shapes (4 degrees of freedom total), which helps with improving the dexterity and versatility of the robot. In addition, the pitch bending and yaw bending of the tail are decoupled due to the perpendicular joint axes. The kinematic modeling, dynamic modeling, and workspace analysis are then explained for the new robotic tail. Three experiments focusing on statics, dynamics, and dexterity are conducted to validate the mechanism and evaluate the new robotic tail's performance.
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- Award ID(s):
- 1906727
- NSF-PAR ID:
- 10155499
- Date Published:
- Journal Name:
- Journal of Mechanisms and Robotics
- Volume:
- 11
- Issue:
- 5
- ISSN:
- 1942-4302
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4044067
