The structural origins of brittle star arm kinematics: An integrated tomographic, additive manufacturing, and parametric modeling-based approach

Tomholt, Lara; Friesen, Larry Jon; Berdichevsky, D. B.; Fernandes, Matheus C.; Pierre, Christoph; Wood, Robert J.; Weaver, James C.

doi:10.1016/j.jsb.2020.107481

Cited by 9 publications

(8 citation statements)

References 48 publications

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“…Brittle stars are diverse echinoderms, figure 1, in the class of Ophiuroidea, closely related to starfish [1]. They have five flexible arms with lengths varying from 0.3-60 cm [2]. While brittle stars are pentapedal animals, they have the capacity for movement using lower numbers of limbs (down to bipedal motion), and have sufficient versatility to be able to navigate a range of different terrains.…”

Section: Introductionmentioning

confidence: 99%

Design of a Hall effect sensor controlled brittle star inspired composite robotic limb

Mack

Alam

2022

Eng. Res. Express

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This paper elucidates a method of actuation and feedback for hard-soft composite continuum pentapod appendages to enable both kinematic accuracy and gait. A feedback mechanism based on Hall effect sensors is integrated within a hard exterior/soft interior composite robotic limb, which is unaffected by actuator slippage, and provides accurate (sub $2^\circ$) end point measurements. The proposed method for actuation uses two actuators to control a full semi-spherical range of motion, an improvement to the use of three actuators more commonly reported in the literature. When applied to enable the gait of a complete brittle star inspired pentapod, we find that our design reaches a momentum of 0.52$kg \cdot m/s$, surpassing the momentum of previously reported untethered starfish inspired pentapods by 3.7 times.

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Section: Introductionmentioning

confidence: 99%

Design of a Hall effect sensor controlled brittle star inspired composite robotic limb

Mack

Alam

2022

Eng. Res. Express

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“…The bend sensor is then soldered to the PCB. This assembly is fed through a series of 3D printed "ossicles" (inspired by the vertebratelike structures in brittle star limbs) [20] that hold the sensor and SMA coils in place. At this stage, optional silicone food tubing (3mm ID and 4mm OD) can be threaded onto the SMA and sealed with SilPoxy.…”

Section: Manipulator Designmentioning

confidence: 99%

Robust Control of a Multi-Axis Shape Memory Alloy-Driven Soft Manipulator

Patterson¹,

Sabelhaus²,

Majidi³

2021

Preprint

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Control of soft robotic manipulators remains a challenge for designs with advanced capabilities and novel actuation. Two significant limitations are multi-axis, threedimensional motion of soft bodies alongside actuator dynamics and constraints, both of which are present in shape-memoryalloy (SMA)-powered soft robots. This article addresses both concerns with a robust feedback control scheme, demonstrating state tracking control for a soft robot manipulator of this type. Our controller uses a static beam bending model to approximate the soft limb as an LTI system, alongside a singular-valuedecomposition compensator approach to decouple the multiaxial motion and an anti-windup element for the actuator saturation. We prove stability and verify robustness of our controller, with robustness intended to account for the unmodeled dynamics. Our implementation is verified in hardware tests of a soft SMA-powered limb, showing low tracking error, with promising results for future multi-limbed robots.

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“…Scanning electron microscope (SEM) imaging provides more detailed 2D images for shape analysis than light microscopy but requires destructive physical dissection and chemical preparation. Micro CT (µCT) has gained much attention as a non‐destructive method to generate three‐dimensional images of brittle stars and their ossicles (Clark et al, 2018; Okanishi et al, 2017; Stöhr et al, 2019; Tomholt et al, 2020). However, to date, no µCT data have been used for a 3D geometric morphometric (GM) analysis on ophiuroids.…”

Section: Introductionmentioning

confidence: 99%

“…This is the first study to provide a 3D GM investigation of vertebral variation in relation to different functional and ecological aspects of ophiuroid lifestyles. In addition, compared with the earlier 3D studies on ophiuroids (Clark et al, 2018; Okanishi et al, 2017; Stöhr et al, 2019; Tomholt et al, 2020) a larger sample size ( n = 12 species) was included in this study. Two hypotheses were tested, focusing on static and evolutionary allometry, which follow LeClair (1996): 1.…”

Section: Introductionmentioning

confidence: 99%

“…As Stöhr et al 2020) (here renamed semi-streptospondylous due to its different morphology from transspondylous), streptospondylus (euryalid) based on Mortensen (1933) and transspondylous based on Štorc (2004) of ophiuroid lifestyles. In addition, compared with the earlier 3D studies on ophiuroids (Clark et al, 2018;Okanishi et al, 2017;Stöhr et al, 2019;Tomholt et al, 2020) a larger sample size (n = 12 species) was included in this study. Two hypotheses were tested, focusing on static and evolutionary allometry, which follow LeClair (1996):…”

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confidence: 99%

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The evolutionary relationship between arm vertebrae shape and ecological lifestyle in brittle stars (Echinodermata: Ophiuroidea)

et al. 2021

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Ophiuroidea are one of the most diverse classes among extant echinoderms, characterized by their flexible arms composed of a series of ossicles called vertebrae, articulating with each other proximally and distally. Their arms show a wide range of motion, important for feeding and locomotion, associated with their epizoic and non‐epizoic lifestyles. It remains to be explored to what degree the phenotypic variation in these ossicles also reflects adaptations to these lifestyles, rather than only their phylogenetic affinity. In this study, we analyzed the 3D shape variation of six arm vertebrae from the middle and distal parts of an arm in 12 species, belonging to the intertidal, subtidal and bathyal zones and showing epizoic and non‐epizoic behaviors. A PERMANOVA indicated a significant difference in ossicle morphology between species and between lifestyles. A principal component analysis showed that the morphology of epizoic ophiuroids is distinct from non‐epizoic ones; which may reflect variation in arm function related to these different lifestyles. The Phylogenetic MANOVA and phylogenetic signal analysis showed that shape variation in the vertebral articulation seems to reflect ecological and functional adaptations, whereas phylogeny controls more the lateral morphology of the vertebrae. This suggests a convergent evolution through ecological adaptation to some degree, indicating that some of these characters may have limited taxonomic value.

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The structural origins of brittle star arm kinematics: An integrated tomographic, additive manufacturing, and parametric modeling-based approach

Cited by 9 publications

References 48 publications

Design of a Hall effect sensor controlled brittle star inspired composite robotic limb

Design of a Hall effect sensor controlled brittle star inspired composite robotic limb

Robust Control of a Multi-Axis Shape Memory Alloy-Driven Soft Manipulator

The evolutionary relationship between arm vertebrae shape and ecological lifestyle in brittle stars (Echinodermata: Ophiuroidea)

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