Design and benchmarking of a robust strain-based 3D shape sensing system

Napoli, Isaac M. Di; Harwood, Casey

doi:10.1016/j.oceaneng.2020.107071

Cited by 3 publications

(4 citation statements)

References 7 publications

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“…The load cell possesses a calibrated range of 3.6 kN in lift and drag and 680 N m in all moments, with estimated uncertainty of the mean values. A kinematic shape-sensing spar, of the design described by Di Napoli & Harwood (2020), was inserted into a milled slot along the hydrofoil's mid-plane, providing measurements of the flexural and torsional deformations of the hydrofoil along its span. Readers should refer to Part 1 for details and images of the test set-up and analysis methods.…”

Section: Experimental Set-up and Analysis Proceduresmentioning

confidence: 99%

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Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 2. Cavitating and ventilating flows

Young,

Valles,

Di Napoli

et al. 2023

J. Fluid Mech.

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The objective of this paper is to understand the effects of waves and vaporous cavitation upon the hydrodynamic and hydroelastic responses of a flexible surface-piercing hydrofoil, adding to the subcavitating results presented in Part 1. In general, the presence of a sufficiently large vaporous cavitation bubble facilitated the formation of a ventilated cavity, substantially reducing the angle of attack or speed required to induce fully ventilated flow, relative to subcavitating conditions. A new co-analysis procedure was used to isolate synchronous hydrodynamic modes and structural operating deflection shapes. Significant dynamic load amplification occurred when the resonant frequencies of the first twisting and second bending modes coalesced in both fully wetted and partially cavitating flows. The presence of waves did not diminish the effect of frequency coalescence, but did encourage intermittent lock-in with both leading edge cavity shedding and trailing edge vortex shedding at certain speeds. Partial cavity shedding typically had a negligible impact on the power spectral densities of structural motions because of incoherent cavity shedding. However, lock-in between the cavity shedding frequency and modal coalescence frequency led to shifting of the primary frequency peak, as well as amplified harmonics and interactions between the cavity shedding frequency and vortex shedding frequency. The transition from partially cavitating to fully ventilated flow caused sudden and large drops in the mean hydrodynamic loads and deformations, as well as substantial reductions in the intensity of the fluctuations.

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Section: Experimental Set-up and Analysis Proceduresmentioning

confidence: 99%

“…demonstrates an approximately inverse relationship with sectional cavity lengths (Franc & Michel 2004).…”

Section: Characteristic Cavitating Flow Regimesmentioning

confidence: 99%

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 2. Cavitating and ventilating flows

Young,

Valles,

Di Napoli

et al. 2023

J. Fluid Mech.

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show abstract

“…This step was of critical importance as it generated a unique calibration equation for each flex sensor. An algebraic manipulation [16] was used to conjoin and configure a 2-part complex radius about an origin in a 2D plot. Once the calibration equations are found, they are set in MATLAB to generate the radius value from the change in resistance.…”

Section: Shape Sensing Techniquementioning

confidence: 99%

Multi-modal Sensing Soft End-Effector for Underwater Applications

2022

ARME

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The underwater domain of soft robotic end-effector development is an emerging field that calls for advancements to multimodal sensing solutions in order to achieve a wide fluctuation of conformable object manipulation. In this paper, the design of a 3-digit end-effector capable of 6 degrees of shape sensing and 12 points of force sensing is proposed. Integral to the end-effector's design is the presentation of its waterproofed soft-robotic actuators, each capable of 2-point shape sensing and 4-point force sensing. The individual actuator is designed as a uni-directional, bellow-type, PneuNet actuator built from silicone material. Onboard sensors utilize widely available piezo-resistive components which allow the actuator to act as a low-cost entry to shape sensing and force sensing. Each actuator exhibits a 2-part compound radius flex-sensor array and a 4-part single-point force sensor array. Of unique design is the bellow-type actuator's custom chamber layout which gives it the ability to resemble approximated closed curvature of a human pointer finger. A technique for shape reconstruction is presented that estimates the shape of the soft actuator based upon embedded flex sensor measurements. The actuator is interrogated under transient pressure range to examine its grasp performance, shape sensing, and force measuring capabilities. The actuator is tested as a stand-alone unit, tested in tandem with a secondary unit, and also equipped with the proposed 3-digit end-effector. Each actuator and servo motor are subjected to an underwater ground-fault test to examine preliminary electrical integrity when submerged below surface level water, whereas visual inspection of a single 3-digit grasp is performed on a cylindrical object under surface level water. The overall goal of this work is to exhibit a tangible design solution for waterproofed multi-modal sensing within the soft robotic design frame for various underwater robotic applications.

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“…Initially, the individual strains are read from the strain gauges. The strains are then converted to deflection using the method developed by Di Napoli & Harwood (2020). These deflections are then taken as the output measurements for each time instant and the covariances between them are arranged into the Hankel matrix.…”

mentioning

confidence: 99%

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 1. Fully wetted and ventilated flows

Young,

Valles,

Di Napoli

et al. 2023

J. Fluid Mech.

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This work describes the effects of waves on the hydroelastic response of a hydrofoil in fully wetted and ventilated flows. In the absence of vaporous cavitation (described in Part 2 of this paper series), shallow long-period non-breaking waves delayed ventilation inception because velocity fluctuations prevent the formation of a stably separated region of flow at the foil's leading edge. Aerated von Kármán vortex shedding occurred from the blunt trailing edge, producing vortex-induced vibration of the hydrofoil at a near-constant Strouhal number. Regular waves led to near sinusoidal oscillations of the load and deformations at the wave encounter frequency, while the mean response and the dynamic response at other frequency peaks corresponding to hydrodynamic and structural modes remained mostly unaffected. Significant dynamic load amplification was observed at a submerged aspect ratio of 2 for cases with low angles of attack because of coalescence between the second and third wetted structural modes; at high angles of attack, the amplitude of the load fluctuations and flow-induced vibrations reduced because energy was diverted away from the coalescence frequencies to the nearby vortex shedding frequency. In both calm water and wave conditions, transition from fully wetted to fully ventilated flow resulted in sudden and significant reduction in the load coefficients, as well as foil deflections. An impulse-like signature was observed in the time-frequency spectra during these transitions. In many of the cases, transition to fully ventilated flow also led to substantially reduced amplitudes in the load and deformation fluctuations.

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Design and benchmarking of a robust strain-based 3D shape sensing system

Cited by 3 publications

References 7 publications

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 2. Cavitating and ventilating flows

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 2. Cavitating and ventilating flows

Multi-modal Sensing Soft End-Effector for Underwater Applications

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 1. Fully wetted and ventilated flows

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