Analysis and optimization of fully foam-based capacitive sensors

Totaro, Michele; Bernardeschi, Irene; Wang, Hongbo; Beccai, Lucia

doi:10.1109/robosoft48309.2020.9116014

Cited by 9 publications

(7 citation statements)

References 22 publications

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“…First, we analyzed the mechanical behavior of C1 and C2 sensors. In both cases, a highly viscoelastic behavior can be observed, as already investigated in our previous studies ( Wang et al, 2019 ; Joe et al, 2020 ; Totaro et al, 2020 ), with a relevant hysteresis. Moreover, both samples were tested with 200 loading/unloading cycles for 8 h, showing the variations of mechanical characteristics (as displayed in the dashed curves of Figure 3B and in normalized inductance versus cycles of Figure 3C ).…”

Section: Resultssupporting

confidence: 73%

Sensing Deformation in Vacuum Driven Foam-Based Actuator via Inductive Method

et al. 2021

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Perception in soft robotics is crucial to allow a safe interaction to effectively explore the environment. Despite the inherent capabilities of soft materials, embedding reliable sensing in soft actuators or robots could introduce constraints in the overall design (e.g., loss of deformability, undesired trajectories, etc.) or reduce their compliant characteristics. Consequently, an adequate stiffness for both sensor and actuator becomes a crucial design parameter. In particular, for sensing the deformation related to actuation motion, sensing and actuating strategies must work in full mechanical synergy. In this view, an inductive sensing solution is presented, exploiting open-cell foam and a copper (Cu) wire in an Inductive Foam Sensor (IFS). Due to entangled air cells high deformability is enabled upon vacuum pressure, and proprioceptive information is provided. The IFS is then successfully integrated into the earlier developed Ultralight Hybrid Pneumatic Artificial Muscle (UH-PAM), which encases an elastomeric bellow skin and plastic rings. Such sensorized UH-PAM (SUH-PAM) is capable of a high contraction ratio (54% upon −80 kPa), while the inductive sensing shows a high sensitivity of 0.01031/1% and a hysteresis of 5.35%, with an average error of 1.85%, respectively. In order to implement a robust feedback control system, an adaptable proportional sliding mode control is presented. As a result, the SUH-PAM motion can be controlled to the mm-scale, with an RMSE of 0.925 mm, and high robustness against disturbances is demonstrated.

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Section: Resultssupporting

confidence: 73%

Sensing Deformation in Vacuum Driven Foam-Based Actuator via Inductive Method

et al. 2021

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“…Such viscoelastic behavior is due to the foam used in these prototypes. However, as already demonstrated in our previous works [53,54], foam mechanical properties can be finely tuned (i.e., varying the porosity and/ or constituent material) with custom-made structures, obtaining porous materials with proper softness and good linearity.…”

Section: Plos Onementioning

confidence: 83%

Development of the Ultralight Hybrid Pneumatic Artificial Muscle: Modelling and optimization

et al. 2021

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Pneumatic artificial muscles (PAMs) are one of the key technologies in soft robotics, and they enable actuation in mobile robots, in wearable devices and exoskeletons for assistive and rehabilitative purposes. While they recently showed relevant improvements, they still present quite low payload, limited bandwidth, and lack of repeatability, controllability and robustness. Vacuum-based actuation has been recently demonstrated as a very promising solution, and many challenges are still open, like generating at the same time a large contraction ratio, and a high blocking force with enhanced axial stiffness. In this paper, a novel Ultralight Hybrid PAM (UH-PAM), based on bellow-type elastomeric skin and vacuum actuation, is presented. In particular, open-cell foam is exploited as a structural backbone, together with plastic rings, all embedded in a thin skin. The design and optimization combine numerical, analytical, and experimental data. Both static and dynamic analysis are performed. The weight of the optimized actuator is only 20 g. Nevertheless, a contraction ratio up to 50% and a maximum payload of 3 kg can be achieved. From a dynamic point of view, a rise time of 0.5 s for the contraction phase is observed. Although hysteresis is significant when using the whole contraction span, it can be reduced (down to 11.5%) by tuning both the vacuum range and the operating frequency for cyclic movements. Finally, to demonstrate the potentiality of this soft actuation approach, a 3 DoFs Stewart platform is built. The feasibility of performing smooth movements by exploiting open-loop control is shown through simple and more complex handwriting figures projected on the XY plane.

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“…An interesting approach is to employ foam (like in the UH-PAM [38]) as a constituent material, or porous structures where the air-cells dimensions can be decided upon the desired stiffness. Notably, given the recent advances in foam-like sensing, (e.g., capacitive [129], inductive sensing [130], resistive sensing [131,132], etc. ), it can be construed that, in a near future, new designs should consider such transduction mechanisms embedded in V-PAMs.…”

Section: Discussionmentioning

confidence: 99%

Rehabilitation of the Human Bone-Muscle System

2022

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Analysis and optimization of fully foam-based capacitive sensors

Cited by 9 publications

References 22 publications

Sensing Deformation in Vacuum Driven Foam-Based Actuator via Inductive Method

Sensing Deformation in Vacuum Driven Foam-Based Actuator via Inductive Method

Development of the Ultralight Hybrid Pneumatic Artificial Muscle: Modelling and optimization

Rehabilitation of the Human Bone-Muscle System

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