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Wyatt Felt

Publications and source records attributed to Wyatt Felt.

2 recordsLinked to original sources

Reconsidering Fascicles in Soft Pneumatic Actuator Packs

This paper discusses and contests the claims of ``Soft Pneumatic Actuator Fascicles for High Force and Reliability'' a research article which was originally published in the March 2017 issue of the Journal Soft Robotics. The original paper claims that the summed forces of multiple thin-walled extending McKibben muscles are greater than a volumetrically equivalent actuator of the same length at the same pressure. The original paper also claims that the purported benefit becomes more pronounced as the number of smaller actuators is increased. Using reasonable assumptions, the analysis of this paper shows that the claims of the original paper violate the law of conservation of energy. This paper also identifies errors in the original methodology that may have led to the erroneous conclusions of the original paper. The goal of this paper is to correct the record and to provide a more accurate framework for considering fascicles used in soft pneumatic actuator packs.

cs.RO

An Inverting-Tube Clutching Contractile Soft Pneumatic Actuator

This paper presents the simple synergistic combination of a novel contracting soft pneumatic actuator with a soft clutch (linear brake). The device is designated the Inverting-tube Vacuum ACtuator with Clutch (InVACC). The actuator alone (no clutch) is designated "InVAC" and uses vacuum pressure to invert a thin tube into a shorter section of reinforced flexible tubing. The inverting tube acts as rolling diaphragm and a flexible tendon. This allows the actuator to contract to one third of its extended length. The contractile-force-per-unit-pressure is approximately constant over the stroke. The theoretical maximum of this force is the product of the vacuum gauge pressure and half the interior cross-sectional area of the tube. The experimental evaluation revealed hysteretic losses that depend on the actuation direction and rate. With -81 kPa, the prototype produced 12.7 N of tension during extension and 7.5 N during retraction. The reinforced tubing of the InVAC was integrated with an inner collapsible "clutching" tube to create an InVACC. The clutch is engaged by applying a positive pressure between the reinforced tube and the clutching tube, which collapses the clutching tube onto the flexible tendon. With a pressure of 50 kPa, the InVACC clutch tested in this work was able to support a peak tensile load of 120 N before slipping. Though the fatigue life of the current prototypes is limited, improved fabrication methods for this novel actuator/clutch concept will enable new applications in robotics and wearable haptic systems.

cs.RO