Closed-Loop Haptic Feedback Control Using a Self-Sensing Soft Pneumatic Actuator Skin

• Published in: Soft robotics Vol. 7; no. 1; p. 22
• Main Authors: Sonar, Harshal A, Gerratt, Aaron P, Lacour, Stéphanie P, Paik, Jamie
• Format: Journal Article
• Language: English
• Published: United States 01.02.2020
• Subjects: soft pneumatic actuators; wearable technology; tactile feedback device; strain sensor; haptic device; liquid metal sensor
• ISSN: 2169-5180
• DOI: 10.1089/soro.2019.0013

In this article, we achieve a closed-loop control over haptic feedback, first time for an entirely soft platform. We prototyped a novel self-sensing soft pneumatic actuator (SPA) with soft strain sensors, called SPA-skin, which withstands large multiaxial strains and is capable of high-frequency sensing and actuation. To close-loop control the haptic feedback, the platform requires a cohesively integrated system. Our system consists of a stretchable low profile (<500 μm) SPA and an ultra-compliant thin-metal film strain sensor that create a novel bidirectional platform for tactile sensing via force-tunable vibratory feedback. With this prototype, we demonstrated control of the actuator shape in real time up to 100 Hz at output forces up to 1 N, maintained under variable mechanical loadings. We further characterized the SPA-skin platform for its static and dynamic behavior over a range of actuation amplitudes and frequencies as well as developed an analytical model of this system to predict the actuator inflation state only using the embedded sensor's resistance. Our SPA-skin is a multifunctional multilayer system that can readily be implemented as a high-speed wearable bidirectional interface for contact sensing and vibrotactile feedback.