Fringe field sensors based on piezo dielectrics offer opportunities in under water sensing as they are solid state, incompressible and robust. Questions remain regarding their susceptibility to noise. Specifically, we refer to anomalous outputs when the sensor is brought in close proximity to or just touching a conductive object. One solution involves isolation through a flexible Faraday cage. We have investigated two approaches for such a Faraday cage. One approach utilizes a conductive fabric while the other is based on a carbon filled dielectric. We compared the performance of both shielding approaches regarding noise suppression and their influence on sensitivity. The anomalous effects upon contact with conductive objects leading to inconsistent measurements were overcome. Furthermore, their response to salinity levels and submersion time were investigated and the influence of design parameters on the performance of the sensor determined in a Design of Experiment study. Varied parameters include overall footprint alongside electrode spacing and width. Performing a full factorial design plan enabled us to quantify the relations between the parameters. This investigation improved signal stability in the piezo dielectric fringe field sensors, making it possible to design a broader range of sensory systems able to withstand the harsh marine environment. The sensor will assist fish robots in their exploration of the ‘Silent World’.
We have developed a diver-robot empathetic communication system that allows the diver to feel the disturbance around the robot and control the robot remotely using hand gestures. The underwater robot is embedded with soft dielectric elastomer (DE) sensors to sense the direction and amplitude of the disturbance around its surroundings, defined as the physical indentation of the eye sensors. The direction and intensity of the disturbance communicate to the user remotely via an array of vibrotactile actuators in the form of a bracelet. Wears of the glove will feel what the robot is going through, represented by different vibration intensities and patterns. The smart glove employs five dielectric elastomer sensors to capture finger motion and implements a machine-learning classifier in the onboard electronics to recognize gestures. Hence allowing the wearer to send commands in the form of hand gestures for correcting the underwater robot’s posture. The system will be tested in a user study to determine performance improvement over the traditional robotic control interface. Our work has demonstrated the capability of DE sensing for advanced human-machine interaction.
For long-range swimming fish, low cost of transportation is a critical requirement. This also applies to autonomous fishlike robots (AFR). As with their biological cohorts, AFR require sensory input that characterizes the flow of the water surrounding them. Thus, there is a need for low power hydrodynamic sensors that can be deployed on a fish-like robot, and which can provide flow information from open water conditions. Electroactive polymers offer opportunities for flow sensing on soft and flexible AFR. We developed and evaluated an approach for capacitive electroactive polymer flow sensing. This uses dielectric elastomer sensor membranes mounted on a liquid-filled cavity protruding into the flow. Flow speed and incident angle on a hydrofoil standing in for the fish are registered through electrical capacitance changes resulting from deformation of its 350μm thick membrane. Through its triple-electrode design, measurements are largely shielded against the influence of the surrounding water on the capacitor. Differences in flow speed along the sensor can be detected with high reproducibility for extended durations of time. The developed sensors were assessed regarding accuracy, reliability, and durability. For performance and long-term testing, an automated tabletop water tunnel test rig was created. This setup enables sensor testing for flows up to 1 m/s with automated incident angle control and data logging. We are thus presenting further steps towards robust ocean-faring hydrodynamic sensory systems by demonstrating advances in electroactive sensory technology and testing facilities.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.