Dome shaped array of pressure sensors for underwater flow sensing and object detection
Kanhere, Elgar Vikram
Date of Issue2018-11-19
School of Mechanical and Aerospace Engineering
Autonomous underwater vehicles (AUVs) play a critical role in underwater surveys and explorations, which are beneficial to commercial sectors like oil and gas industry and scientific research disciplines like oceanography. AUVs rely on acoustic and optical sensing systems to be aware about their surroundings. However, the applicability of these conventional sensing systems is hindered in dark and turbid waters. Passive mechanoreception provides an alternative approach to overcome the limitations of conventional sensing systems, which assists in gathering information about surroundings by discerning flows and disturbances in the vicinity of AUVs. This work is an attempt to develop a passive mechanoreceptive system by drawing inspiration from the mechanosensory expertise of crocodiles. Crocodiles possess dome shaped pressure receptors called integumentary sensory organs (ISOs) on their skin, which assist them in flow sensing and in locating the origins of disturbances created by movements of other animals. The surface of each ISO is equipped with mechanoreceptors and free nerve endings, which together carry out the task of receiving mechanical stimulus. The mechanoreceptors associated with ISOs are of two types – slowly adapting (SA) which sense steady pressures and rapidly adapting (RA) which sense oscillating pressures. The bio-inspiration drawn from ISOs involves three aspects – dome shape, array of mechanoreceptors on its surface and types of mechanoreceptors. Inspired by SA and RA receptors of ISOs, two types of dome structures are constructed – SA dome, equipped with piezoresistive sensors to sense steady pressures and RA dome, embedded with piezoelectric sensors to sense oscillating pressures. With the proposed SA dome, direction and magnitude of steady flows can be perceived in three dimensions by analyzing the output pattern of sensors mounted on the dome surface. The SA dome manifests the ability to detect movement of an object in its vicinity and to determine parameters such as speed, distance and direction of the movement. The proposed RA dome can be employed to detect the position of the source of oscillatory disturbances. The applicability of SA domes in real time applications is demonstrated through sea trial experiments using a kayak equipped with one. It is critical to conceive a method to construct a dome with large number of sensors positioned at precise locations on its surface. This is achieved by combining MEMS fabrication technology and rapid prototyping technology with a novel strategy of contractively wrapping a hemispherical surface by patterned polymer petals. A dome of radius 1 cm, with a dense array of 17 piezoresistive sensors on its surface, is constructed. This dome can be used for flow sensing, direction detection and profiling flows over a hemispherical surface. This project demonstrates that ISO-inspired dome shaped pressure sensors can be employed as a comprehensive passive mechanoreception system for AUVs. To the best of our knowledge, this is the first attempt to develop a mechanoreception system by drawing inspiration from ISOs. It is expected that the work undertaken in this project would be a prelude to many more ventures, which will develop sensing systems to mimic the multi-sensory abilities of ISOs on crocodiles in order to enhance sensing capabilities of AUVs.
DRNTU::Engineering::Electrical and electronic engineering::Microelectromechanical systems