Researchers Develop Underwater Sensor That May Help Robots Swim Like Fish

Thursday, December 13, 2012

Underwater robot

 Sensor Technology
Singapore's Nanyang Technological University researchers have invented a new underwater sensor array, similar to a string of ‘feelers’ found on the bodies of the blind cave fish, which enables the fish to sense their surrounding and so navigate easily. The system has potential applications for underwater robots, or AUVs as well as other sea vessels.
Scientists at Singapore's Nanyang Technological University have invented a new underwater sensor array, similar to a string of ‘feelers’ found on the bodies of the blind cave fish, which enables the fish to sense their surrounding and so navigate easily.

Using a combination of water pressure and computer vision technology, the sensory device is able to generate a 3D image of nearby objects and map its surroundings.

Some of the possible applications of this fish-inspired sensor are enormous. The sensor can potentially replace the expensive ‘eyes and ears’ on Autonomous Underwater Vehicles (AUVs), submarines and boats that currently rely on cameras and sonar to gather information about the environment around them.

The revolutionary, low-powered sensor is superior to a camera which cannot see in dark or murky waters; or sonar whose sound waves pose harm to some marine animals.

The new sensors require much less power to operate than other systems, and the researchers are also working on developing a sensor version that is powered by the water moving past it, which could virtually eliminate the need for a battery altogether.

 Furthermore, at around $100 to produce, the new sensors are much cheaper than cameras or sonar systems.
Blind Cave Fish
The researchers were inspired to create the sensor by the blind cave fish.
These extremely small sensors (each sensor is 1.8mm x 1.8mm) are now being used in AUVs developed by researchers from Singapore-MIT Alliance for Research and Technology (SMART), a research centre funded by the National Research Foundation. The centre is developing a new generation of underwater ‘stingray-like’ robots and autonomous surface vessels.

The new sensors, made using Microelectromechanical Systems (MEMS) technology, will make such robots smarter and prolong their operational time as battery power is conserved.

Associate Professor Miao Jianmin from the School of Mechanical and Aerospace Engineering, and his team of four have spent the last five years in collaboration with SMART to develop micro-sensors that mimic the row of ‘feelers’ on both sides of the Blind cave fish’s body.

Miao Jianmin and colleagues
PhD student Kottapalli Ajay Giri Prakash; Assoc Prof Miao Jianmin and Research Associate Mohsen Asadniaye Fard Jahromi holding the new underwater MEMS sensors. Image Source: Nanyang Technological University

Miao said the line of sensors present on the fish’s body is the reason why it can sense objects around it and still travel at high speeds without colliding with any underwater obstacles.

“To mimic nature, our team created microscopic sensory pillars wrapped in hydrogel - a material which is similar to the natural neuromasts of the blind cave fish - into an array of two rows of five sensors,” Prof Miao said.

“This array of micro-sensors will then allow AUVs to locate, identify, and classify obstacles and objects in water through water pressure and also to optimise its movement in water by sensing the water flow.”

The aim of the AUVs is for environmental sensing, to detect environmental pollution, contaminants and to monitor the overall water quality in Singapore’s waters. The AUVs will have chemical sensors installed to detect the chemical condition of water (dissolved oxygen, nutrients, metals, oils, and pesticides), and biological sensors to monitor water conditions such as harmful bacteria and pathogens.

Other potential application of these MEMS sensors, which specialises in near-field detection include defence applications. These can detect nearby submarines without the use of sonar thatgives away one’s location.

This collaborative research resulted in two breakthrough papers being accepted for presentation at a prestigious MEMS conference next January in Taiwan, organised by the Institute of Electrical and Electronics Engineers (IEEE).

To further improve the sensor, Miao’s team is now looking to develop a hybrid sensor which will combine both the zero-energy piezoelectric sensor’s high accuracy with the low-powered static sensor’s ability to detect objects in still water.


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