Gliding-Robot-ACE Fish Helps Sample Harmful Algal Blooms

Xiaobo Tan is an associate professor of electrical and computer engineering and one of the driving forces behind “Grace,” a robotic fish that swims lakes and streams gathering data such as water temperature and quality.

Robofish with Tan inset

July 2. Hickory Corners, Mich. Partly cloudy, low-to-mid 70s, breezy. What a perfect field-trip day, especially for “Grace,” a robotic fish my lab developed for scouting aquatic environments.

Curious about her name? I coined it – Gliding-Robot-ACE – because, in addition to swimming, she was designed to be capable of traveling in water through effortless gliding.

There she was, wandering about on Wintergreen Lake located near the MSU Kellogg Biological Station. Her black antenna, dark GPS receiver and red wings complete with Spartan logo, were clearly visible. Members of my lab and Professor Elena Litchman’s lab occupied three canoes, watching Grace from a distance.

Elena is an aquatic ecologist interested in harmful algal blooms. These blooms are caused by rapid accumulation of cyanobacteria, which deplete oxygen in water, release toxins and threaten water quality and ecosystems all over the world. Monitoring these blooms is important but very challenging – the concentration of cyanobacteria could vary greatly with location and time.

Elena’s lab can only afford to come out and sample at a fixed location in the lake once or twice a week. Rowing a boat on the lake is a refreshing workout, but it is time-consuming and could become tedious if you have to do it every week, especially during days with unrelenting weather. It is our hope that, one day, robots like Grace will take over the sampling chore and do it better, providing data with much higher spatial and temporal resolution.

Grace is equipped with an optical sensor under her belly, which measures the cyanobacteria concentration by shooting out a blue laser beam and measuring the intensity of fluorescence excited off harmful algae. The purpose of this field trip was to test whether Grace would be able to provide accurate measurement and perform desired locomotion and communication functions.

For that reason, Elena and her team members were reading off the measurements from their handheld instrument, which were then compared with the numbers reported by Grace. We were gratified that agreement was found for comparisons at different locations.

This was not the first field trip Grace had taken. Last November Grace swam in the Kalamazoo River and sampled crude oil concentrations near the site of the 2010 oil spill. One difference this time was that we were able to compare the measurements from Grace with “ground truth” and therefore confirm her value to ecologists. Another difference was that, in addition to swimming on surface, Grace took a few dives. We were pleased to see, seconds after Grace reemerged from each dive, data collected underwater were successfully streamed to the base station, a laptop on one of the boats.

At the end of test, Elena requested that we (I should say Grace) come back in November so that her research staff is saved from rowing the boat in the cold weather. She also invented another interpretation for “Grace” – Gliding Robot Autonomously Cruising in the Environment.

Aside from sampling water quality, robots like Grace have many other potential applications that we are pursuing. These include inspecting bridge scours, monitoring seaports and maritime borders, and even tracking invasive species. We are working with MSU Technologies and Spartan Innovations to transition the technology to the market place, so that it can effectively address these applications. Stay tuned.

Our work on robotic fish has been supported by the National Science Foundation (NSF), including the NSF Science and Technology Center, BEACON.


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