NASA Goddard Space Flight Center, Greenbelt, MD
While a single, peer-to-peer rover can cover a large territory and gather a wealth of information, an entire fleet of rovers could cover even more ground. However, controlling multiple platforms poses a much different set of criteria. To answer the need to control and communicate with multiple vehicles doing a similar task, the Adaptive Sensor Fleet (ASF) software was developed by NASA researchers, and is able to coordinate several platforms at once. Julia Loftis oversaw the strategic planning of the project.
NASA Tech Briefs: What is the Adaptive Sensor Fleet software, and how does it work?
Julia Loftis: The Adaptive Sensor Fleet software, or ASF, is a supervisory control system for a fleet of mobile platforms. It’s a very open, extensible system in that each platform can be completely different — they can be configured with different sensors, they could move at different rates, they can be stationary. They can be of all types in a single fleet. You would define each platform and its sensors in XML, and the control software is then able to control these platforms as a group and optimize their performance to accomplish a goal. Basically, it allows a user to specify a goal of the entire system, and then it directs each platform as how to best accomplish that goal. ASF is a conservative approach. There is a central supervisory function. ASF can accommodate intelligent platforms, or very simplistic platforms, or a mix of the two. Having a supervisor reduces the risk a bit, and can also help with optimization (ability to see the forest instead of just the trees). Other approaches, such as a pure peer-to-peer architecture, rely on a degree of intelligence for each platform. This can be more advanced and/or innovative, but also more risky. In summary, both approaches are valid and for each application you need to weigh the benefits vs. risk.
NTB: Is ASF being utilized now?
Loftis: It is. A good example is the OASIS project, which is a fleet of autonomous boats. The OASIS boats use ASF to monitor harmful algal blooms. The original application idea was for Martian rovers, and then boat idea came along and the ASF worked really well. We were able to adapt the XML and control the boats in the same way. A user would decide what bloom to monitor, or even a satellite might discover a bloom, and based on that, and based on direction to monitor a bloom, the ASF software would the divide up the area of that bloom and give each platform directions as to where to go and give it waypoints.
Now, say that one platform accomplishes its goal faster, or the bloom moves, or some other dynamic event happens — the ASF control software will keep track of the data collected and the area that has been covered, and will continuously adapt what it is directing each platform to do to optimize how that platform is working. We also did a technology demonstration with three miniature rovers. They did path planning and mapping of an area that was a simulation of a Marian terrain. That was a demo; OASIS is the first real application. We don’t have the resources to launch into space a fleet of rovers yet, but it is in the future. Monitoring algal blooms, which is experimental, is where we are getting started. Because we don’t have to launch them, we can have more boats. I think it is good to start with something that is less risky, more controlled, to see if ASF works well and doesn’t get into anything dangerous. Once that works, we might let the platforms be more autonomous and take a little more risk.