Worn sensor can digitally map an area in real time

A prototype sensor array that can be worn on the chest and that can automatically map the wearer’s environment has been developed by researchers from MIT. The prototype system, described in a paper slated for the Intelligent Robots and Systems conference in Portugal next month, has been developed as a tool to help emergency services coordinate their response to a possible disaster. In experiments conducted on the MIT campus, a user wearing the sensor system was able to wander the halls and the sensors wirelessly relayed data to a group of observers who were able to track the student’s progress on a map that sprang into being as he moved.

Connected to the array of sensors is a handheld pushbutton device that the wearer can use to annotate the map. In the prototype system, depressing the button can designate a particular location as a point of interest. The researchers said that emergency services could use a similar system to add voice or text tags to the map — indicating, for example, structural damage or a toxic spill.

Similar research has been undertaken by a number of companies including BAE Systems in the UK.

“The operational scenario that was envisioned for this was a hazmat situation where people are suited up with the full suit, and they go in and explore an environment,” says Maurice Fallon, a research scientist in MIT’s Computer Science and Artificial Intelligence Laboratory, and lead author on the new paper. “The current approach would be to textually summarise what they had seen afterward — ‘I went into this room on the left, I saw this, I went into the next room,’ and so on. We want to try to automate that.”

Fallon is joined on the paper by professors John Leonard and Seth Teller, of, respectively, the departments of Mechanical Engineering and of Electrical Engineering and Computer Science (EECS), and EECS grad students Hordur Johannsson and Jonathan Brookshire.

The new work builds on previous research on systems that enable robots to map their environments. But adapting the system so that a human could wear it required a number of modifications.

One of the sensors that the system uses is a laser rangefinder, which sweeps a laser beam around a 270-degree arc and measures the time that it takes the light pulses to return. If the rangefinder is level, it can provide very accurate information about the distance of the nearest walls, but a walking human jostles it much more than a rolling robot does. Similarly, sensors in a robot’s wheels can provide accurate information about its physical orientation and the distances it covers, but that’s missing with humans. And as emergency workers responding to a disaster might have to move among several floors of a building, the system also has to recognize changes in altitude, so it doesn’t inadvertently overlay the map of one floor with information about a different one.

So in addition to the rangefinder, the researchers also equipped their sensor platform with a cluster of accelerometers and gyroscopes, a camera, and, in one group of experiments, a barometer (changes in air pressure proved to be a surprisingly good indicator of floor transitions).

The prototype of the sensor platform consists of a handful of devices attached to a sheet of hard plastic about the size of an iPad, which is worn on the chest like a backward backpack. The only sensor whose volume can’t be reduced significantly is the rangefinder, so in principle, the whole system could be shrunk to about the size of a coffee mug.

Wolfram Burgard, a professor of computer science at the University of Freiburg in Germany, says that the MIT researchers’ work is on the general topic of SLAM, or simultaneous localisation and mapping. “Originally, this came out as a problem of robotics,” Burgard says. “This idea of having a SLAM system that is attached to a human’s body, for figuring out where it is, is actually innovative and pretty useful. For first responders, a technology like this one might be highly relevant.”

Both the U.S. Air Force and the Office of Naval Research supported the work.

 

 

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