Entry Date:
May 24, 2007

Guiding People and Robots with Sensor Networks

A wireless sensor network can extend the sensory perception of people and robots far beyond their normal range. Wireless sensors are also small computers. When the sensors are used to detect danger they can perform distributed computations to compute the safest path along which a person or robot can be guided. Sensors that detect their own network connectivity can be used to guide a robot to repair holes in that connectivity. Sensors that detect a fault in an industrial process can guide a robot or person to the location of the fault for further inspection. Robots and people can also store information in a sensor network which can later be used for guidance, or by the sensor network itself (for example by telling the sensors their GPS coordinates.)

We have been exploring all these concepts in a large variety of experiments. In the picture on the left, USC's AVATAR autonomous flying robot is repairing the gaps in connectivity in a sensor network. The sensor network computed the locations of missing sensors, the robot queried the network for the gap location, and then flew over the gap, dropping new sensors to repair the network.

In the picture on the right, a crane robot at CMU is interacting with a sensor network. The robot is controlled by precision winches connected to the four cables attached to the robot from the ceiling. This type of robot might be used inside a factory to maintain sensors that monitor industrial processes. The robot first broadcasts location messages while moving in a precise pattern to localize the sensors. A radio message was then broadcast to the sensor network and followed a precise geographic path through the sensors. The robot then queried the sensors to follow the same path as the radio message.

We have also been looking at using maps of sensed data to guide people and robots. The picture on the left shows a temperature map as it varies over time in a room where a large fire has been started. Guidance algorithms can make use of such maps to bring people to safety, or to guide firefighters to the danger. A device we call a "flashlight", shown in the center of the sensors in the picture on the right, can be carried by a person or robot to find their way through an area based on the data stored in the sensors or on the readings from the sensors.