(Georgia Institute of Technology, 2014-09)
Deyle, Travis; Reynolds, Matthew S.; Kemp, Charles C.
We address the challenge of finding and navigating
to an object with an attached ultra-high frequency radio-
frequency identification (UHF RFID) tag. With current off-the-
shelf technology, one can affix inexpensive self-adhesive UHF
RFID tags to hundreds of objects, thereby enabling a robot
to sense the RF signal strength it receives from each uniquely
identified object. The received signal strength indicator (RSSI)
associated with a tagged object varies widely and depends
on many factors, including the object’s pose, material prop-
erties and surroundings. This complexity creates challenges for
methods that attempt to explicitly estimate the object’s pose.
We present an alternative approach that formulates finding
and navigating to a tagged object as an optimization problem
where the robot must find a pose of a directional antenna
that maximizes the RSSI associated with the target tag. We
then present three autonomous robot behaviors that together
perform this optimization by combining global and local search.
The first behavior uses sparse sampling of RSSI across the
entire environment to move the robot to a location near the
tag; the second samples RSSI over orientation to point the robot
toward the tag; and the third samples RSSI from two antennas
pointing in different directions to enable the robot to approach
the tag. We justify our formulation using the radar equation
and associated literature. We also demonstrate that it has good
performance in practice via tests with a PR2 robot from Willow
Garage in a house with a variety of tagged household objects.
(Georgia Institute of Technology, 2013-05)
Deyle, Travis; Tralie, Christopher J.; Reynolds, Matthew S.; Kemp, Charles C.
We present a unique multi-antenna RFID reader (a sensor) embedded in a robot's manipulator that is designed to operate with ordinary UHF RFID tags in a short-range, near-field electromagnetic regime. Using specially designed near-field antennas enables our sensor to obtain spatial information from tags at ranges of less than 1 meter. In this work, we characterize the near-field sensor's ability to detect tagged objects in the robots manipulator, present robot behaviors to determine the identity of a grasped object, and investigate how additional RF signal properties can be used for “pre-touch” capabilities such as servoing to grasp an object. The future combination of long-range (far-field) and short-range (near-field) UHF RFID sensing has the potential to enable roboticists to jump-start applications by obviating or supplementing false-positive-prone visual object recognition. These techniques may be especially useful in the healthcare and service sectors, where mis-identification of an object (for example, a medication bottle) could have catastrophic consequences.