LOBOT Technique Provides Accurate, Real-Time, 3-D Positions for Robotic Vehicles

A Wayne State University researcher understands that the three most important things about real estate also apply to small ground robotic vehicles: location, location, location.

In a paper recently published in the journal IEEE Transactions on Parallel and Distributed Systems, Weisong Shi, Ph.D., associate professor of computer science in the College of Engineering, describes his development of a technique called LOBOT that provides accurate, real-time, 3-D positions in both indoor and outdoor environments. The project was supported in part by the Wayne State Career Development Chair award, which gives Shi an opportunity to explore other areas after receiving tenure at WSU.

Scientists believe small ground robotic vehicles have great potential for use in situations that are either uncomfortable or too tedious for humans. For example, a robot may become part of industrial operations, assist senior citizens or serve as a tour guide for an exhibition center. Keeping a robot as small as possible enables it to move through narrow passageways, such as tunnels.

To complete such missions, a robotic vehicle often must obtain accurate localization in real time. But because frequent calibration or management of external facilities is difficult or impossible, a completely integrated self-positioning system is ideal. In addition, that system should work indoors or outdoors without human calibration or management and cost as little as possible.

In the paper titled "LOBOT: Low-Cost, Self-Contained Localization of Small-Sized Ground Robotic Vehicles," Shi and lead author Guoxing Zhan, one of his former graduate students, describe their technique, which combines a GPS receiver, local relative positioning based on a 3-D accelerometer, a magnetic field sensor and several motor rotation sensors.

The researchers noted that IEEE Transactions, the leading journal in the field, prominently featured their paper in its April 2013 issue. They are proud that their work was in progress before President Barack Obama's June 2011 announcement of the National Robotics Initiative, which seeks to accelerate the development and use of robots in the United States that work beside, or cooperatively with, people.

Shi's technique combines elements of common localization schemes for ground robotic vehicles, noting that each of those schemes has limitations. One scheme, using GPS alone, requires a lot of power. Another, radio-based positioning, requires proper calibration, a friendly environment and a set of external devices to generate or receive radio signals.

A third scheme, the use of vision techniques, relies heavily on recognition of objects or shapes and often has restricted spatial and visual requirements. Additionally, those objects and shapes must be captured and loaded into a computer which, like GPS, requires a lot of power.

A fourth scheme, inertial sensors, is part of the LOBOT design. Inertial sensors often are used to detect movement, but unlike radio- or vision-based techniques, operate independently of external environmental features and need no external reference. However, previous methods of maintaining their accuracy have resulted in high cost and calibration difficulty.

LOBOT uses a hybrid approach that localizes robotic vehicles with infrequent GPS use, a 3-D version of the accelerometer used in other inertial sensor systems and several motor rotation sensors - all installed on the robotic vehicle. All of the components are commercially available, with some costing as little as $20.

"Our goal has been to solve a problem by building a robot that leverages a number of existing technologies that can be used to address the problem of location, which is the key to many possible applications" Shi said. "Because of the increasing number of things robots will be needed to do in the next five to 10 years, it is very important to develop a cheaper, low-powered approach that can address that problem as accurately as possible."

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