Cooperation of Autonomous NXT Robots Using Bluetooth Wireless Technology

A 2013 University of North Texas report from the NSF Research Experience for Teachers program on two LEGO NXT robots that coordinate over Bluetooth. A lead robot follows a line and sends instructions to a follower.

Dated 2013, the report documents a project from the Research Experience for Teachers (RET) in Sensor Education program at the University of North Texas (UNT), funded by the National Science Foundation. The UNT Digital Library lists high school teachers Jesse Bell and Elizabeth Freeman and Omar Costilla, credited as research assistant, as its authors, with Kamesh Namuduri as faculty mentor. Dr. Costilla Reyes was then a graduate research assistant; the two teachers spent July and August 2013 in the university’s engineering labs, and he supported their project. The report and a companion poster are archived in the UNT Digital Library.

The project used LEGO Mindstorms NXT robots, which are programmable bricks with motors and sensors, programmed in a graphical language called NXT-G, together with Bluetooth, a short-range wireless link. A lead robot follows a path with a light sensor, which reports how bright the surface beneath it is, so that a dark line can be told apart from the floor. The lead robot turns that reading into a numerical message and sends it over Bluetooth to a second robot, which decodes the number into a series of motor movements and follows the same route without a sensor of its own. The task combines embedded sensing, control logic, and wireless communication, elements that larger multi-robot systems also have to coordinate.

The report follows the whole chain of cooperation, from the light sensor’s reading of the line, through the numerical message sent over Bluetooth, to the motor movements the follower performs. The authors point to the sensitivity of the light sensor and to the rate at which Bluetooth messages are sent as the settings that shape how closely the follower tracks the leader, and they suggest that adjustable message rates are a promising way to improve coordination.

The work is a hands-on engineering project carried out by high school teachers with research-assistant support, and its value lies in showing the engineering decisions involved in coordinating autonomous devices, from sensing and message exchange through movement. Teachers who took part could carry the same ideas about sensors, control and wireless communication back to their classrooms. The project is also described on the Research Experience for Teachers — Cooperative Robotics page.