Swarming Robots Get Cheaper

Nov. 30, 2011
Harvard and Rice University are tackling swarm robotics with low cost robots.

Fig 1. A 50-MHz Texas Instrument Stellaris microcontroller controls Rice University’s r-one robot. It has 802.15.4 wireless support as well as IR-based neighbor location and communication.
Fig 2. Harvard University’s Kilobot is not much larger than its battery. An Atmel ATmega microcontroller handles a pair of vibrating motors to move the three-leg robot.

Unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) are now commonly used on the battlefield and by fire and police departments. Most of them are remotely controlled and operated as individual robots. They’re also rather expensive. At the other end of the spectrum are robot swarms that need to be autonomous and inexpensive.

Swarms are still in the research phase, which has been more limited than other robot research because of cost. Plus, swarms only get interesting when there are dozens or hundreds of robots working together. Now, two universities are churning out inexpensive robots that can be used for teaching robotics in general and then moving on to swarms.

Rice’s Rolling Swarm

James McLurkin’s r-one from the MultiRobot Systems Lab at Rice University builds on his experience with swarm robots (Fig. 1). He built robot ants at the Massachusetts Institute of Technology and larger versions of the r-one at iRobot. Those larger versions cost more than $2000, which the r-one cuts by a factor of 10 while expanding on the functionality.

The r-one is about the size of a DVD and hides some wheels that provide locomotion. There are two circuit boards, one with a 50-MHz Texas Instruments (TI) Stellaris microcontroller. A TI MSP-430 provides power and peripheral control. The 2000-mAh battery is designed for smart phones.

The r-one has a host of sensors and LEDs including a 3D gyro, a 3D accelerometer, and three light sensors. There are 30 LEDs including five around three buttons. The red, true green, and blue LEDs provide better feedback, especially when the robot is in a swarm because reading a tiny LCD or organic LED (OLED) display would be rather difficult. Audio output is also a useful debugging tool. Even the plastic skirt is part of the bump sensor system.

There are two communication mechanisms. The 802.15.4 wireless support is used for programming and general communication. Four IR transceivers spaced around the bottom of the top board provide peer location information as well as peer-to-peer communication. There is an expansion header next to the JTAG header on the top board that some students are already trying to mate with a Gumstix (see “A Pack Of Gumstix” at electronicdesign.com).

Right now, the robots are running a variant of FreeRTOS. The r-one operating system (OS) provides basic control. IR communication/location software is available for experimentation. Students are using Mentor Graphics’ Soucery CodeBench for some work, and a Python interpreter is running on the Stellaris. Like most research facilities, there are better things to come.

The r-one can operate alone, and Rice University plans on providing each student with one for robotics class. Putting the robots together will be for more advanced classes.

Harvard’s Vibrating Swarm

Designed by the Self-Organizing Systems Research Group of the Harvard School of Engineering and Applied Sciences (SEAS), the Kilobot cuts the cost of a swarm robot by another factor of 10 (Fig. 2). Swiss company K-Team will be selling Kilobots and support hardware like charging stations and USB-based PC communication hubs.

The Kilobot is tiny, only slightly larger than its 3.4-V lithium battery. It sits on three fixed metal legs. The pair of vibration motors on the side of the battery holder allows these legs to move the robot fairly accurately. An 8-bit Atmel ATmega 328 microcontroller controls the motors.

An RBG LED on the top provides debug support while an IR transceiver on the bottom provides communication with nearby Kilobots. They need to be within 7 cm of each other, though positional information like the data that the r-one can obtain is not available to Kilobots. The same IR link can be within 1 m of the communications hub, which can be used to program a lot of Kilobots simultaneously.

Kilobots are designed specifically for swarm research. The limited sensor and locomotion system restricts the robots, but the hardware can be used to examine a host of problems.

Rice and Harvard are only a couple of places where robots and students are swarming. As you might guess, I’m very upbeat about robots. These two platforms are open so check out the online docs if you want to build a dozen or more.

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