Linkbot modular robot platform grows with your knowledge
By Paul Ridden
May 27, 2013
Though somewhat time consuming and a bit of a brain drain, robot building can also be rewarding and fun. For those just starting out, however, the prospect of simultaneously playing the roles of designer, tinkerer, programmer and troubleshooter in order to breathe life into a pile of wires, motors, plastic and metal might be just a little overwhelming. Linkbots offer a gentler learning curve with a modular platform that starts with a single working unit, and grows into more complex robots by attaching accessories and connecting other units.
The Linkbot platform was developed by UC Davis Department of Mechanical and Aerospace Engineering professor Harry Cheng and a former graduate student named Graham Ryland, while the latter was studying for his master's degree. Within the polycarbonate housing of each Li-ion battery-powered 10-oz (284-g) modular robot sits an ATmega128RFA1 microcontroller from Atmel with integrated 2.4 GHz radio transceiver, that makes it ZigBee wireless-capable with a 100-m (328-ft) line-of-sight range. It also features multicolor LEDs and a buzzer, physical controls, and a built-in 3-axis accelerometer.
Three of its faces are home to a mounting surface, allowing users to snap connect modules together to build a bigger, badder, meaner Linkbot monster, or attach components like legs, joints, grippers, and even camera mounts. The current accessories are 3D-printed, and the developers have made all of the necessary files available for download and home printing. Users will be able to upload their own designs and share with other Linkbot users. Each mounting surface also sports #6-32 bolt patterns to further extend accessory attachment possibilities.
There's a rotating hub on either side that's reported capable of delivering 100 oz-in (7.2 kg-cm) of torque. The supplied firmware can accurately rotate the motors between zero and 120 degrees per second, with up to 300 deg/sec possible by tweaking the code. This should be enough for walking motion using accessories or connected Linkbots for limbs, as well as driving on wheels. Power supplied to the motors is kept steady courtesy of an integrated voltage regulator circuit.
Something dubbed BumpConnect allows Linkbot modules to wirelessly connect to each other with NFC-like ease. One bot can then be used to remotely control others in TiltDrive mode, which involves tilting the unit back, forward, left or right to issue cable-free speed and direction commands. There's another mode which sees any paired unit following the movements of one master, and another that makes it possible to program movement patterns using your hands instead of a keyboard.
The latter is called PoseTeach and, after physically connecting the bot to a computer running some special BaroboLink Windows/Mac/Linux software, the recorded motions are automatically converted into code. More advanced tools are on offer to enable students of Linkbotics to use different programming languages to control the robots. It's also possible to flash custom firmware onto a Linkbot, so advanced users can extend functionality beyond what's already provided by Barobo (the company formed by Cheng and Ryland to market the technology).
"The C and Python libraries enable you to access every last input and output on the Linkbot, from the battery voltages to the accelerometer readings, LED colors, and even reprogramming the buttons to execute C/Python code," says the company's software engineer. "As an example, one could do some simple room/maze mapping by using the accelerometer readings as a simple 'bump' detector. Or, the robot could be programmed to open blinds if it senses motion triggered by, say, a cat or a sleeping person."
Linkbots are Arduino-compatible for more advanced hacking, and an optional Bluetooth 2.0-capable expansion board for attaching sensors or external devices can be plugged into a module through an I2C bus/phone plug on the top face.
The tech has already found its way into the hands of local schoolchildren, but to get the system into the homes of consumers, the Barobo team has headed to Kickstarter, where a modest funding target of US$40,000 has been set. The first 50 single Linkbot units (with two wheels and eight mounting screws) have all gone, but another 50 have been made available for pledges of $139 or more. After that, the cost rises to $169. If you want that Bluetooth expansion board, too, you'll need to stump up at least $199.
A single Linkbot is ready to roll, turn, crawl, stand, and tumble out of the box, but if you think that one module won't be enough to satisfy your creative needs, the first double Linkbot kit has a $349 funding level. This comes with four wheels, a bridge bone accessory, 16 mounting screws and a snap connector. Other pledge levels are available for multiple bots and accessory packs. The funding campaign runs until June 18.
The Kickstarter pitch video outlines the main features and educational goals of the Linkbot project.