Tuesday, May 16, 2006
Robot Controllers
Being very interested in robotics, I have been always on the look out for a good robot controller. I have quite a few robotic controllers but all of them are very specific to their intended need. The Mindstorm robotics Brick is neat and with all the hacks available, it has become even more functional. With the introduction of their new robotics controller, the NXT, even more cool designs are possible. But still, the NXT processing and options are quite limited. Then there is the Robix Construction Kit which offers a general Parallel/'USB interface to servos with an aluminum set of links with all the hardware to make quite a few different kits. The controller connects to a computer, and it is controlled through the use of the included software and developed control language. Then there is the Evolution ER1 which supplies a interface to motors, etc. all controlled by a laptop with software, complete with camera and aluminum construction pieces. Then there is the Xport Robot Controller, from Charmed Labs, which is the Cool Pick Of The Day.
In general, for learning robotics, it is best to have a controller board and a separate "brain". I think it is preferable to have a computer processor that is linked to the controller, with a generic control language that sends commands to the controller, while still being capable of doing other tasks. To accomplish this, one option is to have a multitasking Operating System on the processor. This usually involved a pretty substantial architecture and OS. An Intel computer with an OS such as Linux would fit the bill but this adds substantial cost to the Robot. The other option is to have the controller be powerful enough to take care of all the tasks it is given and have the processor be the interface and overall task manager.
The second approach is used for the Charmed Lab's XRC. For the processor, Charmed Labs chose a very easy to buy, very inexpensive, pretty powerful computer- the Game Boy Advance (Series). Another neat feature is that you can use LEGO's with the setup which extends the functionality and flexibility of this robotics controller.
The XRC consists of 2 components- the Xport 2.0 which is the embedded system development module and an IO controller in the form of a daughter card that works with the XPort. For power, it uses 6 NiMH (recommended) or NiCd batteries that can also power the GBA.
Xport 2.0 features a fully programmable FPGA (available with 50,000 or 150,000 logic gates),64 user-programmable I/O signals, 4 Mbytes of flash memory,16 Mbytes of SDRAM (optional), built-in high-speed communications and debug port,and free FPGA synthesis software. Also, supplied is several pre-tested logic configurations,in system programmability,open source software,and source level debugging. The real-time operating system used in the XPort is eCos 2.0, the bootstrap environment is RedBoot, and the debugger is Insight.
The XRC daughter card provides: 4 closed-loop back-EMF motor controllers,16 digital sensor inputs,8 analog sensor inputs,In-system NiCd, NiMH battery charger,battery voltage monitor,comprehensive open-source software to program in C/C++, wireless communication via an optional bluetooth module, and option XIR module.
The XRC plugs into a GBA (not included but you can surely get one for under $99 maybe even $50) and utilizes the powerful 32-bit RISC CPU. You can program in C or C++, use the PCM sound, utilize the 240x160 TFT color LCD as an interface for control and status, for your robot experiments. The controllers cost between $140-$269 and the modules are $16 for the XIR, $89 for the Bluetooth modules and the Omniwheels are $9 each
Without a doubt the XRC provides a flexible and functional robotics development environment by combining advanced cost-effective technologies.
