Logitraxx Snow Cat Explorer
by SLI, published
The Snow Cat Explorer cab bolted to the Logitraxx platform and using up about 25 or so GPIO.
The bot was designed by SL Interphase, LLC
The Snow Cat utilizes a custom 182mm (Logitraxx) board that supports the Tamiya Vehicle Chassis kit mounting hardware that is widely available. It also uses the Tamiya 70168 twin motor gearbox. The Snow Cat is part of a vehicle offering currently available on Kickstarter. http://kck.st/W9gPef
Our FPGA based snow cat uses a second generation autonomous drive algorithm we've been tinkering around with that employs two sonic range finders. The first sensor is fixed mounted on the front and serves as the main obstacle avoidance sensor. The second is mounted on a servo up on the roof and looks around when the vehicle cannot move forward. There is also a light sensor controlling the headlights, taillights, porch, and KC lighting.
The Logitraxx uses a Spartan 6 LX9 FPGA for its brain and does not have a CPU or run any software. We also integrated a RC receiver so that we could switch out from autonomous mode to RC mode when the vehicle gets stuck. One of the pleasant features of the FPGA is that the GPIO is so incredibly flexible, you can program it to behave in almost any manner rather quickly and communicate with almost anything.
Every time we got something working, we starting looking around to see what else we could integrate with it. Our latest integrated device is a Specktrum AR6115e RF receiver, which we quickly integrated into the FPGA logic. The nice thing about the AR6115e is that it works on a wide voltage range. We ran the AR6115e from a +3.3v source and connected its outputs directly to the FPGA GPIO.
The video link below demonstrates the remote control being switched on/off...
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The cab and top simply glue together. We used hot glue so that we could remove the top when we wanted. We may update these with screw holes later. The servo mount on the roof supports the CSCR-55 servo. The cab mounted sonic sensor is designed to fit the Parallax Sonic Range Finder, but will need clearancing when you print it to make it fit.
The track legs are designed to fit the Tamiya vehicle chassis kit bolt holes. The Logitraxx board is 182.85mm in total length. A bit longer than the wooden chassis that comes in the kit. You'll need to cut out your own board (we did this with a 9x6" bare copper PCB) if you want to use the Snow Cat on something besides the Logitraxx board since its not available for purchase yet. However the Tamiya parts will all fit and work with the Snow Cat mechanicals.
The Snow Cat Cab is designed to mount backwards on the Tamiya Vehicle Chassis kit mechanicals and drive the vehicle "backwards". This left us with plenty of room to plug in all the GPIO connections. So, notice the RF, LF, RR, LR designators on the cab mount struts.