some rocky first tests

xanadu

I decided to start building a large(r) robot platform to accommodate all the sensor and payload space I've always dreamed of. I got two electric wheelchair motors and a motor controller and had some fun with indoor testing. I ended up using 'Holey' tube (from Lowe's) for the frame because it is easily reconfigurable. Lots of lock nuts hold everything tight. I initially started out with two caster wheels in the front but ended up with one. The robot is not designed for off-road and has no suspension. I needed to test it in a much harsher environment than my office as a stress test. Once the testing is done then I will make a real frame.

The three wheel design seems cheesy, but saved a lot of money. The caster wheel is greased and has ball bearings, but it can adversely steer the robot. This really only happens at slow speed because the wheels have less authority I guess. At higher speeds it's not an issue but I am using a lead acid battery so I didn't want to bump it too hard. In the video is remote controlling it. Occasionally I would connect to the MCU and check the temp and amp log. Didn't see any temps higher than 10 degrees over ambient, and the maximum amps drawn between both wheels was less 9.1.

I'm still not entirely sold on the wheel config, any comments would be great, thanks.

[video=youtube_share;kITSnt1fPd4]

Holey tube frame (Lowe's)
Nuts and bolts (Lowe's)
Motor mounts (metal fab shop)
Parallax Propeller Protoboard (Parallax)
MDC2250C (Roboteq)
Two 24v Framco motors and wheels (eBay)
35Ah SLA Battery (Amazon)
D-Link Dcs920 IP Cam (Fry's)
Xbee Link (Parallax)
GoPro Hero
Thinkpad T60
Wireless keyboard

ElectricAye

Looking great! Keep it up and keep us posted!

ElectricAye

Just curious. Any idea how difficult it might be to use only two wheels instead of three and create a self-balancing bot to go over terrain like that?

I was just looking at this video and wondering if it could be done for off-road bots:
http://www.youtube.com/watch?v=engi16bLJe0

mindrobots

Check out a Segway X2 - an all-terrain Segway. I would imagine you'd need low pressure tires and pretty torquey motors to respond to the more rapid changes in balance from the rough terrain.

Post video when you got it working!!

xanadu

Thanks for the comments. I haven't thought about the balancing robot concept, or tried it on a smaller scale yet.

For my setup so far, I thought the pneumatic tires would absorb a lot of shock. They don't, so you really do need big tires preferably with air in them. Even thought it's not an off road setup, I think I will put in some rubber bushings where the front caster attaches and increase the rubber around the electronics. I'm glad I took it to the rocky area and was able to see how bad the vibrations could get, I don't think I would have included much in the design for vibrations otherwise.

I would love to ride one of those Segway X2s

xanadu

Moar parts! I added some ITX computer parts so I have a clean 6v source and also a UPS with built in SLA standby battery charger. One cool thing about that is that I can pull the standby battery out and plug in an external power source while bench testing. That way the Prop never loses power and the main battery can be replaced etc.

Here's the current code: xbee_robot w ptz v4.spin

My 'schematic diagram':

Video of interface that didn't come out last weekend:
[video=youtube_share;8opDCNzlnIg]