PDA

View Full Version : [Project] Need Advice: Laptop based autonomous rover



Merik
01-09-2009, 10:30 AM
Hi,
Let me first say its great to find a helpful community here; im sure alot of people wouldn't be able to start experimenting with robotics without yall's help.

I'm posting because i need some advice, direction, and a knowledgeable assement of my current proposed build.

I'm a programmer professionally and after working with a phidget servo motor controller for a job, a light bulb turned on in my head and I decided to finally take the plunge into robotics. I have a pretty good idea of the platform i want to build to start experimenting. My goal is to build a pc based robot that can rove indoors autonomously using sonar initially, and later vision based. Id like to be able to take it outdoors eventually to do gps based navigating. The brain of the robot will be a dual core laptop sitting on the robot with all control being via usb.

Preferably I would like to build a four wheeled robot platform with two motors, using "tank style" turning; something like the lynxmotion a4wd1 robot (http://www.lynxmotion.com/Category.aspx?CategoryID=111) but larger so it could carry the laptop and some additional stuff.

Below is my current proposed equipment list:
1. Phidget InterfaceKit 8/8/8
2. Phidget MotorControler HC
3. Phidget 8-Motor Phidget USB Servo Controller
4. A bunch of servos for pan/tilt camera, sonar sensors, and maybe a manipulator down the road
5. A banebots 20:1, 28mm Planetary Gearmotor, RS-385 Motor (http://www.trossenrobotics.com/store/ProductDetails.aspx?itemID=4224) x 2
6. Off Road Robot Tire - 5.0"D x 2.25"W (pair) (http://www.trossenrobotics.com/store/ProductDetails.aspx?itemID=3393)x 2
7. A pan and tilt assembly
8. LV-MaxSonar-EZ1 x 3
9. 5mm IR reflector detector x 2 (for the wheels as a speed detector)

So, my questions:
1. Is there anything that sticks out as unneeded or a poor choice?
2. Is that motor a good choice? Do i need something more powerful? Do i need 4 motors? If i use 2 motors, should i connect the other two wheels to the motors using chains, or just let them spin free?
3. Batteries and charger? Can you recommend a battery for this motor setup and a charger for it?
4. Any other suggestions?

I hope this isn't too much at once. I really appreciate any direction or advice someone could give me. Cheers from Australia,
Merik

lnxfergy
01-09-2009, 10:35 AM
A 4 wheel bot like you describe would work OK for outside GPS based navigation, but if you want it to be able to actually navigate inside with any idea of where it is - that's not gonna work.

The problem with tank-style skid steer is that it induces a large amount of variability in turning and such, it is going to make your programming a lot more difficult if you want the robot to use any sort of indoor mapping and navigation. There is a reason most intelligent bots use differential drive with 1 wheel on a side and a third (preferably omni-directional) caster - it works for autonomous mapping and navigation.

-Fergs

metaform3d
01-11-2009, 03:53 PM
I'd drop the Phiget motor controller and use 2 servo channels to drive a dedicated ESC. You'll have a lot more flexibility that way and it'll cost less.