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## Comments

1,326(I just made that up, you can use that if you want to.)

-Tommy

20,060Has Parallax ever called it Scribbler 2 or 3 ?

1,326It is listed as "Scribbler 2(S2)" http://www.parallax.com/catalog/robotics/complete-robots it's a free for all now.

20,0604,050I'm using an aRobot I picked up on eBay for about half its new price. The trike steering is a natural for this sort of challenge, and its encoder allows for fairly precise odometry as long as you are traveling in arcs. Here's the code:

The coprocessor make for short work of it since there's no tending servos, motors, or the encoder. The BS2 just kicks back and plays a tune.

1,326-Tommy

20,060Who else will answer the call?

20,060Anyway, my first shot start at a figure 8. Needs work.

4,0508erco said

Here's another video:

[video=youtube_share;iyDPer_6UaE]

My ActivityBot DC needs a little more work.

John

20,060The "stack attack" was cool, Stingray carrying S2. Would love to see a 2-stage, where the S2 auto-detaches from Stingray (rolls down a ramp?) And commences its 8.

Excellent work, Sir Williams!

4,185702My suggestion for the asymmetric figure 8,(post#263) has exactly that purpose. We know only the distances X and Y from the two points A and B and we give them as input in our code. Personally although I can do a perfect figure 8 with the Artist, I havent achieved yet to give the radius as an input (That exactly Im trying now).

Martin, has done an excellent asymmetric figure 8 (post#276) but I didnt see the radius as an input on his code.

Williams also on his video (post#281), on 1:57 changes the distance between the two plates (distance A, in order to achieve the figure 8 with the Activity bot. So I suspect that he hasnt also the radius as an input.

4,050Thanks. With tricycle drive the radius of curvature is specified indirectly via the angle you turn the wheels. So on the first loop I set the wheels to a shallow angle, while in the second I set it to a tight angle. I could probably work out a scaling factor between wheel angle and radius of curvature.

Update: It turns out the math has already been worked out on this one. A tricycle drive has two radii of curvature. The one for the front wheel, and the one for the back wheels. The formula for the respective radii is:

front wheel radius of curvature = Wheel base / sin (front wheel angle)

rear wheels radius of curvature = Wheel base / tan (front wheel angle)

So arcsin and arctan can be used to compute the wheel angle from a desired radius. So if we're measuring the front wheel we would use:

front wheel angle = arcsin (wheel base / desired radius of curvature)

20,060Great idea to keep count, maybe even regularly edit your original post to include that info up front on a big toteboard.

BTW, I've had two differential bots do the figure 8, my first BS1 bot with encoder in post #13 and the can-blasting Terminator in post #244 .

And I have two walking bots, Spiderbot in post #248 and Penguin in post #255 . Reminds me that I haven't had Theobot do the 8 yet. Top of my to-do list!

Duane has at least one walker, too. Have to go back & count 'em all sometime.

3,629http://www.nwupgradesplus.com/Downlo...Test_Run_1.avi

20,0604,1853,629Thanks, but it is actually 3 wheel drive. One side is stationary while the other side moves.

1,3261,152I also posted the (extremely crude, ugly and primitive) code.

Massimo

942My old entry was based on that exactly. It did arcing turns by supplying the radius of the circle, then the distance the outside wheel would travel around that circle was calculated and the inside wheel calculated for (radius) - (wheelbase) at the correctly reduced steps/sec. Because of step frequency resolution issues some values worked better than others. My new bot has all the CPU in the world to figure arcs out but the dang L6470 chips for the motors only adjust speed in 15.25 step/sec increments so for any given outside wheel speed there are only a few possible arcs that can be correctly traced. Still trying to figure out how to work the math on that.

10,507I think the new "ARC" command I added to the Eddie code does this pretty well (though not as well as your code does it). (Jump to 1:24 to see the figure 8.)

Since the speed parameter of the ARC command is applied to the center of the robot, it doesn't work with a radius set to zero. If the radius is set to less than the radius of the robot, then one wheel will move backward.

The spins at the end of the video used the "TURN" command.

(It sure is nice to have the forums up and running again.)

3,62910,507I think the general consensus is you're welcome to cheat anyway you want as long as you let us know how you're cheating.

My PropBOE-Bot figure 8 was under remote control (at least the first one was).

12,255Andy,

Are you going to mount some IR detectors on the feet? How would that work?

I think the toddler challenge would just be brute force PULSOUT., and outputs adjusted to achieve the correct turns and time.

3,62912,25512,25520,060