Author Topic: NOW PUTS OUT FLAME!!!! Three wheeled omni directional robot (Read 7450 times)

sonictj · « **on:** July 24, 2009, 05:03:35 PM »

This platform is based off of my atmega640 prototype PCB I created a little while ago. This platform uses 6 s148 Futaba servos (free courtesy of my father an RC hobbyist). The three wheel servos are modified for 360 degree rotation. The platform has the ability to move in any direction while maintaining a consistent heading. I designed this bot to be a little bit showy, so that I can bring it to an interview to demonstrate my skills.

The video shows the robot doing a counterclockwise circle. You will note that the robot pauses to rotate individual wheel assemblies. This is necessary because the steering servos have a maximum rotation of 180 degrees. I also intentionally slowed the spinning to put less stress on the servos. Oh, and the bot is orange and blue because I go to UF. Let me know what you think, and also if you can think of a good name.

[youtube]DPz-ullMOqc[/youtube]

Joker94 · « **Reply #1 on:** July 25, 2009, 06:23:53 AM »

nice job sonictj, cannot think of a name as thinking of names has never been one of my strong points.

Just out of curiosity what material is the main orange and blue structure made from.

sonictj · « **Reply #2 on:** July 25, 2009, 10:05:12 AM »

the structure is .25" oak plywood. Its just what I had lying around. I wouldn't recommend it because of how porous it is. I had to put around 5 coats of paint on the thing. If your gonna use wood I recommend Masonite. Masonite does not splinter as easily and its also very smooth like plastic.

Admin · « **Reply #3 on:** July 29, 2009, 07:32:51 AM »

Reminds me of my Taurus 2

(but yours looks much better designed, as I was a noob way back then)

wil.hamilton · « **Reply #4 on:** July 29, 2009, 08:45:30 AM »

very nice, i like it. i don't suppose there would be anyway to get around the stopping to spin a servo unless you went to gear motors with encoders for spinning the wheels. You kind of have to rely on the position control offered by a servo right?

sonictj · « **Reply #5 on:** July 29, 2009, 10:24:08 AM »

Quote

very nice, i like it. i don't suppose there would be anyway to get around the stopping to spin a servo unless you went to gear motors with encoders for spinning the wheels. You kind of have to rely on the position control offered by a servo right?

I may go to steppers eventually, but the spinning of wheels is unavoidable even with a 360 degree setup. The wheel motor power cables can only be twisted so much. I decided to go with servos because I wanted to decrease the amount of circuitry on the robot.

Admin · « **Reply #6 on:** July 29, 2009, 01:30:53 PM »

The rotation servos don't need to overcome much torque. Considered using high speed servos instead?

sonictj · « **Reply #7 on:** July 29, 2009, 02:24:41 PM »

Quote from: Admin on July 29, 2009, 01:30:53 PM

The rotation servos don't need to overcome much torque. Considered using high speed servos instead?

I've already ramped up the speed. I was intentionally being conservative at first to not break anything. I don't see much reason to spend the money to get the faster servos at the moment. I like free servos

. Thanks for the suggestion though.

Oh, and the bot should remind you of Taurus 2 because thats where I drew the concept from

.

ericthered · « **Reply #8 on:** July 29, 2009, 10:31:50 PM »

I like it though I fell they're should be a gripper or something on the end

sonictj · « **Reply #9 on:** July 29, 2009, 11:01:20 PM »

Quote from: ericthered on July 29, 2009, 10:31:50 PM

I like it though I fell they're should be a gripper or something on the end

I'm adding stuff for sure no gripper planned yet. What you guys saw was the finished base and nothing more. At this point I've created a custom LCD mounding bracket to hold my 20x4 display, a 180 deg sonar turret, Sharp IR x4 for wall following/obstacle avoidance, and a second sonar for the rear of the robot. My plan is to use a wii remote again for tracking IR hot spots. I also have reflective sensors x6 that I may add on for line following behaviors. I'll post some cad drawing in a minute or two.

sonictj · « **Reply #10 on:** July 29, 2009, 11:18:33 PM »

Here is what I've CADed up. My robot has all of these features now too. I just finished making/fiitting the parts today. I'll post more pics and video soon.

Joker94 · « **Reply #11 on:** July 30, 2009, 05:06:21 AM »

nice cading, the best and clearest i have seen in a long time.

SmAsH · « **Reply #12 on:** July 30, 2009, 05:39:05 AM »

this robot really looks like its going to be a success!
well planned out, professionally made parts and great dedication...
great job sonic, i hope to see those cads become reality...

sonictj · « **Reply #13 on:** July 30, 2009, 08:43:37 AM »

Quote

i hope to see those cads become reality...

Here is the pic.

sonictj · « **Reply #14 on:** July 30, 2009, 09:16:34 AM »

Here is the latest video demonstration of the robot's mobility

[youtube]hxUIS3_RGGY[/youtube]

wil.hamilton · « **Reply #15 on:** July 30, 2009, 09:46:29 AM »

very nice, with the turning of the individual wheels sped up, it makes up for the fact that they have finite rotation. With the being fast, the robot having to pause for a second doesn't seem like that big of a deal.

sonictj · « **Reply #16 on:** July 30, 2009, 09:53:29 AM »

Quote from: wil.hamilton on July 30, 2009, 09:46:29 AM

very nice, with the turning of the individual wheels sped up, it makes up for the fact that they have finite rotation. With the being fast, the robot having to pause for a second doesn't seem like that big of a deal.

yeah I think watching the robot position the wheels is the best part. I set it up so they cascade too. This prevents the robot from shifting too much from all the wheels moving at once.

SmAsH · « **Reply #17 on:** July 30, 2009, 03:14:01 PM »

the new guy looks great!
i really like how you sped up the turning of the wheels, although watching the robot turn its wheels does look kinda cool

Joker94 · « **Reply #18 on:** July 31, 2009, 06:03:24 PM »

the new added hardware looks great sonic. can't wait to see what happens next

sonictj · « **Reply #19 on:** August 03, 2009, 06:48:50 PM »

This is another video of my three wheeled omnidirectional robot. This video shows the robot ("
GatorKS") following the wall of my kitchen.

First you will see the robot align itself parallel to my kitchen cabinets. Then the Ping)) sonar is used to position the robot a set distance from the wall. The robot then runs along the wall trying to maintain that distance. The Ping)) sonar is used when the robot encounters sharp turns.

The way the thing drives is servos A and B pivot, while C stays parallel to line AB on the robot frame.

setup:
A
wall / /\
/ / \
/ / \
/ B______C

two Sharp IR sensors are used for the calibration with the wall, and then only the front is used for the wall following. The one IR sensor's initial value taken, after the sonar spaces the robot from the wall, referenced against current values for wall following. The calibration stages use PI (proportional, Integral) controllers while the wall following behavior is purely P (proportional).

***Sorry for any poor video quality. I have no means of editing at the moment.

[youtube]pcNQixSV63A[/youtube]

Joker94 · « **Reply #20 on:** August 04, 2009, 06:00:16 AM »

another great adaptation/addition to your bot. Your new sytem of wall tracking will help heaps when it comes to the hard code, not that the hard code will stay the same for very long

sonictj · « **Reply #21 on:** August 04, 2009, 08:42:31 AM »

Quote

another great adaptation/addition to your bot. Your new sytem of wall tracking will help heaps when it comes to the hard code

when you say hard code what do you mean? wall following with this type of drive train wasn't exactly a cake walk

.

sonictj · « **Reply #22 on:** August 05, 2009, 01:03:28 AM »

The next behavior I plan to implement is firefighting just like I did with woody.
[youtube]SgPHQ5h_wlQ[/youtube]

I already strapped a speaker to the back of GatorKS and have proven it can put out candles and such up to 6" away. The blower is intentionally weak to show off the precision and accuracy of the robot. The speaker-blower mechanism is the white thing on the back of GatorKS in the previous video.

Question what behaviors do you guys think I should program into GatorKS. At the moment my sensor array includes sharp IR on the left and right sides, sonar on the back, and a panning sonar in the front of the robot. I'm gonna put a wiimote on a tilting servo mechanism on the back of the robot very soon. I want to come up with some behaviors that show off the unique drive train, like my wall following behavior. The wiimote will enable GatorKS to track IR blobs. Input is appreciated, I want a sweet robot to show off my skills when I go to my school career fair in the fall semester.

Joker94 · « **Reply #23 on:** August 05, 2009, 01:32:26 AM »

sorry i was not clear.

What i ment by hard code was the code that will eventually becoome the full control code of the robot

do you know what i mean

sonictj · « **Reply #24 on:** August 05, 2009, 03:13:28 AM »

Quote

What i ment by hard code was the code that will eventually becoome the full control code of the robot

umm... The way I've built the robots code is that each movement has a variable setting that can be tweaked for a given motion. for instance I built in a move function where I only have to code is move(int angle,int time,bool _stop). The angle is any angle between 0 and 360, this automatically positions the wheels at this heading. All the geometry is handled in the function. "time" represents the delay in between each degree of motion the wheel servo's move. I typically select 2 ms. Last stop determines if the wheels should stop turning during positioning. I have similar functions for pivoting the robot about different wheels, and spinning. I've basically created movement libraries. Is that the kind of code you are talking about?

Joker94 · « **Reply #25 on:** August 05, 2009, 04:34:21 AM »

yeh thats it

Admin · « **Reply #26 on:** August 05, 2009, 07:03:48 AM »

Whats that spinning thing on top of woody?

wil.hamilton · « **Reply #27 on:** August 05, 2009, 07:54:20 AM »

it looks like a wiimote, esp. since he mentioned using a wiimote to track ir

sonictj · « **Reply #28 on:** August 05, 2009, 08:13:01 AM »

Its a wiimote. They connect over bluetooth and can be used for ir tracking. The remote has a resolution of 1024x768. The remote sends back the center of mass pixel value (x,y) for IR blobs. I mounted it on a stepper motor for a continuously rotating turret. I've got some other vids that may help explain. I just have to upload them to youtube first.

sonictj · « **Reply #29 on:** August 05, 2009, 12:55:49 PM »

This video was taken very early on. I was demonstrating how the wiimote tracking could be performed while woody did obstacle avoidance. As you can see Woody's obstacle avoidance code was less than desirable. The robot seemed way to claustrophobic. However the wiimote tracking worked very well, which was the point of the demonstration.

[youtube]7GOyWxkQbmY[/youtube]

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Author Topic: NOW PUTS OUT FLAME!!!! Three wheeled omni directional robot (Read 7450 times)

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