The "Artist" robot - Page 2 — Parallax Forums

# The "Artist" robot

## Comments

• Posts: 20,235
edited 2014-05-31 21:09
Nikos: Looks fantastic, love all your dead reckoning precision. Didn't you Greeks give us Pi?

One concern about your pneumatic tires: when tire pressure varies, so will the circumference of your wheel. That can throw off calibration, so keep an eye on consistent pressure in both tires when you start testing. I know because I bike a lot and low tire pressure throws my cyclocomputer (odometer) off.

For best accuracy, use the highest tire pressure you can, which also makes the air leak out faster.
• Posts: 1,326
edited 2014-06-01 08:19
You make it look easy Nikos. You somehow make the math seem interesting,

As a curiosity, I googled the word "Atrist", and really didn't find anything relative to a Robot like yours, so i was wondering,
Is 'Atrist' a misspelling of 'Artist'? or is there special meaning? I don't mean to be a spelling nazi, but was just curious..

Keep up the good fun.

-Tommy
• Posts: 705
edited 2014-06-01 10:00
erco wrote: »
Nikos: Looks fantastic, love all your dead reckoning precision. Didn't you Greeks give us Pi? (

Thank you Erco! Yes indeed Pi, this magic number is something that Greeks must be very proud!!!

Working on some formulas to find the " ticks" that needs a robot (general and not specific) to rotate ω degrees, I ended up that this number is independent from Pi !
This is trully amazing!
Althought Pi seems to by necessary for this calculation (see my proof for the Activity Bot) I found that the Ticks for a rotation depends only on robots characteristics!

I' ll explain on the next post.....
• Posts: 705
edited 2014-06-01 10:04
Ttailspin wrote: »
......Is 'Atrist' a misspelling of 'Artist'? or is there special meaning? ....

-Tommy

Hi Tommy,

is a misspelling .....

I can't change it...
I don't Know if Forums monderator could help to change it...
• Posts: 1,326
edited 2014-06-01 10:46
A Forum Moderator can do anything, they are all powerful, I've Often heard of them referred to as "Sky Gods", for their ability to appear suddenly, without warning,
Making changes, and twisting things to do their bidding...

I was just curious if it was misspelled, or if I had missed something in the Greek translation...:)

No matter how you spell it, Your Robot is cool.:thumb::thumb:

-Tommy

Edit: poof!! it's fixed, almost like magic, and from out of no where...
• Posts: 705
edited 2014-06-02 17:18
Encoders-spokes-ticks  Distance between wheels & Angles of Rotation

Following the same method that I used in order to calculate the rotations for the ActivityBot,
I finally verified my first rough measurements for the rotations of the Artist robot (Post #30)

I proved that if I want to program the Artist in order to rotate ω degrees using the Drive_goto command, I must multiply ω by the number 0,367.
This product gives me the number of ticks that uses the Drive_goto command, in order to rotate clockwise the robot ω degrees.
Replacing the numbers with variables I ended up that this number is independent from Pi.
• Posts: 705
edited 2014-06-06 08:00
General formulas for rotations and distances based on various robots features

Since there is no meaning to give formulas only for the Artist robot, (because Artist Robot is not a commercial Robot),
I made my calculations based on features we can find on many other differential robots like: ActivityBot,Arlo, Eddie, Stingray etc.
These features are the encoders spokes, the distance between wheels and the diameter of the wheels.
So if you have a differential robot you must count the encoders spokes, and you must also measure the wheels diameter as well as the distance between wheels.
In the next image you can see some examples that explain the use of these formulas.

If you use the Drive_goto Command in your program, you can verify the above formulas giving the features of your robot. Personally I tested the formulas with success on the Artist and on my ActivityBot..

Nikos Giannakopoulos
• Posts: 12,366
edited 2014-06-06 08:38
Nikos,

Thank you so much for that valuable write up! I'm sure many students can use this information in their projects.

I now I will!

Jim
• Posts: 705
edited 2014-07-05 04:40
The Artist and wireless communication.

I gave the Artist two options for wireless communication following the ActivityBotts examples:
1) The first option with IR Receiver and Remote. I followed exactly the article , Remote Control Rock, Talk, and Roll ActivityBot from Parallax Tutorials Submitted by Stephanie Lindsay ,as well as the circuit for the IR-remote control
2) For the X-Bee option I followed the example Full-Duplex Serial from Parallax Tutorials Submitted by Andy Lindsay ,as well as the circuit from the XBee and USB Connections.

The most impressive is that we can use the same code as the ActivityBot examples, replacing only the librarys name. So everyone who has a big-size Robot, similar to The Artist (like Arlo, Eddie or any other) must only change the library abdrive.h with the arlodrive.h. So we can take all the advantages form the pre-written code for the ActivityBot!

Now I feel ready to proceed in the next step of the Project, that is the painting mechanism.....
• Posts: 705
edited 2014-07-27 02:16
The Artists painting mechanism
Since the robot will be for outdoor use the painting mechanism is essential to have two features:
1 )Not permanent writing. (the writing must be temporary and the user must be able to erase it in order to avoid graffiti pollution and the fines from the authorities)
2) Writing on rough surfaces. (Roads, pavements courtyards, and walk sides usually have rough surfaces much more scabrous from a boards surface. Painting mechanism must be robust and able to write despite the vibrations due to the frictions and small obstacles, and also despite rubble, small obstacles dirty etc.). Paint injection is the best choice for this.

Here is a first design of the painting mechanism.
It uses an electric pump that gets chalk paint from a water botlle in order to paint......

Nikos Giannakopoulos
• Posts: 20,235
edited 2014-07-27 06:41
Nikos: Great project. I'm sure you've already discovered this, but you'll want to flush the liquid chalk out of your pump regularly before storing, more likely after every use. Once that stuff dries up inside your pump, the game is over. Chalk powder is also mildly abrasive, so try to keep it below 5000 PSI.
• Posts: 1,326
edited 2014-07-27 08:53
That's really cool Nikos,
What does the "Brush" look like? have you a design in mind?
• Posts: 705
edited 2014-07-29 03:00
erco wrote: »
Nikos: Great project. I'm sure you've already discovered this, but you'll want to flush the liquid chalk out of your pump regularly before storing, more likely after every use. Once that stuff dries up inside your pump, the game is over.
Erco, thank you for the information!. I know almost nothing about Chalk paint. I havent even tried to create some. I have only seen how to make chalk paint and Ill hope that will be ok.

erco wrote: »
Chalk powder is also mildly abrasive, so try to keep it below 5000 PSI.

Im not sure if the electric pump that Im experiment with is the appropriate for the chalk paint but according to the manufacturer this pump is suitable for the printing industry - inkjet printers, inkjet printer and so on.

Any suggestion or more information about temporary paint, pumps etc is welcome
• Posts: 705
edited 2014-07-29 03:15
Ttailspin wrote: »
That's really cool Nikos,
What does the "Brush" look like? have you a design in mind?
Ttailspin, this is also my big question.

The design I have in mind is verry similar to a common paint brush.

The sponge will be the part of the brush that will paint the ground. I think that a rolling sponge is the most suitable tool for all the rough surfaces.

The pipe will flush out the paint in to the sponge.

Of course I must have a "pen Up " Pen- Down" mechanism for the entire brush.......

I'm still on the design process.......

The sure is that I need and a second Robot for my tests......
A twin brother of the "Artist" is about to arive very soon .....
• Posts: 1,326
edited 2014-07-29 11:40
It will be difficult to control the liquid chalk flow onto the roller. and chalk dust is much courser than any ink, your poor pump isn't going to survive very long i'm afraid.
I'm not sure the pump will hold back liquid if it is not pumping, and may continue to leak during a 'brush-up' routine.
Another thing to consider is the weight of the water itself, how many letters can you get from one 500ml bottle...

I wonder if it would be possible to pressurize dry chalk (or wet chalk for that matter) in the bottle with your pump, and add a solenoid to open a spray tip,
Much like an ink jet printer works.
I don't think it would take more than a few pounds of pressure to move the chalk, and then it could be spread with a brush, if needed.

Just throwing that out there, I know you will come up with something good. :thumb:

-Tommy
• Posts: 20,235
edited 2014-07-29 14:31
Nikos: Thank you for re-igniting an old project in my mind. I've had one of those "somebody ought to do that" ideas for so long that maybe I'll get to it before someone else does!

Not quite a sidewalk painter, but similar and ecologically friendly. Will advise if & when it happens!
• Posts: 705
edited 2014-08-12 05:27
Artists service

The artist robot needs two things for its service:

Air for the tires and power for the battery.
In order to fill the tires with air I use a slime air compressor. This air compressor is designed for various vehicles and takes current for the lighter plug of the vehicle. Using the compressor at home I had no lighter plug to power it but I found another great solution to overcome this problem. I used the artists battery to take power with two crocodile clips  , that were included in the compressors pack.

I order to charge the battery I used an Ultimate speed car battery charger with a charging plug attached in to the robot.

I believe that Parallax must create a supporting service pack (Air compressor and battery charger) for the Arlo Robot.!
• Posts: 6
edited 2014-08-12 22:37
Just reading your thread and i love the artist robot. I came across a different chalk paint that uses cornstarch and food coloring instead of grinding chalk and adding water it might be better for your pump http://www.wikihow.com/Make-Sidewalk-Chalk-with-Cornstarch although you might have to add something to the paint tank to keep it mixed up
• Posts: 1,326
edited 2014-08-13 20:23
Cornstarch and Food coloring sounds like it would be more kind to the pump, Have never tried it, wonder if it leaves any staining?

That's a nice little air pump from the Slime company, Have you tried any of the tire sealant they sell? I use it for my bike tires, it is self sealing, and works great,
Haven't had to patch any tire I have used it in.
• Posts: 705
edited 2014-08-15 06:47
Eagle8587 wrote: »
I came across a different chalk paint that uses cornstarch and food coloring instead of grinding chalk ....... although you might have to add something to the paint tank to keep it mixed up

Thank you Eagle. It sounds very interesting!
Also a mixer mechanism is not very difficult. A Cheap DC Motor is enough.

However the entire painting mechanism will be more tricky because I must to synchonize all these divices (Pump, mixer, Up and Down mechanism etc.)

The only experiment I have done till now with the pump, is using olny pure water.
However I have a lot of mess and I face the danger to cause damages on robot's electronics.

So I' m working on a second Artist chassis to achieve this goal.
The way will be long........
• Posts: 705
edited 2014-08-15 07:19
Ttailspin wrote: »
Have you tried any of the tire sealant they sell? .....

Ttail, Altought my robot's tires lose some Air (I must to fill them once every 7-8 months), I haven't use any tire sealant. From my experience these products cause damage on the tube.
Parallax tires and tubes I think have a very good quatity and the haven't leak of air . However when it happens the valve is resposible for this.

You can change the valve (is very Cheap and you can find it on gas stations) or simply screw it using a screwdriver.
• Posts: 705
edited 2014-08-18 12:58
Discovering the Artist’s limits using a treadmill

I stopped for a while the painting mechanism to realize a crazy idea with my son Andrew. We wanted to see the robot’s limits using a treadmill. It was very interesting to see how much time the robot could run , what max speed could reach and what distance could travel.

We charged full the Artist’s battery and we started the experiment.

To avoid the accidents we used two safety ropes in order to keep the robot on the lane. Then using the Artist’s remote and simultaneously controlling the treadmill’s speed up and speed down buttons, we achieved a perfect balance between speed and robot’s location into the lane.
We left the robot to run until it started to stumble due to the low power!

The experiment lasted 71 minutes and the Artist run 2,7 km ! The average speed was 2,28km/h
I must also say that I had and some power consumption from the PING sensor which was enable during the experiment!

Another point that is worth to mention is the max speed of the robot.
During the experiment, we could achieve only 2,4km/h maximum speed (according the treadmill’s readings)
This max speed was by far fewer from the theoretical max speed that I had calculated on post #22 and it was 1,21m/sec = 4,35 km/hI suspect that the reason is the code that I used.

Anyway, the sure is that Andrew and I have a lot of fun with this experiment and why not? I think that is a very good idea to test robots!

You can see the Artist running on the treadmill in the next video:

[video=youtube_share;SfobMwh7VzY]

At the end of the video you can see on treadmill’s readings, that the robot runs 1,5 Km in about 39 minutes. The average speed is (1,5/39) * 60= 2,3km/h.
• Posts: 129
edited 2014-08-18 13:44
Oh wow! Great idea! Hmm, I have a treadmill . . . .
• Posts: 705
edited 2014-08-21 06:18
ChrisL8 wrote: »
Oh wow! Great idea! Hmm, I have a treadmill . . . .

Thank you ChrisL8 !

Go ahead !
I want to see your Arlo running on your treadmill! You have done an excellent review about Building Arlo.
I think that an exploration on the limits of the Arlo (max speed, max distance that can travel etc.) using a treadmill, is something that everyone would like to see!.

Nikos
• Posts: 705
edited 2014-08-21 06:50
Meanwhile the Artist stares the birth of his new brother.........

This 2nd Artist robot will help me to build the painting mechanism and will also be an second choice for microcontroller with an alternative brain,
probably Arduino with the Board of Education Shield.....
• Posts: 20,235
edited 2014-08-26 07:45
Put some small wings on the Artist, and test the theory...

http://forums.parallax.com/showthread.php/142067-jet-plane-on-conveyor
• Posts: 351
edited 2014-08-26 22:04
Oh, please... don't start THAT thread going again!
• Posts: 20,235
edited 2014-08-27 04:46
Nikos: Did you consider using kids' big sidewalk chalk, and make what's really a big Scribbler robot? No pump to mess with, and you could stop and manually change colors.

http://www.ebay.com/itm/POOF-Toys-Sidewalk-Chalk-48-Pieces-New-In-Box-Variety-Colors-/261568880361?pt=LH_DefaultDomain_0&hash=item3ce6b85ee9

You could test it on a treadmill, but you might start flying...
• Posts: 705
edited 2014-08-27 11:23
Erco,
That exactly I had in my mind!
Im working on a simple Up & Down mechanism for chalks!
However, I use common chalks (1 cm width  8 cm length), and Im afraid that these chalks are very fragile.

I had no idea the existence of bigger sidewalk chalks!!! This information is really very valuable for me! Thanks a lot!
Ill try to find them here in Greece.
The link that you suggest offers 48 chalks in 2.99\$ (This price is very good). However the shipping cost is very expensive 38.77\$!!!

P.s. I can assure you that Artist have no chance to take off with or without wings, Conveyors rockets etc! Every time Im doing experiments and tests with Artist, my girlfriend became very upset and stares the robot very strange! The only possibility to fly the Artist is if she throws it out of the window!!!
• Posts: 1,326
edited 2014-08-27 21:03
I wonder if you could wrap one of those in paper?, like a Crayon is wrapped.
With the right paper, it would wear off on the sidewalk while it was writing, and yet still add some strength to the chalk stick.

Or using a Painters type of tape, you could just wrap the part of the chalk you are trying to grip.
Sounds better than messy liquid chalk spilling all over the "Artist".

-Tommy
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