[EV3] Omnidirectional Robot Concept and Discussion

[Jim]

Last week I made some progress building the base of the robot. Even up to the point that I can start programming it. I am very happy with this design, since it is very sturdy by nature. I haven't done much bracing and I can already pick it up using a single hand.

I am currently in the midst of doing some programming and I need to overcome some challenges and make some decisions. I my next post I will address these issues.

My baby's first movement 

 

[BusterHaus]

Great to see this project coming to life and that you are still working on it. What other functions are you planning? 

[Bublehead]

@jim, This is a fascinating project, it reminds me of the Lego Factory Robots a little, the ones that follow the magnets in the floor, but following magnets is not a hard thing to program... I need to read through a lot of the content here on the new forum, I have recently acquired a used EV3 set and have not got around to doing anything with it yet (seems I have been building amusement rides for some reason  )  Is the programming specific to the omnidirectional control, like converting inputs like forward/back/right/left into relative wheel motion based on platform orientation? 

[Jim]

With some pointers on daisy chaining by @Hanso (thanks a lot), I made some progress with controlling the robot. 

 

On 10/15/2018 at 5:16 AM, BusterHaus said:

Great to see this project coming to life and that you are still working on it. What other functions are you planning? 

I am not really sure how this will end, but the next things on my wish list are:

• Rotate to certain direction using a compass sensor and a PID controller
• Using the IR transmitter and receiver to make the robot follow me
• Implement these functions using EV3Dev or leJos or any non graphical programming language

When I have accomplished this, I am thinking of these things

• Make a body for the base (i.e. make it look better with panels etc)
• Implement the LED strip controller
• Link the LED controller to some distance sensors to change LED color based on proximity of objects
• Using PFMate to controller the PFx brick to have better sound than the regular brick

 

On 10/15/2018 at 8:29 PM, Bublehead said:

Is the programming specific to the omnidirectional control, like converting inputs like forward/back/right/left into relative wheel motion based on platform orientation? 

I still need to work on the math so I can steer the robot in different directions (simultaneously). It would be cool to use another EV3 unit and turn this into a remote.
(basically like this. Sorry for the Facebook link)

[Jim]

Okay, here's an update for my Robot project. After toying around with Brick Pi's and Python, it was time to do some (re)work on the hardware. This was the design when I added the Brick Pi's.

However, the gears weren't properly braced. I already suspected problems and they indeed occurred. And I didn’t like the motors on the outside of the robot.

So, I decided to do a complete redesign of the wheel units, placing the two motors next to each other. I also changed the gears, driving the turntable. This will speed up the robot a bit, and I think the combined motors will have enough torque.

Since the weak point of this robot are the axles, I decided to order four aluminum stainless steel axles. These axles turned out the be slightly (very slightly) too big (maybe only half a mm or so), but nothing a little push couldn't handle. They seem quite strong, which is appropriate for my robot.

Here's the current state of Robob (that's how I call my robot)  Now I need to finish the wheel units, so I can go for another test drive. I really love the new compact design. It leaves ample space to place the Brick Pi's in the center and there are no motors on the outside of the robot. This leaves me with much better design options. All in all very satisfied with the rework.

[oracid]

I don't understand why do you need two servos for each wheel. How much heavy is this ?

Are you sure this axles are aluminium ? Where did you get that ?

I hope one day, Lego will make a 3 axles beam connection.

[Jim]

What you see is the base of the robot. There will be a big (thus heavy) upper structure. Powering a wheel with a single servo might not be sufficient. Hence the two motors per wheel.

It says aliminum on the Bricklink page: https://store.bricklink.com/Eezo

[oracid]

20 hours ago, Jim said:

It says aliminum on the Bricklink page

No, it is written "stainless steel". It is not the same.

Please try with a magnet. If contact, then this is not aluminium.

I have powered a 7kg tank with only 4 servos. How heavy will be your project ?

Edited December 24, 2018 by oracid

[Jim]

Yes, you are right. The beams are aluminum, not the axles.  

I don’t know how heavy my project turns out to be, but it could easily be between 10-20 kg, as I have written in one of my earlier posts. In my first post you can read my plans for it.

Maybe four motors are enough, but I like to be on the safe side and power it sufficiently. And why wouldn’t I use eight motors?! I would hate to come to the conclusion that I do need eight, when I have finished the upper structure.

If you scroll back to the first pages, you can read when I decided to switch from four to eight.

[oracid]

6 hours ago, Jim said:

I don’t know how heavy my project turns out to be, but it could easily be between 10-20 kg,

So it is a good idea for 8 motors.

This is a very interesting topic !

[Jim]

I don't know where this will end, so it is interesting for me as well 

Tomorrow I will complete version 6.2 of the base, so I can do a test drive with the new setup.

[BusterHaus]

On 12/24/2018 at 2:19 AM, oracid said:

Please try with a magnet. If contact, then this is not aluminium.

Most common grades of stainless steel (AISI 302, 304 and 316) are not magnetic. AISI 400 series is magnetic, but not commonly used. 

An additional test would be weight/density. Without measuring the axle and its weight, you can judge by the feel of the axle. Aluminum is much lighter than stainless steel, but a bit heavier than a similar plastic axle. Stainless steel axles would feel more like a small fork or other similar table utensil, much heavier than a similar plastic axle. 

Of course the ultimate test is calculating density, but we'd rather spend time building. 

[Jim]

Hehe. For me it's important that they are stronger than ABS, and I am sure they are 

They are pretty heavy, so I reckon stainless steel is the right material.

[oracid]

14 hours ago, BusterHaus said:

Most common grades of stainless steel (AISI 302, 304 and 316) are not magnetic. AISI 400 series is magnetic, but not commonly used. 

Thank you for the clarification. I did not know that.

[Bob De Quatre]

Great to see some progress here 

It looks pretty cool! And I can't wait to see that thing running free in your living room 

On 12/22/2018 at 11:45 AM, Jim said:

Robob

[Jim]

9 minutes ago, Bob De Quatre said:

It looks pretty cool! And I can't wait to see that thing running free in your living room 

Slowly, but steady, I am getting there. It's my life's work, but given my age and building speed, I probably need to pick up the pace 

[LucyCol]

To quote Mr Spock  "Fascinating Jim, fascinating"

I watch on from the sidelines with interest and awe.

[Jim]

1 hour ago, LucyCol said:

To quote Mr Spock  "Fascinating Jim, fascinating"

1 hour ago, LucyCol said:

I watch on from the sidelines with interest and awe.

I hope it will be more interesting than only the base of the robot. Hopefully I will be able to finish the base in the next couple of weeks. After that I need to start thinking about the upper structure. I am planning to use the big (banana) worm gears as the top of the base, so I can put different attachment on top of it. Not sure how this will work out, but that's what I have in mind at the moment.

[bluatigro]

i m planning a mecrano weeled robot

the robot wil be smaller that the one you are oplanning

the [ remote ] control program in ev3-g is al ready but not tested

[Jim]

On 1/16/2019 at 12:54 PM, bluatigro said:

i m planning a mecrano weeled robot

the robot wil be smaller that the one you are oplanning

the [ remote ] control program in ev3-g is al ready but not tested

Cool. Looking forward to seeing it. Make sure to post it here in a separate topic  

[Dannylonglegs]

My father mentors a first robotics team and he's been trying to get them to implement Swerve drive. This could make an omnidirectional robot if you programmed it properly.

 

 

The solution you went for however is elegant and looks so amazing! I can't wait to see the end product! Wonderful work!

~Insectoid Aristocrat

Edited March 22, 2019 by Dannylonglegs
Edit

[BrickbyBrickTechnic]

15 hours ago, Dannylonglegs said:

My father mentors a first robotics team and he's been trying to get them to implement Swerve drive. This could make an omnidirectional robot if you programmed it properly.

Swerve drive is a huge step for teams. My team tried to do one but got stuck on the manufacturing part of it (though they did program it). However, swerve drive can do more than being omnidirectional, so seeing it in a lego project would be pretty cool!

[Jim]

Actually, I have contemplated on making a Swerve Drive robot too. I love the concept. I might give it a go one day.

I still need to post an update. I do have a "working" prototype. I was busy programming the thing, but life happened 

[1963maniac]

On 8/23/2016 at 5:50 AM, Jim said:

 

Jim, I was wondering if you know where this picture came from?

I think this is a particular cool design, and I will more or less try to replicate the color scheme.

(however, the color scheme isn't important right now. The actual design is)

Here's the updated file:

https://www.dropbox.com/s/gf4ag38bvdt0tlz/Base-v2.lxf?dl=0

 

[Jim]

Not entirely sure where this pic came from, but it's "Evan", created by Lee Magpili.

http://www.legoengineering.com/meet-the-creator-lee-magpili/

http://burfdevelopment.com/lee-magpili-lead-designer-of-the-lego-mindstorms-ev3-at-the-bett-show/

https://www.facebook.com/pg/EV3Android/posts/