Canada
Asked
Resolved Resolved by Jeremie!

Navigator With Mecanum (Omni) Wheel Robot Platforms

Has anyone played with Robot platforms that use Mecanum wheels and navigation and tracking?  My Roomba, Turtle bot, Roli etc are difficult to navigate when you are trying to line something up using navigation software. I am looking for something that would work well with ARC and Navigator but never having any experience with Mecanum wheels not sure where to start.  There are a bunch of mecanum wheels on line and some robot platforms but was hoping someone else had played with them before I rush out and purchase something.


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Synthiam
#1   — Edited

I never have. I’m mostly turned off by them after watching various videos showing the trouble with friction (or lack of) on various surfaces.

But that doesn’t mean I’m not curious:)  Is there one that you’re looking at?

ps, the navigator kind of sucks compared to the better navigator. I’d consider using that if you’re not yet

PRO
Canada
#2  

I really haven't selected a platform yet. I may just buy 4 wheels on Amazon (approx $30 to $40) and throw something together to have a play.  I was looking for something that can support a robot arm Lidar, Sensors etc so about 40 to 50 pound weight.

But then I just saw this.  NO DON'T DO IT.  but it has gesture control and its only $55 CAD on amazon (OK I am sidetracked).  Yeah just gonna buy 4 wheels and attach them to a bridge and some motors ... umm but its its in my cart NO, having flashbacks to Jeremies hack remember his $20 Walmart car (Oh they are still in stock)  https://www.walmart.ca/en/ip/150th-scale-yamaha-nano-yxz-with-drift-function-wheels-carbon-blue-color-carbon-and-blue/6000201633689

PRO
Synthiam
#3  

Yah that video shows what I’ve been seeing. Had to change surfaces for the sideways traction to work. Think it’s fun for rc toys but not sure about robots needing resolution

PRO
Canada
#5  

Hello @Nink!

I have! It started with my Live hack where I hacked a $20 RC toy with Mecanum wheels from Walmart. While that didn't work out as planned, I broke the gear boxes in the car likely from feeding them too much voltage, I did move on from there and have had great results.

I wanted to point out that there is a difference between Omni-wheels and Mecanum wheels. Omni-wheels have their rubber barrels running in parallel with the wheel, whereas mecanum wheels have their barrels mounted at an angle.

While you will have problems with Omni wheels on a slanted surface, you won't have any issues with mecanum wheels. Mecanum wheels work against each other when not spinning, there are two types L and R that won't let you slide on a tilted surface. I feel that mecanum wheels are also far superior as they give you the ability to do NW,SW,NE, & SE strafing patterns.

Omni Wheel:

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Mecanum Wheel (there are two types in a set L and R):

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PRO
Canada
#6   — Edited

Thanks for the detailed info Jeremie,  I appreciate you provided the difference between omni and mecanum wheels.  Looking forward to getting the little test platform and hopefully this should be sufficient to mount a Rock Pi X, Battery, Lidar and a couple of sensors to see how well it performs.

#8  

Nice and classy. Low profile. Looks like it would be good on flat surfaces but easy to get stuck on anything else.

PRO
Canada
#9  

Finally turned up looks like it will do. Seems to be enough space to mount a rock pi x in a case and some sensors.  Will need to make some brackets up for the intel sensors and mount a battery to power motors for wheels and PC.  But for $51 Canadian quality seems ok. Will add some hbridges and i guess an Iotiny and a lidar etc. 

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Portugal
#11  

Planning to use a Lidar Nink?

PRO
Synthiam
#12  

Id use an ardunio pro micro instead of iotiny if there’s an onboard pc. The iotiny requires wifi and the arduino is usb

plus the arduino gives you a lot more ports.

PRO
Canada
#13  

@DJ Sadly  I don’t have an arduino pro micro kicking around but I have a bunch of esp32 so I guess i will try one of these.

@Proteusy on the LiDAR yeah I have an old Neato xv11 but I think  ARC NMS only works with the Hitachi so I may have to buy one of these but I think I will save that for later as navigation is pretty slick with the two intel sensors.

PRO
Synthiam
#14  

You can read the NMS page to see supported sensors

PRO
Canada
#15   — Edited

OK thanks @DJ  BTW does your ESP32 code support connection via a com port in ARC or just WiFi (I have only ever connected to ESP32 via WiFi but this obviously isn't ideal since PC is beside ESP and I would have to add a USB WiFi adapter)

Edit: OK I see on the ARC page it says ESP32 only supports WiFi and not COM port  https://synthiam.com/Products/ARC

PRO
Canada
#16   — Edited

I will put Jeremie as the person who solved this one as he gave me lots of info on the Mecanum wheels and how they work.  DJ I appreciate all the help and guidance and recommendation to switch to arduino. I have a solution running now but difficult to control so I think I will upgrade to a sabertooth and an Arduino Pro Micro.   I will post a video of the finished product when complete.

PRO
Synthiam
#17  

Why is it difficult to control? Sabertooth is an expensive item.

PRO
Canada
#18   — Edited

Hi DJ getting back to this one. I have 2 Dual hbridges as I need to control all 4 wheels independently as the Mecanum wheels go forward backwards left right and sideways left and sideways right.  I added the two PWM Hbridge Skills so I have Hbridge PWM  and HBridge PWM 2 and I can control the car with these so all ports are configured etc but its impossible to drive.  The Hbridge Movement Panel only supports 1 dual hbridge so I am looking for some guidance on the best way to do this either with a custom Movement Panel or maybe through AutoPosition panel etc

i also added 4 wheel encoders to track positions but the Arduino code only supports 2 left and right wheels. Not sure if modifying code to support 4 wheel encoders as the NMS probably doesn’t support 4 so I guess I am better off with the intel sensor for position only. Also think I would need to merge esp32 code and wheel encoder code on the EZB firmware or add a second Arduino.

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PRO
Synthiam
#19  

Haha, you can't have four encoders reliably:D. The math would say one wheel is 20 cm away from the car over time. The error would be significant, but it sure would be funny. You could add the code, but that gives you a more substantial degree of error. Also, you're Arduino would need to double the interrupted use, which exceeds the interrupts available. So you'd need two Arduinos. If you wanted four encoders, haha, it would be easiest/smartest to do it on the Arduino side. Add each side wheel value and divide them by 2 to get the average, which will grow in errors over time. But it's the only way you could do it. Four encoders don't make sense.

Also, wheel encoders on a wheel designed to slip are a terrible idea:). Make sure you use a lidar with the real sense if that's the route you're going. But really, a good lidar (such as the RPLidar A1) and you won't need the real sense tracking camera. The lidar does a far better job on its own.

As for your Movement Panel question would be to use a custom movement panel. That's precisely what it is for. The way that the robot navigates will be somewhat challenging to control. With the custom movement panel, you'll have control over what you need out of the robot for navigation. That's going to be an exciting configuration when you're done! It'll be like a drone - so maybe using the joystick would be a good start.

PRO
Canada
#20  

thanks for the advice @DJ. I will play with the custom Movement Panel and intel sensor for now. My Lidar is still on order from China but its only been two weeks.  I ordered a monitor from dell thinking it was next day delivery in January, it turned up on Tuesday.

PRO
Synthiam
#21  

Electronic components are crazy. China really is stating our dependency on them. But at least people eventually get their stuff.

I ordered my RPI from RobotShop. It took longer than they said as well.

The RPI has an rpm spin. That will affect how accurate the slam pose is predicted. So having the robot move slower will help accuracy. Can your Omni wheels move slow and still move the robot?

i don’t have any experience with those wheels. And the only times I’ve seen them are on r/c toys. They’re driving one million miles an hour and banging into things like bumper cars haha