They're mounted incorrectly. There are two recommended configurations for the mechanums, one where the instant centers of rotation of the rollers lie outside the robot frame (more common), and they other where they lie inside the robot frame (less common). The former will allow for a better ability to resist moment loads about the z-axis (yaw), the latter will allow for easier skid steering. In the configuration in this video, one instant center is oriented inside the frame, and the other is oriented outside the frame, resulting in an asymmetric center of stiffness. The wheels will operate in this configuration, but results in this ridiculous wobbly behavior despite being driven with steppers.
Isn't the wobbly behaviour in this video due to the wonkiness of the chassis and the pigtail pulling on it? It's causing different wheels to touch the rolling surface at different times.
@@Milamberinx No, look at the wheels, then use your brain. Mecanum wheels can be wonky on uneven terrain, but on a near mirror finish countertop handling should be predictable. Rule: opposite corner wheels should match, adjacent wheels (side by side AND front/back) must be mirrors of one another. This balances the sideways thrust vectors produced by each.
Much is correct in this video although much is not. They mentioned the orientation of the wheels, I noticed the robot in the video's wheels were not oriented correctly. I would imagine this was compensated for in how they set up the algorithms.
ya they are on wrong. There might be different ways to do it but I was testing them without motors just pushing it and they seem to be mounted with the same direction wheel on opposite corners.
I do like the videos ! Keep it up I'm also happy you addressed the steering type by both known names. Skid steer and tank operation most only call it tank steer which sounds funny to me . I was also wondering if these wheels hold good ground when not in motion for example pushing your mini not around by hand or parking it on a slope do they free wheel I'm working on a lawn not and considers this movement for the machine to get in hard areas but by looking at it .. It seems like it would slip
OK how about a version 3 with roller locks, this would be of use in situations with limited traction. allowing you to override the drawbacks of Mecanum wheels in poor tractions situations.
Top down rollers should form an x, so that if the robot were turned upside-down it could be spun freely. This is the behavior you don't want, which is why the x goes up, not down. should not be a sideways chevron as you have here, as you will have no way to control the rotation center when turning.
Say i wanted to use scoreless motors with these mecanum wheels, how do i know the position of the robot as its moving? Im new to these kinda projects and designing phase. thanks!
This flawed video reflects poorly on Sparkfun and the mecanum wheels. As has been pointed out a dozen times in the comments, the vehicle can't track properly because the wheels are on wrong. It's ridiculous to use four precision stepper motors then slap the wheels in the wrong locations. If it was my company, I'd definitely spend the minute required to put the wheels on correctly and nine minutes to make & post a new video.
Don't be too hard on the guy. He's obviously gone to a lot of trouble to make this video, as he looks like he got his hair caught and torn out by those wheels.
JohnBotJR The roller axles should form an x on the top, o on the bottom. Same principle behind a robot with 4 omni wheels. The robot shown in the video is built properly. If you put o on top, x on bottom, you just lose your ability to turn (effectively).
They're mounted incorrectly. There are two recommended configurations for the mechanums, one where the instant centers of rotation of the rollers lie outside the robot frame (more common), and they other where they lie inside the robot frame (less common). The former will allow for a better ability to resist moment loads about the z-axis (yaw), the latter will allow for easier skid steering. In the configuration in this video, one instant center is oriented inside the frame, and the other is oriented outside the frame, resulting in an asymmetric center of stiffness. The wheels will operate in this configuration, but results in this ridiculous wobbly behavior despite being driven with steppers.
Isn't the wobbly behaviour in this video due to the wonkiness of the chassis and the pigtail pulling on it? It's causing different wheels to touch the rolling surface at different times.
@@Milamberinx No, look at the wheels, then use your brain. Mecanum wheels can be wonky on uneven terrain, but on a near mirror finish countertop handling should be predictable. Rule: opposite corner wheels should match, adjacent wheels (side by side AND front/back) must be mirrors of one another. This balances the sideways thrust vectors produced by each.
@@StefanBacon being 'advised' by someone who insults me but doesn't understand the word "chassis" is not very convincing.
Your mecanums are on wrong. The rollers should form a diamond or x shape.
Ugghhhh that orientation makes me cry.
Much is correct in this video although much is not. They mentioned the orientation of the wheels, I noticed the robot in the video's wheels were not oriented correctly. I would imagine this was compensated for in how they set up the algorithms.
Thanks PewDiePie you made this possible
aren't the wheels on wrong? we thought that the rollers had to make a diamond shape
ya they are on wrong. There might be different ways to do it but I was testing them without motors just pushing it and they seem to be mounted with the same direction wheel on opposite corners.
+TechKnow Difficulties i think it also works if you have it as a X shape.
It's just a simple three strand braid, like braiding hair. I like to braid big bundles of wire to keep them neat without wire loom.
I do like the videos ! Keep it up I'm also happy you addressed the steering type by both known names. Skid steer and tank operation most only call it tank steer which sounds funny to me . I was also wondering if these wheels hold good ground when not in motion for example pushing your mini not around by hand or parking it on a slope do they free wheel I'm working on a lawn not and considers this movement for the machine to get in hard areas but by looking at it .. It seems like it would slip
I thought the rollers have to make an X for the wheels to work, but in this video, they don't seem to...
Can these wheels be used in 4x4 vehicles? Or any other type of vehicle?
OK how about a version 3 with roller locks, this would be of use in situations with limited traction. allowing you to override the drawbacks of Mecanum wheels in poor tractions situations.
Nice little review, very didactic, prefer this to "junk of the week" Friday videos. Thanks.
they look neat indeed, gotta try it some time, zip ties sucks
Top down rollers should form an x, so that if the robot were turned upside-down it could be spun freely. This is the behavior you don't want, which is why the x goes up, not down. should not be a sideways chevron as you have here, as you will have no way to control the rotation center when turning.
It took you this long to bring out a demo!!
OK, but the wheels can only in flat surface or is all terrain?
@spark fun electronics
Hi
I want to make a mecanum wheel car and I wanted to know do you sell stepper motor shield to Arduino mega
Say i wanted to use scoreless motors with these mecanum wheels, how do i know the position of the robot as its moving? Im new to these kinda projects and designing phase. thanks!
This flawed video reflects poorly on Sparkfun and the mecanum wheels. As has been pointed out a dozen times in the comments, the vehicle can't track properly because the wheels are on wrong. It's ridiculous to use four precision stepper motors then slap the wheels in the wrong locations. If it was my company, I'd definitely spend the minute required to put the wheels on correctly and nine minutes to make & post a new video.
I'm having trouble in line following using mecanum wheels. Please help.
I know!!! I'm sorry, this thing just kept getting put on the back-burner but there's a lot of cool stuff coming soon.
I didn't know Vaas was into robotics. :)
thought the same xD
will they make some kind of offroad version
how did you weave the wires?
Wheels are on wrong, you should delete this video, fix the chassis, and make a new video.
yea.. back wheel is not connected in right orientation
Don't be too hard on the guy. He's obviously gone to a lot of trouble to make this video, as he looks like he got his hair caught and torn out by those wheels.
Also, where is part 2 of the SparkFun AVC Robot Build?
What about Omni wheels
nice
JohnBotJR The roller axles should form an x on the top, o on the bottom.
Same principle behind a robot with 4 omni wheels. The robot shown in the video is built properly.
If you put o on top, x on bottom, you just lose your ability to turn (effectively).
You're right, haha! My bad. It might help- though not much. I think the wiggle is a symptom of the rollers not having enough overlap.
Where do I get the motor controller?
um, dont know where you got that name from but everyone elce calls them omni wheels. you know. like omni directinal
+Sparky Hart Google it, it really is something different.
More Robotic stuff please :)
Great wheels but wrost tutorial..