Team 1658 flying inverse differential swerve Video+CAD files

[Electronica1]

Can you guys tested pushing stuff with it yet?

[MaGiC_PiKaChU]

Why are motors making so much noise even when it's not moving? Feels like a car on neutral

[sanelss]

Originally Posted by MaGiC_PiKaChU

Why are motors making so much noise even when it's not moving? Feels like a car on neutral

when it's not moving it doesn't make any noise. However when we go at low speeds in Differential mode then indeed it is a noisy machine. That's because the top motors are going full speed and the bottom motors are going nearly full speed the opposite direction. So there are a few parts spinning at very high speeds. That's kind of the whole point of the differential system, we can have high power at very low speeds.

[asid61]

Originally Posted by sanelss

when it's not moving it doesn't make any noise. However when we go at low speeds in Differential mode then indeed it is a noisy machine. That's because the top motors are going full speed and the bottom motors are going nearly full speed the opposite direction. So there are a few parts spinning at very high speeds. That's kind of the whole point of the differential system, we can have high power at very low speeds.

Have you thought about trying to optimize this so that the CIM is running at the RPM at which it has the highest power? Or does running them like you describe automatically result in that?

[sanelss]

Originally Posted by asid61

Have you thought about trying to optimize this so that the CIM is running at the RPM at which it has the highest power? Or does running them like you describe automatically result in that?

it all depends how you want to run the cims. There are various modes of operation which is one of the nice things about the design. We can certainly chose what reference speed the cims run at for varied effects such as most efficiency, or most available power(all out) or anything in between. We will certainly be playing with various methods but as far as which ones we end up using,who knows.

[JesseK]

Is it a correct statement that it is impossible to stall the top motor? If so it seems like it'd be a good candidate for a lighter and more efficient open-air motor (new 775, e.g.) so long it's geared correctly.

[sanelss]

Originally Posted by JesseK

Is it a correct statement that it is impossible to stall the top motor? If so it seems like it'd be a good candidate for a lighter and more efficient open-air motor (new 775, e.g.) so long it's geared correctly.

you can still stall out the motors and while it would work to a degree the total capable speed and power is still reliant on both of the motors so if you used a 775 you will lose in both regards compared to a cim.

[SndMndBdy]

I'm curious about that worm gear that you've got. It looks 3D printed - is that right? Can you give us some specs and tell us how you made it? Does it seem like it will be sturdy enough to hold up well?

[sanelss]

Originally Posted by SndMndBdy

I'm curious about that worm gear that you've got. It looks 3D printed - is that right? Can you give us some specs and tell us how you made it? Does it seem like it will be sturdy enough to hold up well?

they are NOT 3d printer. They are plastic though(nylon?)they are actually very common garage door opener gear sets you can buy at sears. Though they are twice as cheap online. In fact, andymark uses the exact same set(but they hex broach theirs) on one of their 90 degree transmissions. We used two sets last year to drive our elevator mechanism and they held up just fine.

As far as specs/how it was made take a look at the CAD files.

[GeeTwo]

Originally Posted by sanelss

when it's not moving it doesn't make any noise. However when we go at low speeds in Differential mode then indeed it is a noisy machine. That's because the top motors are going full speed and the bottom motors are going nearly full speed the opposite direction. So there are a few parts spinning at very high speeds. That's kind of the whole point of the differential system, we can have high power at very low speeds.

If the top motors are going "full speed" (which I read as free speed, or nearly so), they are generating no torque and thus producing no mechanical power. The bottom motors are going "nearly full speed", they are generating low torque, and are operating well down on the power curve. Where does this "high power" originate?

[Electronica1]

I just want to double check, the transmission you are using is similar to this, correct?

[sanelss]

Originally Posted by Electronica1

I just want to double check, the transmission you are using is similar to this, correct?

Maybe? From what he said it indeed sounds like he just made an overly complicated inverse differential but he seems to hide the fact that he has another motor somewhere counter driving one of the gears and doesn't mention that both motors need to be able to provide the torque you want out of the system. This seems like one of those try to scam investors out of money schemes but since he seems to be hiding information can't really say.

[sanelss]

Originally Posted by GeeTwo

If the top motors are going "full speed" (which I read as free speed, or nearly so), they are generating no torque and thus producing no mechanical power. The bottom motors are going "nearly full speed", they are generating low torque, and are operating well down on the power curve. Where does this "high power" originate?

In that situation there wouldn't be much as you mentioned. If we drive the system like that and we try to move, as we increase the load on the system the speeds of both motors will be loaded down and slowed down until it hits a point where it has sufficient torque to move. Or we can try to keep it in the higher power band but that would arbitrarily limit our top speed when that amount of torque isn't required. With a desired output speed, the faster we run the motors the faster total speed differential we can get making the top speed of the robot higher. But indeed there isn't much power available there but as in a regular control system when you apply a load the speed will be reduced to the point where torque is high enough for the task. In our case both motors will be slowed down so our torque will vary while our total speed output remains the same.

Or at least that's what we think, could be wrong. The whole point of building the prototype was/is to find out if we're just kind of wrong or completely wrong XD

[sanelss]

Originally Posted by Electronica1

Can you guys tested pushing stuff with it yet?

We did some small tests but no video of it. Nothing is properly setup(the robot is 80 lbs short so traction is very low, we're using clamps to hold some parts on, the chain doesn't have proper guides/tensioners, need more time to refine and implement more code, etc...) so there would be little point in even attempting it. This prototype was a proof of concept and it succeeded at that task for our needs. Real testing will be after we see what the game is to see if we want to continue on this route at which point we will attempt a competition rated prototype.