Team 1658 flying inverse differential swerve Video+CAD files

[sanelss]

As previously seen here: http://www.chiefdelphi.com/forums/sh...d.php?t=140181

Here is a video of a quick test run we did. We don't have full functionality yet but serves well for initial demonstration purposes of this system.

https://www.youtube.com/watch?v=WfxK...ature=youtu.be

Here are CAD(autodesk inventor) files of the system. I'm fairly confident all the parts and dimensions are accurate but as a disclaimer: Accuracy is not guaranteed.

https://drive.google.com/file/d/0B4f...ew?usp=sharing

[Ari423]

I still love this idea. The well-controlled slow driving would have been helpful in 2015 to not knock over stacks when placing your stack. With some pretty basic (or not so basic if you choose) programming, you could make an 'auto-shifter' from differential mode at low joystick input values for better control to normal mode at higher joystick values for faster driving. One less thing to for the driver to worry about. I look forward to hearing more about this project!

BTW anyway we can get the CAD either in STEP format or on GrabCAD so Solidworks users can take a look?

[sanelss]

Originally Posted by Ari423

I still love this idea. The well-controlled slow driving would have been helpful in 2015 to not knock over stacks when placing your stack. With some pretty basic (or not so basic if you choose) programming, you could make an 'auto-shifter' from differential mode at low joystick input values for better control to normal mode at higher joystick values for faster driving. One less thing to for the driver to worry about. I look forward to hearing more about this project!

BTW anyway we can get the CAD either in STEP format or on GrabCAD so Solidworks users can take a look?

On the higher values differential mode is kind of like normal mode since the motors are driving in the same direction, just not same speed. But at full tilt they are the same so our high end is more or less identical.

As far as the CAD goes, I don't have inventor on my home pc so I wouldn't be able to do any conversion until after the season starts but pretty much all the CAD software packages have the ability to convert files from other formats so i'm sure you'll find a way to import the files into your cad package or at worst use an online converter.

[Ari423]

Originally Posted by sanelss

On the higher values differential mode is kind of like normal mode since the motors are driving in the same direction, just not same speed. But at full tilt they are the same so our high end is more or less identical.

As far as the CAD goes, I don't have inventor on my home pc so I wouldn't be able to do any conversion until after the season starts but pretty much all the CAD software packages have the ability to convert files from other formats so i'm sure you'll find a way to import the files into your cad package or at worst use an online converter.

Interesting, on the video it looked like it went faster in normal mode. Maybe the driver just wasn't pushing the stick as far on differential mode.

[sanelss]

Originally Posted by Ari423

Interesting, on the video it looked like it went faster in normal mode. Maybe the driver just wasn't pushing the stick as far on differential mode.

Ye it was the first time that driver picked up the controls. It can go both faster and slower in a more controller manor but he wasn't familiar enough with it yet to properly show what it's capable of doing. I had a bit more practice with it and could have showed off the various aspects a bit better for comparison but I had to do the recording so can't do both xD we attempted to have someone else record while I drove prior to this but i'm pretty sure that video would make a lot of people puke.... so I ended up having to take the video myself. Certainly not a shining achievement from what can be seen in this video but I kind of like that too so others don't get a full proper demonstration and while it can be seen working the finer details are left to their own imaginations =p Until competition that is then this system will shine in all it's glory xD (if we end up deciding to use it anyway) or they can attempt making one themselves to find out.

[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.

[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