pic: 6 wheel drive with a suspension

[joeweber]

Originally Posted by AdamHeard

It's an interesting concept, but is certainly a lot of complexity to pull it off. If I recall correctly teams with mecanums have been able to climb ramps, 40 in 2006 and 1540 in 2007 for example. Have you also given thought to how this would affect any manipulators? The two segments pivot a lot in regards to each other, that looks like it'd be quite a hassle.

The only complexity is the ball differential. The rest is off the shelf items. The ball differential must have an adjuster to tension the slippage. I have some ideas on how to do it. For the suspension I am not sure at this time how much movement to allow or to add springs to help control the movement. I have to build it first to find out.

[Mike Nawrot]

We were tossing this idea around just for kicks at some point this year. We never had any intentions to go through with it, or to even take the time to draw it up. I'm glad somebody did though. But, as awesome as it is, I'm not sure there's not much of an advantage to it. We did a mecanum drive this year, and though we had some problems with strafing, it turned just as well as, if not better than a six wheel drive. In general, the addition of an omni wheel won't help the maneuverability of the drive train. The traction provided by the omni wheel might improve the pushing ability of the drive train, but only if you use soft rubber rollers and an overlapping roller design so you have constant contact between the rollers and the ground. IMHO, the complexity, and thus increased probability of failure of the system outweighs the few performance benefits such a design provides. Though, to quote a friend, "if it looks good, it is good". And this design looks pretty awesome.

[joeweber]

We have plans on using two omni wheels on both sides for the traction. Many have said how complex it is to build, but from the drawings that we have made there are only 5 parts that we have to make multiple times and the design for these parts are straight forward flat pieces with hole and slots. Very easy to C & C and only requires assembly. When we complete the drawings we will post them. The drawing that we have posted is only missing two parts but is pretty much completed. We will take that assembly and make four units and connect them at the omni wheel with an axel. To attach them to the robot we will have two steel tubes that a drive side will slide onto and then the bumper bolts will slide into the tube and two cotter pins will hold it all together. We have tried to make it simple so the student can understand what they are assembling and can make repairs when needed.

[JesseK]

After studying a bit of vector analysis with this design I still believe there is a fundamental design flaw in this concept; however I suppose that depends on the functionality that is intended for the final product. Is the final design supposed to be fully holonomic or is it only supposed to be a tank drive-style drive train that has the capability to do a 90 degree sideways lateral?

[Dowjonesbotics]

I don't really understand where the suspended part is. Coudl someone explain it for me?

[joeweber]

You may be correct, but from what I have observed from the ball differential it should work. The omni wheels will be attached to the shaft that is attached to the disc holding the balls. The balls will be pressed on each side by the sprockets. If the sprockets are going the same direction than the wheels must be moving the same speed. If the sprockets are going in opposite directions (equal full speed) than the omni should be stationary. Correct? Now if one sprocket is not moving while the other is moving at full speed than the omni wheel should be moving one direction at half speed. Thus allowing for a 45% angle run of the robot. Any other difference should be also of the same ratio. On paper the ratios work out but in practice I may be wrong. We will be building a test system this fall to find out.

I don't really understand where the suspended part is. Coudl someone explain it for me?

Go to our site http://www.team1322.org/ideas.htm and scrol down to see a drawing of the suspention movement. The robot will be attached (with a pivot) to the drives in two places center of each moving drive.

[Dowjonesbotics]

Originally Posted by joeweber

Go to our site http://www.team1322.org/ideas.htm and scrol down to see a drawing of the suspention movement. The robot will be attached (with a pivot) to the drives in two places center of each moving drive.

Ohh, I see. Thanks.

That's seems like a very logical and feasible idea.

[AdamHeard]

Originally Posted by joeweber

We have plans on using two omni wheels on both sides for the traction. Many have said how complex it is to build, but from the drawings that we have made there are only 5 parts that we have to make multiple times and the design for these parts are straight forward flat pieces with hole and slots. Very easy to C & C and only requires assembly. When we complete the drawings we will post them. The drawing that we have posted is only missing two parts but is pretty much completed. We will take that assembly and make four units and connect them at the omni wheel with an axel. To attach them to the robot we will have two steel tubes that a drive side will slide onto and then the bumper bolts will slide into the tube and two cotter pins will hold it all together. We have tried to make it simple so the student can understand what they are assembling and can make repairs when needed.

Complexity isn't just how many parts have to be made. You could use all COTS components and still have the most complex robot out there. This design is inherently more complex than a 6wd or a 4 wheel mecanum (the two most similar designs). Also, the pivoting frame throws a huge curveball when considering mounting manipulators.