What type of drive train is the most maneuverable?

[BrittanyV]

Our team has, in the past few years, had a problem with robots that cannot move around very well. While our driver has compensated for it quite well, I know she could be ten times better if our robot could move around more.

What do you think is the most maneuverable (and practical. We're on a tight budget.) drive train?

Thanks for your thoughts!
-Brittany

ps. I realize I'm programming/ electrical, but I'd like to be able to program our robot to go where it's supposed to go!

[Richard Wallace]

In another thread there has been some good recent discussion of a very maneuverable drive train using mecanum wheels.

A good compromise between maneuverability and defensive capability is the popular 6WD system.

[Stephen Kowski]

On a tight budget? I'd have to go with a 6 wheel drive train with a lowered middle wheel. There are tons of examples of it done well here on CD, just search around CD Media.

[petek]

A very simple and highly-manuverable chassis is two-wheel drive with ball casters, as used recently by 56, 103 and many others.

Pros: It is very light weight and easy to implement, has fewer components than six-wheel drive and has very low scrub (frictional) losses when changing direction.

Cons: While it can push strongly in the forward direction, it has very low pushing ability off-axis or backward (due to weight transfer off the drive wheels). This system is best-suited to a flat and level field, as it has relatively poor drive dynamics when sideways on a sloped surface, such as a ramp, and would probably have a really tough time on steps!

Stay away from swivel casters, as they steer the robot in the direction they're turned towards - which often seems to be the wrong way!

[Tom Bottiglieri]

A well designed 6 or 4 wheel drive system has always had the best ratio of pros to cons in my opinion.

http://www.chiefdelphi.com/media/papers/1443

That paper should show you how to get it set up correctly.

[thegathering]

While mecanum provides a nice balance of maneuverability with traction, the wheels themselves are fairly complicated, fragile, and can be expensive to machine/purchase. A two drive wheel two caster design is cheap in comparison and still provides great maneuverability. We chose the two caster design for our bot this past year.

[EHaskins]

another drive is the holonomic drive. It uses 3/4 wheels mounted 120/90 degrees apart. It is very maneuverable, but can be easy to push.

Vex Holonomic(the 8th post in this thread has the code needed to drive the robot) http://www.chiefdelphi.com/forums/sh...ad.php?t=46560
3 wheel vs. 4 wheel http://www.chiefdelphi.com/forums/sh...ight=holonomic
advantages of holonomic http://www.chiefdelphi.com/forums/sh...ight=holonomic
The math involved in driving a holonomic http://www.chiefdelphi.com/forums/sh...984#post354984

[Bill_Hancoc]

What have you done in past years. We usually do a 4 wheel skid steer drive type and have not had many problems with maneuverability. We usually do some grippy wheels in the back and some less grippy wheels in the front to reduce scrub when turning.

Kiwi and Mencanum seem very complicated to me if you are a lower budget team and unless you have access to a machine shop (and have people who know how to use it) i wouldnt recommend them to a team on a tight budget.

[AdamHeard]

team 294 has used a very simple solution the past two years.

Kit transmissions to 6 skyway wheels, the center wheels were treaded with waffle tread and lowered. We didn't have the best traction or turning ability, but we turned well and could push decently. Also, we were able to finish the base assembly in a day.

[Pavan Dave]

Team 118 used a crab drive, drive train. A crab drive lets all four wheels move together. So if you want to go left, your robot is still facing forward, but your wheels all turnto the left. It is THE most manuverable because it lets you get anywhere in a short amount of time because instead of wasting time turning your robot around, all you do is move the wheels and that made this previous years game easy because we could score while moving from one side of the field to another.

This what our wheel box looked like for our practice bot,


and this is what all four of them looked like.

[mluckham]

Originally Posted by Pavan

Team 118 used a crab drive, drive train. ...

What are the joystick controls you use? I can see that the robot can slew around very easily, but what if you really do want to face the robot to a different heading?

[Pat McCarthy]

Originally Posted by mluckham

What are the joystick controls you use? I can see that the robot can slew around very easily, but what if you really do want to face the robot to a different heading?

When HOT did crab in 2005, we used a regular black Flightstick (forward, backward, left strafe, right strafe) and a Playstation steering wheel to change the robot's orientation.
We just opened up the case of the steering wheel and soldered some wires onto the potentiometer to put into a gameport connector.

[PandaMan]

Although swerve drive can maneuver around objects, it is not the most physical of drive trains. From what I've seen, the most effective drive seems to be the 6WD.

[Lil' Lavery]

In terms of pure maneuverability, mecanum is the best, as it can travel in any planar direction, change direction almost instantly, and can conquer inclines easier than a holonomic drive. Holonomic and ball drives can also travel in any planar direction and change direction almost instantly. Swerve drives can also travel in any planar direction, but they recquire time (often very small though) to change the orientation of their wheels. "Crab drives" (a variant of swerve drives where all the wheels are linked together) are the simplest swerve drive, but recquire more power (as the have to overcome more scrub) to move in curves. Afterwards comes the plethora of different scrub (tank/skid) steer systems.
4WD, 6WD, 2WD (and 2WD+caster), and many others all fall into this category. While some may recommend the caster system, I would advise against it. From my personal preferance, while quite maneuvable, the lack of control on the casters can cause more problems that it solves. It significantly reduces your control over your bot, and therefor reduces the amount of accuracy you can drive with. Momentum can often cause the rear end (assuming your casters are in your rear) of your bot to swing further than you want it to. It also makes you a relatively easy target to push (and incredibly easy to rotate out of position).
The "best buy" for maneuverability (in my opinion) would be a 4WD with 2 omni-wheels.

[Andrew Blair]

I definently agree with Lil' Lavery- The best bang for the buck if you're not concerned with lots of defence or complication will be the four wheel setup and omni's out front.

Six wheel is another excellent choice with a lowered center wheel- but it also requires more time, complication, and weight budget. However, it's nearly impossible to be spun sideways, or lose traction on inclines, bumpy ground, etc.


Mechanum and swerve are very impressive and capable designs when the game warrants them, but compared to standard drive-trains, a huge amount of design and fabrication muscle needs to go into them.