Re: What type of drive train is the most maneuverable?
 

Yes it is. And effective. Recall this rather intimidating scene?

Re: What type of drive train is the most maneuverable?
 

in the idea of a slim budget, the omnis are about $80 for 2.....extra skyways that can easily be set up with the kit drive train are much cheaper. if you have the extra money the 4wd with omnis are a good option, but if you don't have the cash or would rather save it for another area id stay with kit 6wd drive with the lowered middle wheel and I know 25 doesn't lower their middle wheel which is fine, but the kit bot is already setup for it.....

Re: What type of drive train is the most maneuverable?
 

I think the simplicity and low energy requirements of a 2 wheel drive system are being overlooked:

1. with a 2 wheel drive system you dont have to scrub any wheels to turn. It takes very little power to steer

2. instead of using castors, you can use low friction material and have skid plates on the corners. Anyone who has ever pushed a shopping cart knows castors take some force to get them to point in the direction you want them to go. The result is the force required to turn is non-linear until the castor rotates. A skid plate solves this problem, or you could use a ball style castor (its like a big ball bearing that is free to rotate in any direction.

3. You can compensate for the 'being pushed sideways' and 'hard to steer up a ramp' issue very simply, using the yaw rate sensor (gyro chip) that has been in the KOP, and using a simple feedback loop to close the loop on the steering. Then you have the best of both worlds, a robot that will spin on a dime, taking very little energy to do so, and that will use all of its available motor power to keep pointing in the direction the joystick is commanding, no matter who or what (gravity) is trying to make it turn.

Re: What type of drive train is the most maneuverable?
 

i think we're all over looking the hovercraft... ( :p )

For a really tight budget, that would probably rule out crab, mecanum, or omni (spending money on wheels and the drivetrain might not be most well spend, depending on the game)

Probably one of the easiest (and cheapest) to impliment would be the 2 wheel / skid plates.
!*caution*! with the gyro, make sure its rated to a high rotation, when we tried to use that with our robot this year, it messed up because it could only do 80 degrees/sec !/*caution*/!

I would say experiment as much as you can in the off-season, build a generic frame, and try different configurations with the wheels, OR browse soap's collection of matches, and take a peak at each of the videos.

Re: What type of drive train is the most maneuverable?
 

I personally can reccomend the swerve system, as 114 had great fun with one of those. The only issue is how to program the thing, and still have it driveable.

As far as most cost effective and still maneuverable, a 6 wheel with the middle wheel lowered is pretty nice.

Re: What type of drive train is the most maneuverable?
 

mecanum and holonomic are very maneuverable, but they only have on average at best 70% efficiency. And they're arguably more complicated to program, needs sensors, etc.

swerve is a complicated system of wheel modules and takes time and money to fabricate, but is more efficient (more pushing power) than mecanum/holonomic. Still has a bit of programming to do, and sensors. swerve can also get heavy if weight isnt seriously taken into consideration during design.

6 wheel drive is simpler to fabricate, cheaper, and easy to program. however, you cant strafe sideways. you can turn arguably better than most other drives, but your robot will rock back and forth a little, which isnt always good.

personally, I'd go with 2 speed swerve. all you guys that think its too hard to pull off, too heavy, too expensive, too complicated, or overkill can have their opinions.

Re: What type of drive train is the most maneuverable?
 

I guess you want to have your cake and eat it too!

Some words of advice.. Don't try to do too much! If you want to be agile and escape defenders, then do it. If you want to push defenders out of the way, the n do it. Don't try to switch up mid match as it will only cause you to waste valuable time.

The smartest thing you can do is analyze the game when it comes out and devise a strategy to your liking. Base your design goals off of this, and seriously consider what each available setup can add to your overall design.

Re: What type of drive train is the most maneuverable?
 

Agreed!
Ball casters solve this problem nicely (McMaster-Carr #2364T1).

If you go with these parts, be sure to reinforce the mount - the stud mount sees a bunch of stress and breaks easily if you run into something.

Re: What type of drive train is the most maneuverable?
 

I think there are three vesions of the Analog Devices solid state gyro (yaw rate sensor) with different max turn rates, with the highest being 300°/S.

The faster sensor lets you spin your bot quicker with the loop closed, and it will stay 'locked' if your bot is hit, or hits something, and spins at a rate below 300°/S - but neither of these things are show stoppers.

the slowest sensor: 80° / S is a fast enough turn rate for normal driving. If you are spinning your robot 360°/ Second, you are not driving, you are doing a victory spin!

Two things: when the sensor is turned faster than its max rate, it outputs the full scale reading - your control loop will continue to respond with its max output, so the robot does not go berzerk, it acts predictably.

The only shortfall is if you are integrating the sensor to get compass heading, the reading will be wrong if the robot is spun too fast (by an external force). In this case you need a way to reset the heading (if the sensor is being used that way) during a match.

2. If you close the loop on steering with a gryo sensor, I recommend you have a disable switch on the control panel. That way you can drive with the loop closed, giving you very precise steering, and the robot will fight on its on to hold its heading (when something external tries to push it sideways), and then if you want to drive the robot open-loop (victory spins and stuff) you can, with the flip of the switch.

yes, and ball castors or skid plates take up very little space, which means, you could also have pnuematic feet that extend down, with high friction plates, that can be deployed when you want your robot to stay where you parked it!.

Re: What type of drive train is the most maneuverable?
 

We have used those in the past and fount that the 4" version #2364T2 work better.


And I agree that 2 wheel drive (75-80% weight over the drive wheels) and 2 ball casters gives the best manuverability for the dollar.

And when you want to 'stay in place' either drop a skid plate (anchor) or raise the ball casters with a cylinder or leadscrew.

Re: What type of drive train is the most maneuverable?
 

Nice ideas! Personally I'm in love with the holonomic (4-wheel kiwi) drive train for maneuverability and cost... However the diagonally mounted omni/traction wheel is an excellent idea in my opinion (if you don't want to move sideways)! I just think that maneuverability is increased dramatically when you ad another degree of freedom!

Now, for the complaint about holonomics not being able to go up ramps, I think you have a good point in that it's relatively hard, but definitely essayer to maneuver once on the ramp! I believe I can speak about this as the driver of a 4-wheel drive all-sky wheel drive train in the '06 competition. Once I got on the ramp (really easy) I could hardly move along it, it was something to do with the insane difference between driving on a level ground, and having one wheel atop the ramp providing bookoo friction against a turn... Now for a kiwi drive friction may be the deciding factor regarding your movement at all on said metal ramp, but you could definitely provide force in any direction you choose!

But for overall simplicity of design, and a good two degree of freedom drive train ideal for getting around your opponents... I'd pick the diagonally mounted omni/traction, because your not a rookie team, and you can probably handle it!

Re: What type of drive train is the most maneuverable?
 

Wow, I posted yesterday, and there's already fifty million posts! This is awesome, I love Chief Delphi :p .

Another question: For a defensive type robot that is still maneuverable, what do you think is the best? (For our sadly depleted bank account :( )

(I'll probably be asking a lot of different questions. I have no idea what our robot will be doing this year.)

Thanks for your thoughts!

-Brittany

Re: What type of drive train is the most maneuverable?
 

If you want the best capability, 6 wheel is the way to go, in my opinion. You may use a long-style frame orientation (more suitable for pushing), and six wheel gives you a great number of wheels on the ground without sacrificing manueverability.

*Note- More wheels does not typically mean more traction. It's simply advantageous to have more wheels because when on obstacles or being shoved around, it's more likely that you'll have a wheel on the ground, and less likely you'll bottom out.

Re: What type of drive train is the most maneuverable?
 

Either a 6 wheel drive with the kitbot, or the alternating omini & traction wheels.

Re: What type of drive train is the most maneuverable?
 

I would totaly agree that a 6-wheel drive system would be ideal, a 4-wheel system would work but would not be as mobile. This all really depends on how low your center-of-gravity (CoG) is. If you are focusing on a defensive robot it should have a very low CoG and most drive systems will turn well. Try and get your hands on some traction wheels, look at ifi, and if you are willing to spend the cash grab some andymark 2-speed servo-shifting :yikes: gearbox's would be a very nice addition. Have a look at a team like 1305 from this year for a sweet 6-wheel drive system.