Skunkworks Drive Train??

[Billfred]

Originally Posted by JesseK

2 Tips from my point of view of seeing alot of holonomic drives and researching to the extent of creating my own:

1.) Make it driver-centric holonomic. Figure out your driver's controls as well. I'd recommend having a circular nob for rotation as the Z axis and a joystick for all lateral movement. Then, when the joystick moves right, no matter what direction the robot is facing, it laterally moves right from the driver's point of view. If you push the joystick away, no matter what the robot moves down the field away from you. You'll need a gyro for this. Making a true-holonomic drive train is both hard & fun to learn, but it also can provide the agility you seek over a tank drive.

2.) Your manipulator/shooting mechanism/whatever else had better work. If your arm breaks in 2007 or doesn't work well you can't exactly go play effective defense. If your gathering or shooting mechanism in 2006 broke or didn't work you were in the same boat. Climbing ramps with omni drives this year was fairly easy *if* the ramp-bot had rails to guide you up -- otherwise you'd gun it too much and fall right off the side.

Fully agreed on the second part (boy, am I glad that Mike Walker talked me out of pressing for kiwi this year), though I still can't wrap my head around going driver-centric. Is it possible to do while allowing for different starting orientations? How does it work off the field?

[JesseK]

It works based upon the initial orientation of the gyro. If you orient the gyro 90 degrees offset from where the driver is facing, every movement you make will be 90 degrees off unless you somehow compensate.

It's the true-vs-relative crap I do all day while coding for submarines -- it's second nature to me now, and the hard part is encoding it in a language that has no built-in geometric calculator.

Without giving too much away too early, see if you can figure out how to control it. I'll give you some hints for the smoothest, most scalable (but not THE fastest) control: use unit vectors from the gyro.

[nsr]

nice

[T3_1565]

Originally Posted by JesseK

1.) Make it driver-centric holonomic. Figure out your driver's controls as well. I'd recommend having a circular nob for rotation as the Z axis and a joystick for all lateral movement. Then, when the joystick moves right, no matter what direction the robot is facing, it laterally moves right from the driver's point of view. If you push the joystick away, no matter what the robot moves down the field away from you. You'll need a gyro for this. Making a true-holonomic drive train is both hard & fun to learn, but it also can provide the agility you seek over a tank drive.

This is another great idea that is being thrown around our team in the past few weeks! We have decided that if this were the route to go, the best way to control it is with an xbox 360 controller (as many of us on the team play video games ALOT. lol) this way it makes it seem like an FPS game, which gives a driving advantage to anyone who can play FPS games well as you already have practice in! (if only we could make our robot jump... )

[Billfred]

Color me interested. A few questions:

1) What's the diameter on the omniwheels?
2) Why roll your own omnis over getting a set from AndyMark or elsewhere? (There are valid reasons for it, perhaps even answered by the first question, but it's nice to know.)
3) How are you attaching the omniwheels to the BaneBots shaft? It almost looks like they're floating in space.

[Bob Steele]

Here are a few answers.

Omni and standard wheels in this configuration really would not allow movement in all direction. If we use standard wheels perpendicular to the omni wheels the omnis would have to push the standard wheels sidewise to travel in that direction. Our drive train last year had omni wheels on the corners and other drive trains I have used in the past have had omnis on one end and standard on the other. These are certainly viable configurations but do not give an unlimited range of direction without turning the robot as this drive should give.
It is simply impractical to push standard wheels sideways. Even in our drive train last year we saw the "hopping" of the robot as standard wheels were pushed in a direction slightly off the rolling axis. Completely sideways would require much higher powered motors and breakers... and of course is impractical...

We are using the wheels from the TechnoKat drawings. they are 7.7" diameter approximately. We can purchase wheels from AM and have done so in the past. We would like to make our own this year. Materials for these 8 wheels come to approximately the same cost as 8 omnis from AM...
It is the process we are interested in... One can always purchase solutions and sometimes that is the best way. We want to develop our own as part of the engineering process. The off-season is a good time to do this in our opinion. We are starting with the TechnoKat design and modifying it to suit our needs and to try and improve on the design both technically and in a way that will allow it to be made cheaper and within the constraints of our resources...

The wheels will be direct driven by the banebot motors. Application of the power will probably be done through a keyway...this will require a modification of the banebot shaft.