Crab Drive Programming!!! HELP!!!!!!!!!

Technical Programming
1

Hey, all you Robo Peoples…

My team (698) needs a bit of help programming our crab drive system on LabVIEW.

What we need help is how to program it to drive.

:confused: :confused: :confused:

Any help we could get would be amazing!!

THANK YOU!!!

2

Give us some more details as to what you have so far.

Are you saying that you built a crab, and have no code whatsoever (nor an idea of where to start?).

Or are you saying you have something started, but it’s not working?

If you give us more details, we’ll be able to help you probably.

3

The crab programming has difficult, all of our programmers are rookies, and we have very little idea of where to start. Currently we are trying to code the poteniometers so that way they can line up with the values for the joysticks. Mainly, we need help on the crab drive.

We have very little programming for the crab drive. At this point, any advice or ideas would be appericated.

4

All right, can you describe the phsyical nature of it in entirety? or better yet, post a picture of the drive?

To fully explain it, we’ll need to know how it’s driven (motors in the modules? motors in seperate gearboxes? two wheels per motor? a single motor per wheel?) and how it’s steered. We’ll also need to know what sensors are where.

5

Here are two pictures:

http://i705.photobucket.com/albums/ww57/Megy698/0212091605b.jpg

http://i705.photobucket.com/albums/ww57/Megy698/0212091605a.jpg

6

I have not worked on a crab drive software before, but I can at least get you started with the pots. They need to be connected to analogue inputs (slot 1 by default). When programming, use the analogue input get voltage vi.
The voltage should correspond to what direction the pot is facing in. I recommend changing the values as they are imputed so that the read radians (multiply the value by 2PI/5), and the subtracting or adding so that all your values point to the same direction.

7

Ok.

First, write up how it should work.

  1. Driver pushes joystick in a direction.
  2. Robot takes that direction and changes it to an encoder value.
  3. Robot turns wheels to that encoder value.

Next, start iterating that write up, adding details as you go.

  1. Drive pushes joystick in a direction.
    A. How will we measure that angle? (in Degrees)
    B. How do we make sure that when the robot turns, we keep track of how much and keep it relative to the joystick? (Gyro)
  2. Robot takes that direction and changes it to an encoder value.
  3. Robot turns wheels to that encoder value.

Iterate again

  1. Drive pushes joystick in a direction.
    A. How will we measure that angle? (in Degrees)
    i. We can use the labview .vi that changes rectangular coordinates
    to polar to give us the angle and magnitude of the joystick.
    B. How do we make sure that when the robot turns, we keep track of
    how much and keep it relative to the joystick? (Gyro)
    i. We’ll need to somehow know the angle the robot starts relative to
    the field, add that to the gyro, then keep that relative to the
    joystick position
  2. Robot takes that direction and changes it to an encoder value.
    A. Angle / 360 * counts in one rotation of encoder
  3. Robot turns wheels to that encoder value.
    A. PID loop

This is how I teach our team to program. It’s kind of a verbal flowchart, but it helps you think through the program very systematically. If, at any point, you start getting confused on what you need to do, then you probably haven’t broken it down far enough.

I am going to warn you though - programming a crab drive is NOT a trivial task by any means. Probably at this point your easiest bet would be to remove one of the globe motors, connect both the front wheels by the same chain so they are turned together, and use one joystick for speed of the wheels, and the other to turn them left/right.