How to code Macanum ddrive

[Ether]

Originally Posted by buildmaster5000

You can also use a second joystick. The first joystick will control what I call "move" (forward/ backward relative to the robot's center) and "translate" (left/right relative to the robot's center). Assign the Y axis to move and the X axis to rotate the robot. The second joystick can have its X axis assigned to rotate the robot about its center.

I think there's a typo. You have "rotate" assigned twice. One of them should be strafe, right ?


If you have drivers who are already proficient with a tank drive interface, and you want to take advantage of that, you can use two 2-axis joysticks in standard "tank drive" mode to control the mecanum vehicle.

The left and right joystick Y-axes act just like tank drive to control fwd/rev and turning.

The X-axis on one of the joysticks controls strafing. To avoid inadvertent strafing, you can activate the X-axis command only when a trigger held down.

[whcirobotics]

@ Buildmaster5000 and @ Ether

I have attached a picture of what you guys suggested. Is it correct?

And plus, how do i get "Macanum - Cartesian" under the Holonmic Drive. Like what Mark has in his picture.

@ RoboMaster

so the Joystick, Attack 3 we got in the kit is not sufficient? What joystick is to be used then? And if any what extra bit coding is involved?

1514
Whcirobotics

[Joe Ross]

Originally Posted by whcirobotics

And plus, how do i get "Macanum - Cartesian" under the Holonmic Drive. Like what Mark has in his picture.

Have you installed the LabVIEW update released 2/15/2010?

[whcirobotics]

Originally Posted by Joe Ross

Have you installed the LabVIEW update released 2/15/2010?

O there is an update :S i will do that right away

[Ether]

Originally Posted by whcirobotics

Is it correct?

That depends on what driver interface you are trying to implement. Can you explain what you think this will do, from the driver's point of view?

[RoboMaster]

The Attack 3 joystick is not sufficient for extremely simple, basic wire-up programming and control of holonomic drive. If you want to use it, you'll have to do a little more programming to work with what you've got. But that's where you have options based on how advanced you want to be or what you think is easiest to drive or program.



I think Ether and buildmaster5000 were actually talking about two different drive techniques. But they're both good basic ideas. Let's see if I can describe them:

"Strafing-based holo drive" (what I was describing with buttons and buildmaster5000 with a joystick): one joystick controls strafing (wire up X and Y from joystick to X and Y on holo drive VI), while buttons or another joystick axis control direction/rotation (wire something else up to the Rotation terminal). This means that to turn around a corner you drive straight with the first joystick, but at the same time you need to rotate with your buttons/other joystick so that your direction changes too.

"Tank-based holo drive" (what Ether was describing): robot is driven normally like a tank: two joysticks control the left and right wheels of the robot. But, when the driver presses a button, the robot switches to strafing only, where one joystick controls strafing. This might be a little trickier and would require a combination of the holo drive VI and the tank drive VI (switching between the two based on if the button was pressed). However, this is nice and easy to drive because you normally just drive with the tank drive technique, which is intuitive. The strafing is like an added bonus.
(Note: you could use arcade drive instead of tank drive, which would require only one joystick. The point is that you're switching between that and holo drive to enable strafing).

Sorry if that was super abstract and hard to describe. But there are many ways to actually drive and control the robot with holonomic drive, just like how you can control a basic drive with arcade or tank drive, take your pick. So yes, the holo drive programming itself is easy since we have a nice holo drive VI, but there's still a bit more you have to do to apply it.

I might post visuals of the programming I described if you want. Right now I have to do something else, though. Hope that helps!

[Ether]

Originally Posted by RoboMaster

"Tank-based holo drive" (what Ether was describing): robot is driven normally like a tank: two joysticks control the left and right wheels of the robot.

Correct. You use the Y axis of each joystick for tank drive.

But, when the driver presses a button, the robot switches to strafing only

That's not what I was describing. When you hold a button down, it enables the X axis of, say, the right joystick. The X-axis controls strafing. But the Y axes are not disabled. The Y axes of the 2 joysticks continue to operate as tank drive in this mode, controlling the fwd/rev and rotate degrees of freedom. So the driver, if skilled enough, can control all three degrees of freedom simultaneously.

The button is not required. You could leave the X-axis (strafe command) enabled all the time. Field experience has shown, however, that it is useful to disable the X-axis unless it is needed. This way, the driver doesn't unintentionally command strafe when he doesn't want it.

This might be a little trickier and would require a combination of the holo drive VI and the tank drive VI (switching between the two based on if the button was pressed).

All it requires is the cartesian mecanum vi. No switching is required. Calculate (Y1+Y2)/2 and feed it to the cartesian mecanum vi "Y" input (fwd/rev). Calculate (Y1-Y2)/2 and feed it to the "rotation" input. Feed X to the X input (strafe). This will provide tank drive with the left and right joystick Y axes; and when X is not zero you will get strafing too.

However, this is nice and easy to drive because you normally just drive with the tank drive technique, which is intuitive. The strafing is like an added bonus.

Exactly.

(Note: you could use arcade drive instead of tank drive, which would require only one joystick. The point is that you're switching between that and holo drive to enable strafing).

You could use 2 joysticks for arcade+strafe with the cartesian mecanum vi: Y1 for fwd/rev, X1 for rotate, and X2 for strafe.

[whcirobotics]

I think the code will enable the Joystick 1 ( also called move joystick) to control the Up and down and Strafing part of the driving. And the Joystick 2 ( also called the Translate Joystick) to control the left to right part of driving.

[Mark McLeod]

For a first test to make sure everything works the way you expect, I'd suggest using just one of the Attach 3 joysticks and using the simple code as-is.
Assuming you get the LabVIEW update installed.

That just means rotate will be controlled by the throttle on the Attack 3, so make sure that's centered when you start.

Once you're sure the mechanics all work properly and the PWM wiring goes to all the correct motors, then start improving the controls.

[Ether]

Originally Posted by Mark McLeod

For a first test to make sure everything works the way you expect, I'd suggest using just one of the Attach 3 joysticks and using the simple code as-is.

Wise advice.

Something I've found to be helpful too: Put the robot up on blocks and observe the wheels:

• When you command straight forward, all four wheels should spin forward.
  
• When you command straight backward, all four wheels should spin backward.
  
• When you command pure CW rotation, the front and rear port side wheels should spin forward and the front and rear starboard wheels should spin backward.
  
• When you command pure CCW rotation, the front and rear port side wheels should spin backward and the front and rear starboard wheels should spin forward.
  
• When you command pure strafe left, the front port and rear starboard wheels should spin backward, and the front starboard and rear port wheels should spin forward.
  
• When you command pure strafe right, the front port and rear starboard wheels should spin forward, and the front starboard and rear port wheels should spin backward.

Pay careful attention to how you have the mecanum wheels mounted too: Right way Wrong way

[RoboMaster]

Good points, Ether, thanks.

Yes, I suppose I should have said it was my version of your describe drive, but I was just being general and as simple as (I thought) possible. But you explained your control ideas very well in your (second to) last post, thank you. I new you could probably drive a robot tank style with the holo drive VI, but it would require complex converting of two joystick axis into the X and Y holo drive terminals. Thanks for your explanation of how to do it easily!

[whcirobotics]

I have finished coding it and i have attached a picture. Is it accurate? i just want to make sure so i dont disappoint the construction crew that worked so hard to make me a test frame with attached macanum wheels.

[Ether]

Originally Posted by whcirobotics

I have finished coding it and i have attached a picture. Is it accurate?

What user interface are you trying to implement?

I don't recognize Tank, Arcade, or Halo in the code you made.

Did you mean to set the holo vi for polar? If so, doesn't look like direction input is scaled correctly.

Did you mean to use the throttle for rotation? Seems awkward. Driver needs three hands.

[whcirobotics]

O.o I meant to have it on "cartestian" not polar. slight error woops! I wanted it to be like 1 joystick controls the up and down motion of robot, and the other joystick the starfing part, thats why i attached the y axis to one joystick(up down) and the starfing and x to other joystick. Isnt that what my code is doing? :S

And plus * mark posted this picture earlier in this post > http://www.chiefdelphi.com/forums/at...9&d=1287950414 > in which he has 3 wires that can go into the holonomicdrive(cartestian) but i only have 2 terminals :S i did the update , how come he has an extra bit? i only have x, y, rotation and robotdevref and gyro angle ? i connected the x and y but where does the throttle go?

[Ether]

Originally Posted by whcirobotics

I wanted it to be like 1 joystick controls the up and down motion of robot, and the other joystick the starfing part, thats why i attached the y axis to one joystick(up down) and the starfing and x to other joystick.

You've got Y2 controlling fwd/rev, X1 controlling strafe, and throttle controlling rotation. This sounds like an extremely awkward driver interface to me. Driver needs 3 hands.

Why not use a more standard driver interface like one of the following:

1) Tank Drive plus strafe. See posts 9 and 17 in this thread. Takes advantage of driver's familiarity with tank drive.

2) Halo plus rotate. Y1 controls fwd/rev, X1 controls strafe, X2 controls rotation. Takes advantage of driver's skill at playing Halo-style videogames.

3) Arcade plus strafe. See post 17 in this thread.


You can use the throttle to adjust joystick sensitivity (gain) so different drivers can adjust it to their liking.