How to code Macanum ddrive

[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 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.

[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.

[whcirobotics]

I did the Halo + rotate and attached the up/down to y1, starfing to x1, and rotation to x2. But where does the axis three throttle go? In the picture which mark posted he had it going to one of the terminals in the cartestiandrive, but in the picture i attached, i only have x, and y, and rotation :S am i missing something? an update perhaps? I have attached the code, is it accurate now?

[Ether]

Originally Posted by whcirobotics

I did the Halo + rotate and attached the up/down to y1, starfing to x1, and rotation to x2. But where does the axis three throttle go? In the picture which mark posted he had it going to one of the terminals in the cartestiandrive, but in the picture i attached, i only have x, and y, and rotation :S am i missing something? an update perhaps? I have attached the code, is it accurate now?

I'm not a LabVIEW programmer so I can't tell you if it's accurate, but I'm pretty sure it's not correct: If you want your robot to go up and down and starfe, you're going to have to write your own vi for that. The built-in LabVIEW vi supports only fwd/rev, strafe, and rotate. :-)

But seriously, as for the throttle, where you "attach" it depends on what you want it to do. What do you want it to do? You need to re-read Mark's post to understand that he attached the throttle to the rotation input "For a first test to make sure everything works the way you expect" with one Attack3 joystick. If you now have two joysticks (or a joystick with a twist axis), you don't need to do that.

[whcirobotics]

I meant the up/down as in forward and reverse. And i am using two joysticks so i guess i wont need to attach throttle to anything. I will try this code(hopefully it works) but you are saying it is wrong so i am not so sure as to try it or not. :S

[Ether]

Originally Posted by whcirobotics

I meant the up/down as in forward and reverse... but you are saying it is wrong

Yes I assumed that or we couldn't have had this conversation. The smiley at the end was meant to convey that I was just joking.

but you are saying it is wrong so i am not so sure as to try it or not.

All I can tell you is that it looks like you now have the inputs to the holo vi wired correctly for two-joystick "Halo plus rotate" driver interface.

As for the rest of the diagram, I am not a LabVIEW programmer so maybe someone else will take a look at it to see if there are errors.

I will try this code(hopefully it works)

Have you checked to see that the mecanum wheels are mounted correctly? This is a common error. Checking this can save you a lot of frustration.

[RoboMaster]

As a LabVIEW programmer, your newest screen shot looks good to go.

[whcirobotics]

Hi CD, I got 5 team members and 1 mentor to come on a Wednesday(December 22, 2010) and we build a test robot with the macanum wheels in 4 hours. We finished and i deployed the code and pressed enable on teleop. This is a video of what happend:

http://www.youtube.com/watch?v=es7OF_V-LWU

Is there something wrong with the code? It is the same code as the one attached above. But the problem was that one wheel kept turning. I tried attaching the pwms to other than that of 7, 8 , 9 , 10 and put them in 3 , 4 , 5 , 6 and again that wheel kept turning. :S

The mentor suggested that that one might be calibrated other than 0, but what else could possibly be wrong? Maybe the software? :S Help please.

[Ether]

Originally Posted by whcirobotics

Hi CD, I got 5 team members and 1 mentor to come on a Wednesday(December 22, 2010) and we build a test robot with the macanum wheels in 4 hours. We finished and i deployed the code and pressed enable on teleop. This is a video of what happend:

http://www.youtube.com/watch?v=es7OF_V-LWU

Is there something wrong with the code? It is the same code as the one attached above. But the problem was that one wheel kept turning. I tried attaching the pwms to other than that of 7, 8 , 9 , 10 and put them in 3 , 4 , 5 , 6 and again that wheel kept turning. :S

The mentor suggested that that one might be calibrated other than 0, but what else could possibly be wrong? Maybe the software? :S Help please.

Others may have different suggestions, but if I were you here's what I'd do in your situation:

- Create a separate new software project with VERY SIMPLE CODE that allows you to control each wheel one at a time. This should be very quick and simple to do.

- Run this code and test each wheel individually to make sure each wheel responds properly (both forward and reverse) and equally with respect to the others.

- If your robot passes this test, it is mechanically and electrically sound. The problem is in your mecanum software.

- If the robot fails this test, first double-check your simple code. Then check the PWM indicator light on the Dashboard for that motor. If everything checks out, then you have a hardware problem. Check the indicator lights on each Jag when it is being commanded. If OK, check the voltages for that circuit (motor out, power in).