20-02-2011 01:22

Ether

Re: paper: LabVIEW Mecanum Programming

Nice presentation. This should prove helpful to teams just getting started with LabVIEW and mecanum.

There's a small error on Page 19 which may lead some astray:

angle_error = joystick_angle - gyro_angle;
angle_error -= 360*floor(0.5+angle_error/360);
setpoint = gyro_angle + angle_error;
process_variable = gyro_angle;

20-02-2011 08:26

Jogo

Re: paper: LabVIEW Mecanum Programming

Thank you Ether. I added in a solution that I used but neglected to include in the first version. Now that I look at your solution closer, however, yours seems a great deal more elegant.

02-02-2012 20:04

maria_edu

Re: paper: LabVIEW Mecanum Programming

I have a question on slide 9; what is the blue thing within the case structure? Sorry 1st time programming mechanum drive. Very helpful presentation

02-02-2012 21:16

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

I don't know what it is you're referring to. Can you describe the "blue thing" a little better? Blue typically means an integer value.

02-02-2012 21:22

maria_edu

Re: paper: LabVIEW Mecanum Programming

Sorry about that; I mean in the true/false case structure, there is the"blue thing" that says"L1 rotate_mode." My question is where is that located in labview?

02-02-2012 21:30

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

rotate_mode is a global variable that was defined on the immediately preceding slides. L1 is an enumerated constant that was obviously created by right-clicking the input terminal of the variable and choosing Create Constant.

06-02-2012 20:26

2829ron

Re: paper: LabVIEW Mecanum Programming

Hello,

I did all the steps in page 8, but can not get my robot global data to read the "rotate mode" enum. Any help would be appreciated.

Thanx,

David

06-02-2012 22:36

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

I'm not sure what you mean. The robot global data doesn't "read" or "write" the values. It just provides a place that contains them.

Are you trying to say you can't get the global variable to appear on the Teleop block diagram?

07-02-2012 09:26

2829ron

Re: paper: LabVIEW Mecanum Programming

Yes sir. That is what I meant. I defined it's values in the Robot Global Value.vi but they won't show in teleoperated.

Thanks,

David

07-02-2012 10:56

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

It's not exactly obvious how to place a reference to an existing global variable. Here's how to do it:

Right-click on an empty spot in the block diagram to call up the function palette. Choose "Select a vi..." and navigate to the folder containing your robot project. Open "Robot Global Data.vi" and you'll have a global variable attached to your cursor (it will likely be named "Enable Vision" -- don't worry about it). Click to place that variable on the block diagram. Now you can click on the middle of the variable to bring up a list of all the globals that are part of the Robot Global Data vi. Choose the one you want.

The default is to make a "write" reference. To change it to "read", right-click on the variable and choose "Change To Read".

07-02-2012 23:00

2829ron

Re: paper: LabVIEW Mecanum Programming

Okay. I got the global variable to show up, and I can connect the constant to it. But when I change the global variable to read, I can't connect my constants anymore. Did I totally mess up somewhere? This is my third year programming, but I've never messed with the global robot data vi.

Thanks,

David

07-02-2012 23:43

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

If you want to put a constant in the global variable, you need to write to it. You would read it if you want to do something with the value it contains.

08-02-2012 20:49

2829ron

Re: paper: LabVIEW Mecanum Programming

Okay. On to page 14 I'm getting tired of asking questions. But thanks to everyone for your help. The rotate mode runs into the case structure and then connects to the symbol I can't seem to find. It's blue with an arrow and a box with a circle under it.

Also, do need to create a global variable called "header"? If so, what properties does it need to have?

And... what is connect to the PID on page 15?

Thanks again,

David

08-02-2012 22:53

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

Quote:

Originally Posted by 2829ron The rotate mode runs into the case structure and then connects to the symbol I can't seem to find. It's blue with an arrow and a box with a circle under it.

11-02-2012 12:05

2829ron

Re: paper: LabVIEW Mecanum Programming

Thanks for all your help. I've got a few more questions here, and then I think I'll have it.

Do I need to create a global variable called "header"? If so, what properties does it need to have?

And... what is connected to the PID on page 15?

Thanks again,

David

11-02-2012 22:04

Jogo

Re: paper: LabVIEW Mecanum Programming

Hello David. You do need to add a global variable called "header" (numeric), which is used to store the gyro angle each time rotate_mode changes to "straight".

For tuning the PID function, first right click on the "PID gains" terminal and add a control or a constant, and follow the instructions on page 16. There are plenty of good resources around the web for PID tuning specifics: http://zone.ni.com/devzone/cda/tut/p/id/3782.

If you have more implementation-specific questions, feel free to PM me.

29-02-2012 11:53

Ernesto

Re: paper: LabVIEW Mecanum Programming

Ok My names Ernesto
I am still stuck on the global header and would like to ask if you could explain more on how to make it.

03-04-2012 13:19

mjgard

Re: paper: LabVIEW Mecanum Programming

I am also trying to figure out the global variable header. I wasnt sure where to create it or how. So i created a numeric and then create a local variable from the numeric and called it header and used that within my teleop code. Will this work or do i need to create a global somehow?

03-04-2012 13:41

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

The Robot Global Data.vi is where you create global variables (if you need them). It's only a front panel, with no block diagram. Place (or paste) a control of the appropriate type on the front panel, then right-click it and make its label visible if it isn't already. Change the label to whatever name you want the global variable to be.

To use a global variable, you can either copy one from elsewhere, or use the "Select a VI" item in the function palette to pick the Robot Global Data. You'll end up with something on your block diagram with a popup menu that lets you choose among all the globals. You can use the right-click menu to make it a "read" or a "write".

15-05-2012 19:18

xule

Re: paper: LabVIEW Mecanum Programming

I followed the directions (somehow I must have missed something).

15-05-2012 21:05

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

Quote:

Originally Posted by xule I followed the directions (somehow I must have missed something).

15-05-2012 23:49

xule

Re: paper: LabVIEW Mecanum Programming

L2,R2,and R1 are there as laid out in Step 4, same structure as L1 just different constant for rotation.

[IMG][/IMG]

[IMG][/IMG]

double clicking highlights the whole structure.

16-05-2012 07:44

Mark McLeod

Re: paper: LabVIEW Mecanum Programming

Is there a blank in the enumeration list?
Sorry, I can't see your posted images. They get blocked where I am.

16-05-2012 07:57

xule

Re: paper: LabVIEW Mecanum Programming

Thanks, that was it. A blank space in the enumerated list.

16-05-2012 08:06

Alan Anderson

Re: paper: LabVIEW Mecanum Programming

Quote:

Originally Posted by xule double clicking highlights the whole structure.

16-05-2012 08:33

xule

Re: paper: LabVIEW Mecanum Programming

Thanks, that was it. Program runs.

22-11-2012 16:18

Priyesh69

Re: paper: LabVIEW Mecanum Programming

Quote:

Originally Posted by Alan Anderson It's not exactly obvious how to place a reference to an existing global variable. Here's how to do it: Right-click on an empty spot in the block diagram to call up the function palette. Choose "Select a vi..." and navigate to the folder containing your robot project. Open "Robot Global Data.vi" and you'll have a global variable attached to your cursor (it will likely be named "Enable Vision" -- don't worry about it). Click to place that variable on the block diagram. Now you can click on the middle of the variable to bring up a list of all the globals that are part of the Robot Global Data vi. Choose the one you want. The default is to make a "write" reference. To change it to "read", right-click on the variable and choose "Change To Read".

22-11-2012 18:27

Mark McLeod

Re: paper: LabVIEW Mecanum Programming

There is no Block Diagram for Global Data, so ignore that.

1. Open the Global Data.vi (front panel) since you already discovered how from the Project Explorer.
2. Right-click to get the front panel menu, choose an Enum control and place it on the Global Data.vi front panel.
3. Follow the rest of the powerpoint directions.

13-08-2014 12:10

tr6scott

Re: paper: LabVIEW Mecanum Programming

We purchased a Mecanum kit as an off-season project and played with the code last night. I believe there are some errors in the code, that I thought I would post here in case others also did not get the results expected.

First, let me thank you for taking the time to develop this, it was a huge asset with trying to get students to get the code working.

Now to the issues.

On page 14, I believe the feedback node needs to be outside of the case structure for "Straight"... What we saw is that the only way you can get into the "Straight" structure is for the rotate_mode to be equal to "Straight" and therefore the feedback node can only be equal to "Straight" and since they never not equal each other, you never update the "Header" value.

When you add the PID on page 15, the PID now will unwind whatever rotation you do, because the Header is not updated, and stuck at the default, which we set to 0. So spin the bot 3 times CCW, and the let go of the sticks, the PID runs the 3 times CW and stops.

The simple fix for this is to move the feedback node out, and the header updates correctly.

On slide 17, when you add the case structure to make sure the rotate momentum is less than 10, this also breaks Header updating. As written the Header can only update the first loop after you took your finger off the sticks, so if you are spinning faster than the 10, the Header will not update, and if spinning slower than 10, you really didn't need this case anyways....

I have not fixed this one yet. It seems we almost need another enumeration state.. Say the joysticks put you in a "WaitingForStraight" and the case structure for WaitingForStriaght would check that rate less than 10 while sending 0 to the rotation, once the rate is less than ten we would write Straight to the "Rotate_Mode"

I'll post back in a couple weeks on this fix, and debugging of page 21.