Chief Delphi - Arcade Drive Troubles in Autonomous

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Tanner

13-06-2010 16:28

Arcade Drive Troubles in Autonomous

Hi all,

I'm almost done with reprogramming this year's robot in C++ instead of LabVIEW. The only thing holding me back from marking it done is the autonomous.

In autonomous I'm telling the robot to go forward like so:

Code:

static const float autonomousForwardPower = -0.5;



//Move forward!

drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

Same exact drivetrain I use for teleop. I even use the function in teleop. Though it seems no matter what I do the robot turns left at full speed instead of going straight.

I even tried it in teleop and it does the same thing.

So, yeah - I'm confused why this is happening. Thoughts?

-Tanner

Radical Pi

13-06-2010 16:40

Re: Arcade Drive Troubles in Autonomous

Have you checked the hardware? Does it work if you re-load the LabVIEW code?

Tanner

13-06-2010 16:46

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Radical Pi (Post 966435)

Have you checked the hardware? Does it work if you re-load the LabVIEW code?

Hardware is fine as far as I know. Like it drives in teleop fine.

In teleop the code is:

Code:

//Drive the robot

drivetrain->ArcadeDrive(driverJoystick->GetRawAxis(4),driverJoystick->GetRawAxis(2));

Which works perfectly fine. The robot drives straight and turns where I want it to.

The LabVIEW code would probably work if I hadn't lost my flash drive with it on it.

-Tanner

Ether

13-06-2010 17:34

Re: Arcade Drive Troubles in Autonomous

Are you using Simple Robot or Iterative Robot ?

What other code do you have in autonomous besides what you posted ?

Tanner

13-06-2010 17:41

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Ether (Post 966445)

Are you using Simple Robot or Iterative Robot ?

What other code do you have in autonomous besides what you posted ?

Iterative.

Code:

void AutonomousContinuous(void) {

        printf("Running in autonomous continuous...\n");



        GetWatchdog().Feed();



        if (kicker->HasBall())

        {

                //We have a ball, thus stop moving and kick the ball

                drivetrain->Drive(0.0, 0.0);

                kicker->SetKickerMode(KICKER_MODE_KICK);

        } else {

                //We do not have a ball

                if (kicker->IsKickerInPosition())

                {

                        //Move forward!

                        drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

                } else {

                        //If not in position, wait for it to be there...

                        drivetrain->ArcadeDrive(0.0, 0.0);

                        kicker->SetKickerMode(KICKER_MODE_ARM);

                }

        }



        //Run the kicker

        kicker->Act();

}

-Tanner

Ether

13-06-2010 18:18

Re: Arcade Drive Troubles in Autonomous

Save what you've got, then get rid of everything in autonomous except

drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

...and see if it drives properly.

If it does, then you've got a weird problem somewhere else in your code. Like for example, are you protecting kicker->Act(); from re-entering?

Edit: I just saw your other post. Uncontrolled re-entry could cause a stack overflow and crash your code.

Tanner

13-06-2010 18:40

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Ether (Post 966453)

If it does, then you've got a weird problem somewhere else in your code. Like for example, are you protecting kicker->Act(); from re-entering?

Edit: I just saw your other post. Uncontrolled re-entry could cause a stack overflow and crash your code.

Protecting kicker->Act(); from re-entering? Sorry, but what do you mean by that? I've never heard of that.

-Tanner

Radical Pi

13-06-2010 18:44

Re: Arcade Drive Troubles in Autonomous

re-entering is when a function is called again before it finishes being called the first time. The variables in your kicker object may not be in a clean state for the second call, causing a crash

Tanner

13-06-2010 18:54

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Radical Pi (Post 966455)

re-entering is when a function is called again before it finishes being called the first time. The variables in your kicker object may not be in a clean state for the second call, causing a crash

Ah. How would one prevent this?

I think though re-entering has more to do with the robot crashing than the robot not being able to drive straight from arcadeDrive(). Unless they're somehow weirdly related and the kicker is affecting the drivetrain.

-Tanner

Ether

13-06-2010 18:58

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Tanner (Post 966454)

Protecting kicker->Act(); from re-entering? Sorry, but what do you mean by that? I've never heard of that.

-Tanner

You are running AutonomousContinuous, which means the cRIO is repeatedly running your autonomous code as fast as it possibly can. You are calling the kicker->Act() method each time. I haven't seen the rest of your code; if there's another concurrent thread which also calls kicker->Act() it might cause a problem.

Removing everything except
drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);
and testing to see if that fixes the problem is a quick way to help pinpoint the problem.

Ether

13-06-2010 19:01

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Tanner (Post 966457)

Unless they're somehow weirdly related and the kicker is affecting the drivetrain.

That's why you should remove all the code except

drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

and see if it fixes the problem.

Tanner

13-06-2010 19:12

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Ether (Post 966459)

That's why you should remove all the code except
drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);
and see if it fixes the problem.

I'll have to see tomorrow as I'm done with the robot for today.

I'm not sure how I would rethink to fix this. How would I protect the function from reentry? A google search on the topic didn't bring up anything other than NASA links.

-Tanner

Ether

13-06-2010 19:21

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Tanner (Post 966462)

How would I protect the function from reentry? A google search on the topic didn't bring up anything other than NASA links.

It's pretty easy. Here's some pseudocode:

Code:

Declare a static boolean within the method, say "kicker_busy".



if kicker_busy exit;



kicker_busy=1;



// put your code here.  It's now protected from re-entry.



kicker_busy=0;



//return

But before you do that, please see what happens when you remove everything except
drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

Tanner

13-06-2010 19:23

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Ether (Post 966466)

It's pretty easy. Here's some pseudocode:

<CODE>

But before you do that, please see what happens when you remove everything except
drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);

Ah. That seems pretty simple. I was so over thinking it.

I'll take a look at that tomorrow and then get back.

Thanks for the help.

-Tanner

Pat Fairbank

13-06-2010 20:01

Re: Arcade Drive Troubles in Autonomous

I suspect that your problem is that your RobotDrive class is not set up properly for the way your robot is wired (one side is either not inverted (using RobotDrive::SetInvertedMotor()), or inverted when it shouldn't be).

It's probably just working in teleop mode by lucky coincidence, because your joystick setup looks strange - you're feeding what seems to be the twist axis (4) into the moveValue parameter of ArcadeDrive, and the Y-axis (2) into the rotateValue parameter.

I doubt the non-reentrancy of your kicker function is the issue, because non-reentrant functions only cause problems when they're called more than once at the same time (i.e. by different threads), and I'm pretty sure all the Periodic/Continuous methods in IterativeRobot execute in the same thread.

Tanner

13-06-2010 20:12

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Pat Fairbank (Post 966482)

I'm not sure how that would work, cause then wouldn't teleop not drive correctly at all? There's only one way a drivetrain will correctly work, yeah (unless the joystick values are strange)?

Quote:

Originally Posted by Pat Fairbank (Post 966482)

It's probably just working in teleop mode by lucky coincidence, because your joystick setup looks strange - you're feeding what seems to be the twist axis (4) into the moveValue parameter of ArcadeDrive, and the Y-axis (2) into the rotateValue parameter.

Well, I'm not using the kit joysticks. I'm using two XBox 360 controllers, so the numbers don't exactly correspond to the names in the WPI library.

-Tanner

Pat Fairbank

13-06-2010 20:18

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Tanner (Post 966484)

I'm using two XBox 360 controllers, so the numbers don't exactly correspond to the names in the WPI library.

Okay, that makes sense, then. If you haven't already, maybe you should check the outputs of those axes directly with printf statements to make sure they are doing what you think they are doing in terms of axis and polarity.

Ether

13-06-2010 20:32

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Pat Fairbank (Post 966482)

I'm pretty sure all the Periodic/Continuous methods in IterativeRobot execute in the same thread.

Good point.

Tanner

13-06-2010 20:34

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Pat Fairbank (Post 966485)

Yeah, I should do that. I kinda just took it directly from LabVIEW thinking that things would be the same, but you never really know. I'll write that down to check as well.

-Tanner

Tanner

15-06-2010 21:38

Re: Arcade Drive Troubles in Autonomous

Haven't been able to get to the office to test on the robot. Worked overtime today.

Yeah...

-Tanner

Tanner

16-06-2010 12:46

Re: Arcade Drive Troubles in Autonomous

Tested autonomous with just the drivetrain movement (i.e. - drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);, and it still turns.

Didn't have time to test anything else (I was on my lunch break), but I will this afternoon. We're doing nothing at work today so I should be able to get off early.

-Tanner

Ether

16-06-2010 14:01

Re: Arcade Drive Troubles in Autonomous

Quote:

Originally Posted by Tanner (Post 966814)

Tested autonomous with just the drivetrain movement (i.e. - drivetrain->ArcadeDrive(autonomousForwardPower, 0.0);, and it still turns.

Well it wasn't time wasted - you've eliminated an entire realm of possibilities and narrowed down the problem.

Try putting
drivetrain->ArcadeDrive(0.5, 0.0);
in TeleOp and see if it still turns there.

If so, maybe "0.0" doesn't mean "straight ahead".

Do a printf of the value you are feeding in when the 'bot is going straight ahead in TeleOp, and see if it is "0.0" or some other number.

~

Tanner

16-06-2010 15:44

Re: Arcade Drive Troubles in Autonomous

I think the arguments for RobotDrive::ArcadeDrive are backwards somehow. Cause when I do drivetrain->ArcadeDrive(0.0, autonomousForwardPower); the robot goes forward, but when I do drivetrain->ArcadeDrive(autonomousForwardPower, 0.0); the robot turns left.

So, I checked the joystick numbers and the inversion of the drivetrain motors - they were totally wacky. The joysticks for the ArcadeDrive function were backwards and the inversion was programmed in that format, hence the robot worked, but everything was backward. Heh.

Autonomous drives in the right direction now (or rather it turns in the right direction...). All is well.

What did we learn? Never program the drivetrain with joysticks first and then do the inversions. Figure out what those values are, determine what they should be (positive or negative) or use magic numbers (like 1 and 0), then figure out the inversions.

Glad that is figured out. Now to see if it still crashes...

Thanks all!

-Tanner

Edit: And it doesn't crash with the updates, yay!

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