Mechanum with XBox Controller

[LFRobotics]

As of now our team has the XBox controller working using ArcadeDrive. But we now want to use mechanum wheels.. I have an okay understanding of how to do this with a joystick using x, y, and twist but how do I do it with an XBox controller. I don't even know how I would begin to structure the code.

ANY help would be GREATLY appreciated! THANKS!

[cyborgstx]

What template are you using? I could give you Iterative sample code.

[SuperBK]

Something like this:

float gyroAngle = 0.0; // we don't have a gyro connected
myRobot->MecanumDrive_Cartesian(stick.GetX(), stick.GetY(), stick.GetZ(), gyroAngle);

[afiolmahon]

I would just pick one of the sticks for your X and Y axis, and then a good replacement for the joystick twist would be using the analog triggers on the xbox controller. If you need Axis numbers, the input tab on the driver station has live controller readings and axis/button numbers.

[daniel12997]

Could you use one of the joysticks for forward backward and strafing and the other joystick for rotation.

[LFRobotics]

Im using command base but just any code examples will do - its easy to change over.

Yeah I was thinking about what daniel was saying - using one stick for x and y and the other for rotation - right now only one is being used.

[LFRobotics]

Okay here is what I was thinking - use L1 and R1 to turn slow and L2 and R2 to turn fast. Then use left joystick x to move left and right and left joystick y to move up and down - if I push up on the joystick AND move it right the robot should move diagonally - will this work and if so how would I implement it? I also want to be able to have a button - probably the up arrow and down arrow - that I can change the speed with.

THANKS for the help!

[Ethan_P]

for mechanum wheels, our team also uses a Xbox controller. We have the right joystick axis mapped to the linear movement of the robot, and the the left joystick x axis mapped to the rotation.
Here's a simplified version of our code:

//FLMotor = Front Left Motor
//FRMotor = Front Right Motor
//BLMotor = Back Left Motor
//BRMotor = Back Right Motor
//x = right joystick, x axis
//y = right joystick, y axis
//yaw = left joystick, x axis

FLMotor = y + x + yaw
FRMotor = y - x - yaw
BLMotor = y - x + yaw
BRMotor = y + x - yaw

The values will have to be limited, other-wise it will go beyond the accepted values (-1 to 1). Make sure the wheels are set up properly, and good luck!

[Ether]

Originally Posted by Ethan_P

The values will have to be limited, other-wise it will go beyond the accepted values (-1 to 1).

Make sure you do the limiting via normalization, not clipping.

[LFRobotics]

And how exactly do I do that?

[Ether]

Originally Posted by LFRobotics

And how exactly do I do that?

Search for the word "normalize" in these docs:

http://www.chiefdelphi.com/media/papers/download/2783

[jszipszky]

Originally Posted by Ethan_P

for mechanum wheels, our team also uses a Xbox controller. We have the right joystick axis mapped to the linear movement of the robot, and the the left joystick x axis mapped to the rotation.
Here's a simplified version of our code:

//FLMotor = Front Left Motor
//FRMotor = Front Right Motor
//BLMotor = Back Left Motor
//BRMotor = Back Right Motor
//x = right joystick, x axis
//y = right joystick, y axis
//yaw = left joystick, x axis

FLMotor = y + x + yaw
FRMotor = y - x - yaw
BLMotor = y - x + yaw
BRMotor = y + x - yaw

The values will have to be limited, other-wise it will go beyond the accepted values (-1 to 1). Make sure the wheels are set up properly, and good luck!

We do something very similar to this. I don't want to hijack this thread but how are you limiting the values? Right now in our rough code we have a mess of if-elses determining if the values are over 1. I imagine that there is a better way to do this?

[Ether]

Originally Posted by jszipszky

I don't want to hijack this thread but how are you limiting the values? Right now in our rough code we have a mess of if-elses determining if the values are over 1. I imagine that there is a better way to do this?

You don't need any "elses"

max=fabs(s1);
if (fabs(s2)>max) max=fabs(s2);
if (fabs(s3)>max) max=fabs(s3);
if (fabs(s4)>max) max=fabs(s4);
if (max>1) {s1/=max; s2/=max; s3/=max; s4/=max;}

[lynca]

Originally Posted by LFRobotics

But we now want to use mechanum wheels..

What size mechanum wheels and what gearbox ratio ?

[LFRobotics]

6in and we have not decided on the ratios yet - what is suggested - also should we purchase Heavy Duty or Standard Duty wheels?

Okay thanks Ethan I think im starting to get a picture of what I need to do