Tank Drive is backwards

[roknjohn]

Ok, I have a strange issue that makes me think that my joysticks Y axies are 'inverted'. Here's the deal, I'm driving with code like this:

m_robotDrive->TankDrive(LeftJoystick, RightJoystick);

I know that my left and right joysticks are defined correctly because the buttons of each control the desired actions. However, the drive train output isn't correct.

When I press forward on the left joystick, the left hand jaguar leds turn RED and the left motors run backwards. Similarly, when I move the right joystick forward, the right side motors run backwards and the leds are again RED. Moving the joysticks backward, cause the respective motors to run forward and the jaguar LEDs turn GREEN.

Now, obviously I could rewire the motors to get the robot to travel in the correct direction. But shouldn't the LEDs be GREEN for FORWARD and RED for REVERSE?

[Alan Anderson]

The Y axis value for a standard joystick is indeed "inverted" from what most non-pilots would expect. Forward is negative.

[whatabouteve]

the colors mean nothing. it basically means the flow of electricity.
you shouldn't judge the movement of the robot by the colors.
i would change the power to the motors that way when u run autonomous, you have code like...
myRobot.Drive(1.0,1.0);//for forward
instead of
myRobot.Drive(1.0,-1.0);// for forward

this makes it easier from a coding standpoint

[byteit101]

Originally Posted by whatabouteve

the colors mean nothing. it basically means the flow of electricity.
you shouldn't judge the movement of the robot by the colors.
i would change the power to the motors that way when u run autonomous, you have code like...
myRobot.Drive(1.0,1.0);//for forward
instead of
myRobot.Drive(1.0,-1.0);// for forward

this makes it easier from a coding standpoint

you are using Drive, not TankDrive, that example is doing donuts at full speed! I think you meant
myRobot.TankDrive(1.0,1.0);//for forward
instead of
myRobot.TankDrive(-1.0,-1.0);// for forward

[roknjohn]

Originally Posted by Alan Anderson

The Y axis value for a standard joystick is indeed "inverted" from what most non-pilots would expect. Forward is negative.

Actually, I am a pilot (instrument rated, too). Now as soon as we get our robot flying, the controls would make sense.

But obivously, we want our drivers to push the stick (yoke) forward to drive the robot forward. So, full forward on the stick is -1.0 on the Y-axis? OK, then robotDrive.SetLeftRightMotorSpeeds(-1.0, -1.0) is supposed to drive the robot forward?

It just seems counter intuitive to me, but I've recently rejoined the team after a two year absence - so my thinking may be a bit "old school".

[roknjohn]

Originally Posted by whatabouteve

the colors mean nothing. it basically means the flow of electricity.
you shouldn't judge the movement of the robot by the colors.
i would change the power to the motors that way when u run autonomous, you have code like...
myRobot.Drive(1.0,1.0);//for forward
instead of
myRobot.Drive(1.0,-1.0);// for forward

this makes it easier from a coding standpoint

If memory serves me correctly, on the spikes and victors, the LEDs glowed green for normal polarity and red for reversed polarity. As such, we've always wired our motors and control logic to match. It just made things simpler to troubleshoot, code, etc.

So, please correct me if I'm wrong.. If we used the RobotDrive class, we have to think of "forward" as the "negative" direction? Sounds just like the economony?

[roknjohn]

I think I'm going to try something like this later today:

 
myRobot.SetInvertedMotor(myRobot.kFrontLeftMotor, true);
myRobot.SetInvertedMotor(myRobot.kRearLeftMotor, true);
myRobot.SetInvertedMotor(myRobot.kFrontRightMotor, true);
myRobot.SetInvertedMotor(myRobot.kRearRightMotor, true);

[pafwl]

The invert is the answer. Forget about the colors. If you add 1 gear the direction is reversed. Add 2 reversed again.

The Joystick is -1 for full forward. It does not make sense except at a binary level reverse has (-1) more bits on than forward.

[whatabouteve]

here is exactly what i did.
Joystick leftstick;
Joystick rightstick;

Victor *left;
Victor *right;

left = new Victor(4,1);
right = new Victor(4,2);


float leftdrive = leftstick.Get();//do the same with the right and you can change the joystick values to make say halfspeed by dividing by 2

left->Set(leftdrive);

[nathanww]

You can do it either by telling RobotDrive to "invert" the motors, or using whatabouteve's example. I personally prefer the latter because it allows your program to very easily hook into your drive code(i.e.you don't have to re-do your ramping system for when the robot is running on camera tracking)

[Al3+]

Couldn't you also do the following:

drive = new RobotDrive(1, 2);

float leftSpeed = -leftStick.Get();
float rightSpeed = -rightStick.Get();

drive->TankDrive(leftSpeed, rightSpeed);

That's similar to what I've done at the moment. It's not as "proper" as SetInvertedMotor, but it appears to work.

[jblay]

I would just go with taking the joysticks and flipping them backwards

[cmh0114]

You could always reverse the wiring on your bot so that it matches up with the joysticks. That would probably be the easiest solution and the best if you're really short on time. But if you have time before your next competition and can edit your code, multiply the values of the y-axis of the joysticks by -1 whenever you input them. That should fix your problem without adding too much extra code.

[Fletch1373]

Originally Posted by roknjohn

Ok, I have a strange issue that makes me think that my joysticks Y axies are 'inverted'. Here's the deal, I'm driving with code like this:

m_robotDrive->TankDrive(LeftJoystick, RightJoystick);

I know that my left and right joysticks are defined correctly because the buttons of each control the desired actions. However, the drive train output isn't correct.

When I press forward on the left joystick, the left hand jaguar leds turn RED and the left motors run backwards. Similarly, when I move the right joystick forward, the right side motors run backwards and the leds are again RED. Moving the joysticks backward, cause the respective motors to run forward and the jaguar LEDs turn GREEN.

Now, obviously I could rewire the motors to get the robot to travel in the correct direction. But shouldn't the LEDs be GREEN for FORWARD and RED for REVERSE?

I believe that the Jaguars' LED doesn't turn green... but anyone feel free to correct me

[Alexa Stott]

Originally Posted by cmh0114

You could always reverse the wiring on your bot so that it matches up with the joysticks. That would probably be the easiest solution and the best if you're really short on time. But if you have time before your next competition and can edit your code, multiply the values of the y-axis of the joysticks by -1 whenever you input them. That should fix your problem without adding too much extra code.

Yup. Just reversing the wires on your bot will solve this problem quickly. Just remember that in case you need to change a motor or speed controller out.