Holonomic Drivetrain

IMPORTANT

This page outlines how to use the mecanum drivetrain command to control your robot in TeleOp. Even though it has mecanum in the name, it works for x-drives as well.

INFO

Any holonomic drive can be controlled in one of two ways: robot centric or field centric.

Robot-centric assumes that each push of the joystick is in relation to the local position of the robot—this means that whenever the user pushes the drive stick forward, the robot will drive in the direction of its front-facing side.

Field-centric assumes that each push of the joystick is in relation to the global position of the robot—this means that whenever the user pushes the drive stick forward, the robot will move away from the driver no matter its orientation. This is done by rotating the direction of the joystick clockwise by an angle measurement equivalent to the global heading of the robot.

Usage

First, you need to create your motors. Let's create variables for their names:

val frontLeftName = "front_left"
val frontRightName = "front_right"
val backLeftName = "back_left"
val backRightName = "back_right"

Next, we'll create variables for the motors and an array of the motors:

lateinit var frontLeftMotor: MotorEx
lateinit var frontRightMotor: MotorEx
lateinit var backLeftMotor: MotorEx
lateinit var backRightMotor: MotorEx

lateinit var motors: Array<MotorEx>

Then, we'll create a variable for the imu. Only do this if you are using field centric driving.

lateinit var imu: IMU

Lastly, we'll create a variable for the command:

lateinit var driverControlled: Command

Now, in the onInit() function, we will initialize all our variables:

frontLeftMotor = MotorEx(frontLeftName)
backLeftMotor = MotorEx(backLeftName)
backRightMotor = MotorEx(backRightName)
frontRightMotor = MotorEx(frontRightName)

// Change your motor directions to suit your robot.
frontLeftMotor.direction = DcMotorSimple.Direction.REVERSE
backLeftMotor.direction = DcMotorSimple.Direction.REVERSE
frontRightMotor.direction = DcMotorSimple.Direction.FORWARD
backRightMotor.direction = DcMotorSimple.Direction.FORWARD

motors = arrayOf(frontLeftMotor, frontRightMotor, backLeftMotor, backRightMotor)

// Only include this if you are using field centric. If using, change your control hub orientation to suit your robot.
imu = hardwareMap.get(IMU::class.java, "imu")
imu.initialize(IMU.Parameters(RevHubOrientationOnRobot(
    RevHubOrientationOnRobot.LogoFacingDirection.UP,
    RevHubOrientationOnRobot.UsbFacingDirection.FORWARD)))
imu.resetYaw()

Lastly, in onStartButtonPressed(), we will create and schedule our command.

You can run it robot centric:

driverControlled = MecanumDriverControlled(motors, gamepadManager.gamepad1)
driverControlled()

Or field centric:

driverControlled = MecanumDriverControlled(motors, gamepadManager.gamepad1, false, imu)
driverControlled()

That's it! Now you are able to control your holonomic drivetrain using a gamepad.

NOTE

See the MecanumDriverControlled reference for more information.