DifferentialDrive

class wpilib.drive.DifferentialDrive(leftMotor: wpilib.interfaces._interfaces.SpeedController, rightMotor: wpilib.interfaces._interfaces.SpeedController)

Bases: wpilib.drive._drive.RobotDriveBase, wpiutil._wpiutil.Sendable

A class for driving differential drive/skid-steer drive platforms such as the Kit of Parts drive base, “tank drive”, or West Coast Drive.

These drive bases typically have drop-center / skid-steer with two or more wheels per side (e.g., 6WD or 8WD). This class takes a MotorController per side. For four and six motor drivetrains, construct and pass in MotorControllerGroup instances as follows.

Four motor drivetrain:

import wpilib.drive

class Robot(wpilib.TimedRobot):
    def robotInit(self):
        self.front_left = wpilib.PWMVictorSPX(1)
        self.rear_left = wpilib.PWMVictorSPX(2)
        self.left = wpilib.MotorControllerGroup(self.front_left, self.rear_left)

        self.front_right = wpilib.PWMVictorSPX(3)
        self.rear_right = wpilib.PWMVictorSPX(4)
        self.right = wpilib.MotorControllerGroup(self.front_right, self.rear_right)

        self.drive = wpilib.drive.DifferentialDrive(self.left, self.right)

Six motor drivetrain:

import wpilib.drive

class Robot(wpilib.TimedRobot):
    def robotInit(self):
        self.front_left = wpilib.PWMVictorSPX(1)
        self.mid_left = wpilib.PWMVictorSPX(2)
        self.rear_left = wpilib.PWMVictorSPX(3)
        self.left = wpilib.MotorControllerGroup(self.front_left, self.mid_left, self.rear_left)

        self.front_right = wpilib.PWMVictorSPX(4)
        self.mid_right = wpilib.PWMVictorSPX(5)
        self.rear_right = wpilib.PWMVictorSPX(6)
        self.right = wpilib.MotorControllerGroup(self.front_right, self.mid_right, self.rear_right)

        self.drive = wpilib.drive.DifferentialDrive(self.left, self.right)

A differential drive robot has left and right wheels separated by an arbitrary width.

Drive base diagram:

|_______|
| |   | |
  |   |
|_|___|_|
|       |

Each Drive() function provides different inverse kinematic relations for a differential drive robot. Motor outputs for the right side are negated, so motor direction inversion by the user is usually unnecessary.

This library uses the NED axes convention (North-East-Down as external reference in the world frame): http://www.nuclearprojects.com/ins/images/axis_big.png.

The positive X axis points ahead, the positive Y axis points to the right, and the positive Z axis points down. Rotations follow the right-hand rule, so clockwise rotation around the Z axis is positive.

Inputs smaller then 0.02 will be set to 0, and larger values will be scaled so that the full range is still used. This deadband value can be changed with SetDeadband().

RobotDrive porting guide:

  • tankDrive() is equivalent to RobotDrive.tankDrive if a deadband of 0 is used.

  • arcadeDrive() is equivalent to RobotDrive.arcadeDrive if a deadband of 0 is used and the the rotation input is inverted, e.g. arcadeDrive(y, -rotation, squareInputs=False)

  • curvatureDrive() is similar in concept to RobotDrive.drive with the addition of a quick turn mode. However, it is not designed to give exactly the same response.

Construct a DifferentialDrive.

To pass multiple motors per side, use a MotorControllerGroup. If a motor needs to be inverted, do so before passing it in.

class WheelSpeeds

Bases: pybind11_builtins.pybind11_object

Wheel speeds for a differential drive.

Uses normalized voltage [-1.0..1.0].

property left
property right
arcadeDrive(xSpeed: float, zRotation: float, squareInputs: bool = True) None

Arcade drive method for differential drive platform.

Note: Some drivers may prefer inverted rotation controls. This can be done by negating the value passed for rotation.

Parameters
  • xSpeed – The speed at which the robot should drive along the X axis [-1.0..1.0]. Forward is positive.

  • zRotation – The rotation rate of the robot around the Z axis [-1.0..1.0]. Clockwise is positive.

  • squareInputs – If set, decreases the input sensitivity at low speeds.

static arcadeDriveIK(xSpeed: float, zRotation: float, squareInputs: bool = True) wpilib.drive._drive.DifferentialDrive.WheelSpeeds

Arcade drive inverse kinematics for differential drive platform.

Note: Some drivers may prefer inverted rotation controls. This can be done by negating the value passed for rotation.

Parameters
  • xSpeed – The speed at which the robot should drive along the X axis [-1.0..1.0]. Forward is positive.

  • zRotation – The rotation rate of the robot around the Z axis [-1.0..1.0]. Clockwise is positive.

  • squareInputs – If set, decreases the input sensitivity at low speeds.

Returns

Wheel speeds [-1.0..1.0].

curvatureDrive(xSpeed: float, zRotation: float, allowTurnInPlace: bool) None

Curvature drive method for differential drive platform.

The rotation argument controls the curvature of the robot’s path rather than its rate of heading change. This makes the robot more controllable at high speeds.

Parameters
  • xSpeed – The robot’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • zRotation – The normalized curvature [-1.0..1.0]. Clockwise is positive.

  • allowTurnInPlace – If set, overrides constant-curvature turning for turn-in-place maneuvers. zRotation will control turning rate instead of curvature.

static curvatureDriveIK(xSpeed: float, zRotation: float, allowTurnInPlace: bool) wpilib.drive._drive.DifferentialDrive.WheelSpeeds

Curvature drive inverse kinematics for differential drive platform.

The rotation argument controls the curvature of the robot’s path rather than its rate of heading change. This makes the robot more controllable at high speeds.

Parameters
  • xSpeed – The robot’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • zRotation – The normalized curvature [-1.0..1.0]. Clockwise is positive.

  • allowTurnInPlace – If set, overrides constant-curvature turning for turn-in-place maneuvers. zRotation will control turning rate instead of curvature.

Returns

Wheel speeds [-1.0..1.0].

getDescription() str
initSendable(builder: wpiutil._wpiutil.SendableBuilder) None
stopMotor() None
tankDrive(leftSpeed: float, rightSpeed: float, squareInputs: bool = True) None

Tank drive method for differential drive platform.

Parameters
  • leftSpeed – The robot left side’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • rightSpeed – The robot right side’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • squareInputs – If set, decreases the input sensitivity at low speeds.

static tankDriveIK(leftSpeed: float, rightSpeed: float, squareInputs: bool = True) wpilib.drive._drive.DifferentialDrive.WheelSpeeds

Tank drive inverse kinematics for differential drive platform.

Parameters
  • leftSpeed – The robot left side’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • rightSpeed – The robot right side’s speed along the X axis [-1.0..1.0]. Forward is positive.

  • squareInputs – If set, decreases the input sensitivity at low speeds.

Returns

Wheel speeds [-1.0..1.0].