# Differential Drive Kinematics

The `DifferentialDriveKinematics` class is a useful tool that converts between a `ChassisSpeeds` object and a `DifferentialDriveWheelSpeeds` object, which contains velocities for the left and right sides of a differential drive robot.

## Constructing the Kinematics Object

The `DifferentialDriveKinematics` object accepts one constructor argument, which is the trackwidth of the robot. This represents the distance between the two sets of wheels on a differential drive.

**Note**: The trackwidth must be in meters.

## Converting Chassis Speeds to Wheel Speeds

The `toWheelSpeeds(ChassisSpeeds speeds)` method should be used to convert a `ChassisSpeeds` object to a `DifferentialDriveWheelSpeeds` object. This is useful in situations where you have to convert a linear velocity (`vx`) and an angular velocity (`omega`) to left and right wheel velocities.

```java
// Creating my kinematics object: track width of 15 inches
DifferentialDriveKinematics kinematics =
  new DifferentialDriveKinematics(15.0 / 254.0);

// Example chassis speeds: 2 meters per second linear velocity,
// 1 radian per second angular velocity.
ChassisSpeeds chassisSpeeds = new ChassisSpeeds(2.0, 0, 1.0);

// Convert to wheel speeds
DifferentialDriveWheelSpeeds wheelSpeeds =
  kinematics.toWheelSpeeds(chassisSpeeds);

// Left velocity
double leftVelocity = wheelSpeeds.leftMetersPerSecond;

// Right velocity
double rightVelocity = wheelSpeeds.rightMetersPerSecond;
```

## Converting Wheel Speeds to Chassis Speeds

One can also use the kinematics object to convert individual wheel speeds (left and right) to a singular `ChassisSpeeds` object. The `toChassisSpeeds(DifferentialDriveWheelSpeeds speeds)` method should be used to achieve this.

```java
// Creating my kinematics object: track width of 15 inches
DifferentialDriveKinematics kinematics =
  new DifferentialDriveKinematics(15.0 / 254.0);

// Example differential drive wheel speeds: 2 meters per second
// for the left side, 3 meters per second for the right side.
DifferentialDriveWheelSpeeds wheelSpeeds =
  new DifferentialDriveWheelSpeeds(2.0, 3.0);

// Convert to chassis speeds.
ChassisSpeeds chassisSpeeds = kinematics.toChassisSpeeds(wheelSpeeds);

// Linear velocity
double linearVelocity = chassisSpeeds.vxMetersPerSecond;

// Angular velocity
double angularVelocity = chassisSpeeds.omegaRadiansPerSecond;
```


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