Types of Velocities

There are many different types of velocities that the Follower reports, and it may be confusing to tell them apart.

This page walks through the different kinds of velocity types you can get from the Pedro Pathing API.

Scalar Tangential Velocity

You can get your robot's tangential velocity along the curve with the following method:

double tangentialVelocity = follower.tangentialVelocity();

Intuitively, this gives you the component of the robot's velocity that points along the curve. This is the velocity used to determine whether the Follower has finished following the path.

World-Frame Velocity

You can get your robot's world-frame velocity with the following method:

Velocity velocity = follower.velocity();

This returns an immutable object of type Velocity, which gives the robot's velocity in each axis of the absolute coordinate frame. For instance, the x-component of this velocity gives your robot's velocity in the x-axis, i.e. with the same coordinate system you used to define your poses and curves.

To extract the velocity along each axis from this object, you can use the following methods:

double xVelocity = fieldVelocity.vx;
double yVelocity = fieldVelocity.vy;
double omega = fieldVelocity.omega;

Here omega corresponds to the robot's angular velocity.

Body-Frame Twist

You can get your robot's body-frame velocity (referred to as a "twist") with the following method:

Twist twist = follower.twist();

This returns an immutable object of type Twist, which gives the robot's velocity in each axis of the robot's local frame. For instance, the x-component of this twist gives your robot's velocity in the forward direction, i.e. with the same coordinate system you used to define your odometry offsets. Reminder: positive x is forward, positive y is left for the robot

To extract the velocity along each axis from this object, you can use the following methods:

double forwardVelocity = twist.vx;
double strafeVelocity = twist.vy;
double omega = twist.omega;

Here omega corresponds to the robot's angular velocity.