Localization

Knowing where the robot is on the field, with goBILDA's Pinpoint and two odometry pods.

The localizer

A localizer knows where the robot is: its pose, where its center is on the field and which way it faces, and its velocity. Create it first on the robot, so it updates before anything that drives by it:

class MyRobot(host: RobotHost) : Robot(host) {
    val localizer = PinpointLocalizer(this)
    val drive = MecanumDrive(this)
}

Every loop, localizer.pose is where the robot is, as a Pose with x, y and heading in field coordinates (see Units and geometry). Setting it tells the localizer where the robot is, like at the start of autonomous:

robot.localizer.pose = Field2026.tile("A1BL").withHeading(0.degrees)

The pose carries over from one opmode to the next, while the robot app runs: TeleOp starts where autonomous ended, unless it sets the pose itself. After the app restarts, the pose starts at zero.

The pose is graphed as x cm, y cm and heading deg on the robot’s graphs page.

goBILDA’s Pinpoint

PinpointLocalizer uses goBILDA’s Pinpoint odometry computer with two odometry pods, one measuring forward motion and one sideways. The Pinpoint is named pinpoint in the robot configuration. It is read on a thread of its own every localizer.readInterval (15 ms), so the loop never waits for it.

INIT calibrates the Pinpoint’s gyro, which takes a quarter second with the robot standing still. Until then, and while the Pinpoint reports a problem, like a pod not plugged in, the pose stays where it was and the Driver Station shows the problem.

Setting it up

1. Where the pods are, measured from the robot’s center, with goBILDA’s signs. Both are required:

   # The forward pod's distance left of the center; negative when it is right of it
   localizer.forwardPodLeft = -3.2cm
   # The strafe pod's distance forward of the center; negative when it is behind it
   localizer.strafePodForward = -0.9cm
   

2. Which pods: localizer.pods = FOUR_BAR (the default) or SWINGARM, goBILDA’s two kinds. For other pods, localizer.ticksPerMm sets their resolution instead.
3. Which way they count: start an opmode that shows the pose, like the Quickstart’s Driving, and push the robot by hand. x should grow when it moves forward, and y when it moves to its left. A pod counting the wrong way gets localizer.forwardPodDirection = REVERSED or localizer.strafePodDirection = REVERSED.
4. The gyro, for the best accuracy: turn the robot ten full turns by hand and look at the heading. If it reads a bit more or less than the turns made, set localizer.yawScalar to the old value times the real turns over the turns read; the Pinpoint’s own is around 1.002.

These settings can be changed on the robot’s settings page while the robot runs, and the Pinpoint takes them right away.

Field-centric driving

Field-centric TeleOp drives by the localizer’s heading: see Drivetrains.

Localizers of your own

A localizer is a part of the robot that extends Localizer, with a pose that can be read and set, and a velocity. To carry the pose over between opmodes, it starts from Localizer.lastPose in init() and saves its pose there in stop().