MCL -> SLAM

x: pose m: map u: robot motions z: observations

The SLAM Problem Given: -Robot’s controls (u) -Observations of features (z) Produce: -Map of features (m) -Path of the robot (x)

Indoors Space Undersea Underground

Can’t map without a pose! Can’t localize without a map!

Given: -Robot’s controls (u) -Observations of features (z) Produce: -Map of features (m) -Path of the robot (x) Given: -Robot’s controls (u) -Observations of features (z) -Map of features (m) Produce: -Path of the robot (x)

8 Landmark 1Landmark 2Landmark M … x, y,  Landmark 1Landmark 2Landmark M … x, y,  Particle #1 Landmark 1Landmark 2Landmark M … x, y,  Particle #2 Particle N … So, what’s a particle?

So how do we represent a landmark? MCL Landmark’s location: known Landmark: SLAM Landmark’s location: estimated Landmark: covariance matrix

So how do we represent a landmark? MCL Landmark’s location: known Landmark: SLAM Landmark’s location: estimated Landmark: covariance matrix

How do we run this particle filter? =robot_motion obs=robot_observations foreach p in Particles p.weight=1 p.move( ) // Motion Model! foreach in obs if never seen before p.map.add_landmark( ) // Sensor Model! else p.map.update_landmark( ) // Sensor Model! p.weight=p.weight * p.update_weight( ) // Independence! resample()

13 FastSLAM – Action Update Particle #1 Particle #2 Particle #3 Landmark #1 Filter Landmark #2 Filter

14 FastSLAM – Sensor Update Particle #1 Particle #2 Particle #3 Landmark #1 Filter Landmark #2 Filter

15 FastSLAM – Sensor Update Particle #1 Particle #2 Particle #3 Weight = 0.8 Weight = 0.4 Weight = 0.1

Discussion Questions What happens to one landmark’s estimated location if another landmark is observed wrongly? What will happen if each landmark is seen exactly once in a trajectory? What happens if the robot should see a landmark, and doesn’t? (negative information) What happens if the robot misidentifies a landmark?

Discussion Questions What if your robot gets re-kidnapped? What will happen if your robot never moves? What happens if the robot should see a landmark, and doesn’t? (negative information) What happens if the robot misidentifies a landmark?