What if a particle hit the wall in a scenario of a particle filter?

Question

Now I am trying to implement a particle filter. I am given a wall-mounted map, and I try to localize a robot in this map. Based on particle filter method, I initialize 1000 random particles, and in each step, I move these 1000 particles according to a certain movement instruction, i.e. an angle-odometry pair. After a move, I calculate the likelihood of the measurements compared to the sensed distance to the wall, and then resample the particles based on their likelihoods. I think this is the basic process for particle filter. What confuses me now is that how should I deal with the situations where some of the particles hit the wall while they are forwarding?

Answer 1

I think it is too late for you. However, it may help other people. Particle filter is a probabilistic approach, where particles can be sampled everywhere based on motion and prior distributions.

In your case, you can sample on the wall without any worry. Afterwards, the likelihood process will return a very low probability for that particle and it will be automatically resampled to another one with higher probability.