CLAP: Clustering to Localize Across n Possibilities, A Simple, Robust Geometric Approach in the Presence of Symmetries

Abstract-- In this paper, we present our localization method called CLAP, Clustering to Localize Across n Possibilities, which helped us win the RoboCup 2024 adult-sized autonomous humanoid soccer competition. In addition, our robot had to deal with varying lighting conditions, dynamic feature occlusions, noise from high-impact stepping, and mistaken features from bystanders and neighboring fields. Therefore, we needed an accurate, and most importantly robust localization algorithm that would be the foundation for our path-planning and game-strategy algorithms. CLAP achieves these requirements by clustering estimated states of our robot from pairs of field features to localize its global position and orientation. Correct state estimates naturally cluster together, while incorrect estimates spread apart, making CLAP resilient to noise and incorrect inputs. CLAP is paired with a particle filter and an extended Kalman filter to improve consistency and smoothness. T ests of CLAP with other landmark-based localization methods showed similar accuracy. However, tests with increased false positive feature detection showed that CLAP outperformed other methods in terms of robustness with very little divergence and velocity jumps. Our localization performed well in competition, allowing our robot to shoot faraway goals and narrowly defend our goal. Every year, the Robocup Federation hosts a humanoid soccer competition in hopes of one day playing a live match of robots versus humans. To ensure a fair match, rules are put in place such that robots must be able to play autonomously, be of similar physiological proportions to a human, and only be equipped with sensors that have biological equivalents.