A Framework for Spatial map Generation using Acoustic Echoes for Robotic Platforms

In this work, we present a framework for constructing a spatial map of an indoor environment using the concept of echolocation. More specifically, we propose a non-linear least squares (NLS) estimator which is combined with a spatial filtering technique, e.g., beamforming, to estimate both the time-of-arrival (TOA) and direction-of-arrival (DOA) of the acoustic echoes. The proposed framework is complemented with an echo detector to classify a spurious estimate and an acoustic reflector, i.e., a wall. Based on these estimators, we then propose two algorithms that can complement existing range sensors and aid a robotic platform in acoustic reflector localization and mapping: a singlechannel localization and mapping (ScLAM) and a multi-channel localization and mapping (McLAM). Compared to commonly used sensors, e.g., lidar and cameras, our proposed method can detect transparent surfaces that are typically found in an office environment. To test our algorithms, a proof-of-concept robotic platform was built. According to our evaluation, both qualitative and quantitative experiments reveal that the proposed methods can detect an acoustic reflector up to a distance of 1.5 m at a signal-to-diffuse-noise ratio (SDNR) of 0 dB in a simulated environment and 10 dB in a real environment with an accuracy of 80 %.