Adaptive rover behavior based on online empirical evaluation: Rover-terrain interaction and near-to-far learning

Due to the fundamental nature of all-terrain exploration, autonomous rovers are confronted with unknown environments. This is especially apparent regarding to soil interactions, as the nature of the soil is typically unknown. This work aims at establishing a framework from which the rover can learn from its interaction with the terrains encountered and shows the importance of such a method. We introduce a set of rover-terrain interaction (RTI) and remote data metrics which are expressed in different subspaces. In practice, the information characterizing the terrains, obtained from remote sensors (e.g. a camera) and local sensors (e.g. an Inertial Measurement Unit) is used to characterize the respective remote data and rover-terrain interaction (RTI) model. In each subspace, which can be described as a feature space encompassing either a remote data measurement or a RTI, similar features are grouped to form classes, and the probability distribution function over the features is learned for each one of those classes. Subsequently, data acquired on the same terrain is used to associate the corresponding models in each subspace and to build an inference model. Based on the remote sensor data measured, the RTI model is predicted using the inference model. This process corresponds to a near to far approach and provides the most probable RTI metrics of the terrain lying ahead of the rover. The predicted RTI metrics are then used to plan an optimal path with respect to the RTI model and therefore influence the rover trajectory. The CRAB rover is used in this work for the implementation and testing of the approach, which we call Rover Terrain Interactions Learned from Experiments (RTILE). This article presents RTILE, describes its implementation and concludes with results from field tests that validate the approach.