Operating with Inaccurate Models by Integrating Control-Level Discrepancy Information into Planning

Typical robotic systems rely on models for planning. Therefore, the quality of the robot's behavior is heavily dependent on how accurately the model can predict the outcome of the robot's actions in the environment. A challenge, however, is that no model is perfect; moreover, we often do not know where discrepancies between the model's prediction and the actual outcome occur prior to observing executions in the real-world. One way to address this is to bias the planner away from these discrepancies by inflating the cost of states and actions where we previously observed the model to be inaccurate. Making such decisions about where and how to bias purely at the planning-level, however, neglects valuable information from the control-level, which gives a more fine-grained understanding of where and how the model went wrong during execution. Based on this observation, our key idea is to first infer a statistical model over discrepancies in the control-level's model. Then, we translate this model to the planning-level, where we use it to more informatively bias the planner away from states and actions where the model's predicted outcome is likely to be inaccurate. We demonstrate that our framework enables a robot to complete tasks, despite an inaccurate planning model, with greater efficiency than existing approaches. We do so through an experimental evaluation in simulation and real-robot experiments on NASA's Astrobee free-flyer.

I. Introduction

Robots rely on models to plan intelligent behaviors and complete tasks. Therefore, robots require models that accurately predict the outcome of actions in the real-world. Unfortunately, however, regardless of how we construct a model — from first-principles, through data-driven methods, etc. —it will never be accurate everywhere. An important challenge, therefore, is how to enable robots to complete tasks despite using inaccurate models.