Learning to Select State Machines using Expert Advice on an Autonomous Robot

Hierarchical state machines have proven to be a powerful tool for controlling autonomous robots due to their flexibility and modularity. For most real robot implementations, however, it is often the case that the control hierarchy is hand-coded. As a result, the development process is often time intensive and error prone. In this paper, we explore the use of an experts learning approach, based on Auer and colleagues´ Exp3 (1995), to help overcome some of these limitations. In particular, we develop a modified learning algorithm, which we call rExp3, that exploits the structure provided by a control hierarchy by treating each state machine as an ´expert´. Our experiments validate the performance of rExp3 on a real robot performing a task, and demonstrate that rExp3 is able to quickly learn to select the best state machine expert to execute. Through our investigations in these environments, we identify a need for faster learning recovery when the relative performances of experts reorder, such as in response to a discrete environment change. We introduce a modified learning rule to improve the recovery rate in these situations and demonstrate through simulation experiments that rExp3 performs as well or better than Exp3 under such conditions.