Mixed-Type Query Selection for Robotic Scientific Data Collection

We propose combining preference and rating query types into a mixed-type query selection to learn reward functions for robotic decision making to improve scientific data collection. Mixed-type query selection allows the scientist operating a robot to specify the robot's tradeoffs and goals in terms of both rating, giving a score to one robot plan, and preferences, selecting a preferred plan to another plan. While previous methods have used active learning to allow the user to specify tradeoffs between objectives using rating and preferences individually, our proposed method considers using multiple query types. We assume a user responds to these queries with some noise on their true preferences. Online estimation of error model parameters is difficult; therefore, we show results with both a tuned known error model and a heuristic mixed-type query selection method. When the error model is known, we show performance increases using our mixed-type query selection versus using only ratings or only preferences. In the more realistic case with an unknown error model, we show our heuristic performs better than the worst case single query type in all cases we tested.