Policy Learning with Hypothesis based Local Action Selection

For robots to be effective in human environments, they should be capable of successful task execution in unstructured environments. Of these, many task oriented manipulation behaviors executed by robots rely on model based grasping strategies and model based strategies require accurate object detection and pose estimation. Both these tasks are hard in human environments, since human environments are plagued by partial observability and unknown objects. Given these difficulties, it becomes crucial for a robot to be able to operate effectively under partial observability in unrecognized environments. Manipulation in such environments is also particularly hard, since the robot needs to reason about the dynamics of how various objects of unknown or only partially known shape interact with each other under contact. Modelling the dynamic process of a cluttered scene during manipulation is hard even if all object models and poses were known. It becomes even harder to reasonably develop a process or observation model, with only partial information about the object class or shape. To enable a robot to effectively operate in partially observable unknown environments we introduce a policy learning framework where action selection is cast as a probabilistic classification problem on hypothesis sets generated from observations of the environment. The action classifier operates online with a global stopping criterion for successful task completion. The example we consider is object search in clutter, where we assume having access to a visual object detector, that directly populates the hypothesis set given the current observation. Thereby we can avoid the temporal modelling of the process of searching through clutter. We demonstrate our algorithm on two manipulation based object search scenarios; a modified minesweeper simulation and a real world object search in clutter using a dual arm manipulation platform.

Authors

• Bharath Sankaran
• Jeannette Bohg
• Nathan Ratliff
• Stefan Schaal

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