Carnegie Mellon University
The
Pre- and post-contact policy decomposition for planar contact manipulation under uncertainty

Michael Koval, Nancy Pollard , and Siddhartha Srinivasa
International Journal of Robotics Research, August, 2015.


Download
  • Adobe portable document format (pdf) (1MB)
Copyright notice: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Abstract
We consider the problem of using real-time feedback from contact sensors to create closed-loop pushing actions. To do so, we formulate the problem as a partially observable Markov decision process (POMDP) with a transition model based on a physics simulator and a reward function that drives the robot towards a successful grasp. We demonstrate that it is intractable to solve the full POMDP with traditional techniques and introduce a novel decomposition of the policy into pre- and post-contact stages to reduce the computational complexity.

Our method uses an offline point-based solver on a variable-resolution discretization of the state space to solve for a post-contact policy as a pre-computation step. Then, at runtime, we use an A* search to compute a pre-contact trajectory. We prove that the value of the resulting policy is within a bound of the value of the optimal policy and give intuition about when it performs well. Additionally, we show the policy produced by our algorithm achieves a successful grasp more quickly and with higher probability than a baseline QMDP policy on two different objects in simulation. Finally, we validate our simulation results on a real robot using commercially available tactile sensors.

Keywords
Tactile sensing, planning under uncertainty, manipulation under uncertainty, non-prehensile manipulation

Notes
Sponsor: NASA Space Technology Research Fellowship, the National Science Foundation, and the Toyota Motor Corporation
Associated Center(s) / Consortia: Quality of Life Technology Center, National Robotics Engineering Center, and Center for the Foundations of Robotics
Associated Lab(s) / Group(s): Personal Robotics

Text Reference
Michael Koval, Nancy Pollard , and Siddhartha Srinivasa, "Pre- and post-contact policy decomposition for planar contact manipulation under uncertainty," International Journal of Robotics Research, August, 2015.

BibTeX Reference
@article{Koval_2015_7998,
   author = "Michael Koval and Nancy {Pollard } and Siddhartha Srinivasa",
   editor = "SAGE",
   title = "Pre- and post-contact policy decomposition for planar contact manipulation under uncertainty",
   journal = "International Journal of Robotics Research",
   month = "August",
   year = "2015",
}