: Gripper Stereo and Assisted Teleoperation Stanford University December 13, 2010
Outline 1. Introduction 2. Hardware 3. Research 4. Packages 5. Conclusion
Introduction Hardware Research Packages Conclusion Motivation (1/2) Why use a gripper stereo sensor? It is easy to obtain good viewpoints. Object modeling Exploration I Data from multiple I See in and around perspectives. occluding objects. I Potentially less noise from I Low cost to exploration; distance. base does not move.
Motivation (2/2) Why use a gripper stereo sensor? There is no kinematic chain between sensor and end-effector. Uncalibrated URDF Head stereo and gripper stereo differ by >3cm Grasping based on gripper stereo works fine
Outline 1. Introduction 2. Hardware 3. Research 4. Packages 5. Conclusion
Small-Baseline Stereo (1/3) The off-the-shelf approach Custom mounting of Logitech C905 webcams. Rolling shutter, not synchronized Baseline = 25mm FOV 65 Minimum distance 8cm 640x480 resoution
Small-Baseline Stereo (2/3) The custom camera approach Custom stereo camera made from WGE100 cameras - functionally identical to PR2 head stereo. Synchronized, global (instantaneous) shutter. Baseline = 30mm Wide-angle, FOV 90 Minimum distance 10cm 640x480 resoution
Small-Baseline Stereo (3/3) How do they compare? Trade off between FOV and depth noise. Rolling shutter is fine for static scenes only. Narrower angle for autonomy, wider angle for teleop.
Introduction Hardware Research Packages Conclusion Hardware Calibration I Stereo camera calibration is natively supported in ROS. I pr2_calibration was modified to calibrate the gripper stereo frame location on the PR2 model.
Outline 1. Introduction 2. Hardware 3. Research 4. Packages 5. Conclusion
Grasp Adjustment - Overview Developed novel grasp adjustment for cluttered environments. Versatile, feature-based local point cloud grasp planner. Ideal for co-oriented sensor and gripper. Published in ISER 2010.
Grasp Adjustment - Evaluation Grasp quality is computed from features of local points. Distance to Centroid - Pulls gripper into object. Points in Collision - Penalizes collisions! Symmetry - Even distribution of points in vicinity of gripper. Normals - Point normals aligned with gripper frame axes.
Grasp Adjustment - Search Seed poses chosen from a grid centered at the input pose. Brief gradient search corrects unlucky seed poses. All poses are ranked according to cost. The best poses are selected for full optimization.
Introduction Hardware Research Packages Conclusion Assisted Teleoperation "So... am I helping the robot, or is it helping me? Developed joystick teleop of PR2 arms with grasp assistance. I Multiple control perspectives aid maneuvering. I Preset shortcuts for gripper orientations aid positioning. I Grasp adjustment is used to suggest grasp poses. I Rviz is used for viewing cameras and the virtual scene.
Outline 1. Introduction 2. Hardware 3. Research 4. Packages 5. Conclusion
pr2_gripper_stereo Package for managing and using gripper cameras. Launch files for calibration, stereo processing. URDF and meshes for modified hardware. Proof-of-concept nodes for point-cloud concatenation.
pr2_gripper_grasp_adjust Package for running grasp adjust server. Service uses GripperGraspAdjust service message. Could be expanded to general grasp planner. NOT dependent on gripper stereo.
pr2_remote_teleop Package enables full teleoperation of PR2. Head and base control is similar to pr2_teleop package. Grippers controlled using Cartesian J-inverse controller. Spacenav and ps3 controller supported by default. Config file supports button remapping on any joystick. Useful as local pr2_teleop replacement, or for remote operation.
What s Next? Object modeling using gripper stereo. Multiple cloud registration, surface smoothing. Integration with octomap framework. Human-in-the-loop robotics. Find strategies for human-robot multi-tasking. Robot: Grasp assist, collision avoidance, object tracking. Human: Object identification, edge-case recovery. > Teleoperation would greatly benefit from RVE / Rviz2.
Conclusion Gripper stereo provides valuable new viewpoint. Grasp adjustment works well on cluttered scenes. Remote operation is ready for added levels of autonomy.
The Final Slide Acknowledgments: Kaijen Hsiao, WG mentor Blaise Gassend, much camera help Kenneth Salisbury, PhD advisor Questions?