Introduction Hardware Research Packages Conclusion

Intern Presentation:Gripper Stereo and Assisted Teleoperation

Adam LeeperStanford University

December 13, 2010

Introduction Hardware Research Packages Conclusion

Outline

1. Introduction

2. Hardware

3. Research

4. Packages

5. Conclusion

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Motivation (1/2)Why use a gripper stereo sensor?

It is easy to obtain good viewpoints.

Object modelingI Data from multiple

perspectives.I Potentially less noise from

distance.

ExplorationI See in and around

occluding objects.I Low cost to exploration;

base does not move.Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Motivation (2/2)Why use a gripper stereo sensor?

There is no kinematic chain between sensor and end-effector.

I Uncalibrated URDFI Head stereo and gripper

stereo differ by >3cm

I Grasping based ongripper stereo works fine

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Outline

1. Introduction

2. Hardware

3. Research

4. Packages

5. Conclusion

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Small-Baseline Stereo (1/3)The off-the-shelf approach

Custom mounting of Logitech C905 webcams.

I Rolling shutter, notsynchronized

I Baseline = 25mm

I FOV 65◦

I Minimum distance 8cm

I 640x480 resoution

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Small-Baseline Stereo (2/3)The custom camera approach

Custom stereo camera made from WGE100 cameras -functionally identical to PR2 head stereo.

I Synchronized, global(instantaneous) shutter.

I Baseline = 30mm

I Wide-angle, FOV 90◦

I Minimum distance 10cm

I 640x480 resoution

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Small-Baseline Stereo (3/3)How do they compare?

I Trade off between FOV and depth noise.I Rolling shutter is fine for static scenes only.I Narrower angle for autonomy, wider angle for teleop.

Intern PresentationAdam Leeper

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.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Outline

1. Introduction

2. Hardware

3. Research

4. Packages

5. Conclusion

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Grasp Adjustment - Overview

Developed novel grasp adjustment for cluttered environments.I Versatile, feature-based local point cloud grasp planner.I Ideal for co-oriented sensor and gripper.I Published in ISER 2010.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Grasp Adjustment - Evaluation

Grasp quality is computed from features of local points.I Distance to Centroid - Pulls gripper into object.I Points in Collision - Penalizes collisions!I Symmetry - Even distribution of points in vicinity of gripper.I Normals - Point normals aligned with gripper frame axes.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Grasp Adjustment - Search

I Seed poses chosen from a grid centered at the input pose.I Brief gradient search corrects unlucky seed poses.I All poses are ranked according to cost.I The best poses are selected for full optimization.

Intern PresentationAdam Leeper

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.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Outline

1. Introduction

2. Hardware

3. Research

4. Packages

5. Conclusion

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

pr2_gripper_stereo

Package for managing and using gripper cameras.I Launch files for calibration, stereo processing.I URDF and meshes for modified hardware.I Proof-of-concept nodes for point-cloud concatenation.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

pr2_gripper_grasp_adjust

Package for running grasp adjust server.I Service uses GripperGraspAdjust service message.I Could be expanded to general grasp planner.I NOT dependent on gripper stereo.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

pr2_remote_teleop

Package enables full teleoperation of PR2.I Head and base control is similar to pr2_teleop package.I Grippers controlled using Cartesian J-inverse controller.I Spacenav and ps3 controller supported by default.I Config file supports button remapping on any joystick.I Useful as local pr2_teleop replacement, or for remote

operation.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

What’s Next?

I Object modeling using gripper stereo.I Multiple cloud registration, surface smoothing.I Integration with octomap framework.

I Human-in-the-loop robotics.I Find strategies for human-robot multi-tasking.I Robot: Grasp assist, collision avoidance, object tracking.I Human: Object identification, edge-case recovery.

–> Teleoperation would greatly benefit from RVE / Rviz2.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

Conclusion

I Gripper stereo provides valuable new viewpoint.I Grasp adjustment works well on cluttered scenes.I Remote operation is ready for added levels of autonomy.

Intern PresentationAdam Leeper

Introduction Hardware Research Packages Conclusion

The Final Slide

Acknowledgments:I Kaijen Hsiao, WG mentorI Blaise Gassend, much camera helpI Kenneth Salisbury, PhD advisor

Questions?

Intern PresentationAdam Leeper