Dr. Skaar conducts his research in the Automation and Robotics Laboratory at Fitzpatrick Hall of Engineering.
Current Research Topics
Automatically-Guided Wheelchair
Camera-Space Manipulation
"Point and Click" Camera-Space Manipulation
Additional research related links:
Camera-Space Manipulation
The potential of simple vision to expand the use and enhance the performance of multi-degree-of-freedom manipulators has been limited in practice due to problems that are associated with calibration and image analysis. The problems of calibration, including calibration of the relationship between the vector of manipulator joint coordinates with the position and orientation of the end-effector, and the relationship between the appearance of objects in the image plane with their physical or "world" position, are addressed with the method. Camera-space manipulation eliminates the reference to any particular world frame altogether, and uses a low-order nonlinear stochastic estimation model to estimate in a precise and ongoing way the direct relationship between the vector of joint coordinates and the position in each image plane of manipulated objects. Trajectory plans and objectives are formulated in each of a minimum of two image planes, and physical joint-trajectory plans are determined based on a least-squares resolution of participating camera-space objectives combined with current estimates as described above. Recent work which is being carried out for NASA/JPL entails the use of both wheels and on-board degrees of freedom to carry out remotely user-designated tasks. This approach has been implemented and now operates day and night at Smurfit Stone Container Corporation.
Point-and-Click Camera-Space Manipulation
Many tasks which require robotic dexterity can be described in terms of the action of an end member relative to designated points on a surface. Such tasks include welding, scrubbing, nondestructive flaw detection, etching, painting, and so on. The method of camera-space manipulation is applicable to each of these without new issues of image analysis with a combination of a graphical user interface for surface-location designation, a laser pointer mounted on a pan/tilt unit, and visually distinct cues moving with the robot-controlled tool. User direction of the robot to achieve such control occurs using the patented method of "Point and Click Camera-Space Manipulation." (US Patent 6,304,050; Oct. 2001).
Automatically-Guided WheelchairAn example of
a nonholonomic control system is a wheeled vehicle. Depending on the application,
autonomous control of such a vehicle may require high precision. Using wall
markings, the experiments combine visual observations from the vehicle with
integrals of the of the kinematic differential equations to determine optimal
estimates of the position and orientation of the vehicle, via an extended
Kalman filter. A special controller uses these estimates to enforce tracking
of a reference trajectory. Currently, this approach is being applied to an
automatically-guided wheelchair. This application permits a degree of autonomy
and mobility to certain categories of the disabled for whom direct steering
control is difficult or impossible. Successful testing at the Hines V.A. Research
Hospital with several severely disabled veterans has led to current commercialization
efforts sponsored by the V.A..
Gonzalez-Galvan, E.J., Pazos-Flores F., Skaar, S.B., Cardenas-Galindo, Al, "Camera Pan/Tilt to Eliminate the Workspace Size-Pixel-Resolution Tradeoff with Camera-Space Manipulation", Robotics and Computer-Integrated Manufacturing, 18(2) pp. 95-104, April 2002, Elsevier.
Seelinger, M., Yoder, J.-D., Baumgartner, E.T., Skaar, S.B., "High Precision Visual Control of Mobile Manipulators", Accepted for publication in IEEE Transactions on Robotics and Automation, 2002.
Gonzalez-Galvan, E.J., Skaar, S.B., Seelinger, M., "Efficient Camera-Space Target Disposition in a Matrix of Moments Structure using Camera-Space Manipulation", provisionally accepted for appearance in the International Journal of Robotics Research, 1999.
Yoder, J-D., Baumgartner, E. T., and Skaar, S. B., 1996, "Initial Results in the Development of a Guidance System for a Powered Wheelchair," IEEE Transactions on Rehabilitation Engineering, 4 (3): 143-151.
Recent BooksSkaar, S.B., and Ruoff, C.F. (editors), Teleoperation and Robotics in Space, Progress in Aeronautics and Astronautics Series, Vol. 161, AIAA: Washington, D.C., 1994.
Direct comments, questions, and corrections to amedept@nd.edu