Research Interests
Computer Graphics, Computer Vision, Robotics, Sensor Networks:
Behavior-based computer animation, autonomous characters for computer animation
and games, autonomous agent architectures, cognitive vision
Teaching
Introduction to Visual Computing (CSC320): Summer 2006, Summer 2007
Computer Graphics (CSC 418): Fall 2004
As early as the 1980s, the National Aeronautics and Space Administration
realized the importance of on-orbit servicing for protecting their assets in
space.
The Need for Autonomy
Currently, on-orbit satellite servicing operations are carried out manually;
i.e., by an astronaut. However, manned missions are usually very costly and
there are human safety concerns. Furthermore, it is currently impracticable
to carry out manned on-orbit servicing missions for satellites in
geosynchronous equatorial orbit (GEO), as the space shuttle can not reach
them. Unmanned, tele-operated, ground-controlled missions are infeasible due
to communications delays, intermittence, and limited bandwidth between the
ground and the servicer. A viable alternative is to develop the capability
of autonomous on-orbit satellite servicing.
Autonomy entails that the on-board controller be capable of estimating and
tracking the pose (position and orientation) of the target satellite and
guiding the robotic manipulator as it 1) approaches the
satellite, 2) maneuvers itself to get into docking position, and 3) docks
with the satellite. The controller should also be able to handle anomalous
situations, which might arise during an AR&D operation, without jeopardizing
its own safety or that of the satellite.
Solution: Cognitive Controller (CoCo) Architecture
We proposed CoCo architecture that combines an ethologically-inspired,
reactive module with a deliberative unit to automatically capture a
non-cooperative, free-flying satellite using only computer vision.
Autonomous satellite capture controller developed in ROSA is the first of
its kind. Other satellite capture controllers typically require other
sensing modalities, such as GPS, radar, and laser range finders, and assume
a cooperative target satellite.
Besides, to the best of our knowledge, it is the only satellite capture
controller capable of deliberative activity to resolve anomalous situations.
Rosa is a large research effort and it uses target satellite pose estimation
and servo routines developed by other partners.
Success Stories
Rosa helped Boeing win the 12 million dollars Orbital Express contract!
Demonstrations
The demonstration system exhibited robust completion of goal in spite of
repeated induced 'failures'.
The following demos shows the CoCo-controlled robotic arm capturing a
free-flying satellite. The capture procedure is initiated by a single
high-level command from the ground station. Upon receiving the command, the
system initializes the long-range vision module to commence a visual search
procedure. Once the satellite is found, and its identity confirmed, the
systems guides the robotic arm to move closer to the satellite. The
performance of the long-range vision module deteriorates as the separation
between the robotic arm and the satellite becomes smaller; this is due to
the fact that the cameras are mounted on top of the end-effector. The
cognitive vision system, therefore, turns on the medium range vision module.
The long-range vision processing is turned off (to conserve the power
consumption) once the medium range system is fully initialized and is
"reliably" tracking the satellite. At this stage the robotic is arm tries to
match satellite's linear and angular velocities, a procedure known is
station keeping. Short-range vision processing is initiated, and a message
is sent to the ground station to turn off the satellite's attitude control
system. The robotic arm should not capture a satellite whose attitude
control system is functioning, as that might destroy the satellite, or the
robotic arm, or both. When the attitude control system is not active, the
satellite begins to drift; however, the robotic arm still follows it by
relying upon the short-range vision system. Upon receiving a confirmation
from the ground station that the attitude control system is off, the robotic
arm goes in for the kill.
When there is an error, such as a vision system failure, the reactive system
responds immediately and tries to increase its separation from the
satellite. In the absence any new perceptual information, the system relies
upon its time-aware and context-sensitive mental state. Meanwhile, the
deliberation module is using its knowledge base to 1) explain the error and
2) suggest a recovery.
In the videos (at top), the inlay shows the view from Autonomous Agent
Design & Simulation Testbed---a software framework for designing cognitive
vision systems. The wireframe represents the position of the satellite as
estimated by the robotic arm. Notice, the estimated position of the
satellite is more accurate when the satellite is closer to the robotic arm.
Furthermore, the estimated position is maintained when no new perceptual
information is available.
Stills
In the following figure despite a simulated vision system failure, the
servicer robot captures the satellite using vision by making use of its
cognitive abilities. On the right of each frame, we show the view from the
simulation environment that runs the controller code. The simulation
environment communicates with the physical robots over the network. Here,
the wireframe represents the position of the satellite as estimated by the
robotic arm. The 3D model of the satellite represents the actual position of
the satellite according to the sensors on the Fanuc robot arm. The gray
cylinder represents the position of the chaser robot end-effector according
to the telemetry information. Note that the estimated position is maintained
in the absence new perceptual information (Frame 3 and 4). A vision failure
was induced by shutting off the ambient light.
It is an on going project and the related publications are available here.
References
[1] D. Terzopoulos, “Perceptive agents and systems in virtual reality,” in Proc. 10th ACM Symposium on Virtual Reality Software and Technology, (Osaka, Japan), pp.1–3, Oct. 2003.
[2] W. Shao and D.Terzopoulos, “Autonomous pedestrians,” in Proc. ACMSIGGRAPH/Eurographics Symposium on Computer Animation, (LosAngeles, CA), pp. 19–28, July 2005.