soft copy for robonaut
DESCRIPTION
One of the most interesting things about space travel is human beings place themselves into amazing vehicles and travel into a completely hostile environment that is almost beyond imagination. However, the problem with human space exploration is that the human body is too fragile for the harsh conditions of space, like the temperature of space ranging from 248 degrees Fahrenheit (120 degrees Celsius) to -148 f(-100 c). There also isn’t the earth’s atmosphere to shield us from the sun’s radiation. In order to survive, astronauts must wear bulky spacesuits which are highly expensive each and are not practical for an emergency situation. For example, if the international space station (ISS) were struck by an object and needed to be repaired immediately. It takes an astronaut at least three hours to perform such repairs. NASA has recognized the frailty of our bodies and is new breed of astronauts to perform some of the more difficult tasks in space. These new space explorers won’t need space suits or oxygen to survive outside of spacecraft. They are the robot-astronauts or the Robonauts. In this paper the development of Robonauts, how they will assist humans in future missions in space and on earth, and hoe they are different from the other robotic devices is being discussed.TRANSCRIPT
PRESENTATION ON ROBONAUT
SUBMITTED TO: MAHAVEER INSTITUTE OF SCIENCE AND TECHNOLOGY
SUBMITTED BY:
A.PRADEEP eee DEPT
CONTENTS
1. ABSTRACT
2. INTRODUCTION
3. ROBONAUT CONTROL SYSTEM
ARCHITECTURE
4. EXTERNAL INTERFACE
5. COMPUTING ENVIRONMENT
6. PARTS OF A ROBONAUT
7. TELEPRESENCE
8. VISION
9. MATERIALS
11. CONCLUSION
12. REFERENCES
ABSTRACT
One of the most interesting things about space travel is human beings place themselves into
amazing vehicles and travel into a completely hostile environment that is almost beyond
imagination. However, the problem with human space exploration is that the human body is
too fragile for the harsh conditions of space, like the temperature of space ranging from 248
degrees Fahrenheit (120 degrees Celsius) to -148 f(-100 c). There also isn’t the earth’s
atmosphere to shield us from the sun’s radiation. In order to survive, astronauts must wear
bulky spacesuits which are highly expensive each and are not practical for an emergency
situation. For example, if the international space station (ISS) were struck by an object and
needed to be repaired immediately. It takes an astronaut at least three hours to perform such
repairs.
NASA has recognized the frailty of our bodies and is new breed of astronauts to perform
some of the more difficult tasks in space. These new space explorers won’t need space suits
or oxygen to survive outside of spacecraft. They are the robot-astronauts or the Robonauts. In
this paper the development of Robonauts, how they will assist humans in future missions in
space and on earth, and hoe they are different from the other robotic devices is being
discussed.
I NTRODUCTION
ROBONAUT CONTROL SYSTEM ARCHITECTURE
The Robonaut control system combines operator commands, force data and kinematic
algorithms with safety rules to provide real-time joint control for Robonaut. The Robonaut
control system architecture must respond to several interesting challenges. It must provide
safe, reliable control for 47+ degrees-of-freedom. It must be controllable via direct
teleoperation, shared control, and full autonomy. It must maintain performance in a harsh
thermal environment. It must execute at the required rate on reasonable computing hardware.
These challenges cannot be met by using only classical robot control methods. Advanced
control theory in the areas of grasping, force control, intelligent control, and shared control
must be developed to the point where the control is suitable for critical applications to fully
realize the capability of the Robonaut.
System sub-autonomies include task sequences, Cartesian control, vision, teleoperator
interface, joint control, and grasping among others. Higher level sub-autonomies make
decisions as to what services the lower level sub-autonomies need to provide to implement
the required tasks. The overall system design makes conflicts in requests for services either
impossible or allows for arbitration by system level autonomies. Each sub-autonomy handles
its own internal safety and decision making. If a failure occurs, a lower level sub-autonomy
an request a shutdown or reconfiguration from a higher level sub-autonomy or the main
system controller which will handle the system level actions required.
EXTERNAL INTERFACE
A recent augmentation to the control system is the ability to command Robonaut remotely.
Through this Application Programmer's Interface (API), every degree-of-freedom on the
Robonaut system is available to be controlled remotely. Opening Robonaut to the external
world sets the stage for growth opportunities, including ground control of a very remote
Robonaut. From within the Robonaut team, the human tracking software and two separate
force feedback controllers were developed and rapidly integrated through the API.
For external researchers looking to work with Robonaut, the API allows a pathway into
Robonaut without becoming intimately familiar with the internal workings of the system. The
API is also compatible with the Robonaut simulation. This will allow development under the
safety of simulation. Once the algorithms are working in simulation, they will be able to be
ported seamlessly to hardware.
COMPUTING ENVIRONMENT
The computing environment chosen for the Robonaut project includes several state-of-the-art
technologies. The PowerPC processor was chosen as the real-time computing platform for its
performance and its continued development for space applications. The computers and their
required I/O are connected via a VME backplane. The processors run the VxWorks real-time
operating system. This combination of flexible computing hardware and operating system
supports varied development activities.
The software for Robonaut is written in C and C++. Control Shell, a software development
environment for object oriented, real-time software development, is used extensively to aid in
the development process. Control Shell provides a graphical development environment which
enhances the understanding of the system and code reusability.
PARTS OF A ROBONAUT
HEAD
Robonaut's head is still a work in progress, but the existing system includes an
articulated neck that allows the teleoperator to point Robonaut's camera as eyes. The
head's two small color cameras deliver stereo vision to the
operator's helmet display, yielding a form of depth perception.
The inter-ocular spacing of the cameras is matched to typical
human eye spacing, with a fixed vergence at arm's reach.
The neck drives are commanded using a 6 axis Polhemus
sensor mounted on the teleoperator's helmet, and can track the
velocities of typical human neck motions. Like the arms, the
neck's endoskeleton is covered in a fabric skin, which is fitted into and under the
helmet.
The helmeted approach is unusual in the robotics world, where cameras are typically
mounted in exposed locations on pan-tilt-verge units. Robonaut's requirements for a
rugged design, working with Astronauts in cluttered environments drove the
development towards a better protection system, such as the helmets that humans
wear here on Earth. The helmet is made of an epoxy resin, "grown" using a stereo
lithography machine which protects Robonaut from collisions.
The neck joint designs share substantial commonality with the arm joints, and are
controlled with the same real time control system. Their kinematics is based on a pan
tilt serial chain, with the first rotation about Robonaut's spine, and then a pitch motion
about a lateral axis.
A new set of articulating eyes has been built for Robonaut. The pointing system
directs two pairs of eyes, independently verging them for tracking humans and
objects. Each pair includes a large camera with computer controlled zoom, focus and
iris adjustments, as well as a smaller camera to provide peripheral vision. The system
has been assembled, and integrated with the brainstem for pointing control and
calibration. The next step will be integration with the visual cortex, and then insertion
of the system into the robot's helmet, replacing the old cameras.
HANDS
Many ground breaking dexterous robot hands have been developed over the past two
decades. These devices make it possible for a robot manipulator to grasp and
manipulate objects that are not designed to be robotically compatible. While several
grippers have been designed for space use and some even tested in space, no
dexterous robotic hand has been flown in EVA conditions.
The Robonaut Hand is one of the first under
development for space EVA use and the
closest in size and capability to a suited
astronaut's hand.
Robonaut's hands will be able to fit into all the required places and operate EVA tools
like this tether hook. Joint travel for the wrist pitch and yaw is designed to meet or
exceed the human hand in a pressurized glove.
The hand and wrist parts are sized to reproduce the necessary strength to meet
maximum EVA crew requirements. EVA space compatibility separates the Robonaut
Hands from many others. All component materials meet out gassing restrictions to
prevent contamination that could interfere with other space systems.
Parts made of different materials are toleranced to perform acceptably under the extreme
temperature variations experienced in EVA conditions. Brushless motors are used to ensure
long life in a vacuum. All parts are
designed to use proven space lubricants.
Each Robonaut Hand has a total of fourteen degrees of freedom. It consists of a forearm
which houses the motors and drive electronics, a two degree of freedom wrist, and a five
finger, twelve degree of freedom hand. The forearm, which measures four inches in diameter
at its base and is approximately eight inches long, houses all fourteen motors, 12 separate
circuit boards, and all of the wiring for the hand.
The hand itself is broken down into two sections:
A dexterous work set which is used for manipulation, and a grasping set which allows the
hand to maintain a stable grasp while manipulating or actuating a given object. This is an
essential feature for tool use. The dexterous set consists of two 3 degree of freedom fingers
(pointer and index) and a 3 degree of freedom opposable thumb. The grasping set consists of
two, 1 degree of freedom fingers (ring and pinkie) and a palm degree of freedom. All of the
fingers are shock mounted into the palm.
ARMS
Robonaut's arms, shown in the
Figures, are human scale manipulators
designed to fit within the exterior
volume of an Astronaut's suit (the EMU). Beyond its volume and design objectives
are human equivalent strength, human scale reach, thermal endurance to match an 8
hour EVA, fine motion, high bandwidth dynamic response, redundancy, safety, and a
range of motion that exceeds that of a human limb.
The arm has a dense packaging of joints and avionics developed with the
mechatronics philosophy. The endoskeletal design of the arm, houses thermal vacuum
rated motors, harmonic drives, fail safe brakes and 16 sensors in each joint. Custom
lubricants, strain gages, encoders and absolute angular position sensors are being
developed in house to make the dense packaging possible for these advanced
actuators.
The Roll-Pitch-Roll-Pitch-Roll-Pitch-
Yaw kinematic tree is covered in a
series of synthetic fabric layers, forming
a skin that provides protection from
contact and extreme thermal variations
in the environment of space.
Two of these arm joints have undergone
early testing in a thermal vacuum
chamber at JSC, where they performed
well as the temperature was varied from -25C to 105C. The new lubricants developed
for making this possible are a major breakthrough in Harmonic Drive technology.
The two arms are mounted two a central junction, with a third limb, called the tail,
and a fourth called the neck. This junction of four segments is described in the web
page section labeled body.
BODY
Endoskeleton Torso and Backpack
The Robonaut torso consists of a structural aluminum endoskeleton covered by a
protective outer shell. The endoskeleton terminates in a mounting flange for each
robot limb, providing convenient locations for three six-axis load cells used to
measure external forces affecting the robot.
When the distal end of the tail is held fixed, it becomes a leg capable of repositioning
the body. In this configuration, the tail sensor measures external forces acting on the
arms, the head, and the outer shell. When contact does occur, all three load cells may
be used in concert to classify the collision as either internal or external and to estimate
the contact force and location.
Traditionally, unintended physical contact between a robotic manipulator and its
environment is treated as a failure and drastic measures are taken to limit the
consequences. A robot is typically shut down when the controller detects a collision
and then it waits helplessly for a human to resolve the problem. Humans, on the other
hand, are adept at managing contact forces and routinely use them to great advantage,
as when carrying bulky items.
Because Robonaut's manipulator workspaces overlap and because the robot will work
in cluttered environments, frequent contact is expected and must be tolerated, even
exploited through judicious use of the robot's various sensors. For added protection,
the body is covered with a custom-fitted fabric skin designed to contain electrical wire
harnesses while keeping foreign material out of the mechanical joints.
The torso section also features a subcutaneous layer of foam padding designed to
absorb impact energy while permitting contact forces to build up gradually. Future
enhancements to the skin may include a force-sensing array capable of resolving the
magnitude and location of an external force. The torso outer shell was produced in
sections by first laying up dry carbon fiber fabric on a female mold and then injecting
it with resin in a vacuum forming process.
The outer shell protects the robot in two ways. First, it hides fragile electronic
components and wire bundles which would otherwise present a serious entanglement
hazard. Second, it softens impact through a combination of a padded jacket and a
floating suspension. Much like the human ribcage, the outer shell hangs from the
backbone of the robot. In response to an external force, the shell deflects elastically
while gradually building up reaction force until the controller responds.
An orbital mobility platform.
In order to become a truly useful tool, Robonaut must achieve mobility. This goal is not
unrealistic, considering the pace of miniaturization and the selection of wireless technologies
available today. But making everything fit in a smaller, self-sustained package is only half the
battle. Depending on the environment, moving around may involve operating in harsh
conditions with poor lighting and limited fuel. EVA astronauts work in a microgravity
environment that presents special challenges unfamiliar to most people
Future Robonaut body development work will address these mobility issues by incorporating
the required capabilities and interfaces. The next generation backpack, for example, might
have a grapple fixture compatible with the Space Shuttle arm, enabling the two robots to team
up on spacewalks as shown in figure.
TELEPRESENCE
Robonaut uses several novel techniques for establishing remote control of its subsystems and
enabling the human operator to maintain situation awareness.
The goal of telepresence control is to provide an intuitive, unobtrusive, accurate and
low-cost method for tracking operator motions and communicating them to the
robotic system. Some of the component technologies used in Robonaut's telepresence
system is shown. They include Helmet
Mounted Displays (HMD), force and tactile
feedback gloves and posture trackers.
Telepresence requires that a human operator
control the actions of a remotely operated
robot. In the case of the Robonaut project, the
human operator must control forty-three
individual degrees of freedom. The use of
three axis hand controllers would present a
formidable task for the operator.
Because Robonaut is anthropomorphic, the logical method of control is one of a
master-slave relationship whereby the operator's motions are essentially mimicked by
the robot. The operator performs the arm, head and hand motions for the required
tasks and a master-slave control mechanism duplicates the same motions in the Robot.
Telepresence uses virtual reality display technology to visually immerse the operator
in the robot's workspace. This way the teleoperator feels as if he or she is in the place
of the robot. Visual feedback is provided by a stereo display helmet and includes live
video from Robonaut's head cameras.
The HMD provides a view into the robot's environment, facilitating intuitive
operation and natural interaction with the work site. To be an effective tool for the
robonaut project, the HMD must take into account image registration (stereo or bi-
ocular view), field-of-view (FOV), graphical overlay capabilities and speech
recognition capabilities.
Controlling Robonaut's highly dexterous fingers and hands is made possible by
mapping the motions of the teleoperator's fingers onto the hand and finger motions of
Robonaut. Finger tracking is accomplished through glove based finger pose sensors.
Bend sensitive materials are used to track the orientation of each of the fingers.
That information is used to command the action of Robonaut's fingers. Complex
manipulation tasks are then made as intuitive as performing the task with your own
hands.
Force sensors are built into Robonaut's hands. The forces imparted on Robonaut's
fingers can be displayed to the teleoperator by means of a mechanical exoskeleton
worn by the teleoperator. The Figure demonstrates how the finger forces measured by
Robonaut's force sensors can be used to convey haptic information back to the
teleoperator.
Arm, torso and head tracking is accomplished with the use of magnetic based position
and orientation trackers. Mapping the motions of the human appendages to the
motions of Robonaut's arms and head is accomplished similarly to the way the finger
tracking is performed.
The telepresence system will generate robot position commands through teleoperator
pose tracking. Future telepresence control will address new methods and algorithms
that will significantly improve safety and performance of teleoperated human-scaled
dexterous robots during in-space operations.
Developing dedicated software tools for real-time, camera based, human posture
tracking and, text and graphical advising capabilities will achieve this goal for robot
operators. These features will allow the natural and unencumbered control of
anthropomorphic robots, while minimizing training and maximizing robot
performance.
These new technologies have the potential to provide any telepresence interface with
real-time operator tracking and audio-visual task feedback. Operators of dexterous
space robots will take full advantage of the robots' high performance only if
teleoperation is made easy and safe.
VISION
The first vision function added to Robonaut is a stereo vision tracker. This tracker uses a
stream of stereo image pairs from Robonaut's head to distinguish foreground objects from the
background. Robonaut tracks the closest foreground object by panning its head to keep the
selected object centered in its field of view as the object moves; for example, it can track a
person walking around the laboratory. Each image is filtered using a sign of Laplacian-of-
Gaussian filter, a bandpass filter that emphasizes the edges in the image while smoothing out
small scale detail. Binary correlation is then used to find matching patches between the left
and right images of a stereo pair. 3-D world constraints are used to limit the volume over
which this matching is allowed to take place.
An initial target is acquired on the basis of a sparse set of stereo matches obtained by
searching in a stereo pair over a limited depth range centered at nominal 3-D location. If
more than one target is found, the closest one is used. When the next stereo pair is available,
Robonaut searches over the same depth range now centered on the location of the target
found in the previous stereo pair. This simple scheme causes Robonaut to switch to a new
target if a person walks in front of and close to the current target. However, if someone walks
in front of the current target but at some distance from it, he will be ignored since Robonaut
starts its search from the previous location of the target. Likewise, if the current target ducks
down out of the field of view, Robonaut will switch its tracking to the closest foreground
object. If necessary, the search range will be expanded until a foreground object is found.
These behaviors can be observed in this video of Robonaut tracking a person walking around
the laboratory.
MATERIALS
HEAD
Robonaut's helmet is formed in a rapid-prototyping process to reduce fabrication costs. Unit
A's helmet consists of a translucent, amber-colored resin that is hardened in a stereo
lithography process to build a three-dimensional object, one layer at a time. Unit B's helmet,
formed using a different rapid-prototyping process and subsequently painted gold, is built up
of sintered glass fibers and is opaque.
Hardened resin helmet Glass fiber helmet
CHASSIS
Robonaut's endoskeleton comprises hundreds of aluminum alloy parts machined to close
tolerances from various stock geometries. Due to their geometrical complexity, the forearms
and palms are cast and then post-machined to specified tolerances. Because of tight
volumetric constraints, stainless steel is used extensively in the hands and wrists. To reduce
complexity and fabrication costs, aluminum alloy and stainless steel sheet metal brackets are
used to support various avionics and electrical power components throughout the
body.Robonaut's torso section contains the system's CPU, a large electronic junction board,
distributed power converters, and many exposed wires and connectors. These delicate
components are protected by a black, rigid carbon fiber breastplate and backpack suspended
from the robot's endoskeleton.
COVERING
The robot's high-strength, gold-anodized aluminum alloy endoskeleton is covered with a
white fabric spacesuit designed to soften collisions while keeping foreign materials out of the
moving joints. The suit encloses all wire harnesses to prevent entanglement and presents an
attractive, uncluttered exterior reminiscent of the spacesuit used by astronauts, called the
External Mobility Unit (EMU).
In fact, Robonaut's spacesuit consists mainly of Orthofabric, the same fabric forming the
outermost layer of the EMU. It is a very flexible weave with high tensile strength, good
abrasion resistance and fire retardant properties.
CONCLUSION
Finally to conclude, robonauts do not actually replace humans but rather improve their
ability to operate through the small incisions. In programming these devices, considerable
effort is put into creating proper algorithms, accurate sensors, and improved user interfaces.
One of the main goals of Robonaut is matching task requirements with a robot system
configuration, synthesized with computational methods, interactive design and 3D
visualization. Developed as a program called Optimus, the software's main analysis modules
are kinematics, power flow (from electrical input into work and heat), thermal transient
endurance modeling, and deflection of the multi- armed system subject to loading on all
limbs. This software is then used to analyze specific tasks, with a spectrum of tasks then
being considered for overall system optimization.
Technology is becoming more and more integrated into the medical system. From imaging
systems to preprogrammed robots, each specialty is finding benefits from these advances.
REFERENCES
1. http://www.patentstorm.us/patents/6733329.html
2. http://en.wikipedia.org/wiki/Robonaut
3. http://www-robotics.jpl.nasa.gov/systems/system.cfm?System=4#urbie
4. JPL's Robotic website