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