10-12-2012, 12:06 PM
A SEMINAR REPORT ON SPACE ROBOTICS
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ABSTRACT
Robot is a mechanical body with the brain of a computer. Integrating
the sensors and the actuators and with the help of the computers, we can use it to
perform the desired tasks. Robot can do hazardous jobs and can reach places where
it’s difficult for human beings to reach. Robots, which substitute the manned
activities in space, are known as space robots. The interest in this field led to the
development of new branch of technology called space robotics. Through this
paper, I intend to discuss about the applications, environmental condition, testing
and structure of space robots.
INTRODUCTION
Robot is a system with a mechanical body, using computer as its brain.
Integrating the sensors and actuators built into the mechanical body, the motions
are realised with the computer software to execute the desired task. Robots are
more flexible in terms of ability to perform new tasks or to carry out complex
sequence of motion than other categories of automated manufacturing equipment.
Today there is lot of interest in this field and a separate branch of technology
„robotics‟ has emerged. It is concerned with all problems of robot design,
development and applications. The technology to substitute or subsidise the
manned activities in space is called space robotics.
Various applications of space robots are the inspection of a defective
satellite, its repair, or the construction of a space station and supply goods to this
station and its retrieval etc. With the over lap of knowledge of kinematics,
dynamics and control and progress in fundamental technologies it is about to
become possible to design and develop the advanced robotics systems. And this
will throw open the doors to explore and experience the universe and bring
countless changes for the better in the ways we live.
SPACE SHUTTLE TILE REWATERPROOFING ROBOT
TESSELLATOR
Tessellator is a mobile manipulator system to service the space
shuttle.The method of rewaterproofing for space shuttle orbiters involves
repetitively injecting the extremely hazardous dimethyloxysilane (DMES) into
approximately 15000 bottom tile after each space flight. The field robotic center
at Carneige Mellon University has developed a mobile manipulating robot,
Tessellator for autonomous tile rewaterproofing. Its automatic process yields
tremendous benefit through increased productivity and safety.
In this project, a 2D-vehicle workspace covering and vehicle routing
problem has been formulated as the Travelling Workstation Problem (TWP). In
the TWP, a workstation is defined as a vehicle which occupies or serves a certain
area and it can travel; a workspace is referred to as a 2D actuation envelop of manipulator systems or sensory systems which are carried on the workstation; a
work area refers to a whole 2D working zone for a workstation.
ROBOTS TO REFUEL SATELLITES
The US department of defense is developing an orbital-refueling robot
that could expand the life span of American spy satellites many times over, new
scientists reported. The robotic refueler called an Autonomous Space Transporter
and Robotic Orbiter (ASTRO) could shuttle between orbiting fuel dumps and
satellites according to the Defense Advance Research Projects Agency. Therefore,
life of a satellite would no longer be limited to the amount of fuel with which it is
launched. Spy satellites carry a small amount of fuel, called hydrazine, which
enable them to change position to scan different parts of the globe or to go into a
higher orbit. Such maneuvering makes a satellites position difficult for an enemy to
predict. But, under the current system, when the fuel runs out, the satellite gradually
falls out of orbit and goes crashing to the earth. In the future the refueler could also
carry out repair works on faulty satellites, provided the have modular electronic
systems that can be fixed by slot in replacements.
VACUUM EFFECT AND THERMAL EFFECT
The vacuum in space can create heat transfer problems and mass loss of
the material through evaporation or sublimation. This is to be taken care by
proper selection of materials, lubricants etc., so as to meet the total mass loss
(TML) of <1% and collected volatile condensable matter (CVCM) of <0.1%. The
use of conventional lubricants in bearings is not possible in this environment.
The preferred lubricants are dry lubricants like bonded/sputtered/ion plated
molybdenum disulphide, lead, gold etc. Cold welding of molecularly similar
metal in contact with each other is a possibility, which is to be avoided by proper
selection of materials and dry lubricants. Some of the subsystem that cannot be
exposed to vacuum will need hermetical sealing. The thermal cycles and large
thermal variations will have to be taken care in design of robot elements. Low
temperature can lead to embrittlement of the material, weaken adhesive bonding
and increase friction in bearings. Large thermal gradients can lead to distortion in
structural elements and jamming of the mechanism. This calls for the proper
selection of the materials whose properties are acceptable in the above
temperature ranges and the selection of suitable protective coatings and
insulation to ensure that the temperature of the system is within allowable limits.
SPACE MODULAR MANIPULATORS
The unique thermal, vacuum and gravitational conditions of space drive
the robot design process towards solutions that are much different from the typical
laboratory robot. JSC's A&R Division is at the forefront of this design effort with
the prototypes being built for the Space Modular Manipulators (SMM) project. The
first SMM joint prototype has completed its thermal-mechanical-electrical design
phase, is now under construction in the JSC shops, and is scheduled for thermal-vac
chamber tests in FY94.
FY93 was the SMM project's first year, initiating the effort with a
MITRE Corporation review of the existing space manipulator design efforts (RMS
and FTS) and interaction with ongoing development teams (RANGER, JEM,
SPDM, STAR and SAT). Below this system level, custom component vendors for
motors, amplifiers, sensors and cables were investigated to capture the state-of-theart
in space robot design.
PERFORMANCE EVALUATION
As part of a verification procedure, specific performance tests were
carried out on a robot by Krypton under contract to ESA. The first was an accuracy
test in which the robot had to adapt a specified pose and aim at a point, key
characteristics for predictable offline programming. The second test evaluated the
repeatability with which the robot could reach a pose it had been taught to adopt.
This is essential for performing repetitive and routine tasks.