Abstract
Robot is a mechanical body system that uses a machine as its brain. Integrating the sensors and actuators incorporated into the mechanical body; the motions are carried out with the computer software to execute the necessary function. Robots are way more flexible in terms of their ability to perform new tasks or to perform complete sequences of motion than other categories of automated manufacturing equipment. It is concerned with all problems of robot design, development, and applications. The technology to substitute or subside the manned activities in space is called space robotics. Various uses of space robots are the inspection of a faulty satellite, its repair or the construction of a space station and the supply of goods to that station and its retrieval. With the overlap of knowledge of kinematics, dynamics and control and the development of fundamental technology, advanced robotics systems are about to be designed and built. 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.
1. Introduction
Robotic systems have begun the era of space exploration with a series of spacecraft including Mariner, Ranger, Surveyor and Lunakhod. Robotics enables current missions on planetary surfaces in orbit and deep space, and is essential to all future exploration and operation of space. Assessing the current technological state-of – the-art and forecasting near-term technological advances is critical for mission planning and directing the development of the necessary technology.
Space robotics is the production of general-purpose machines capable of surviving the rigors of the space environment and performing exploration, assembly, building, repair, servicing or other tasks that may or may not have been fully understood at the time of the design of the robot.
Humans monitor space robots from either the “local” or “remote” control console. Space robots are typically designed to perform multiple tasks, including unexpected tasks, within a wide range of competencies (e.g. deployment of payloads, retrieval or inspection; planetary exploration).
Space robots are critical to our overall ability to operate in space because they can perform tasks less expensively or on an accelerated schedule, with less risk and sometimes with improved performance over humans performing the same tasks. They operate for a long period of time, often “sleep” for a long time before their operational mission begins. These can be sent to conditions that are so dangerous that people would not be allowed to go.
Missions to distant destinations such as Titan (a moon of Saturn thought to have liquid methane lakes or rivers) actually require a substantial fraction of human life during transit from Earth to the destination. Access to space is costly, meaning that, for some jobs robots that are smaller than humans and need much less infrastructure (e.g. life support) make them very attractive to a wide range of missions.[1]
2. Issues faced in space robotics
There are four key issues in Space Robotics:
Mobility: moving quickly and accurately between two points without colliding with another robot, astronaut or any other object.
Manipulation: to handle worksite elements safely, quickly, and accurately without contacting any other objects or using excessive forces.
Time Delay: allowing a distant human to effectively command the robot to do useful work
Extreme Environments: operating despite extreme heat or cold, ionizing radiation, hard vacuum, corrosive atmospheres, fine dust, etc.
Time delay is a particular challenge for manipulation in space robotics. Industries that regularly use teleoperation, like the nuclear industry, generally use “master-slave” teleoperators that mimic at the “slave” arm any motion of the “master” arm as maneuvered by the human. This approach only works well if the time-delay between the master and slave is a very small fraction of a second. Due to delays of a few seconds, human operators are very poor at managing the contact forces that the5j, slave arm imparts on the workplace. For such cases, it is more appropriate for the human to command the slave arm by way of “supervisory control.” In supervisory control, the contact forces are rapidly measured and controlled directly by the electronics at the slave arm, so that the time delay back to the human operator doesn’t result in oscillation of the slave arm. The human gives commands for motions that can include contact with objects of the worksite, but those contact forces are managed by the remote-site electronics without any dependency on the motion of the master.[2]
3. The reason why robots are used in space
The reasons why robots are used in space are very close to the reasons why robots are used on Earth. It is, in essence, the relative importance of the factors that shift. In order of importance, Space Robots are implemented as follows:
1. Safety: some tasks are too dangerous (e.g. because of the hostile environment) for astronauts.
2. Performance: the given tasks are too difficult or impossible (e.g. because of large masses involved, high precision and repeatability required, long duration) for astronauts.
3. Cost: Space explorers need a very costly infrastructure to support life, and ultimately, they have to return to Earth, robots just need fuel, and they can be disposed of once they have accomplished their target. [3]
4. Application
Space robot applications can be classified in the following four categories:
1. In-orbit positioning and assembly: for the deployment of satellites and for the installation of satellite / space station modules.
2. Operation: For conducting experiments in space lab.
3. Maintenance: For removal and replacement of defective modules / packages.
4. Resupply: For the supply of tools, materials for research in the space lab and for the resupply of fuel.
5. The state-of-the-art of space robotics
The current state-of-the-art in space robotics is defined by MER, the Canadian Shuttle and Station arms, the German DLR experiment Rotex (1993) and the experimental arm ROKVISS on the Station right now, and the Japanese experiment ETS-VII (1999). A number of systems are waiting to fly on the Space Station, such as the Canadian Special Purpose Dexterous Manipulator (SPDM) and the Japanese Main Arm and Small Fine Arm (SFA). Investments in space robotics research and development worldwide have decreased significantly over the last decade compared to the previous decade; the decline in the US has been higher than in Japan or Germany. Programs such as the NASA Mars Technology Program (MTP) and Astrobiology Science and Technology for Planet Exploration (ASTEP) as well as the recent NASA Exploration Systems Research and Technology (ESRT) programs are an exception to the generally low level of investment over the last decade. Nonetheless, some or all of these projects are likely to be scaled back as NASA seeks to make funds available to support the Moon and Mars Vision for Space Exploration.[4]
6. Conclusion
Space robots are the newest trend in space exploration. They not only offer a broader search aspect and freedom, but also go far beyond the physical limitations of humans. With a few planetary bodies already being explored and many exploratory missions in the pipeline, there is a need for optimal performing robots. Implementing optimization will offer countless benefits for autonomous space robots. In order to make sure the planetary robotic explorers accomplish their tasks and mission goals; certain methods are required to plan their action. With the availability of new information there is a need for developing new plans.The action plan development technique helps to develop a strategy that allows their rover to perform the task without disturbing any of the physical constraints of the problem.This approach thus helps to maximize the capabilities of a robot and avoids the termination of an agreement.
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