It is an inevitable choice for the development of space automation technology to use space intelligent robots to realize space exploration and space resource utilization. China started with the successful launch of the Tianhe main module in 2021, and intends to build a large-scale, long-term national manned space laboratory in 2021-2022, and gradually develop into the China Space Station ( CSS), which raises more requirements to develop the technology of spatial intelligent robots. However, the harsh space environment, including microgravity, complex lighting and strong radiation in space, poses challenges for space robots in large-range stable movements, high-precision dexterous and safe handling, precision detection and high precision measurement. In a research article recently published in Space: Science & Technology, Xiao Huang from the Beijing Institute of Technology reviewed, analyzed and summarized the technical progress and future development trends of intelligent space robots for operational needs. orbiting space stations, satellites and large space constructions.
The author first focused on intelligent space robots for space station applications. Space manipulators, including the Canadarm II and the Chinese robotic manipulator system, are studied. On the other hand, since controlling robots such as astronauts to perform human-like movements and operations becomes an effective way to assist or replace astronauts, robot astronauts have been listed as one of the main directions of development of intelligent space robots. However, it is difficult to perform a wide range of stable movements and safe dexterous manipulations in a small microgravity space, and it is also difficult to effectively verify the 3D movement of the robot astronaut on the ground. Therefore, how to form a parametric representation of the law and study the motion planning and control theory suitable for the space environment is a scientific problem that urgently needs to be solved regarding robot astronauts. Meanwhile, machine vision is an important basis for robotic manipulation. However, there is a strong contrast between the shadow area and the lighted area in space, and the mirror-like coating of the space device may cause multiple refraction and reflection of light, radiation of particles with high energy and other complex interference environments, which seriously interfere with the characteristics of operating objects and challenge existing image processing algorithms.
Next, the investigations of the intelligent space robot for in-orbit maintenance of satellites are carried out. “Orbital Express” focusing on cooperative space objects as well as the “Phoenix Spacecraft Servicing Program” concerning non-cooperative space objects are respectively analyzed. According to the analysis of ongoing research, considering the harsh space environment of high-speed flight and microgravity, the author concluded the key technologies to support in-orbit service as follows: design of coupling manipulators high-precision rigid-flexible, precise, safe and dexterous handling technology, multi-robot collaborative control technology, rapid tool change and tooling system design technology, modular satellite technology and cellular satellites.
Finally, the author discussed current developments of intelligent space robots for in-orbit assembly of large-scale space-oriented structures. Four typical space robots or robotic projects are mentioned to show the growing trends in related technologies. (a) The Skyworker, a robot designed by Carnegie Mellon University, is an attached mobile robot that can move by applying reaction force to objects without grasping hooks or handrails. Skyworker is primarily used for transportation, assembly and maintenance tasks of large payloads, such as in-orbit assembly of solar cell arrays. (b) The SpiderFab project, proposed by Tethers Unlimited, Inc. of America in 2012, primarily uses the 3D printer and the materials carried by the multi-armed space robot to print large trusses in orbit and assemble them in orbit to form a large -scale system. (c) The James Webb Space Telescope (JWST) is a giant space telescope jointly developed by several aerospace agencies to enable a wide range of investigations in the fields of astronomy and cosmology. (d) Chinese scientists have proposed the design scheme of two-stage symmetric reflection space solar power plants (SSPS) and the design concept of multiple rotary joint SPS. Overall, large-aperture space antennas, large-aperture space telescopes and large-scale solar power plants are of great importance to human beings for space exploration and space resource utilization. However, due to the limitation of the carrier size and the carrying capacity of the rocket, it is difficult to launch the full-scale structure directly into space, and it is also difficult for astronauts to perform a in-orbit assembly of large-scale spacecraft due to physiological limitations. Therefore, the author concluded the core technologies to support the in-orbit construction, such as a large inertial load handling system, a fast and stable long-range travel mechanism, a micro space measurement system -high precision nano and special tools and systematic equipment.