Techniques For Collision Prevention, Impact Stability, And Force Control By Space Manipulators

摘要

T HE field of space robotics can be readily divided to planetary and zero-gravity operations. While the harsh environments of other planets will surely require robust robotic hardware, the algorithms controlling this hardware are not likely to be different in kind from Earth-based controllers. Therefore, it is usually the arena of zero-gravity operations where special control algorithms are developed for space robotics.' Among the pertinent issues that this research addresses are sixdegree-of-freedom mobility, zero-friction motion, energy (thrust) minimization, large inertias, flexible structures, etc. Many of these have terrestrial analogs, especially in the field of underwater robotics (as is demonstrated by the utility of buoyancy tanks for astronaut mission training). Particularly, robot manipulation in space has a large overlap with its terrestrial counterpart. Within this overlap of zero-gravity and terrestrial robotics, there are three main issues: unconstrained motion, stability during the contact transition, and force controlled manipulation of the environment. If a space robot is unattached to its environment, the first two of these research areas map closely to the problems of mobile ground robots and underwater vehicles. In this case, the main problems are path planning, obstacle avoidance, and rendezvous and docking. Force control is not pertinent, because any forces exerted between the robot and its environment will tend to repel each away from the other. Whereas this is especially true in space, it can also be a practical matter for mobile robots on land and in water. Therefore, if force control is to be applied, the robot should attach itself to the environment, making a continuous kinematic chain. (Constant force could also be applied by thrusters, wheels, or propellers, but it is inefficient and will cause a