Reducing flexible base vibrations using kinematically redundant robots.

摘要

Due to costs and mission requirements, future space robots will be used to take the place of humans. When these robots are attached to flexible bases such as the Space Shuttle Remote Manipulator System or the truss of the Space Station Freedom, an important issue concerning their performance is the dynamic coupling between the robot and the flexible base. When the robot moves, reaction forces and moments at the base of the manipulator excite flexible modes in the supporting structure that lead to end-effector tracking errors and performance degradation.;Since redundant robots have the ability to track a desired end-effector trajectory while also optimizing secondary criteria, kinematically redundant robots are investigated in the current work as one means of reducing or eliminating the unwanted effects of flexible vibrations. Using local resolved acceleration control, energy dissipation control laws for the manipulator redundancies are derived and are theoretically and numerically shown to be effective for reducing vibration. However, owing to inherent singularity problems in local optimizations, excessively high joint velocities can occur. To overcome this problem, a fuzzy logic supervisor was designed and implemented for adaptively controlling the kinematic redundancies. Compared to the non-fuzzy solutions, the fuzzy solution is better at avoiding singularities while still decreasing flexible vibrations.