Modeling and control of a manipulator joint driven through a worm gear transmission

The wormscrew gearset provides a potential advantage for some robot manipul ator designs because of its simplicity, compactness, and capacity for large speed-reduction ratios. However, an oscillatory behavior has been observed in such implementations that, depending on the extension and loading of th e manipulator, tends to grow as the manipulator is lowered under the influe nce of gravity and disappears as the manipulator is raised. The oscillation s can become quite large, crippling the utility of the manipulator. The gro wing oscillations are indicative of an instability However, it is not immed iately apparent why such a system should be unstable. The objectives of thi s work were to find the source of the oscillatory behavior and to determine whether feedback control can be employed to stabilize such a system.