Inverse dynamics analysis and trajectory generation of incompletely restrained wire-suspended mechanisms

This paper discusses an inverse dynamics problem and proposes a trajectory generation method for wire-suspended mechanisms. The wire-suspended mechanisms are classified into two types, which are completely restrained type mechanisms and incompletely restrained type mechanisms. For the incompletely restrained type mechanisms, consideration of dynamics is important, because the motion of this mechanism is governed by its dynamics and kinematics, whereas the motion of the completely restrained type mechanism is determined by only its kinematics. The current paper discusses mainly the incompletely restrained type mechanisms in the viewpoint of dynamical properties. The incompletely restrained type wire-suspended mechanism has a merit that it enables three dimensional positioning and orientating of suspended object with simple mechanism using a small number of wires. However it also has a drawback that the manipulated object is easy to swing as seen in overhead crane which is a simple incompletely restrained type mechanism. To overcome the problem, inverse dynamics for general incompletely restrained type wire-suspended mechanism is discussed, then a condition on desired trajectory of manipulated object is presented on the basis of the inverse dynamics analysis. Using the desired trajectory, an on-line trajectory modification method for the control of manually operated overhead crane is proposed.