Identification of inaccessible oscillations in n-link flexible robotic systems

A dynamic model is developed for flexible robotic manipulators, and various properties displayed by flexible systems are studied. The formulation is developed for an n-link, spatial robot with m link and joint flexibilities. Manipulator compliance is modeled by nonactuated prismatic- and revolute-type pseudojoints and local springs acting across the pseudojoints. Each actuator is also modeled as a second-order subsystem. For this system, complete dynamic equations are derived for nominal system motion and vibrational subsystem oscillations without any linearization or omitting certain nonlinear terms. It is shown that this model enables the direct use of dynamic model formulation techniques originally developed for rigid robots. It is revealed that in certain robot positions some or all of the oscillations become inaccessible to the driving actuators. These conditions are studied on illustrative examples, and the implications of inaccessible oscillations in architectural design and control areas are discussed