ABSTRACT Spatial mechanism dynamical characteristics generally depend on the actual kinematical configuration assumed in the working space. Whole system performance assessment can be obtained by the evaluation of the operating workspace from a purely kinematical standpoint, and by evaluating the flexibility properties of such systems in some reference kinematical and loading conditions. Computationally expensive non-linear analysis can also be performed by means of multibody numerical techniques with respect to some particular loading and motion user conditions, but such results may generally lack any generalisation content, and can not be used to compare different mechanism design solutions. An effective analytical-numerical approach is presented in this paper to mathematically define a local linear, generalised eigenproblem from a spatial mechanism in the closeness of a kinematically admissible position of interest. The system is modeled by means of rigid bodies connected by standard kinematical and elastic joints. The linearized expression of displacement and velocity of a general point from a local body is obtained, so that linear, condensed equations of motion can result. A generalised eigenproblem is thus formulated, and eigenproperties can be derived to evaluate the system dynamic performances in a specific kinematical configuration. The same procedure is repeated at different steps of a user-defined motion law, to evaluate the parametric dependence of the modal parameters on the assumed motion. A standard non-linear kinematical analysis is performed to obtain the system kinematical configuration initial value d.o.f. vector. The methodology is tested on two 6 d.o.f. robots, with serial and parallel architecture, related to real industrial applications. The results are reported and discussed.
Evaluation of spatial mechanism eigenproperties with respect to kinematical configuration
ZANARINI, ALESSANDRO;CATANIA, GIUSEPPE
2004
Abstract
ABSTRACT Spatial mechanism dynamical characteristics generally depend on the actual kinematical configuration assumed in the working space. Whole system performance assessment can be obtained by the evaluation of the operating workspace from a purely kinematical standpoint, and by evaluating the flexibility properties of such systems in some reference kinematical and loading conditions. Computationally expensive non-linear analysis can also be performed by means of multibody numerical techniques with respect to some particular loading and motion user conditions, but such results may generally lack any generalisation content, and can not be used to compare different mechanism design solutions. An effective analytical-numerical approach is presented in this paper to mathematically define a local linear, generalised eigenproblem from a spatial mechanism in the closeness of a kinematically admissible position of interest. The system is modeled by means of rigid bodies connected by standard kinematical and elastic joints. The linearized expression of displacement and velocity of a general point from a local body is obtained, so that linear, condensed equations of motion can result. A generalised eigenproblem is thus formulated, and eigenproperties can be derived to evaluate the system dynamic performances in a specific kinematical configuration. The same procedure is repeated at different steps of a user-defined motion law, to evaluate the parametric dependence of the modal parameters on the assumed motion. A standard non-linear kinematical analysis is performed to obtain the system kinematical configuration initial value d.o.f. vector. The methodology is tested on two 6 d.o.f. robots, with serial and parallel architecture, related to real industrial applications. The results are reported and discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
