Flexible actuator finite element applied to spatial mechanisms by a finite deformation dynamic formulation

A flexible actuator finite element is developed and applied for the modelling of spatial mechanisms present in several industrial applications. A total Lagrangian framework is employed for the development of the finite deformation dynamic equilibrium using solid-like shell and 3D frame finite elements. Exploiting the total Lagrangian aspect of the formulation, the actuator motion is imposed by controlling the element reference configuration. It has the advantage of retaining the actuated bar flexibility, an important factor when simulating flexible mechanisms, and not requiring special treatments as constraint enforcement impositions. As the employed elements use alternative nodal parameters such as positions and generalized vectors to describe their kinematics, a treatment on the introduction of rotational connections-spherical, revolute and pinned joints-largely present in actuated mechanisms, is developed. The nonlinear equations of motion are solved by the Newton-Raphson method. Examples are presented to evaluate the proposed flexible actuator finite element regarding its dynamical behaviour in mechanisms where its use is of importance. (AU)