Abstract
Several years ago, the authors proposed a method for the efficient simulation of the dynamics of multibody systems: an index-3 augmented Lagrangian formulation with projections in velocities and accelerations to the constraint manifold, which relied on Newmark-type algorithms for the numerical integration in time. The formalism showed to be robust and efficient when facing a number of large and complex problems, as the detailed models of cars and excavators. On the other hand, hydraulic actuators are present in many industrial applications of multibody dynamics techniques, like in the case of the heavy machinery field. When simulating the dynamics of this kind of problems, two different approaches are common: to resort to kinematically guide the variable length of the actuator, thus avoiding the need to consider the dynamics of the hydraulic system; or to perform a multi-rate integration of both phenomena if a more detailed description of the problem is required, for example, when the objective of the study is to optimize the pump control. This work addresses the inclusion of hydraulic actuators dynamics in the method for the simulation of multibody system dynamics mentioned above. The resulting formalism is developed, and the raised numerical issues are discussed. An academic example serves to compare the complexity and efficiency of the simplified (kinematic guidance), multi-rate and unified approaches, leading to conclude that the robustness of the method is preserved and that the efficiency of the method is moderately penalized.
