New Control Parametrization Strategy for Flexible Feed Drives

Abstract

This paper presents a novel parametrization strategy for optimal contouring control of flexible feed drives. The aim of the new strategy is to maximize the structural damping of the drive and counteract the deformations of the structure. Using a simplified flexible multibody model, the analytical relationships for the design of velocity and position control gains were derived. This results in a controller bandwidth increase of up to 20% compared to the previous state-of-the-art in parametrization of standard cascaded controllers. Through analytical and numerical calculations, it was demonstrated that such an increase is feasible without a decrease in structural damping if the position and velocity controller gains are both considered. Furthermore, it is shown that the ratio between the position and velocity loop gains influences the quasistatic deformation between the encoder and tool center point (TCP). A formula for the optimal choice of the ratio was derived to compensate for the error. This leads to a new straightforward step-by-step approach for axis controller setting, which is then applied to a test bench and its simulation model. It can be shown that the new parametrization strategy leads to a significant reduction in path error at the TCP. Importantly, the analytical approach should simplify the task of setting up a standard cascaded controller significantly by avoiding time-consuming iterations.