Adaptive nonlinear contour coupling control for a machine tool system

The quality of products from a machine tool system is largely determined by the tolerances maintained, which is a function of how well the desired contour is tracked. To mitigate contour errors in a three axis machine tool feed drive system, the control development in this paper is based on an error system that is transformed into tangential, normal and binormal components to the desired contour (i.e., a cross coupling controller (CCC)). Unlike previous CCCs, the first controller in this paper does not assume exact knowledge of the inertia and friction matrices. Specifically, an adaptive estimate is developed to compensate for uncertain friction and inertial parameters. Lyapunov-based methods are used to craft the adaptive estimate and to prove global asymptotic contour tracking. A second controller is developed for machine tool dynamics that include unknown friction forces and uncertain cutting force disturbances. The second controller is crafted using an integral signum feedback compensation term that yields semi-global asymptotic contour tracking