Distributed path and speed control in machine-tool axis motion

In a computerized numerical controller, interpolation is usually centralized. Decentralized interpolation schemes have been proposed in response to the drawbacks of centralized interpolators; poor granularity and algorithm complexity. The author extends this idea by showing an application case and dealing with velocity adaptation problems. It is shown that speed can be adapted and that, for machine tool applications, adaptation leads to a system of equations that cannot be solved exactly in most cases but at least provides a suboptimal solution. Provided the path is expressed by parametric equations relying on the curvilinear coordinate, velocity control can fully comply with the requirements. In this way, algorithms can be distributed on each axis, multi-axis interpolation being ensured by a common clock. Some of the problems related to chaining of unitary movements are shown