Adaptronical compensation of geometrical machine errors

Abstract

Static, quasi-static and dynamic displacements influence the accuracy of machine tool results. The low-frequency parts of these displacements can, on the one hand, be traced back to static stresses resulting from gravity as well as process loads and, on the other hand, to geometrical machine errors and the faulty positioning in the working area resulting from this. Dynamic loads, however, are characterised by the distribution of masses and stiffnesses. This paper aims to present an approach to adaptronically compensate for static and quasi-static displacements while, at the same time, showing how a component can fulfill the functions of a sensor and an actuator. In order to achieve this, an intelligent adaptronical strut was designed for which the piezoelectric transducer can fulfill actuated as well as sensoric tasks at the same time. Based on the principle of vibrating strings, a vibrating string is used to induce vibrations which allow for the static, quasi-static and dynamic machine displacements to be recorded using the developed integrated sensors and actuators. A first prototype was integrated into a machine tool to verify the concept. Static and dynamic measurements endorse the functionality of this approach. Machining trial runs show the effectiveness of this approach in a parallel kinematic machine tool with regards to adaptronically compensating for geometrical machine errors.