Influences of closed loop control components on the performance of ultra-precision machines

At Fraunhofer IPT a test bench has been setup to analyze closed loop control components and their interfaces with focus on their application in ultra-precision machining applications. This paper will present the results of the analysis of feedback and servo drive systems and will give a close inside on the influences of linear scales and analog and digital servo drives for applications in ultra-precision machining. The performed measurements include the analysis of the position accuracy and repeatability (step response test) as well as the determination of the dynamic frequency characteristics (stiffness / compliance) of an air bearing axis. With respect to the aforementioned measurements the tests have been performed under the variation of linear scales (vendor, pitch, signal, sampling frequency, etc.) and servo drives (vendor, switching or linear amplifiers, PWM frequency, control architecture, DC bus voltage, etc.). The paper will give a summary on the results of the analyzed topics, carefully chosen regarding their relevance to ultra-precision machining. Finally, a short outlook to future research work concerning the analysis of CNC controls will be given.