Active compensation of the movement inaccuracies of feed drives with profiled rail guides based on high dynamic piezo actuators

• Applicant: Professor Dr.-Ing. Steffen Ihlenfeldt
• Subject Area: Production Automation and Assembly Technology ; Engineering Design, Machine Elements, Product Development
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 499035309

The project addresses ball passage vibration (BPV) in linear guideways (LGWs) caused by the time-varying system stiffness associated with rolling-element (RE) circulation. Passive measures such as crowning (taper in the entry and exit zones) reduce these effects only to a limited extent, and no active compensation method currently exists for LGWs. The aim is therefore to develop a real-time, model-based compensation method that predicts BPV and effectively suppresses it through piezo-actuated corrections. The first project phase established essential foundations: an IPS-based method (inductive proximity sensors) for determining the RE distribution, also referred to as ball grouping; static and quasi-static load distribution models (LDM) for rigid and flexible carriages to predict BPV; and a piezo-actuated 3-DoF positioning stage for compensation. Limitations arose particularly in the crowning region, where RE sliding reduces the accuracy of the ball grouping determination. Furthermore, measurements confirmed that structure-deformation-induced reaction loads in LGWs play a significant role in predicting BPV, which have so far not been taken into account in the LDMs. In addition, no practical measurement method exists for the direct determination of loads in LGWs, including reaction loads. Consequently, the developed approach has only been qualitatively validated in the first project phase. The second project phase focuses on improving ball grouping determination methods and extending the LDMs to enable real-time prediction and active BPV compensation: improve ball grouping detection by using analog IPS signals and a curve-fit method to distinguish between rolling and sliding during RE circulation in the crowning region, extend the LDMs with error models to account for significant reaction loads caused by rail straightness errors, develop a measurement method for directly determining the total loads on carriages using existing sensors to capture all reaction loads, validate the active compensation method under static and dynamic loads, investigate the applicability of the developed method to alternative crowning designs, document the results through publications and the DFG final report. Expected benefit: The combination of extended LDMs and new measurement methods will enable quantitative real-time prediction and significant reduction of BPV. This will close the current gap in active compensation for LGWs and substantially expand their applicability in ultra-precision applications.

• DFG Programme: Research Grants