Active Jerk-Decoupling for Machine Tools

• Applicant: Professor Dr.-Ing. Berend Denkena
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269666724

Machine tools (MT) with high axis dynamics are required for high-speed machining, e.g. of aluminum. This requires a fast increase in maximum acceleration. However, high jerk values in linear direct drives excite the machine structure to vibrate. As a result, the dynamic deflections of the machine bed or tool center point will negatively influence the accuracy of the MT. Therefore, the dynamic capabilities of the controller are usually limited. As a result, the potential of linear direct drives is not fully exploited. New approaches to reduce this effect are jerk or pulse decoupling (passive JDC or PJDC). As a mechanical low-pass filter, an additional spring-mass damper is integrated into the machine structure. However, this adds another resonance to the system. The setting of the JDC parameters allows a compromise between the amplitude of the added JDC resonance and the resulting structural vibrations. This process reaches its limits with highly damped MT and low-frequency oscillations. In addition, the necessary parameters must be determined individually for each machine type. Therefore, in the first project stage of the basic project "Active Jerk Decoupling for MT", the IFW has researched a method with which both, the frame and the JDC resonance can be significantly reduced by additional active elements. In the first project stage, it was shown that the rack and JDC resonances are significantly reduced by the additional actuators. It was also shown that the model-based control approaches for controlling the active elements are susceptible to model inaccuracies due to changes in the dynamic machine properties. In addition, the necessary control parameters must be designed individually for each machine type. Due to the complexity of the control, active jerk decoupling (AJDC) cannot currently be transferred to different machine kinematics without significant additional effort. In the applied second project stage, an autonomous, self-parameterizing, robust AJDC controller (SP-AJDC) is therefore being researched, which enables commissioning without expert knowledge. For this purpose, a robust SP-AJDC controller will first be researched using a test rig. The transferability of the method is investigated by transferring it to another machine structure. By investigating the interactions of SP-AJDC and process forces, the potentials and limits of the SP-AJDC for the machining process are determined.

• DFG Programme: Research Grants