Machine Tool Touch Probe Vibration Suppression via D-Axis Current Control
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Solution Overview
Problem
Machine tools with touch probes attached to a main axis face challenges in accurately measuring workpieces with small radii of curvature or spherical surfaces due to generated vibrations from noise in the rotation axis, limiting measurement accuracy.
Innovation Solution
A machine tool system that includes a main axis with a touch probe, a motor, and a control device with a switching unit that adjusts the electric power supply to the motor based on the rotation angle position detector's output, reducing vibrations by lowering the d-axis current command value and feedback gain during measurement mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a touch probe is attached to perform simultaneous multi-axis measurement, then measurement capability for complex surfaces is improved, but rotation vibrations occur due to noise in the position detector
Solution Approach 1:
The patent extracts and removes the harmful noise components from the position detector output through filtering. By applying a filter with an appropriate filtering constant, the noise that causes rotation vibrations is separated and removed from the control signal, allowing the beneficial multi-axis measurement capability to function without the harmful vibrations.
Solution Approach 2:
The patent converts the harmful effect of noise into a beneficial outcome by using the filtering process. The noise that would normally cause vibrations is identified and removed through the filter, transforming the problematic noise input into improved measurement stability and accuracy during multi-axis operation.
2Stability of the object's composition
If filtering constant is increased to remove high-frequency noise, then vibration suppression is improved, but positioning accuracy during normal rotation is lowered
Solution Approach 1:
The patent makes the filtering constant dynamic rather than fixed. A switching unit detects the operational mode and adjusts the filtering constant accordingly: using a higher first value during measurement mode for vibration suppression, and a lower second value during positioning mode for accuracy. This dynamic adaptation resolves the contradiction between vibration suppression and positioning accuracy.
Data Source
AI summary
A machine tool includes a main axis 30 to which a touch probe 17 is attached, a motor 15 that rotationally drives the main axis 30, a rotation angle position detector 16 that detects a rotation angle position of the motor 15, and a control device 20. The control device, when a measurement mode command for performing measurement of a workpiece by the touch probe 17 is input, multiplies a d-axis current command value Idc by a d-axis current correction coefficient K that is less than 1 to reduce the d-axis current command value Idc to a d-axis current command correction value Idc′, using a d-axis current command correction section 4. Thus, in the machine tool, small rotation vibrations of the main axis, generated when rotating the main axis to which the probe is attached and performing measurements of a workpiece, can be suppressed to thereby increase the measurement accuracy.