Oscillation Cutting Control Device Preventing Overshoot
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Solution Overview
Problem
In machine tools performing oscillation cutting, the issue of overshoot occurs when the oscillation amplitude is reduced near the machining end point, leading to unintended cuts and reduced precision, despite the application of learning control to prevent such issues.
Innovation Solution
A control device that includes a position command generation part, an oscillation command generation part, and a learning controller, which adjusts the oscillation command based on the rotation speed and position deviation, and a determination part that turns off learning control when the oscillation amplitude falls below a threshold, preventing overshoot by setting the oscillation command to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If learning control is applied to oscillation cutting to improve position accuracy, then position accuracy is improved, but overshoot occurs near the machining end point causing unintended cuts
Solution Approach 1:
The determination part detects when the oscillation amplitude falls below a predetermined threshold before the machining end point is reached. Based on this prediction, the learning control is proactively stopped in advance, preventing the correction amount from causing overshoot and unintended cuts near the machining end point.
2Manufacturing precision
If oscillation amplitude is reduced as the cutting tool approaches the machining end point to prevent overshoot, then overshoot is prevented, but position accuracy deteriorates due to learning control correction amounts
Solution Approach 1:
The system predicts when oscillation amplitude will fall below the threshold and stops learning control in advance. This timing control ensures that learning control is active only when oscillation amplitude is sufficient to handle the correction amounts, maintaining position accuracy while preventing overshoot near the end point.
3Speed
If high control gain is set to improve servo responsiveness, then responsiveness is improved, but vibration is generated due to backlash or low rigidity
Solution Approach 1:
The control gain is dynamically adjusted based on oscillation amplitude. When oscillation amplitude is large, high control gain is applied for fast responsiveness. When oscillation amplitude becomes small, control gain is reduced to prevent vibration caused by backlash or low rigidity, maintaining system stability.
Data Source
AI summary
A control part of a control device includes a learning controller and a learning determination part. The learning controller performs learning control in which a correction amount of a resultant command is obtained, based on an oscillation phase obtained from an oscillation command and the resultant command, and the correction amount is added to the resultant command. The learning determination part determines whether or not the oscillation amplitude of the oscillation command is smaller than a predetermined threshold, and when the oscillation amplitude is smaller than the predetermined threshold value, the learning determination part both sets the oscillation command generated by an oscillation command generation part to zero and turns off the learning control or only turns off the learning control.