Oscillation Cutting Control Device Preventing Overshoot at Machining End Point
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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 generates an oscillation command based on the rotation speed and position command, with a learning controller that adjusts the resultant command using the oscillation phase, and an oscillation permission/prohibition notification system to turn off learning control when nearing the machining end point, ensuring the oscillation command is set to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If learning control is applied to oscillation cutting to improve positional accuracy, then the position deviation converges to zero through repeated periodic operations, but overshoot occurs near the machining end point because the correction amount from the previous oscillation cycle is applied even when the oscillation amplitude has been reduced
Solution Approach 1:
The control device determines in advance whether to apply learning control based on the relationship between the current oscillation amplitude and a reference value. When the oscillation amplitude is smaller than the reference value (indicating proximity to machining end point), the learning control is determined not to be applied, preventing overshoot before it occurs
Solution Approach 2:
The application of learning control is made dynamic rather than static. The control device continuously monitors the oscillation amplitude and adjusts the learning control application status accordingly - applying learning control when amplitude is sufficient, and stopping it when amplitude decreases below the reference value, allowing adaptive response to changing machining conditions
2Manufacturing precision
If oscillation amplitude is reduced as the cutting tool approaches the machining end point to prevent overshoot, then the tool position accuracy is maintained, but learning control becomes ineffective because the oscillation pattern changes continuously rather than repeating
Solution Approach 1:
The control device determines in advance whether to apply learning control based on the relationship between the current oscillation amplitude and a reference value. When the oscillation amplitude is smaller than the reference value (indicating proximity to machining end point), the learning control is determined not to be applied, preventing overshoot before it occurs
Solution Approach 2:
The control device uses feedback from the oscillation amplitude measurement to control the application of learning control. By continuously monitoring whether the oscillation amplitude is greater than or less than the reference value, the system adjusts learning control application accordingly, creating a closed-loop control mechanism
Data Source
AI summary
An oscillation permission/prohibition notification part of a control device notifies an oscillation command generation part of generation permission of the oscillation command when a position command value has not reached within a predetermined range of a machining end point of a workpiece, and notifies the oscillation command generation part of generation prohibition when the position command value has reached within the predetermined range. A control part includes a learning controller and a learning determination part. The learning determination part determines whether the oscillation command generation part has been notified of generation permission or generation prohibition of the oscillation command, turns learning control on when notification of generation permission of the oscillation command has been received, and sets the oscillation command to zero and turns off learning control when notification of generation prohibition of the oscillation command has been received.