Numerical Control Apparatus for Smooth Tool Posture Changes
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Solution Overview
Problem
Conventional numerical control systems face challenges in maintaining constant tool-tip speed and accuracy when machining programs include intermittent or discontinuous tool posture changes, leading to degraded surface quality and inaccuracies due to difficulties in moving the translation axis at discontinuous speeds and incorrect interpolation processes.
Innovation Solution
A numerical control apparatus that includes an analysis processor for generating interpolation points, a rotation-axis filtering processor for smoothing angle changes, a timing synchronization unit for synchronizing rotation and translation axis movements, and an acceleration/deceleration processor to transform tool-tip positions into machine coordinates, allowing for smooth tool posture changes and reduced errors in the machining path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If command points are corrected by smooth approximation curve, then tool-tip movement becomes smooth, but position of singular point changes and machine tool movement largely changes
Solution Approach 1:
The patent segments the smoothing process by applying different filtering approaches to different parts of the motion control system. The rotation axis command values are smoothed using a low-pass filter, while the translation axis command values are smoothed separately. This segmentation allows each axis to be optimized independently, preventing the singular point position from changing while still achieving smooth tool-tip movement.
Solution Approach 2:
The patent applies local quality by using different smoothing strategies for different axes based on their specific requirements. The rotation axis receives low-pass filtering to smooth posture changes, while the translation axis receives smoothing that maintains positional accuracy. This localized approach ensures that each axis contributes optimally to the overall smooth motion without compromising singular point position accuracy.
2Manufacturing precision
If command points are corrected by smooth approximation, then tool-tip moves smoothly, but machine tool does not stop at original command position
Solution Approach 1:
The patent segments the command value generation into two independent streams: one for the rotation axis and one for the translation axis. The rotation axis command values are generated by smoothing the posture change commands, while the translation axis command values are generated by smoothing the position change commands. This segmentation ensures that the tool-tip moves smoothly while the machine tool still stops at the original command positions.
Solution Approach 2:
The patent performs preliminary smoothing of the rotation axis command values before they are combined with the translation axis command values. By pre-smoothing the posture change commands and then combining them with the position commands, the system ensures that both smooth motion and accurate positioning at command points are achieved.
3Adaptability or versatility
If translation axis moves at discontinuous speed to accommodate intermittent posture changes, then tool posture changes are achieved, but tool-tip position accuracy degrades
Solution Approach 1:
The patent applies dynamics by making the command value generation adaptive to the specific requirements of each axis. The rotation axis command values are dynamically smoothed to accommodate intermittent posture changes, while the translation axis command values are dynamically adjusted to maintain constant tool-tip speed. This dynamic approach allows the system to handle posture changes while maintaining positioning accuracy.
Solution Approach 2:
The patent changes the parameters of the command value generation process by applying different smoothing filters with different characteristics to the rotation and translation axes. The rotation axis uses a low-pass filter with a time constant optimized for posture smoothness, while the translation axis uses a smoothing approach optimized for position accuracy. This parameter differentiation resolves the contradiction between posture adaptability and position precision.
Data Source
AI summary
In a numerical control apparatus, a rotation-axis filtering processor subjects an angle change amount between interpolation points between rotation angles of a rotation axis to moving average filtering thereby smoothing the angle change amount between the interpolation points. A translation-axis timing synchronization unit subjects a moving amount between interpolation points between tool-tip positions of a translation axis to moving average filtering, to synchronize timing of rotation of the rotation axis being smoothed and timing of movement of the translation axis. A coordinate transformation unit transforms the tool-tip position into coordinates of a machine position of the translation axis according to a configuration of the machine tool, from each tool-tip position after timing synchronization between axes of the translation axis is performed and from each rotation angle of the rotation axis after being filtered.