NC Feed Shaft Control With Coarse-Fine Motion Compensation
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Solution Overview
Problem
Pre-interpolation acceleration/deceleration controls result in longer machining times, while post-interpolation controls lead to increased machining errors when controlling multiple feed axes, and composite servo systems suffer from interfering forces between coarse and fine positioners, affecting accuracy and efficiency.
Innovation Solution
A method that utilizes micro-motion devices to compensate for suppressed accelerations, enhancing the acceleration and deceleration of feed axes, and a servo-control system that includes micro-motion feedforward controllers to manage position, velocity, and acceleration, thereby improving machining accuracy and efficiency, and reducing errors caused by friction and interfering forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-interpolation acceleration/deceleration control is applied to reduce impacts, then machining accuracy is improved, but machining time increases
Solution Approach 1:
The feed axis control system is divided into two independent parts: a coarse positioner that handles main movement with standard acceleration control, and a fine positioner that handles micro-adjustments with separate acceleration control. This segmentation allows each part to be optimized independently, reducing overall machining time while maintaining accuracy.
Solution Approach 2:
The fine positioner performs preliminary micro-adjustments before the main positioning action, compensating for acceleration suppressions in advance. This preliminary action prevents machining errors without requiring extended acceleration time, thus maintaining both accuracy and productivity.
2Productivity
If post-interpolation acceleration/deceleration control is applied to reduce machining time, then productivity is improved, but machining accuracy deteriorates due to inner arcuate tool path
Solution Approach 1:
By separating the position control into coarse and fine components, the system can apply aggressive post-interpolation acceleration control to the coarse positioner while the fine positioner compensates for any tool path deviations, maintaining accuracy without sacrificing productivity.
Solution Approach 2:
The fine positioner acts as a feedback mechanism that detects and corrects tool path deviations caused by acceleration control. This feedback loop ensures that even with rapid acceleration/deceleration, the final positioning accuracy is maintained.
3Manufacturing precision
If composite servo system with coarse and fine positioners is used to improve positioning precision, then machining accuracy is improved, but interfering forces are generated between positioners
Solution Approach 1:
The control system segments the positioning task into coarse and fine components with clearly defined responsibility boundaries. The coarse positioner handles main movement while the fine positioner handles only micro-adjustments, reducing mutual interference between the two positioners.
Solution Approach 2:
The system dynamically adjusts the control parameters of the fine positioner based on the operating state. During high-speed coarse movement, the fine positioner operates in a mode that minimizes interfering forces, while during precision positioning, it provides full correction capability.
Data Source
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AI summary
A numerically controlled machine tool (10) in which a numerical control program acquired from a reading and interpreting unit (52) of a numerical control device is executed by a distribution interpolating unit (54) and servo control units (56), (58) and (60) to drive a feed shaft configured from a coarse movement mechanism and a fine movement mechanism, causing a tool to move relative to a workpiece, and thereby machining the workpiece, wherein the difference between a movement command for the feed shaft, and an output value which varies on the basis of said movement command is obtained, a movement command for the coarse movement mechanism is generated on the basis of said movement command, and a movement command for the fine movement mechanism is generated on the basis of said difference.