Machine Tool Position Feedback Switching for Surface Finish Control
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Solution Overview
Problem
In machine tools performing gentle inclined or tapered surface machining with multiple synchronized feed axes, existing position control systems face challenges in preventing interpolation errors from linear encoders, leading to striped patterns on machined surfaces, and lack direct detection of errors such as pitch errors and thermal expansions without linear encoders.
Innovation Solution
A position control system with each feed axis equipped with both an object position detector and a motor position detector, where position controllers select feedback values based on detected motor positions for axes with larger movements and object positions for those with smaller movements, allowing for direct detection of the controlled object's position and minimizing interpolation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear encoders are used for position detection in gentle inclined or tapered surface machining, then direct detection of controlled object position is achieved, but interpolation errors cause striped patterns on machined surfaces
Solution Approach 1:
The patent segments the position detection function into two independent detection systems: linear encoders for axes with larger movements and motor position detectors for axes with smaller movements. This segmentation allows each detector type to be optimized for its specific application, preventing interpolation errors from linear encoders from affecting gentle machining surfaces while maintaining direct detection capability where needed.
Solution Approach 2:
The patent applies different detection methods to different feed axes based on local requirements: axes controlling gentle inclined or tapered surfaces use motor position detectors to avoid interpolation errors, while other axes may use linear encoders for direct position detection. This local quality approach ensures each axis uses the most appropriate detection method for its specific machining function.
2Measurement precision
If linear encoders are installed on all feed axes, then direct detection of controlled object position is enabled, but system complexity and cost increase
Solution Approach 1:
The patent makes the detection system multi-functional by enabling position controllers to selectively use either linear encoder data or motor position detector data as feedback values based on machining conditions. This universality allows the system to adapt to different machining requirements without requiring separate dedicated detection systems for each scenario.
Solution Approach 2:
The patent changes the feedback value parameter dynamically by allowing position controllers to switch between using linear encoder positions and motor position detector readings based on the specific machining operation. This parameter change enables the system to optimize detection accuracy for each machining scenario while maintaining system flexibility.
3Manufacturing precision
If motor position detectors are used instead of linear encoders, then interpolation errors are eliminated, but direct detection of pitch errors and thermal expansions is lost
Solution Approach 1:
The patent creates a dynamic detection system where the feedback value source is not fixed but can switch between linear encoders and motor position detectors based on machining conditions. This dynamics allows the system to use motor position detectors for gentle machining to eliminate interpolation errors while using linear encoders for other operations where direct detection of mechanical errors like pitch errors and thermal expansions is beneficial.
Data Source
AI summary
Respective amounts of movement of feed axes corresponding to first and second position controllers are determined, and if a value obtained by dividing a smaller amount of movement by a larger amount of movement, in the two amounts of movement, falls within a prescribed reference range, a position controller for the feed axis with the smaller amount of movement selects a detected motor position as a position feedback value and a position controller for the other feed axis selects a detected object position as a position feedback value.