Linear Motor Pole Position Correction for Thrust Consistency
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Solution Overview
Problem
In linear motor systems, positioning precision is compromised due to deviations in the mounting positions of the slider, stator, and position detector, leading to reduced thrust efficiency, especially in large machine tools with long driving strokes and segmented stators, where pitch deviations and mounting errors result in reduced thrust across the entire length.
Innovation Solution
A method to correct the position deviation of the salient pole of the stator based on the stroke position of the slider, using pre-calculated pole position correction values stored for each segment, allowing for accurate phase alignment of current supply to maximize thrust, even with deviations in stator segments and mounting errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear motor is used for axial driving without a ball screw, then positioning precision of the driving axis directly corresponds to positioning precision of the slider, but mounting position deviations of the slider, stator, and position detector cause thrust reduction and efficiency loss
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for salient pole positions at multiple predetermined positions along the stator before actual operation. During operation, the appropriate correction value is retrieved and applied based on the current slider position, eliminating the need for real-time complex calculations and enabling quick compensation for mounting deviations.
Solution Approach 2:
The patent implements feedback by continuously monitoring the slider position and dynamically selecting the appropriate correction value from stored data. The control system compares the actual slider position with the predetermined positions and applies the corresponding correction value to compensate for mounting deviations, creating a closed-loop control system that maintains optimal thrust efficiency.
2Length of moving object
If the stator is divided into multiple segments for long driving strokes, then the linear motor can cover longer distances, but pitch deviations and mounting errors between segments cause reduced thrust across the entire length
Solution Approach 1:
The patent applies segmentation by dividing the stator into multiple segments for long driving strokes, with each segment having predetermined salient pole positions stored in the storage unit. The control system selectively applies correction values corresponding to the active segment based on slider position, enabling the system to maintain consistent thrust performance across the entire extended driving stroke length.
Solution Approach 2:
The patent implements local quality by storing different correction values for different segments and positions along the stator. Each segment has its own set of predetermined salient pole positions and corresponding correction values, allowing the system to apply locally optimized correction values that account for segment-specific mounting deviations and pitch variations.
3Measurement precision
If a high resolution position detector is mounted to detect slider position, then positioning precision is improved, but mounting position deviations still cause current phase angle misalignment and thrust reduction
Solution Approach 1:
The patent introduces an intermediary correction value that mediates between the position detector reading and the actual salient pole position. The correction value acts as a compensating parameter that adjusts the relationship between detected position and current phase angle, eliminating the need for perfect mounting alignment and ensuring accurate current application despite mounting deviations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces thrust reduction across the entire length of the stator, maintaining high positioning precision and efficiency by correcting pole position deviations, thereby minimizing the impact of size and mounting errors on thrust performance.
Implementation Method 1
When a predetermined electric power is supplied to the coil, a moving magnetic field is formed in the direction of extension of the stator, and the slider moves in the direction of extension of the stator due to an interaction between the moving magnetic field and the salient pole.
Data Source
AI summary
In a linear motor used for a driving axis of a large-size machine tool having a very long driving stroke, pole position correction values at a plurality of stroke positions are stored in a memory. A pole position correction value corresponding to an actual stroke position of a slider is calculated based on the stored pole position correction value. A corrected electrical angle offset value derived based on the calculated pole position correction value is used to control the linear motor.