Linear Motor Iron Core Ratio for Stable Sensorless Pole Estimation
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Solution Overview
Problem
The estimation accuracy of the magnetic pole position in linear motors decreases due to changes in saliency characteristics caused by varying current conditions, leading to degraded control performance.
Innovation Solution
A linear motor design where the armature includes windings wound around a first iron core, and the field magnet comprises permanent magnets and second iron cores, with a specific ratio of the first iron core's dimension facing the field magnet to the winding pitch being less than or equal to 0.53, to maintain inductance trajectory alignment and prevent magnetic saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the first iron core dimension ratio is increased to improve magnetic flux utilization, then the motor power increases, but magnetic saturation occurs and saliency characteristics change
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of the first iron core dimension to winding pitch within 0.05 to 0.53. This parameter optimization prevents magnetic saturation while maintaining adequate magnetic flux utilization, thereby preserving stable saliency characteristics across varying current conditions and improving motor power without compromising reliability.
2Device complexity
If sensorless control is used to simplify the system, then the device complexity decreases, but the measurement precision of magnetic pole position deteriorates
Solution Approach 1:
The patent modifies the physical parameters of the iron core and winding arrangement to inherently improve the saliency characteristics. This structural parameter optimization enhances the distinguishability of magnetic pole positions through inductance variations, enabling more accurate sensorless control without requiring additional sensors or complex algorithms.
3Force
If the windings are densely arranged to increase the force output, then the motor force increases, but the inductance trajectory inclination increases and control performance deteriorates
Solution Approach 1:
The patent optimizes the winding pitch and first iron core dimension ratio parameters to achieve a balanced design. This allows dense winding arrangement for high force output while controlling the inductance trajectory inclination to remain within acceptable limits, thereby maintaining both high motor force and reliable control performance.
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 design improves the accuracy of magnetic pole position estimation and enhances the performance of sensorless control in linear motors, especially under medium to high load conditions, by reducing the inclination of the inductance trajectory and preventing magnetic saturation.
Implementation Method 1
an armature and a field magnet, which are arranged to face each other so as to be capable of relative movement, are provided
Implementation Method 2
the field magnet includes a plurality of permanent magnets arranged along the direction of the relative movement
Data Source
AI summary
A linear motor includes an armature and a field magnet facing each other such that relative movement is possible. The armature includes a plurality of windings, each of which being wound around a first iron core and arranged along a direction of the relative movement, the field magnet is arranged to face the armature in a direction orthogonal to the direction of the relative movement, and includes a plurality of permanent magnets arranged along the direction of the relative movement, and a plurality of second iron cores arranged to alternate with the permanent magnets along the direction of the relative movement, and a first ratio of a dimension of a portion of the first iron core facing the field magnet with respect to a pitch at which the windings are arranged in the direction of the relative movement, is less than or equal to 0.53.