Double Air Gap Linear Motor Asymmetric Stator Cogging Force Reduction
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Solution Overview
Problem
Linear motors face challenges in reducing the cogging force, also known as expansion force, which is detrimental to their optimal operation due to magnetic interactions between permanent magnets and iron in the support means, leading to undesirable fluctuations in the pushing force.
Innovation Solution
A double air gap linear electromagnetic motor design with asymmetrical coil support means on either side of the stator, featuring auxiliary teeth of varying heights and offsets, creates a unique magnetic circuit that reduces the cogging force by introducing double asymmetry, allowing for reduced magnetic interaction and improved operational precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If iron support means (teeth) are used to hold the coils, then the coils are securely supported and the magnetic field is enhanced, but the cogging force increases due to magnetic interaction between permanent magnets and iron
Solution Approach 1:
The patent applies asymmetry by making the auxiliary teeth on the first side of the stator have a different configuration than those on the second side. Specifically, the auxiliary teeth on the first side are positioned at different locations relative to the magnets compared to the second side, creating an asymmetric magnetic circuit that prevents the formation of cogging forces while maintaining secure coil support through the iron teeth structure.
2Ease of manufacture
If symmetrical coil support means are used on both sides of the stator, then the structure is balanced and easier to manufacture, but the cogging force is not effectively reduced
Solution Approach 1:
The patent deliberately breaks symmetry by configuring the auxiliary teeth differently on the first side versus the second side of the stator. The auxiliary teeth on each side are positioned at asymmetric locations relative to the permanent magnets, creating an asymmetric magnetic circuit that effectively reduces cogging force while remaining manufacturable through standard machining processes.
3Strength
If auxiliary teeth are added to both longitudinal ends of the stator, then the structural support is enhanced, but the cogging force reduction is insufficient without asymmetrical configuration
Solution Approach 1:
The patent enhances structural support by adding auxiliary teeth at the longitudinal ends of the stator on both sides, while simultaneously configuring these auxiliary teeth asymmetrically. The auxiliary teeth on the first side are positioned differently relative to the magnets than those on the second side, creating an asymmetric magnetic circuit that reduces cogging force while the iron teeth provide robust structural support for the coils.
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
The double asymmetry in the stator's coil support structure effectively minimizes the cogging force, enhancing the motor's speed and precision by reducing magnetic field fluctuations and maintaining force generation performance.
Implementation Method 1
the coils create the magnetic field around the teeth
Implementation Method 2
the presence of iron also has the disadvantage for the linear motor of possessing a residual force called the expansion force when de-energized. This expansion force, also called cogging force in English, is due to the magnetic interaction between the permanent magnets of the actuator of the linear motor and the iron present in the support means
Data Source
Figure 1~3
AI summary
The present invention relates to a linear motor (1) including an actuator (2) comprising a series of magnets (4) extending lengthwise, the stator (3) including a longitudinal central passage for the actuator (2) and a series of coils (5) arranged respectively on a first and second side of the passage on respective supporting means (9), the coils (5) are arranged respectively on a first and second end of a central passage, creating a respective air gap (6) between series of coils (5) and magnets (4), and in that the longitudinal ends (7, 8a) of the stator (3) are asymmetric relative to the respective opposite longitudinal ends (7a, 8) while one longitudinal end (7a) of the stator (3) on the second side is asymmetric relative to the other end (8) of the stator (3). The invention can be used for electromagnetic motors or generators.