Linear Motor Cogging Reduction via Auxiliary Core Positioning
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Solution Overview
Problem
Conventional methods for reducing cogging in linear motors are ineffective due to the introduction of auxiliary cores, which can themselves cause cogging issues, making it difficult to balance magnetic flux and maintain smooth linear movement.
Innovation Solution
The implementation of auxiliary cores positioned at a specific distance from the center salient pole, with a gap or non-magnetic material between them and the core, to generate a cogging force that cancels out the center salient pole's cogging force, thereby reducing overall cogging and maintaining separate components for easier adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If auxiliary cores are provided to strengthen the magnetic flux of salient poles at the respective ends, then magnetic flux balance is improved, but cogging is worsened due to new cogging forces generated by the auxiliary cores
Solution Approach 1:
The invention converts the harmful cogging force generated by auxiliary cores into a beneficial effect by strategically positioning them to generate cogging forces that cancel out the original cogging from the center salient pole. The auxiliary cores, which initially cause new cogging, are placed at specific distances (1/4, 3/4, 5/4, etc. of magnetic pole pitch) from the center salient pole so their cogging forces become opposite in phase, thereby reducing overall cogging while maintaining magnetic flux balance.
Solution Approach 2:
The invention changes the positional parameter of auxiliary cores relative to the center salient pole. By setting the distance to specific values (1/4×(2N+1)×magnetic pole pitch where N is an integer ≥1), the phase relationship between cogging forces changes, transforming the harmful effect into a canceling effect. This parameter optimization allows the system to simultaneously achieve magnetic flux balance and cogging reduction.
2Manufacturing precision
If auxiliary cores are positioned close to the core to strengthen magnetic flux, then magnetic circuit formation is improved, but cogging reduction becomes difficult due to increased interaction
Solution Approach 1:
The invention applies local quality by creating asymmetric positioning of auxiliary cores relative to the center salient pole. The auxiliary cores are placed at specific distances (1/4, 3/4, 5/4, etc. of magnetic pole pitch) rather than symmetrically close to the core, creating a localized magnetic flux distribution that strengthens end salient poles while generating cogging forces that cancel the center pole's cogging. This localized positioning strategy simultaneously achieves flux strengthening and cogging control.
3Object-generated harmful factors
If conventional cogging reduction methods are applied to auxiliary cores, then cogging from auxiliary cores is reduced, but the overall solution becomes ineffective due to intertwined cogging factors
Solution Approach 1:
The invention takes a holistic view that converts the cogging from auxiliary cores into a beneficial canceling force. Rather than trying to reduce auxiliary core cogging separately (which creates a complex intertwined control system), the invention positions auxiliary cores to generate cogging forces that directly counteract the original cogging from the center salient pole. This approach treats the auxiliary cores' cogging not as a problem to be eliminated but as a resource to be utilized for overall cogging reduction.
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 effectively reduces cogging force across the entire core, allowing for balanced movement and simplifying the manufacturing process by avoiding the need for complex redesign of the core, while also reducing the load on guiding components.
Implementation Method 1
the auxiliary cores 18 are provided to strengthen the magnetic flux of salient poles 1a and 1b at respective ends
Implementation Method 2
magnetic attraction is generated between the salient poles of the core and the permanent magnets
Implementation Method 3
the cogging force of the whole core can be reduced by generating a cogging force at the auxiliary cores having such a waveform as to cancel the waveform of the cogging force generated at the center salient pole
Data Source
AI summary
Provided is a linear motor capable of reducing cogging. The linear motor has a field magnet part 5 having a plurality of permanent magnets 21 arranged to form N and S poles alternately; a core 14 having a plurality of salient poles 14a, 14b and 14c arranged facing the field magnet part 5; and a three-phase coil 16 wound around the salient poles 14a, 14b and 14c of the core 14. At respective sides in the moving direction of an armature having the three-phase coil 16 and the core 14, auxiliary cores 18 made of a magnetic material are provided to sandwich the armature 10. The distance P1 between a center of each auxiliary core and a center of a center salient pole 14b is set to be substantially ¼×(2N+1)×a magnetic pole pitch between N poles of the field magnet part 5 (N: an integer equal to or greater than 1).