Multiphase Motor Magnet Assembly Gap Compensation
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Solution Overview
Problem
Conventional multiphase linear or planar motors used in lithographic apparatuses experience significant ripple in motor constant due to the position-dependent force generation, which is undesirable, especially when high accelerations are required, leading to inefficiencies and inaccuracies in positioning systems.
Innovation Solution
A multiphase motor design is introduced, featuring a coil system with non-zero gaps between adjacent coil assemblies and a magnet system with strategically extended dimensions to compensate for these gaps, ensuring a reduced ripple in motor constant across different positions, thereby improving positioning accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a multiphase linear motor with moving magnets and fixed coils is used to achieve high acceleration (up to 400 m/s²), then the required forces are relatively large, but this results in a ripple in the motor constant of up to 8%, which is undesirable
Solution Approach 1:
The patent inverts the conventional motor configuration by making the coils moveable and the magnets fixed. This inversion transforms the source of magnetic fields: instead of moving magnets interacting with fixed coils, moving coils now interact with fixed magnets, fundamentally changing how force is generated and reducing position-dependent ripple in the motor constant while maintaining high acceleration capability
2Reliability
If the magnet assembly dimension is extended to J times the coil assembly dimension plus J/2 times the gap to compensate for gaps between coil assemblies, then the ripple in motor constant is reduced, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by extending the magnet assembly dimension to a specific value (J times the coil assembly dimension plus J/2 times the gap) to optimize the magnetic field distribution. This dimensional parameter adjustment compensates for gaps between coil assemblies, reducing motor constant ripple while maintaining a manageable device complexity through mathematical optimization
3Ease of manufacture
If a non-zero gap is present between adjacent coil assemblies, then manufacturing and assembly ease is improved, but the motor constant exhibits position-dependent ripple
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the harmful effect of gaps between coil assemblies. The magnet assembly is designed with an extended dimension that anticipates and counteracts the disruptive magnetic field effects of the gaps, thereby maintaining force generation consistency despite the presence of manufacturing-necessary gaps
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 proposed motor design significantly reduces the ripple in motor constant, achieving a more consistent and accurate force generation, enhancing the positioning precision and reducing inefficiencies, particularly at high acceleration levels.
Implementation Method 1
the coil system is configured to generate magnetic fields interacting with the magnet system to cause driving forces in the first main driving direction to move the magnet system relative to the coil system
Data Source
AI summary
An electromagnetic motor is described, the electromagnetic motor comprising:a magnet assembly configured to generate a two-dimensional alternating magnetic field having a pitch Pm1 in a first direction and a pitch Pm2 in a second direction;a coil assembly configured to co-operate with the magnet assembly to generate a first force in the first direction and a second force in the second direction, wherein the coil assembly comprises a first coil set comprising a plurality of first coils for generating the first force and a second coil set comprising a plurality of second coils for generating the second force, wherein a ratio R1 of a coil pitch Pc1 in the first coil set in the first direction over Pm1 is different from a ratio R2 of a coil pitch Pc2 in the second coil set in the second direction over Pm2.