Electromagnetic Actuator Magnet Array Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithographic apparatuses face challenges with non-current and current-related ripples in electromagnetic actuators, such as torque ripples, K-factor ripples, and normal force ripples, which affect the performance and precision of moving components, especially with increased masses and dimensions requiring higher coil currents.
Innovation Solution
The electromagnetic actuator design features a magnet array with primary and subsidiary magnets, where the polarization direction of end primary magnets differs from that of intermediate primary magnets, and subsidiary magnets are positioned between adjacent primary magnets, optimizing the magnetic field distribution to reduce torque, K-factor, and normal force ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher coil currents are used to drive higher masses with higher acceleration, then productivity and acceleration are improved, but torque ripple, K-factor ripple, and normal force ripple increase
Solution Approach 1:
The patent applies local quality by differentiating the polarization directions of magnets in different positions within the array. End magnets have different polarization directions compared to intermediate magnets, creating localized magnetic field variations that compensate for position-dependent torque ripples. This local differentiation in magnetic properties reduces the harmful torque ripple effects while maintaining the required acceleration performance.
Solution Approach 2:
The patent introduces asymmetry in the magnetic field configuration by varying the polarization directions of magnets based on their position. The end magnets are configured with different polarization directions compared to intermediate magnets, breaking the uniform symmetry of traditional magnet arrays. This asymmetric configuration effectively reduces torque ripple, K-factor ripple, and normal force ripple while preserving the actuator's ability to achieve high acceleration.
2Force
If coil dimensions and currents are increased to handle higher forces, then force capability is improved, but device complexity and cabling requirements increase
Solution Approach 1:
The patent changes the magnetic field parameters by varying the polarization directions of magnets in the array. This parameter modification optimizes the magnetic field distribution to reduce ripples, allowing the actuator to achieve the required force capability with more efficient coil configurations. The optimized magnetic field reduces the need for excessively large coil currents, thereby simplifying cabling requirements while maintaining force capability.
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 configuration significantly reduces torque ripple by about ±20%, K-factor ripple, and normal force ripple to below ±1%, enhancing the stability and precision of the actuator's movement, thereby improving the overall performance and productivity of the lithographic apparatus.
Implementation Method 1
a stationary part comprising a plurality of coils and a magnetic circuit of magnetizable material, and a movable part comprising a magnet system
Implementation Method 2
The magnet system comprises an array of magnets forming a magnet array having opposite ends, each magnet of the magnet array having a direction of polarization
Data Source
AI summary
A lithographic apparatus is arranged to transfer a pattern from a patterning device onto a substrate and includes an electromagnetic actuator to actuate a part of the lithographic apparatus in a linear direction or in a rotational direction. The actuator has a substantially stationary part and a movable part interacting with each other. The stationary part has a plurality of coils and a magnetic circuit of magnetizable material, and the movable part has a magnet system. The magnet system has an array of magnets forming a magnet array having opposite ends. The magnet array has an array of primary magnets and an array of subsidiary magnets alternating with the primary magnets. A direction of polarization of an end primary magnet at an end position of the array of primary magnets differs from a direction of polarization of an intermediate primary magnet at an intermediate position between the end primary magnets.