Linear Motor Coil Load Balancing for Lithography Stage Control
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Solution Overview
Problem
Existing multi-phase linear motor systems in lithography apparatuses experience local deterioration and performance degradation due to uneven power loads on coils during acceleration and deceleration, leading to temperature rises and reduced motor life.
Innovation Solution
A control method for a driving apparatus that adjusts the position of the stator with respect to a predetermined range and determines output ratios of coils to balance current loads at both acceleration and deceleration points, reducing the bias on coils and minimizing local deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current is applied only to one phase coil during acceleration, then the power load is concentrated on that coil, but this leads to remarkable temperature rise and performance deterioration
Solution Approach 1:
The patent implements periodic switching between two-phase excitation modes (Mode 1 and Mode 2) with 90-degree phase difference. By alternating the active phase coils in a periodic manner during acceleration and deceleration, the power load is distributed over time across different coils, preventing continuous concentration on a single coil and thereby reducing temperature rise and performance deterioration.
2Force
If multi-phase excitation is used to reduce thrust unevenness, then constant thrust is obtained, but local deterioration in the stator still occurs due to biased power loads
Solution Approach 1:
The patent maintains constant thrust through multi-phase excitation while simultaneously preventing local deterioration by periodically switching between two excitation modes with 90-degree phase difference. This periodic switching ensures that no single phase coil bears the full power load continuously, distributing the stress and heat generation across multiple coils over time, thereby maintaining both thrust uniformity and stator reliability.
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 the local deterioration of the stator coils by distributing current loads more evenly, thereby enhancing the performance and lifespan of the linear motor.
Implementation Method 1
a multi-phase linear motor that selectively switches the coil to be energized in accordance with the position of a mover
Implementation Method 2
utilizes the principle of sin2(x)+cos2(x)=1. When driving the stage, the multi-phase excitation driving type linear motor simultaneously applies, to the coils of two phases whose phase angles of the magnetic flux densities are separated by 90°, currents corresponding to the respective magnetic flux densities
Implementation Method 3
the power load is concentrated only on the coil of one phase, and this leads to a remarkable temperature rise. Accordingly, the heat generation of the coil locally increases
Data Source
AI summary
The present invention provides a control method of a driving apparatus that repeatedly performs a process of driving a target object in a predetermined range by a linear motor, wherein the linear motor includes a stator in which a plurality of coils are arrayed, and a mover provided with the target object, the control method comprising: changing a position of the stator with respect to the predetermined range at an arbitrary timing; and determining, in accordance with the changed position of the stator, output ratios of the plurality of coils in the process.