Linear Motor Stage Current Control for Thermal Stability

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Solution Overview

Problem

Existing stage control methods for charged particle beam apparatuses, such as electron microscopes, face challenges in maintaining positioning accuracy due to temperature changes caused by motor heat generation, which affects the service life of the stage and its components.

Innovation Solution

A stage system with a linear motor mechanism and a control section that adjusts the current flowing through the coil to maintain a thrust force greater than the maximum static friction force, reducing temperature changes between driving and static states, and employing a warming up operation to replicate heat generation during non-operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the stage is operated continuously to maintain temperature, then temperature stability is improved, but service life of guide rails and wiring becomes shorter

Engineering Contradiction:

Improvetemperature stabilityVSAvoidservice life of guide rails and wiring

Core Design Contradiction:

TemperatureVSDuration of action of stationary object

Solution Approach 1:

The control section performs preliminary heating of the linear motor coil before actual stage operation begins. By pre-heating the coil to a predetermined temperature, the system eliminates the need for continuous operation during normal use, thereby extending the service life of mechanical components while maintaining temperature stability when needed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the operating state of the linear motor based on real-time temperature monitoring. When the coil temperature falls below the predetermined threshold, the control section activates heating mode; when the temperature is sufficient, it switches to standby mode. This dynamic control optimizes both temperature stability and component longevity.

Inventive Principle:

Principle #15Dynamics

2Temperature

If the current amount is increased to generate more heat, then temperature stability is improved, but energy consumption increases

Engineering Contradiction:

Improvetemperature stabilityVSAvoidenergy consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

Instead of continuous high current flow, the system uses periodic intermittent heating. The control section monitors coil temperature and activates the linear motor only when temperature drops below the predetermined level. This periodic action maintains temperature stability while significantly reducing overall energy consumption compared to continuous operation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system changes the current parameter dynamically based on temperature conditions. During heating mode, high current is applied to rapidly raise temperature; during standby mode, current is reduced to minimal levels. This parameter adjustment optimizes the balance between temperature stability and energy consumption.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If the stage is moved frequently to maintain temperature, then temperature stability is improved, but positioning accuracy deteriorates

Engineering Contradiction:

Improvetemperature stabilityVSAvoidpositioning accuracy

Core Design Contradiction:

TemperatureVSMeasurement precision

Solution Approach 1:

The control section acts as an intermediary that decouples temperature maintenance from stage movement. Instead of moving the stage to generate heat, the system directly controls the linear motor coil temperature through targeted current application. This eliminates the need for frequent stage movements, thereby maintaining both temperature stability and positioning accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention extracts the temperature generation function from the stage movement mechanism. By applying current directly to the linear motor coil, the system generates heat independently of stage position or movement, separating the thermal management function from the positioning function and preserving measurement precision.

Inventive Principle:

Principle #2Taking out (Extraction)

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 improves positioning accuracy without reducing the service life of the apparatus, by maintaining a consistent temperature and heat generation level, thus enhancing the reliability of the stage system.

Implementation Method 1

a linear motor mechanism that moves the stage by a thrust force generated by a current flowing through the coil

Methodology Applied

Scientific EffectElectromagnetic interaction: Lorentz Force

Implementation Method 2

a current flowing through the coil in a state where the stage is maintained in the static state be greater than a minimum current amount required for generating the thrust force

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9502208B2Charged particle beam apparatus, stage controlling method, and stage system

Publication Date: 2016.11.22 HITACHI HIGH TECH CORP

AI summary

A stage system includes a stage that holds an object, a linear motor mechanism that moves the stage by a thrust force generated by a current flowing through the coil, and a control section that controls the current flowing through the coil. The current flowing through the coil in a state where the stage is maintained in the static state be greater than a minimum current amount required for generating the thrust force greater than a maximum static friction force of the stage with respect to the guide rails.