Electromagnet Control Device for Precise Magnetic Flux Density
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Solution Overview
Problem
In plasma processing devices, achieving precise control over magnetic flux density is hindered by residual magnetism due to hysteresis in electromagnets, leading to inconsistencies between target and actual magnetic flux densities, which affects reproducibility and requires materials with low hysteresis, increasing costs and complexity.
Innovation Solution
An electromagnet control device that determines current values based on measured hysteresis data using multiple functions and scaling ratios to apply step or ramp waveforms, ensuring precise control of magnetic flux density, independent of the yoke material's hysteresis characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current is controlled to achieve target magnetic flux density, then magnetic field control precision is improved, but residual magnetism due to hysteresis causes deviation between target and actual values
Solution Approach 1:
The control device measures the actual magnetic flux density generated by the electromagnet and compares it with the target value. Based on the deviation detected, the control device adjusts the current applied to the coil to correct the magnetic flux density, thereby achieving precise and reproducible control despite hysteresis effects
Solution Approach 2:
The control device changes the current parameter dynamically based on the measured magnetic flux density and hysteresis characteristics. By adjusting the current magnitude and direction according to the operational state (increasing or decreasing magnetic flux density), the system compensates for hysteresis and achieves accurate control
2Measurement precision
If yoke material with low hysteresis is used, then magnetic flux density accuracy is improved, but material costs and device complexity increase
Solution Approach 1:
The control device converts the harmful hysteresis effect into a usable characteristic by measuring and storing hysteresis data. This data is then used to determine appropriate current values that compensate for hysteresis, allowing the use of ordinary yoke materials while maintaining high accuracy through software-based correction
Solution Approach 2:
The invention replaces the requirement for special low-hysteresis materials with a control system that uses measurement and calculation. Instead of relying on material properties, the system uses a control device that determines current values based on measured hysteresis characteristics, substituting material science requirements with engineering control
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 reduces the effect of residual magnetism, allowing precise alignment of target and actual magnetic flux densities, improving reproducibility and reducing material costs by enabling the use of less expensive yoke materials with higher hysteresis.
Implementation Method 1
an electromagnet control device for controlling current flowing through a coil of an electromagnet comprising a yoke and the coil
Implementation Method 2
it has been known that magnetic hysteresis (hereinafter, this is simply referred to as 'hysteresis') exists between the controlled current applied to the electromagnet and the generated magnetic flux density
Data Source
AI summary
A target value of magnetic flux density and magnetic flux density actually obtained are made to coincide precisely with each other. An electromagnet control device comprises a current value determining unit for determining, based on a magnetic flux density instruction value, a value of current that is made to flow through a coil. The current value determining unit is constructed to execute a second process for determining, based on a second function, a value of the current, if the magnetic flux density is to be decreased from that in a first magnetization state, and a fourth process for expanding or reducing the second function by use of a first scaling ratio for transforming it to a fourth function, and determining, based on the fourth function obtained after above transformation, a value of the current, if the magnetic flux density is to be decreased from that in a third magnetization state.