Electric Machine Control Using Air-Gap Flux Measurement
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Solution Overview
Problem
Existing control methods for electric machines require precise knowledge of machine parameters and position sensors to operate efficiently, which can be inadequate due to production fluctuations and temperature variations, especially in estimating rotor position without accurate metrological effort.
Innovation Solution
A method using measurement coils in the air gap between the rotor and stator to directly determine magnetic linkage fluxes and phase currents, transforming them into a stator-fixed coordinate system to calculate instantaneous torque and flux-forming components, allowing for sensorless control of electric machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If model-based control with easily measurable variables is used to avoid position sensors, then device complexity is reduced, but measurement precision deteriorates due to insufficient accuracy in estimating rotor position
Solution Approach 1:
The patent introduces measurement coils as intermediary sensors placed in the air gap to directly measure magnetic flux density. These coils serve as a mediator between the rotor position and the control system, providing accurate positional information without requiring complex external position sensors. The measurement coils transform the magnetic field information into electrical signals that can be processed by the control system.
Solution Approach 2:
The patent replaces mechanical/optical position sensors with electromagnetic measurement coils. Instead of using mechanical encoders or optical sensors that require physical contact or line-of-sight, the system uses electromagnetic induction through measurement coils to detect rotor position. This substitution eliminates the need for complex mechanical or optical systems while improving measurement accuracy.
2Measurement precision
If mathematical models with operating conditions are used to improve measurement precision, then measurement precision improves, but device complexity increases due to additional sensors and calculations
Solution Approach 1:
The patent extracts only the essential measurement function by placing measurement coils directly in the air gap to measure magnetic flux density. This extraction approach eliminates the need for complex multi-sensor systems and sophisticated mathematical models. The measurement coils provide direct measurement of the magnetic field, from which rotor position can be determined through straightforward calculations without requiring additional temperature sensors or complex compensation algorithms.
3Device complexity
If production-related parameter fluctuations are not considered, then device complexity remains low, but reliability deteriorates due to inadequate control accuracy
Solution Approach 1:
The measurement coils in the air gap enable the system to self-diagnose and adapt to production-related parameter fluctuations. By directly measuring the magnetic flux density, the system automatically compensates for variations in magnetic properties, winding resistance, and other parameters that may differ between individual machines. This self-service approach eliminates the need for external parameter measurement systems while maintaining high control accuracy.
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
Enables precise control of electric machines without position sensors or inaccurate model-based estimates, improving reliability and energy efficiency by directly measuring control variables and diagnosing potential faults.
Implementation Method 1
measuring magnetic linkage fluxes in the air gap with the aid of measurement coils
Data Source
AI summary
A method for controlling an electric machine using measurement coils arranged in an air gap situated between a stator and a rotor of the electric machine, a plurality of phase windings assigned to different electrical phases being present. Magnetic linkage fluxes are measured in the air gap via the measurement coils, Magnetic linkage fluxes are determined of the plurality of phase windings of the different phases. The determined magnetic linkage fluxes are transformed into a stator-fixed orthogonal coordinate system in order to obtain orthogonal magnetic linkage fluxes. Phase currents flowing through the plurality of phase windings are measured. The measured phase currents are transformed into the stator-fixed orthogonal coordinate system in order to obtain orthogonal phase currents. An instantaneous torque and/or a flux-forming component of a phase current vector are ascertained. The electric machine is controlled based on the instantaneous torque and/or the flux-forming component.