Sensorless Flux Estimation for EPS Motor Control
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Solution Overview
Problem
Existing Electric Power Steering (EPS) systems rely on sensor-based Field Oriented Control (FOC) for motor control, which can fail when position sensors malfunction, leading to Loss of Assist (LoA), and require accurate stator flux estimation for high performance, but existing sensorless control algorithms face challenges in precise flux estimation.
Innovation Solution
A system that estimates flux linkages based on back electromagnetic force and estimated velocity, using a flux estimation module with alpha and beta components, and a velocity estimation module, implemented in a sensorless FOC scheme to provide robust and accurate motor control without physical position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless control is used to avoid position sensor failure, then system reliability is improved, but flux estimation accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the estimated flux linkages are fed back into the velocity estimation process, and the estimated velocity is fed back into the flux estimation process. This mutual feedback loop allows the system to continuously refine its estimates and maintain accuracy despite the absence of physical position sensors, thereby resolving the contradiction between reliability improvement and measurement precision deterioration.
Solution Approach 2:
The patent transforms the control approach by changing from direct position measurement to indirect parameter estimation. It uses electrical parameters (voltages and currents) to estimate mechanical parameters (flux linkages and velocity) through mathematical models, enabling sensorless operation while maintaining control accuracy through proper parameter transformation and estimation algorithms.
2Reliability
If sensorless FOC is implemented without physical position sensors, then fault tolerance is improved, but control precision deteriorates
Solution Approach 1:
The patent introduces flux linkages as an intermediary variable that bridges the gap between electrical inputs and mechanical outputs. By estimating flux linkages from voltages and currents, and then using these flux estimates to determine velocity and position, the system creates an indirect measurement path that maintains control precision without requiring direct position sensor feedback, thus achieving fault tolerance while preserving control accuracy.
Solution Approach 2:
The patent replaces the mechanical position sensing system with an electrical-based estimation system. Instead of using physical position sensors to directly measure rotor position, the system uses electrical measurements (voltages and currents) processed through mathematical models to estimate the mechanical state, substituting a mechanical sensing approach with an electrical-field-based approach that provides fault tolerance while maintaining precision.
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 solution enables fault-tolerant control by accurately estimating flux linkages and motor velocity, preventing performance degradation and Loss of Assist in EPS systems, even without physical position sensors, thus enhancing system reliability and performance.
Implementation Method 1
generates estimated flux linkages based on a back electromagnetic force and estimated velocity of the electric motor
Data Source
AI summary
A system for estimating flux linkage in an electric motor includes a flux estimation module that generates estimated flux linkages based on a back electromagnetic force and estimated velocity of the electric motor, the flux linkages having an alpha flux linkage component and a beta flux linkage component, and a velocity estimation module that generates an estimated motor velocity based on the back electromagnetic force and the estimated flux linkages.