Sensorless Induction Motor Speed Estimation via Flux Coordinate Transformation
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Solution Overview
Problem
Existing speed sensorless control technologies for electric motors face performance degradation when removing position sensors, struggling to accurately and rapidly track fast-changing speed references, limiting their application to low or medium performance fields.
Innovation Solution
A method and system that estimate the speed of an induction motor without sensors by transforming the motor model into a new coordinate system, decoupling unmeasured parameters, and using a set of ordinary differential equations to stabilize the state estimator, allowing for constant gain tuning and improved control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed sensorless control is implemented to eliminate sensors, then cost and reliability are improved, but measurement precision and control accuracy deteriorate
Solution Approach 1:
The patent replaces mechanical sensors (encoders, resolvers) with an electronic state observer that estimates rotor speed and position through mathematical modeling and signal processing. The observer uses stator current and voltage measurements combined with motor parameters to compute rotor flux and speed without physical sensors, thereby eliminating mechanical components while maintaining control accuracy.
2Device complexity
If conventional speed sensorless control methods are used, then device complexity is reduced, but speed tracking performance and responsiveness worsen
Solution Approach 1:
The patent implements a dynamic state observer that continuously adapts to changing motor operating conditions. The observer uses differential equations to model motor dynamics and实时更新 rotor flux and speed estimates based on current measurements. This dynamic approach enables accurate tracking of fast-changing speed references while maintaining relatively simple hardware architecture.
3Measurement precision
If motor model transformation is applied to decouple parameters, then estimation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent transforms the motor model from the stationary reference frame to the rotating reference frame aligned with rotor flux. This coordinate transformation decouples the motor equations, separating flux-producing and torque-producing current components. The transformed model enables independent estimation of rotor flux magnitude and angle, significantly improving speed estimation accuracy while the modular structure manages computational load efficiently.
Data Source
AI summary
A motor drive of an induction motor includes a motion controller to provide a reference signal and a memory to store a transformed model relating dynamics of a transformed state of the motor with measurements through parameters of transformed model including unknown parameters. The transformed state is a function of an electromagnetic state of the motor and parameters of transformed model. The dynamics of the transformed state is defined by a sum of components, each component is a linear function of the transformed state and at least one of the unknown parameters of the transformed model. The motor drive also include a motor controller to produce an estimate of speed and flux of the motor based on measurements and the transformed model, and to produce a reference voltage to track the reference signal based on the estimate of the speed and the flux of the motor.