Sensorless Electric Motor Speed Control via Adaptive Feedback Gain
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Solution Overview
Problem
Speed sensorless control of electric motors faces performance degradation due to the removal of position sensors, limiting its application to low or medium performance fields, as it struggles to accurately and rapidly track fast-changing speed references.
Innovation Solution
A method and system that estimate motor speed without sensors by varying feedback gain based on error analysis between measured and estimated currents, using a feedback gain that adapts to different operational modes and incorporating a feedforward term for improved convergence, allowing for accurate speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed sensorless control is implemented to eliminate position sensors, then cost and reliability are improved, but speed estimation accuracy and responsiveness deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the estimated speed is continuously fed back to correct the current model predictions. The speed estimator uses the difference between actual and estimated currents to generate speed estimates, which are then used to update the motor model, creating a closed-loop feedback system that improves estimation accuracy over time.
Solution Approach 2:
The patent replaces the mechanical/physical speed sensor with an electronic/software-based speed estimator that uses mathematical models and signal processing. The estimator substitutes the physical sensing mechanism with a computational approach using current measurements and motor models to derive speed information electronically.
2Device complexity
If speed sensorless control is implemented to eliminate position sensors, then device complexity is reduced, but tracking performance of fast-changing speed references deteriorates
Solution Approach 1:
The patent employs dynamic adaptation by adjusting the feedback gain based on operating conditions. The gain scheduling mechanism dynamically modifies the estimator's responsiveness to match the motor's operational state, enabling fast tracking during transient conditions while maintaining stability during steady-state operation.
Solution Approach 2:
The patent changes the feedback gain parameter adaptively based on the motor's operational mode. By modifying the gain parameter in response to operating conditions, the system optimizes its tracking performance for fast-changing speed references while maintaining simplicity in the overall control architecture.
3Measurement precision
If feedback gain is increased to improve speed estimation accuracy, then measurement noise and model inaccuracies are amplified
Solution Approach 1:
The patent dynamically adjusts the feedback gain parameter based on operating conditions to optimize the trade-off between estimation accuracy and noise amplification. By changing the gain parameter adaptively, the system achieves high accuracy when needed while minimizing noise amplification during steady-state operation.
Solution Approach 2:
The patent implements a dynamic feedback gain mechanism that adapts to changing operational conditions. The gain is increased during transient states when accuracy is critical and reduced during steady-state operation to minimize noise amplification, creating a dynamic balance between these competing requirements.
Data Source
AI summary
An electric motor is controlled using a feedback signal that includes an error between the measured current and the estimated current determined using the measured current, the measured voltage, and a model of the motor. A feedback gain is determined as an error function of a feedback signal and a speed of the motor is estimated using a product of the feedback gain and the feedback signal. The voltage of the motor is determined using a difference between the estimated speed of the motor and a reference speed of the motor and the motor us controlled using the determined voltage.