Rotor Position Estimation via Load-Adaptive Observer
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Solution Overview
Problem
Existing methods for estimating the rotor position of synchronous motors face accuracy and reliability issues due to significant changes in the salient pole effect with load variations, particularly at low speeds and heavy loads.
Innovation Solution
A method that involves injecting a high-frequency signal into the stator winding to obtain a position error signal, and then compensating this signal based on load parameter-derived direct-current and harmonic component disturbance values, while adjusting observer parameters to improve estimation accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high-frequency injection method is used for rotor position detection, then position detection can be achieved without sensors, but position estimation accuracy deteriorates under heavy load due to salient pole effect distortion
Solution Approach 1:
The patent changes the observer parameters dynamically based on load conditions. Specifically, the gain parameters of the position observer are adjusted according to the estimated load torque, allowing the system to adapt to varying operating conditions and maintain accurate position estimation even under heavy load where salient pole effects distort the current signals.
Solution Approach 2:
The patent implements a feedback mechanism where the estimated rotor position and speed are continuously fed back to update the observer parameters. The system uses the estimated load torque as feedback to adjust the observer gains, creating a closed-loop control that compensates for the distortions caused by salient pole effects under different load conditions.
2Device complexity
If observer parameters are kept fixed for simplicity, then system complexity is reduced, but position estimation reliability deteriorates when load conditions change significantly
Solution Approach 1:
The patent makes the observer parameters dynamic rather than fixed. The gain parameters are continuously adjusted based on the estimated load torque, transforming the static observer into a dynamic adaptive system. This allows the observer to maintain reliability across varying load conditions while adding only moderate complexity through the use of pre-defined parameter lookup tables or calculation formulas.
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
The proposed method enhances the accuracy and reliability of rotor position estimation, improves the stability of high-frequency injection sensorless algorithms at low speeds and heavy loads, and expands the application range of these algorithms.
Implementation Method 1
obtaining a position error signal by injecting a high-frequency signal into a stator winding of the motor
Data Source
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AI summary
A method and apparatus for estimating a rotor position of an electric motor, and an electric motor control system. The method comprises: obtaining a position error signal by means of injecting a high-frequency signal into a stator winding of an electric motor (S1); acquiring a load parameter for indicating a load of the electric motor, acquiring a direct-current component disturbance value according to the load parameter and a first preset relationship, acquiring a harmonic component disturbance value according to the load parameter and a second preset relationship, and acquiring an observer parameter value according to the load parameter and a third preset relationship (S2); compensating for the position error signal according to the direct-current component disturbance value and the harmonic component disturbance value so as to obtain a compensated position error signal (S3); and adjusting a parameter of an observer according to the observer parameter value, and adjusting the compensated position error signal by means of the adjusted observer so as to obtain a rotor position and a rotor speed (S4). Thus, the method for estimating a rotor position can solve the problems of position estimation precision and reliability brought about by a change in the saliency effect of an electric motor along with a load.