AC Motor Angle Detection Noise Compensation
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Solution Overview
Problem
Existing AC rotary machines face challenges in detecting the angular position of a rotor with high precision due to magnetic field interference, leading to increased costs, weight, and reduced productivity, as well as potential over-correction or under-correction of angle errors and high processing loads.
Innovation Solution
A control device for an AC rotary machine that includes an inverter, a magnetic field generator, an angle detector, and a control calculation unit, which corrects angle detection errors caused by noise magnetic fields using a correction signal with specific phase and amplitude determined by the relative positional relationship between the inverter connection unit and the angle detector, allowing for precise angular position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lid unit is disposed between the armature and the magnetic sensor to suppress magnetic field effects, then the angular position detection precision is improved, but the cost and overall weight of the product increase
Solution Approach 1:
The patent extracts and eliminates the harmful magnetic field effects generated by the armature through mathematical compensation algorithms, removing the need for the physical lid unit. The harmful magnetic field interference is separated from the detection system and compensated through software calculation, achieving weight reduction while maintaining detection precision.
Solution Approach 2:
The patent replaces the mechanical lid unit with an electronic/mathematical compensation system. Instead of using a physical structure to block or shield magnetic fields, the system uses signal processing and mathematical models to compensate for magnetic field interference, substituting mechanical means with electronic computation.
2Measurement precision
If a lid unit is disposed between the armature and the magnetic sensor to suppress magnetic field effects, then the angular position detection precision is improved, but productivity is reduced
Solution Approach 1:
The patent removes the lid unit from the assembly process and replaces it with software-based magnetic field compensation. This eliminates the additional manufacturing step of installing the lid unit, thereby improving productivity while maintaining the precision benefits through computational compensation.
Solution Approach 2:
The patent substitutes the mechanical lid unit installation process with an electronic compensation algorithm that can be integrated into the control system software. This replacement eliminates the need for additional assembly operations, improving manufacturing productivity while achieving the same precision improvement.
3Measurement precision
If frequency analysis is implemented on the speed signal to calculate detection errors for each frequency component, then angular position detection precision is improved, but the processing load increases
Solution Approach 1:
The patent changes the approach from frequency-domain analysis (Fourier transform) to time-domain or spatial-domain mathematical compensation. By using alternative mathematical models that operate on the raw sensor signals directly, the system achieves similar precision improvement with reduced computational complexity and processing load.
4Measurement precision
If frequency analysis is implemented on the speed signal to calculate detection errors for each frequency component, then angular position detection precision is improved, but over-correction or under-correction may occur
Solution Approach 1:
The patent performs preliminary characterization of the magnetic field interference patterns during system setup or calibration, storing compensation parameters in advance. This preliminary action allows the system to apply pre-calculated compensation factors during operation, avoiding the need for complex real-time frequency analysis and reducing the risk of over-correction or under-correction.
Solution Approach 2:
The patent converts the harmful magnetic field interference into a predictable, modelable effect that can be compensated through mathematical relationships. By understanding and modeling the interference pattern, the system transforms the harmful effect into a correctable deviation, achieving reliable precision improvement without over-correction.
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 solution enables a simple, low-cost control device for AC rotary machines to detect the angular position of a rotor with high precision, reducing errors and processing loads while maintaining productivity and minimizing weight and cost.
Implementation Method 1
a magnetic field generator for generating an angle detecting magnetic field for detecting a rotation angle of the AC rotary machine by rotating in synchronization with the rotor
Implementation Method 2
an angle detector for detecting two mutually orthogonal components of the angle detecting magnetic field generated by the magnetic field generator as a sine signal and a cosine signal
Implementation Method 3
a noise magnetic field generated by a multi-phase alternating current flowing through the inverter connection unit
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
In a control device for an AC rotary machine, having an angle detector for detecting an electrical angle of the AC rotary machine, a detection error produced by the angle detector due to a noise magnetic field generated by a multi-phase alternating current flowing through an inverter connection unit is corrected using a correction signal having a phase and an amplitude that are determined in accordance with a relative positional relationship between the inverter connection unit and the angle detector and a current vector of the multi-phase alternating current, whereupon an inverter is controlled on the basis of the corrected electrical angle. As a result, a simple, low-cost control device for an AC rotary machine with which an angular position of a rotor can be detected with a high degree of precision is obtained.