AC Rotary Machine Control Device Angle Detection Noise Correction
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Solution Overview
Problem
Existing control devices for AC rotary machines and electric power steering systems face challenges in accurately detecting rotation angles due to disturbance magnetic flux errors caused by DC and AC currents, which cannot be effectively removed using existing correction methods, leading to decreased detection accuracy.
Innovation Solution
A control device that includes a DC power supply, an inverter, a magnetic flux generator, an angle detector, and a control arithmetic unit that calculates and applies correction signals to correct signal errors caused by noise magnetic flux components from DC and AC currents, allowing for improved detection accuracy by using the angle detector in a saturated state with respect to the main component direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic sensor is used in a saturated state with respect to the main component direction of the magnet magnetic flux vector, then the fluctuation of the detection signal can be suppressed and the accuracy of the detected angle is excellent, but noise components of 2nd order rotation (or 3rd order and 7th order rotation) cannot be removed even when the detection signal is corrected in accordance with the component of the disturbance magnetic flux vector
Solution Approach 1:
The patent segments the magnetic flux components into main component (Bs) and disturbance components (Bd). By separating the correction process into two stages - first correcting with Bd1 (in-phase component) and then with Bd2 (quadrature component) - the system successfully removes both 2nd order noise components while maintaining angle detection accuracy in the saturated state
Solution Approach 2:
The patent applies preliminary correction by first calculating and subtracting the in-phase disturbance component Bd1 from the detected magnetic flux vector before performing angle detection. This preliminary action removes the dominant 2nd order noise component, allowing the angle detector to operate accurately even in the saturated state where it would otherwise fail to remove 2nd order noise
2Measurement precision
If disturbance magnetic flux vector Bd is calculated and subtracted from detected vector Bc, then angle error caused by disturbance magnetic flux can be reduced, but angle errors of higher orders (2nd order from amplitude ratio error, 3rd order and 7th order from multi-phase AC currents) cannot be removed
Solution Approach 1:
The patent changes the parameters of the disturbance magnetic flux vector by decomposing it into two distinct components: Bd1 (in-phase component) and Bd2 (quadrature component). This parameter decomposition allows systematic correction of different order noise components through sequential subtraction, achieving comprehensive noise removal without excessive complexity
Solution Approach 2:
The patent implements a feedback mechanism where the corrected magnetic flux vector is used to calculate updated disturbance components, which are then subtracted in a iterative process. This feedback loop continues until all significant noise components are removed, systematically reducing angle errors of various orders while maintaining manageable computational complexity
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 significantly enhances the detection accuracy of rotation angles by effectively correcting noise components, reducing angle errors of various orders, thereby improving the performance of AC rotary machines and electric power steering systems.
Implementation Method 1
a magnetic flux generator configured to rotate in synchronization with a rotor of the AC rotary machine configured to be rotated by a rotating magnetic flux formed by multi-phase AC currents flowing through armature windings, to thereby generate an angle detection magnetic flux for detecting a rotation angle of the AC rotary machine
Implementation Method 2
an angle detector, which is used in a saturated state with respect to a main component direction of the angle detection magnetic flux, and is configured to detect a cosine signal and a sine signal, which are two components orthogonal to each other and form the angle detection magnetic flux
Data Source
AI summary
A control device for an AC rotary machine includes: a DC power supply; an inverter; a magnetic flux generator; an angle detector; and a control arithmetic unit; wherein the control arithmetic unit is configured to: calculate, based on a positional relationship between a current path and the angle detector, a correction signal for correcting signal errors of a cosine signal and a sine signal, which are caused by a noise magnetic flux component due to at least one of a DC current flowing between the DC power supply and the inverter and multi-phase AC currents flowing between the inverter and armature windings; and control the inverter by using angle information obtained from values after the correction by the correction signal.