Rotation Angle Calculation Device Noise Suppression
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Solution Overview
Problem
The existing rotation angle calculation devices for rotary electric machines face challenges in accurately calculating the rotation angle due to noise superimposed on the amplitude-modulated signals, particularly noise components around the excitation frequency, which affects the accuracy of torque control.
Innovation Solution
A rotation angle calculation device that includes an angle calculation part and a shift part, where the shift part performs frequency shifting of the excitation signal to deviate the excitation frequency from noise frequency components in the output voltage, thereby reducing noise interference and improving calculation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchronous detection is performed on the amplitude-modulated signal to calculate the rotation angle, then the rotation angle can be obtained for controlling the rotary electric machine, but noise components around the excitation frequency are superimposed on the signal making high accuracy calculation difficult
Solution Approach 1:
The patent applies preliminary anti-action by pre-shifting the excitation frequency away from noise-prone frequencies before the noise can interfere with the measurement. The frequency shift is performed in advance so that when synchronous detection occurs, the excitation signal operates at a frequency where noise components are minimal, thereby preventing noise interference from degrading the rotation angle calculation accuracy.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the excitation frequency away from the original excitation frequency to a shifted frequency that avoids noise components. This parameter change (frequency shift) transforms the operating conditions to eliminate the harmful noise interference while maintaining the functionality of the rotation angle detection system.
2Reliability
If the excitation frequency is kept constant for stable operation, then the control system is simple, but noise components at that frequency cannot be avoided
Solution Approach 1:
The patent applies dynamics by making the excitation frequency variable rather than constant. The excitation frequency is dynamically shifted based on the operating conditions to avoid noise components. This dynamic frequency adjustment maintains control system reliability while improving measurement precision by adapting to varying noise environments.
Solution Approach 2:
The patent implements parameter changes by modifying the excitation frequency parameter from a fixed value to a shifted value that avoids noise. This parameter change enables the system to maintain stability while achieving higher measurement accuracy by operating at optimized frequency points away from noise sources.
3Measurement precision
If frequency shifting is performed to avoid noise, then rotation angle calculation accuracy is improved, but the device complexity increases due to additional shift processing
Solution Approach 1:
The patent uses an intermediary approach by introducing a frequency shift mechanism that acts as a mediator between the excitation signal and the noise environment. This intermediary frequency shift processing enables the system to achieve high measurement precision while keeping the overall device complexity manageable by using a relatively simple frequency translation technique.
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
This solution enhances the accuracy of rotation angle calculation and torque control by effectively suppressing noise frequencies, leading to improved motor control performance.
Implementation Method 1
outputs an amplitude-modulated signal by modulating an amplitude of the excitation signal in correspondence to a rotation angle
Implementation Method 2
The rotation angle of the rotary electric machine is calculated by performing synchronous detection on the amplitude-modulated signal
Data Source
AI summary
An ECU has a function of calculating a rotation angle, which is used for torque control, based on amplitude-modulated signals SIN and COS outputted from an angle sensor and a synchronous detection signal. Frequency components generated at the time of switching operation of switching elements of an inverter connected to a motor-generator is included in an output voltage of the inverter. The ECU has a function of shifting frequencies of the frequency components and an excitation frequency of an excitation signal from each other so that noise having the frequencies of the frequency components are not superimposed on the amplitude-modulated signals SIN and COS.