Rotor Position Sensing for Higher-Resolution Electric Power Steering
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Solution Overview
Problem
Existing electric power steering systems face challenges in accurately recognizing rotor position, leading to harmonic noise and inconsistent steering feedback due to the reliance on absolute position information and increment pulses, which can result in unchanged sampling values during rotor rotation.
Innovation Solution
An apparatus and method that recalculates rotor position by adding increment values proportional to the rotor's rotation speed when the number of increment pulses remains unchanged, using an absolute position sensor and pulse generator, to improve recognition resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the rotor position is sensed using only absolute position information and increment pulses counted in synchronization, then the system structure remains simple, but the rotor position recognition resolution deteriorates when the rotor rotates during the sampling period
Solution Approach 1:
The patent applies dynamics by making the rotor position recognition system adaptive to varying rotor speeds. The ECU dynamically adjusts the recognition resolution based on the detected rotor speed, transitioning from a static sampling approach to a dynamic one that maintains precision across different operating conditions. This resolves the contradiction by allowing the system to maintain simple structure at low speeds while achieving high precision at high speeds through software-based dynamic adjustment.
2Productivity
If the sampling period is set to execute sampling several times within one period of increment pulses, then the sampling frequency increases, but the sampling value remains unchanged when the rotor rotates, causing loss of position information
Solution Approach 1:
The patent implements feedback by continuously monitoring the rotor speed and using this information to adjust the rotor position recognition process. The ECU detects the rotor speed based on increment pulses and feeds this information back to modify the position calculation, ensuring that the sampling value accurately reflects the rotor position even when multiple rotations occur during the sampling period. This prevents information loss by adapting the recognition process to the actual rotor motion.
3Device complexity
If the rotor position is calculated based on counted increment pulses only, then the calculation method remains simple, but harmonic noise increases and steering feedback becomes inconsistent
Solution Approach 1:
The patent applies parameter changes by modifying the rotor position recognition resolution based on the rotor speed parameter. Instead of using a fixed calculation method, the ECU dynamically changes the recognition resolution parameter according to the detected rotor speed. This resolves the contradiction by maintaining simple calculation at low speeds while eliminating harmonic noise and ensuring consistent steering feedback at high speeds through parameter adaptation.
Data Source
AI summary
An apparatus and method for recognizing a rotor position, and an electric power steering system using the same wherein resolution in rotor position recognition can be improved by software by adding one or more increment values, which is proportional to the rotation speed of a rotor, in an interval where the counted number of increment pulses of a pulse generator is not changed in sampling the counted number of increment pulses of the pulse generator so as to recognize a rotor position of a motor.