Electric Power Steering Sensorless Control Torque Fluctuation
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Solution Overview
Problem
Existing electric power steering apparatuses face issues with torque fluctuations due to estimation errors in sensorless control, where the correction methods incorrectly impose restrictions, failing to distinguish between driver steering torque and motor torque frequency components, leading to increased errors and vibrations.
Innovation Solution
An electric power steering apparatus with a steering torque detection unit, an estimated speed calculation unit, an estimated speed correction unit, and an estimated angle calculation unit, where the estimated speed is corrected based on a determination signal obtained by removing the driver's steering frequency component from the steering torque derivative, ensuring accurate torque control and reduced vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control is used to eliminate rotation angle sensors, then device complexity is reduced, but measurement precision of motor rotation angle deteriorates due to estimation errors
Solution Approach 1:
The patent implements feedback control by detecting steering torque and using it to correct estimation errors in the motor rotation angle. The control apparatus continuously monitors the steering torque and adjusts the estimated rotation angle based on the detected torque values, creating a closed-loop feedback system that compensates for estimation errors without requiring additional sensors.
Solution Approach 2:
The patent uses steering torque as an intermediary parameter to indirectly obtain accurate motor rotation angle information. Instead of directly measuring the rotation angle, the system detects steering torque and uses it as a mediator to calculate and correct the estimated rotation angle, thereby achieving precise measurement without direct sensing.
2Measurement precision
If correction is applied based on steering torque derivative, then measurement precision of estimated angle is improved, but device complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies dynamic correction by using the derivative of steering torque with respect to time to adjust the estimated rotation angle. Instead of using static correction methods, the system dynamically adapts the correction based on the rate of change of steering torque, allowing precise tracking of rapid steering movements while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the parameter used for correction from static torque values to dynamic torque derivative values. By using the time derivative of steering torque as the correction parameter, the system achieves higher measurement precision for rapidly changing steering conditions while managing computational complexity through efficient derivative calculation.
3Measurement precision
If frequency component removal is applied to distinguish driver torque from motor torque, then measurement precision of motor torque is improved, but device complexity increases due to signal processing requirements
Solution Approach 1:
The patent segments the steering torque signal into different frequency components, separating the driver's steering torque (lower frequency) from the motor torque (higher frequency). By dividing the torque signal into distinct frequency segments, the system can accurately extract motor torque information without interference from driver input, achieving precise measurement through signal decomposition.
Solution Approach 2:
The patent replaces mechanical separation methods with signal processing techniques to distinguish between driver torque and motor torque. Instead of using mechanical means to separate the torque sources, the system uses frequency domain analysis and digital signal processing to electronically separate and identify the motor torque component, reducing mechanical complexity while improving measurement precision.
Data Source
AI summary
An electric power steering apparatus including: a steering torque detector to detect a steering torque of a driver; a motor to assist a steering force of the driver; an estimated speed calculator to calculate an estimated speed, which is an estimated value of a rotation speed of the motor; an estimated speed corrector to correct the estimated speed based on the steering torque; an estimated angle calculator to calculate an estimated angle of the motor by integrating the estimated speed after the correction; and an electric power supply to supply electric power to the motor based on the estimated angle, wherein the estimated speed corrector corrects the estimated speed when a determination signal, which is based on a value obtained by removing a frequency component of steering of the driver from a derivative of the steering torque, the steering torque, and the estimated speed have the same signs.