Torque Offset Correction for Motor-Driven Power Steering
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Solution Overview
Problem
The existing electric power steering systems face challenges in accurately determining the hands-off state due to torque offset issues, which can lead to incorrect detection and activation of the lane following assist (LFA) function, causing potential safety concerns.
Innovation Solution
A system and method that corrects torque offset in motor-driven power steering motors by statistically analyzing torque signals, determining a relationship coefficient, and comparing it with a stored comparison range to accurately detect hands-off states, thereby improving the hands-off detection capability of the LFA function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque offset is not corrected in the MDPS motor, then the system structure remains simple, but the hands-off detection accuracy deteriorates due to incorrect torque value interpretation
Solution Approach 1:
The patent applies parameter changes by modifying the torque value parameters through statistical analysis. The controller calculates mean and standard deviation of torque values during hands-off periods, then uses these parameters to dynamically adjust the reference range for hands-off detection. This transforms the fixed threshold approach into a adaptive parameter-based system that compensates for torque offset without adding hardware complexity
Solution Approach 2:
The patent replaces potential mechanical calibration methods with a statistical analysis system. Instead of using mechanical adjustment mechanisms to correct torque offset, the system uses mathematical processing (mean calculation, standard deviation calculation) of torque signals to identify and compensate for offset errors, substituting mechanical correction with computational analysis
2Measurement precision
If a fixed reference range is used for hands-off detection, then the detection process is simple, but detection accuracy deteriorates when torque offset occurs
Solution Approach 1:
The patent applies dynamics by transitioning from a static fixed reference range to a dynamic adaptive reference range. The system continuously learns the torque characteristics during hands-off periods and adjusts the reference range based on calculated mean and standard deviation. This dynamic adaptation allows the detection threshold to automatically compensate for torque offset while maintaining relatively simple detection logic
Solution Approach 2:
The system performs self-service by automatically characterizing its own torque behavior during hands-off periods. The controller collects torque data, calculates statistical parameters (mean, standard deviation), and uses this self-generated information to adjust the reference range for detection, eliminating the need for external calibration or complex predefined thresholds
3Measurement precision
If torque offset correction is implemented, then hands-off detection accuracy improves, but the processing time and computational load increase
Solution Approach 1:
The patent applies preliminary action by pre-characterizing the torque offset during initial hands-off detection periods. The system collects torque data and calculates mean and standard deviation in advance, storing these parameters for future use. This preliminary statistical analysis enables faster real-time detection without repeating complex calculations during actual operation, reducing ongoing processing time
Data Source
AI summary
A method of correcting torque offset of a motor-driven power steering motor, may include activating a lane following assist (LFA) function by an LFA unit of a vehicle, acquiring a comparison range for determining whether the torque offset of the motor included in a motor-driven power steering (MDPS) unit of the vehicle is present under a predetermined comparison condition during a first travel of the vehicle, and determining a relationship coefficient based on a current required torque value required by the LFA unit and a current measured torque value of the motor, acquired by applying the current required torque value by the MDPS unit, and determining whether torque offset of the motor is present when the determined relationship coefficient is within the comparison range during a second travel performed after the first travel and performed in a lane having the same lane condition as the first travel.