Motor Control Device for EPS Angle Error Correction
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Solution Overview
Problem
Conventional motor control devices for electric power steering systems face challenges in accurately estimating the motor electrical angle due to mechanical compliance characteristics like backlash and elastic deformation, leading to angle errors that affect handling feel and torque generation efficiency, especially when the motor position sensor fails.
Innovation Solution
A motor control device that calculates steering angular velocity and estimates motor electrical angle using an advance gain to correct for delays, integrating post-advance steering angular velocity only when a predetermined torque threshold is met, thereby reducing angle errors in a simpler structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor electrical angle is estimated using output shaft steering angle information, then the estimated angle can be obtained, but angle errors are multiplied by gear ratio causing large motor angle calculation errors
Solution Approach 1:
The patent applies preliminary action by correcting the steering angle information before it is used for motor electrical angle estimation. The correction unit pre-adjusts the steering angle based on detected error characteristics (backlash, elastic deformation) to compensate for mechanical compliance effects before the angle is multiplied by the gear ratio, thereby preventing error amplification rather than correcting it afterward
Solution Approach 2:
The patent implements feedback by using the detected steering angle error characteristics to continuously adjust and correct the steering angle information. The correction unit receives feedback about mechanical compliance effects (backlash, elastic deformation) and dynamically modifies the steering angle estimation to compensate for these errors, creating a closed-loop system that improves angle accuracy
2Measurement precision
If learning of error characteristics is performed to eliminate angle errors, then the angle error influence can be eliminated, but the learning method becomes complicated and requires much memory
Solution Approach 1:
The patent applies parameter changes by directly adjusting the steering angle parameter based on detected error characteristics rather than performing complex learning procedures. The correction unit modifies the steering angle parameter in real-time based on simple detected parameters (backlash amount, elastic deformation characteristics) without requiring extensive memory storage or complicated learning algorithms
Solution Approach 2:
The patent extracts only the essential error characteristics (backlash and elastic deformation effects) that cause angle errors and focuses correction on these specific parameters. Rather than attempting to learn and compensate for all possible error sources, the system extracts and corrects only the dominant mechanical compliance effects, simplifying the correction process while maintaining effectiveness
3Measurement precision
If the estimated angle is corrected by error characteristics obtained from output torque-related information, then the corrected estimated angle can be used, but the achievement method becomes complicated
Solution Approach 1:
The patent applies self-service by having the correction unit directly utilize the detected steering angle error characteristics to perform self-correction without requiring complex external learning processes. The system uses its own detected error parameters (backlash, elastic deformation) to automatically adjust the steering angle estimation, eliminating the need for complicated achievement methods involving multiple sensors or complex algorithms
Data Source
AI summary
A motor control device includes a backup electrical angle detection circuit in which an inter-sensor error correction unit calculates an advance gain equal to or more than 1 with respect to input of a steering torque equal to or more than a predetermined torque value, and multiplies an output shaft angular velocity by the advance gain to calculate a post-advance steering angular velocity for correcting the estimated angle error of the direction delayed with respect to the steering direction. Then, an estimated angle calculation unit of the backup electrical angle detection circuit integrates the post-advance steering angular velocity, and, on the basis of a value of the integration, calculates a second motor electrical angle that is an estimated value of a motor electrical angle.