Steering Device Torque Vibration Suppression via Speed-Dependent Offset Correction
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Solution Overview
Problem
Existing steering devices with electric motors experience varying and deteriorating torque vibrations as motor rotation speed changes, due to inappropriate offset correction values.
Innovation Solution
A steering device with a current sensor to sense stator coil current, a motor rotation speed signal receiver, and an offset correction value storage section to adjust the sensed current signal using offset correction values specific to different motor rotation speeds and PWM duty ratio modulation rates, thereby controlling the electric power supplied to the stator coil to minimize torque vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single offset correction value is used for current sensor calibration, then the torque vibration is suppressed at a specific motor rotation speed, but the torque vibration deteriorates when the motor rotation speed changes
Solution Approach 1:
The patent applies dynamics by making the offset correction value variable rather than fixed. The system dynamically selects different offset correction values based on the detected motor rotation speed, allowing the calibration to adapt to changing operating conditions. This resolves the contradiction by enabling effective torque vibration suppression across multiple rotation speeds rather than being limited to a single speed point.
Solution Approach 2:
The patent changes the parameter of offset correction value based on motor rotation speed. By storing multiple offset correction values corresponding to different rotation speed ranges and selecting the appropriate value based on detected speed, the system maintains effective torque vibration suppression across varying operating conditions, thus improving adaptability while preserving reliability.
2Speed
If the PWM duty ratio modulation rate is changed to control motor speed, then the motor rotation speed is adjusted, but the torque vibration characteristics vary and deteriorate
Solution Approach 1:
The patent employs feedback by detecting the motor rotation speed and using this information to select the appropriate offset correction value. This closed-loop approach ensures that the system continuously adapts to changing speed conditions, maintaining optimal torque vibration suppression across the entire operating range rather than being effective only at a fixed speed point.
Solution Approach 2:
The system dynamically adjusts the offset correction value based on the detected motor rotation speed. By making the correction value variable and speed-dependent, the system maintains effective torque vibration suppression across different PWM modulation rates and rotation speeds, resolving the contradiction between speed control and vibration suppression.
Data Source
AI summary
A steering device includes: an offset correction value storing section to store an offset correction value including a first offset correction value and a second offset correction value, the first offset value being a current value for correcting the first sensed current signal so that a value of a vibration of the electric motor is equal to or smaller than a first predetermined value when the motor rotation speed signal is a first rotation speed, and the second offset value being a current value for correcting the first sensed current signal so that the value of the vibration of the electric motor is equal to or smaller than a second predetermined value when the motor rotation speed signal is a second rotation speed.