Motor-Driven Power Steering Shimmy Suppression via Band-Pass Filter
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Solution Overview
Problem
Motor-driven power steering systems face challenges in suppressing shimmy phenomenon-induced steering wheel vibrations, which can deteriorate steering feel and comfort.
Innovation Solution
A motor-driven power steering apparatus that includes a steering shaft, pinion shaft, torque detector, electric motor, base current calculator, band-pass filter, and suppression current calculator, which calculates and applies a suppression current to counteract disturbance torques, adjusting based on torque amplitude and vehicle speed to minimize shimmy-related vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If assistance force is applied to suppress vibration caused by the shimmy phenomenon, then steering wheel vibration is suppressed, but steering feeling may be deteriorated
Solution Approach 1:
The current control is segmented into two independent components: base current for normal steering assistance and suppression current for shimmy vibration suppression. This segmentation allows the system to provide targeted assistance for specific issues without affecting overall steering feel, as each component operates independently based on its own detection criteria
Solution Approach 2:
A band-pass filter acts as an intermediary between torque detection and current control. The filter selectively extracts shimmy-related frequency components from the detected torque signal, allowing the suppression current to be generated only for the specific vibration problem without interfering with normal steering operations
2Object-affected harmful factors
If suppression current is applied to counteract disturbance torque, then shimmy vibration is suppressed, but steering feeling may be deteriorated when shimmy does not occur
Solution Approach 1:
The suppression current is dynamically adjusted based on the amplitude of the band-pass filtered torque signal. When shimmy vibration occurs, the amplitude increases and suppression current is applied; when shimmy does not occur, the amplitude remains low and suppression current is minimized or zero, ensuring steering feeling is not affected during normal operation
Solution Approach 2:
The system continuously monitors the detected torque signal, processes it through the band-pass filter, and uses the filtered signal amplitude as feedback to dynamically adjust the suppression current magnitude. This closed-loop feedback mechanism ensures suppression current is only applied when and to the extent that shimmy vibration is actually present
Data Source
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AI summary
Disclosed is a motor-driven power steering (1) apparatus including: a base current calculator (21) configured to calculate a base current (Ib), which is a base for a target current (It), based on a detected torque (Td) detected by a torque sensor (109); a band-pass filter (271a) configured to allow a predetermined range of frequency components of the detected torque (Td) to the pass through the band-pass filter; a base shimmy compensation current calculator (275) configured to calculate a base shimmy compensation current (Irb), which is a base for a shimmy compensation current (Ir) required to suppress a disturbance torque, based on an extracted torque (Te) after passing through the band-pass filter (271a); a shimmy compensation current calculator (27) configured to calculate the shimmy compensation current (Ir) by correcting the base shimmy compensation current (Irb) according to magnitude of amplitude of the extracted torque (Te); and a final target current determination unit (28) configured to determine the target current (It) based on the base current (Ib) and the shimmy compensation current (Ir).