Electric Power Steering Vibration Suppression via Dual-Filter Torque Correction
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Solution Overview
Problem
Conventional electric power steering systems struggle to effectively suppress resonance of vehicle-body members and vibrations caused by tire rotation, such as shimmy, which are unpredictable and vary by vehicle individuality and deterioration, leading to resonance transmission to the driver's hands.
Innovation Solution
An electric power steering control device with a filter processor that includes a first filter with a fixed cut-off frequency for vehicle-body member resonance and a second filter with a variable cut-off frequency based on tire rotation speed, combined with a gain adder and weighting adjusters, to output a vibration-suppression gain that corrects motor torque and suppresses resonance and shimmy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single fixed-frequency filter is used to suppress resonance, then resonance at that specific frequency is suppressed, but vibrations at other frequencies (such as variable shimmy frequencies) cannot be suppressed
Solution Approach 1:
The patent combines a fixed-frequency filter (first filter) for suppressing known resonance frequencies with a variable-frequency filter (second filter) for suppressing shimmy vibrations. The filter processor integrates both filter types to work simultaneously, allowing the system to handle both stable resonance frequencies and variable shimmy frequencies comprehensively
Solution Approach 2:
The patent introduces a variable-frequency filter whose cut-off frequency can be dynamically adjusted based on detected shimmy frequency. This dynamic adjustment capability allows the filter to track and suppress shimmy vibrations even when their frequency changes due to vehicle speed variations or tire conditions
2Device complexity
If vibration suppression control is not performed, then the control system remains simple, but vibrations are transmitted to the driver's hands and torque due to vibration is increased by assist control
Solution Approach 1:
The patent extracts the harmful vibration components from the steering signal using frequency-based filtering. The filter processor separates vibration frequencies (resonance and shimmy) from the normal steering signal, allowing selective suppression of only the harmful components while preserving the useful steering control signals
Solution Approach 2:
The patent implements a feedback mechanism where the detected vibration frequency (particularly shimmy frequency) is used to dynamically adjust the filter characteristics. The system continuously monitors steering torque and rotational angle, detects shimmy occurrence, and adjusts the variable-frequency filter accordingly to maintain effective suppression
3Device complexity
If the cut-off frequency is fixed, then the filter structure is simple, but it cannot adapt to variable shimmy frequencies that change with vehicle speed and tire conditions
Solution Approach 1:
The patent introduces a variable-frequency filter whose cut-off frequency can be dynamically adjusted based on detected shimmy frequency. This dynamic adjustment capability allows the filter to track and suppress shimmy vibrations even when their frequency changes due to vehicle speed variations or tire conditions
Solution Approach 2:
The patent prepares both fixed-frequency and variable-frequency filter structures in advance within the filter processor. The variable-frequency filter is pre-configured to respond to detected shimmy frequencies, allowing immediate suppression when shimmy occurs without requiring complex real-time frequency analysis
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution stabilizes resonance suppression of vehicle-body members and effectively manages shimmy vibrations across varying frequencies, ensuring suppression without prior knowledge of shimmy occurrence frequencies, enhancing driver comfort by reducing resonance and shimmy transmission.
Implementation Method 1
the resonance frequency of the sub frame, and a shimmy extracting filter which outputs a vibration-suppression gain for suppressing the shimmy by performing the filter processing on the rotational angle of the motor
Data Source
AI summary
Filters output a vibration-suppression gain for suppressing resonance of a sub frame or shimmy by performing a filter processing on a rotational angle of a motor. The filters have respective frequency characteristics that a gain becomes a maximum magnitude and a phase advances by 90° at a cut-off angle frequency. The cut-off angle frequency of the filter is fixedly set at a resonance frequency of the sub frame. The cut-off angle frequency of the filter is variably set in accordance with a tire rotation frequency. A gain adder adds the respective gains of the filters and outputs an added magnitude to a correcting mechanism as a vibration-suppression gain. The correcting mechanism corrects a motor torque set by an assist map by using the vibration-suppression gain outputted by the gain adder.