Steering Control Device Dynamic Low Pass Filter Noise Suppression
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Solution Overview
Problem
Conventional steering control systems interfere with the driver's steering due to noise in estimating transverse road gradients, leading to unwanted assistance.
Innovation Solution
A steering control device that includes a transverse gradient estimator, an assisting amount calculator, a low pass filter, and a motor controller, where the low pass filter adjusts its cut-off frequency based on the change in assisting amount over time to minimize interference with the driver's steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transverse gradient estimator estimates the transverse gradient of the road surface to assist driver's steering, then the steering assistance corresponds to the change in transverse gradient, but noise in the estimation causes interference with the driver's steering
Solution Approach 1:
The low pass filter dynamically switches between two cut-off frequencies (first and second) based on the temporal change of the second assisting amount. When the second assisting amount increases with time, one frequency is selected; when it decreases, the other frequency is selected. This dynamic adjustment allows the system to adapt to changing road conditions while suppressing noise interference.
Solution Approach 2:
The system changes the parameter of cut-off frequency of the low pass filter between two distinct values depending on the direction of change of the assisting amount. This parameter switching enables the system to optimize the balance between responsiveness to transverse gradient changes and suppression of estimation noise.
2Object-affected harmful factors
If the low pass filter uses a lower cut-off frequency to suppress noise, then interference with driver's steering is reduced, but the response to transverse gradient changes becomes slower
Solution Approach 1:
The low pass filter transitions from a static to a dynamic system by switching cut-off frequencies based on the temporal behavior of the assisting amount. This allows the system to achieve both noise suppression and fast response by selecting appropriate frequencies in different operational contexts.
Solution Approach 2:
The system periodically evaluates the change direction of the second assisting amount and switches the cut-off frequency accordingly. This periodic evaluation and switching mechanism enables the system to maintain optimal performance characteristics across varying operating conditions.
3Speed
If the low pass filter uses a higher cut-off frequency to respond quickly to transverse gradient changes, then the steering assistance is more responsive, but noise interference increases
Solution Approach 1:
The system changes the cut-off frequency parameter based on the temporal trend of the assisting amount. By switching between two frequency values, the system optimizes the trade-off between response speed and noise suppression for different driving scenarios.
Data Source
AI summary
A steering control device includes a transverse gradient estimator configured to estimate a transverse gradient of a road surface on which a vehicle travels; an assisting amount calculator configured to calculate a first assisting amount based on the transverse gradient; a low pass filter configured to perform a low pass filter processing for the first assisting amount, and output the processed first assisting amount subjected to the low pass filter processing, as a second assisting amount; and a motor controller configured to control a motor that generates a steering assist torque, using the second assisting amount. The low pass filter switches a cut-off frequency of the low pass filter between a first cut-off frequency and a second cut-off frequency that is set to a value higher than the first cut-off frequency, depending on whether the second assisting amount increases with time or the second assisting amount decreases with time.