Steering Control Notch Filter for Vibration Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional steering control devices face stability issues and increased design complexity when adding a current command value calculated from the differential of the steering torque, leading to self-induced vibration and transmission of road surface vibrations near the crossover frequency.
Innovation Solution
A steering control device that includes a steering torque detection unit, vehicle speed detection unit, motor, first current command value calculation unit, steering torque differentiation unit, notch filter processing unit, and current drive unit, where the notch filter is set to filter the differential value of the steering torque with a frequency higher than the mechanical resonance frequency but lower than the crossover frequency, allowing for easier selection and adjustment of the current command values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a current command value 2 calculated from the differential of the steering torque is added to the current command value 1, then road surface vibrations are suppressed, but the stability of the control system becomes worse and self-induced vibration occurs
Solution Approach 1:
A notch filter is introduced as an intermediary component between the steering torque differentiation unit and the second current command value calculation unit. The notch filter selectively attenuates specific frequency components (road surface vibrations) while allowing other frequencies to pass through, thereby suppressing harmful vibrations without compromising the overall stability of the control system.
Solution Approach 2:
The invention changes the frequency parameter of the steering torque signal by applying a notch filter with a specific cutoff frequency. This frequency-based parameter change allows the system to differentiate between harmful road surface vibrations (higher frequency) and useful steering torque variations (lower frequency), enabling selective suppression of vibrations while maintaining control stability.
2Object-affected harmful factors
If a current command value 2 calculated from the differential of the steering torque is added to the current command value 1, then road surface vibrations are suppressed, but design complexity increases and phase compensation must be redone
Solution Approach 1:
The notch filter is applied preliminarily to the steering torque signal before it enters the differential calculation and current command value generation stages. This preliminary filtering action removes harmful frequency components in advance, allowing the subsequent control algorithms to operate on already-filtered signals without requiring additional phase compensation adjustments or redesign.
3Reliability
If the notch frequency of the notch filter is set to filter the differential value of the steering torque, then stability is enhanced, but the filter must be precisely positioned between mechanical resonance frequency and crossover frequency
Solution Approach 1:
The control system automatically determines the appropriate notch frequency by detecting the mechanical resonance frequency of the steering system and setting the notch filter frequency accordingly. This self-service approach eliminates the need for manual tuning and precise configuration, as the system autonomously adapts the filter parameters based on its own operational characteristics.
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 configuration enhances the stability of the control system, suppresses decline in stability, and facilitates the selection of whether to use the current command value 2, effectively reducing the transmission of road surface vibrations and improving the design process by stabilizing the open loop characteristics.
Implementation Method 1
a notch filter processing unit which has a notch filter and filters the differential value of the steering torque by using the notch filter
Implementation Method 2
a mechanical resonance frequency of the steering control device
Data Source
AI summary
The steering control device includes: current command value 1 calculation unit 11 which determines current command value 1 based on a vehicle speed and a steering torque; current command value 2 calculation unit 14 which determines current command value 2 based on a filtered differential value of the steering torque; and current drive unit 10 which drives motor 5 so that the value of the motor current matches the sum of current command values 1 and 2. When a first crossover frequency represents the crossover frequency of control open loop characteristics in the steering control device as obtained when current command value 2 is determined using a differential value of the steering torque which has not been filtered, the notch frequency of the notch filter is set to be greater than the mechanical resonance frequency of the steering control device and smaller than the first crossover frequency.