Variable Damper Control for Low-Frequency Suspension Response
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Solution Overview
Problem
Existing suspension systems with adjustable damping force shock absorbers fail to provide good sprung damping performance for low-frequency vibrations, leading to increased stroke and delayed damping force rise, which deteriorates vehicle comfort and stability.
Innovation Solution
A suspension system with a shock absorber featuring a damping force variable mechanism and a controller that adjusts damping force using an actuator, incorporates a frequency response unit to reduce damping force at specific frequencies, and controls the actuator to increase the change rate of damping force from soft to hard characteristics, especially for low-frequency vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the cutoff frequency of the frequency response unit is set lower, then high-frequency vibration damping is improved, but the rise of damping force is delayed resulting in deterioration of sprung damping performance
Solution Approach 1:
The patent segments the damping force control into two independent pathways: a frequency response unit for high-frequency vibrations and a low-pass filter for low-frequency vibrations. This segmentation allows each unit to operate optimally in its designated frequency range without interfering with the other, resolving the contradiction between high-frequency damping and low-frequency response.
Solution Approach 2:
The patent changes the parameter of cutoff frequency application by using two different cutoff frequencies: a first cutoff frequency for the frequency response unit and a second cutoff frequency for the low-pass filter. This parameter differentiation enables the system to maintain appropriate damping characteristics across the entire frequency spectrum, preventing the delay in damping force rise while still providing effective high-frequency damping.
2Object-affected harmful factors
If the cutoff frequency of the frequency response unit is set lower, then high-frequency vibration damping is improved, but the stroke of the shock absorber increases
Solution Approach 1:
The patent segments the vibration control function into two distinct units operating in parallel: the frequency response unit handles high-frequency vibrations while the low-pass filter handles low-frequency vibrations. This segmentation prevents the frequency response unit from excessively reducing damping force across all frequencies, thereby maintaining adequate damping for low-frequency movements and limiting shock absorber stroke.
Solution Approach 2:
The low-pass filter acts as an intermediary that supplements the frequency response unit by providing damping force control for low-frequency vibrations. This intermediary component ensures that when the frequency response unit reduces damping for high-frequency vibrations, the low-pass filter maintains appropriate damping levels for low-frequency movements, preventing excessive stroke.
3Object-affected harmful factors
If damping force control is applied only to low-frequency vibration, then high-frequency vibration damping is improved, but low-frequency sprung damping performance deteriorates
Solution Approach 1:
The patent segments the frequency ranges and assigns dedicated control units to each segment: the frequency response unit is responsible for high-frequency vibrations above its cutoff frequency, while the low-pass filter is responsible for low-frequency vibrations below its cutoff frequency. This clear segmentation ensures both frequency ranges receive appropriate damping control simultaneously.
Solution Approach 2:
The patent creates a universal damping control system where two filter units work together to provide comprehensive vibration damping across the entire frequency spectrum. The frequency response unit and low-pass filter collectively serve multiple functions: high-frequency damping, low-frequency damping, and coordinated control to optimize overall suspension performance.
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
The system provides improved sprung damping performance for low-frequency vibrations, reducing damper stroke and enhancing vehicle comfort and stability by quickly adjusting damping forces to target values, even when the cutoff frequency is set lower, thus minimizing noise and improving ride quality.
Implementation Method 1
a damping force variable mechanism configured to use an actuator to adjust communication of working fluid generated in a passage
Implementation Method 2
a frequency response unit configured to reduce the damping force for vibration at a specific frequency
Data Source
AI summary
A suspension system includes: a variable damper configured to use a damping force variable actuator to adjust communication of working fluid generated in a passage by a relative movement between a vehicle body and a wheel, to thereby adjust a damping force over a range of a soft characteristic to a hard characteristic; and a controller configured to control the damping force variable actuator. The variable damper further includes a frequency response unit configured to reduce the damping force for vibration at a specific frequency. The controller is configured to increase a change rate from a soft side to a hard side at a time of controlling the damping force to reach a target damping force when a frequency of the relative movement between the vehicle body and the wheel is lower than a first frequency set to the frequency response unit.