Active Suspension Accumulator Layout for Pump Inertia Stiffness
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Solution Overview
Problem
Active vehicle suspension systems face challenges due to pump inertia, leading to undesirably high stiffness during certain driving conditions, which results in a poor ride experience, especially when responding to high-frequency inputs or low-amplitude external forces, and existing systems struggle to maintain desired stiffness across a wide range of input frequencies.
Innovation Solution
The implementation of a suspension system component with separate compression and extension accumulators, each in direct fluid communication with their respective chambers, allowing fluid flow without passing through the hydraulic pump, and the use of compliant mechanisms to manage stiffness, along with nested accumulator assemblies to optimize packaging and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a hydraulic pump is used in the suspension system to control fluid flow between chambers, then active suspension control is achieved, but pump inertia causes undesirably high stiffness during certain driving conditions
Solution Approach 1:
The patent divides the single pump system into two separate accumulators (compression accumulator and extension accumulator) that can independently manage fluid flow for compression and extension movements. This segmentation allows each accumulator to operate without the inertia constraints of a pump, providing independent compliance control for each movement direction.
Solution Approach 2:
The patent extracts the compliance management function from the hydraulic pump by introducing separate accumulators that directly interface with the compression and extension chambers. This removes the pump's inertial effects from the compliance control path, allowing the accumulators to independently provide the desired compliant behavior without pump-induced stiffness.
2Speed
If the pump responds to high-frequency inputs, then active control response is provided, but pump inertia results in poor ride experience and excessive stiffness
Solution Approach 1:
The patent uses gas-charged accumulators (pneumatic elements) to provide compliance in the suspension system. The gas compression and expansion in the accumulators naturally responds to high-frequency inputs without the inertial constraints of a hydraulic pump, providing both fast response and desired compliance characteristics.
3Adaptability or versatility
If separate compression and extension accumulators are used to reduce pump inertia impact, then desired stiffness is maintained across wide frequency ranges, but system complexity increases
Solution Approach 1:
The patent employs nested accumulator assemblies where accumulators are arranged in a compact nested configuration. This nesting allows multiple accumulators to occupy reduced space, managing the increased component count in a space-efficient manner that mitigates the complexity burden.
Solution Approach 2:
The patent transitions from a single-dimension pump-based control to a multi-dimension accumulator-based system, where compression and extension accumulators operate independently in parallel dimensions. This dimensional expansion provides superior adaptability across frequency ranges by allowing independent optimization of each movement direction.
4Force
If accumulators are made larger to improve compliance and reduce stiffness, then ride comfort improves, but packaging space requirements increase
Solution Approach 1:
The patent uses nested accumulator assemblies where one accumulator is placed inside another, allowing the system to achieve the required compliance volume in a compact footprint. This nesting arrangement provides the necessary accumulator capacity for improved compliance while significantly reducing the overall packaging space required compared to separate, non-nested accumulators.
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 effectively mitigates the impact of pump inertia, maintaining desired stiffness across a wide range of input frequencies and amplitudes, enhancing the ride experience by reducing the transfer of road disturbances to the vehicle body, even under varying driving conditions.
Implementation Method 1
a compression accumulator arranged to exchange fluid with the compression chamber; an extension accumulator arranged to exchange fluid with the extension chamber
Implementation Method 2
a first gas-charged chamber and a first hydraulic fluid chamber
Data Source
AI summary
Presented herein, inter alia, are suspension system components having tuned accumulator sizing and/or stiffness. Such suspension system components are envisioned for use in a distributed active suspension system of a vehicle. In particular, through appropriate sizing of accumulators of a suspension system component of a vehicle, ride quality of the vehicle may be improved and so called “rough ride” issues may be precluded. Alternatively or additionally, various valves or alternative compliant mechanisms may be included in the suspension system component, so that desirable performance may be obtained for a range of operating conditions.