Steering Rack Rattle Index Using Simultaneous Audio and Acceleration
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Solution Overview
Problem
Conventional methods for evaluating steering rack rattle in vehicle steering systems are subjective and prone to interference from extraneous noise, making it difficult to objectively assess and predict the propensity for rack rattle, which can lead to early wear and costly replacements.
Innovation Solution
A method involving simultaneous audio recording and measurement of acceleration and tie-rod end loads to identify common characteristics of rack rattle events, creating a rack rattle index that objectively assesses the steering system's performance and noise levels, allowing for repeatable and accurate testing in a lab setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If audio recording is used to detect rack rattle, then rattle events can be recorded with high accuracy, but extraneous noise from other vehicle components makes objective analysis difficult
Solution Approach 1:
The patent segments the steering rack system into multiple measurable components (rack acceleration, tie-rod end loads, audio) and analyzes them separately. By breaking down the complex noise environment into specific measurable parameters at different locations, the system can isolate rack rattle from extraneous vehicle noises through targeted measurement and analysis of each component's contribution.
Solution Approach 2:
The patent introduces accelerometers and force sensors as intermediary measurement devices between the rack components and the analysis system. These intermediaries provide objective, quantifiable data about rack acceleration and tie-rod loads, serving as mediators that translate physical rack behavior into measurable electrical signals that can be objectively analyzed without being directly affected by extraneous noise.
2Ease of operation
If subjective evaluation methods are used, then rattle assessment can be performed, but repeatability and objectivity are difficult to achieve
Solution Approach 1:
The patent replaces subjective human evaluation with an automated measurement and analysis system. Accelerometers, force sensors, and audio recording devices objectively measure rack acceleration, tie-rod loads, and sound levels, then computer algorithms automatically analyze this data to determine rattle propensity. This substitution of mechanical/electronic measurement systems for human judgment eliminates variability in evaluation methodology and ensures repeatable, objective results.
3Adaptability or versatility
If vehicle-level testing is used, then real-world rattle conditions can be assessed, but other vehicle components generate noise that obscures steering system performance
Solution Approach 1:
The patent extracts the steering rack system from the broader vehicle context and creates a dedicated measurement system focused solely on measuring rack acceleration, tie-rod loads, and associated audio. By isolating the measurement apparatus to specifically target the rack components and their immediate surroundings, the system can extract and analyze rack rattle characteristics without the confounding noise from other vehicle systems like exhaust, engine, or body panels.
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 approach enables objective, repeatable, and accurate assessment of steering system performance, reducing the likelihood of rack rattle issues and allowing for early engineering corrections, thereby minimizing component replacements and costs, and enabling differentiation between suppliers based on rattle propensity.
Implementation Method 1
measuring a test acceleration on the rack and pinion steering assembly resulting from the predetermined force profile applied
Implementation Method 2
simultaneously recording audio... identifying rack rattle events from the audio recording
Implementation Method 3
measuring... a right side tie-rod end load and a left side tie-rod end load
Data Source
AI summary
A method of determining steering rack rattle propensity of a rack and pinion steering assembly may comprise: simultaneously recording audio, and measuring acceleration of a rack, and right and left side tie-rod end loads; identifying rack rattle events from the audio recording; determining common characteristics of the measured rack acceleration and tie-rod end loads during the identified rack rattle events; creating a rack rattle index level; applying a predetermined force profile to a test rack and pinion steering assembly; measuring a test acceleration on the test rack and pinion steering assembly; calculating a test RMS level in a test frequency range using a test time constant; determining a rack rattle index value from the calculated test RMS level; and comparing the rack rattle index value to the rack rattle index level.