Vehicle-Based IRI Estimation Using Vertical Acceleration Signals
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Solution Overview
Problem
Existing methods for measuring the International Roughness Index (IRI) of road pavements are expensive and difficult to implement on a large scale, necessitating faster and easier detection of road pavement irregularities.
Innovation Solution
A method utilizing vehicle vertical acceleration data, tire and suspension damping and stiffness coefficients, and geo-referencing to estimate IRI through vehicle transfer functions, enabling frequent and efficient IRI-like quantification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional IRI measurement methods are used, then measurement precision is maintained, but cost and implementation difficulty increase significantly
Solution Approach 1:
The patent uses a simplified vehicle model that copies the essential dynamics of road response without requiring actual physical profilometers. The model replicates the quarter-car system behavior using readily available vehicle sensor data (accelerometers, GPS) and known vehicle parameters, creating a virtual copy of the measurement process that is much cheaper and easier to deploy while maintaining acceptable IRI estimation accuracy
Solution Approach 2:
The patent replaces complex mechanical IRI measurement systems (profilometers, laser scanners) with a computational mechanics approach. Instead of physically measuring road surface geometry, the system uses vehicle dynamics equations and sensor data to compute IRI values, substituting mechanical measurement infrastructure with software-based calculation that runs on standard vehicle electronics
2Measurement precision
If traditional IRI measurement methods are used, then measurement precision is maintained, but productivity and frequency of measurements decrease
Solution Approach 1:
The patent enables vehicles to perform their own IRI measurement function while traveling. The vehicle's existing sensors (accelerometers, GPS, speed sensors) and control systems are repurposed to collect data and compute IRI values during normal operation, eliminating the need for dedicated measurement vehicles or road closure for profiling. This self-service capability allows continuous, frequent measurements without specialized equipment deployment
Solution Approach 2:
The patent transforms IRI measurement from a periodic, discrete event into a continuous process. As vehicles continuously traverse road segments during normal operations, IRI data is continuously collected and updated. The system processes data in real-time or near-real-time, providing ongoing monitoring of road conditions rather than intermittent snapshots, thereby dramatically increasing measurement productivity and frequency
3Device complexity
If vehicle dynamics data is used for IRI estimation, then measurement cost and complexity are reduced, but measurement precision may be affected by vehicle-specific variations
Solution Approach 1:
The patent systematically accounts for vehicle-specific parameters (suspension stiffness, damping coefficients, tire properties, vehicle mass) in the IRI calculation model. By explicitly incorporating these parameters into the equations of motion and transfer functions, the system compensates for variations between different vehicles, ensuring that IRI estimates reflect road conditions rather than vehicle characteristics. This parameterization allows the same model to accurately process data from multiple vehicle types
4Measurement precision
If comprehensive vehicle parameters are incorporated, then measurement precision is improved, but device complexity and data processing requirements increase
Solution Approach 1:
The patent performs preliminary calculations of vehicle transfer functions and sensitivity coefficients before actual IRI estimation. Vehicle-specific parameters (suspension characteristics, mass properties) are pre-input into the model to generate pre-computed transfer functions that capture the vehicle's dynamic response characteristics. These pre-calculated functions are then reused during operational data processing, avoiding repeated complex computations and reducing real-time processing requirements while maintaining precision
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
Facilitates faster and more frequent IRI estimation by leveraging vehicle dynamics, reducing costs and improving road maintenance efficiency.
Implementation Method 1
the damping and stiffness coefficients of the suspensions of the vehicle
Implementation Method 2
vertical accelerations
Data Source
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AI summary
The invention concerns a method for estimating an International Roughness Index (IRI) of a road or road segment, comprising a preliminary step (1) and an International Roughness Index estimation step (10). The preliminary step (1) comprises collecting (2) values of vehicle tire damping and stiffness coefficients (Ct, Kt) and collecting (3) vehicle vertical acceleration values (Azvehicle) measured on vehicles driven at a constant speed along road segments to which known international roughness index values or known road profiles (profiler) are associated, as well as vehicle geo-referencing data and speed data indicative of the given constant speed associated with the measured vertical acceleration values (Azvehicle).