Overview
It is commonly accepted that the road profile is the principle excitation to the vehicle. Road roughness induces dynamic loads on the vehicles and these dynamic loads cause fatigue damage which ultimately decides life of vehicle. Therefore studies of understanding of actual road roughness are necessary for prediction of vehicle durability.

Hence a research project was taken at ARAI to develop a system to measure the vehicle independent road profiles and study the effect of road roughness on vehicle durability and ride. The study consists of four parts:

	Development of Road Profiling System and field measurement of road profiles of different types of road surfaces
	Classification and comparison of the road profiles based on PSD analysis as per ISO 8608 and International Roughness Index.
	Consideration of the effects of road profile on vehicle aggregates.
	Prediction of vehicle response/road loads by a dynamic virtual model of the vehicle and road profiling facility is portable and compatible to any vehicle. SDL has a databank of around 1000 kms of different Indian road profiles inclusive of city road, country road, national highway, state highway and express way.

Project Methodology

ARAI Road Profile Measurement System

System configuration	System Specification
Lasers – 4 Nos.    Accelerometer – 4 Nos.   GPS   Wheel Encoder   Video Camera – 2 Nos.	Distance resolution – 1 mm   Vehicle speed – 0 to 120 km/h   Sampling -50,000 Sample/s    Wavelength – 5 mm to 100 m   Adaptable to any vehicle

Profiling System Verification
The representative test track was constructed for the verification of the Road profiling system. Initially the master profile of the test track was mapped manually and then this master profile is compared with the road profile calculated by ARAI road profiling system. It is observed that the calculated profile matches very well with master track profile of different patches. The effect of vehicle speed on collected road profile data has been checked and found no effect on final outcome of road profile.
Classification of Indian road profiles
To understand effect of road surface profile /roughness an exercise of road profile measurement was carried on different types of road surface. Some sample road representing typical city road, national highway, state highway, rough road, country road, and express way were selected.


Road Vehicle Interaction Analysis

Road Load Prediction using MBD Simulation
An exercise was carried out at ARAI to find the usefulness of the measured typical road profiles for MBD simulations. A virtual model of SUV vehicle and measured road is created and predicted vehicle response parameters in terms of wheel load, axle, chassis acceleration, suspension displacement were compared as against that of experimentally measured on same road surfaces



Results comparison of actual testing and virtual simulation
Drive file prediction
An exercise was carried out to present a concept for calculating the vehicle dependent drive files for our poster simulation using measured vehicle independent road profiles. For doing this every time the vehicle response in terms of axle, suspension displacement is measured and then simulated on rig.

Following figure shows the methodology adopted for drive file calculation
It observed that the results with drive file predication and simulation correlates well to that with vehicle response simulation.
Predicated Drive file simulation results

Usefulness of the Project for Auto Industry

	Better understanding of vehicle durability and ride   Objective classification of  Indian Road profiles
	Availability of data bank of Indian road profiles for:   Virtual Simulation   Creation of drive files for hydraulic four poster without having to do the repeated DAQ for customer usage pattern   Creation and modification of proving grounds
	Customer correlated driving schedule for accelerated durability testing
	Reduction  in design and development time due to:   Elimination of repeated DAQ exercise as vehicle independent  in-put can be used for product validation   Prediction of Customer usage service loads in design stage  without having the need for first prototype
	The system has been validated and is ready for customer usage for road profiling