Document Type

Theses, Masters


This item is available under a Creative Commons License for non-commercial use only


Transport engineering

Publication Details

Thesis submitted in partial fulfilment of the requirements for the award of the Degree of Master of Philosophy of Dublin Institute of Technology, February 2014.


Vehicle characterization is the process by which a particular vehicle’s inherent dynamic behavior is classified by measuring its response to certain command inputs under standard test conditions. Such information is required when comparing its performance to that of other vehicles in response to the same test event and it is also used to authenticate computer models of the test vehicle. The aim of this research was to determine whether vehicle characterization is possible using data from non- standard tests and to judge whether such data can also be used for the purpose of validating a computer model of the test vehicle.

The tests used as the benchmarking standard against which this proposition was appraised were those prescribed by the International Standards Organization (ISO), in particular, the Steady State Cornering test, the Step Steer (J-turn) test, and the Power- off in a Turn test. A suitably instrumented Ford Mondeo was prepared and subjected to basic versions of these tests that were not conducted in full compliance with the procedures and conditions laid down by the ISO standard, and a body of data was recorded.

This time history data was analyzed and, despite the suboptimal and disparate nature of the individual test runs, it generated two vehicle characteristic values that were shown to comply with expectations for the test vehicle and could be used as part of a validation process. These were the vehicle’s understeer gradient of about 1deg/g and the yaw rate gain of 0.163 deg/sec per deg. In addition, the time history data from all of the non-standard tests performed was subjected to Fast Fourier Transform (FFT) analysis in order to identify the vehicle’s natural frequencies of vibration and the results obtained were used to validate a modal or ‘ride’ model of the test vehicle.

By this means it was demonstrated that neither the process of vehicle characterization nor that of validating a computer model of the vehicle requires data obtained from standardized vehicle tests such as those prescribed by the ISO.