Division of Policy Research and Analysis, National Science Foundation under Grant no. OEP 76-00284

This study presents an analytical approach for the mechanics of the pneumatic tires and the vehicle dynamic simulation. Most of tire dynamic parameters in this study are derived by using the tire geometry rather than experimental data. For the tire dynamic properties, explicit formulations are derived analytically as functions of slip ratio, slip angle, camber angle, and other tire dynamic parameters. These formulations can be efficiently used for the general vehicle simulations of braking/traction and steering maneuvers with a varying camber angle at irregular terrains. For on-highway vehicle simulations, a conceptual sports car is modeled as a twenty-six degrees of freedom multi-body system, while the military 1/4 ton truck M151-A2 is modeled as a fourteen degrees of freedom multi-body system for off-highway vehicle simulations. To study vehicle ride comfort, stability, and maneuverability, numerous vehicle simulations are performed using the comprehensive tire model, steering, braking, traction, nonlinear suspension, and realistic irregular terrains. For these simulations, a general-purpose multi-body dynamic analysis code (named MBOSS) has been developed.

A dissertation submitted to the Faculty of Engineering and the BuiltEnvironment,University of the Witwatersrand,Johannesburg,in fulfilment of the requirements for the degree of Master of Science in Engineering, 2019 / A Performance-based Standards(PBS) framework legislates the dynamic performance and road-width usage of heavy vehicles,allowing the length and mass of a vehicle to exceed prescriptive legislation.The PBS framework defines the safe performance envelope of vehicles but does not optimise their safety and productivity.The design process to achieve the optimal productivity of PBS vehicles is highly iterative.An initial design is evaluated using multi-body dynamic ssimulation.If the required PBS performance is not achieved,design iterationsare made until the required PBS performance is achieved.The process is costly,time-consuming andcomputationallyexpensive.Theobjectiveofthisresearchistoquantifytherelativeeffect ofeachVehicleDesignParameter(VDP)ofamulti-bodyvehicledynamicsmodelonthevehicle safetyasmeasuredwithinthePBSframeworktoassistinthePBSassessmentprocess.To achievethis,threerepresentativebaselinePBSvehiclesweredeveloped(aquadsemi-trailer, trideminterlinkandrigiddrawbarcombination)fromPBSassessmentsconductedinSouth Africa.AsetofrangeswithinwhicheachVDPcouldbevariedwasdevelopedbyconsidering OriginalEquipmentManufacturer(OEM)data,legalrestrictions,physicalconstraintsand SouthAfricanPBSassessments.EachVDPforeachbaselinecombinationwasvariedin isolationtoevaluateitsinfluenceonthevehiclesperformancewithinthePBSframework.A comparative matrix was developed for each baseline vehicle comparing the relative influence of each VDP on each of the PBS performance measures.The matrices yield insight into which VDP shave the most influence on each performance measure for each of the baseline vehicles.Furthermore VDPs that have an egligible influence on the performance of all baseline vehicles can be conservatively estimated in the absence of OEM data while still predicting representative vehicle performance.These insights will guide designers to focus onVDPs with a high influence on vehicle performance,allow PBS assessors to determine which design parameters can be modelled with generic approximate data in the absence of OEMdata,and speedup the process of assessing vehicles with in the PBS framework. / TL (2020)

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