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Technical Paper

Effectiveness of the Slip Circle, “COMBINATOR”, Model for Combined Tire Cornering and Braking Forces When Applied to a Range of Tires

The slip circle, COMBINATOR, model was developed to predict combined driving or braking and cornering performance of tires from straight-line torqued data and free-rolling cornering data only. In the original COMBINATOR paper, limited verification was presented. In the current paper, the model is shown to be broadly applicable to tires of all types. This is demonstrated through successful modeling of heavy-duty tires as large as 425/65R22.5 and by modeling of racing tires. The heavy duty tire models and summarized data are available from SAE Cooperative Research on electronic media.
Technical Paper

Example Utilization of Truck Tire Characteristics Data in Vehicle Dynamics Simulations

The ability to accurately simulate vehicle dynamics behavior with a mathematical model is limited by the quality of the tire model. In fact, the tire is often the single most important component in determining correlation between a mathematical vehicle model and measured experimental results. Tire data for heavy trucks are more difficult and expensive to acquire than passenger car and light truck data, and, consequently, there has been little published experience testing or modeling these tires. This paper shows how the analysts can integrate heterogenous tire modeling methods into one coherent tire model suitable for the simulation of an over-the-road 18-wheel tractor-trailer configuration. The methods used in this paper are: Tire F&M modeling that represents the effect of tread wear, water depth, and speed, as well as combined longitudinal and lateral slip conditions.
Technical Paper

Truck Tire Wet Traction: Effects of Water Depth, Speed, Tread Depth, Inflation, and Load

The traction effects of water depth, speed, tread wear, inflation, and load on typical 295/75R22.5 truck tires have been examined in a set of designed experiments conducted on a single pavement. The results have been typified in terms of regression models of aligning moment and lateral force at 4 degrees slip angle plus peak longitudinal force and longitudinal force at slide during braking. The effects of the principal parameters are catalogued. An approximate idea of the effect of the operational and tread wear state parameters on the ability to control vehicle motion is provided within the discussion.
Technical Paper

A Model for Combined Tire Cornering and Braking Forces

The objective was derivation of a tire braking/cornering force model based on only a few standard tests, so that elaborate testing of all possible combinations of lateral and longitudinal forces could be avoided Such a model would be particularly useful for truck and bus tires because testing large tires is expensive and appropriate testing facilities are rare The required model can be derived from the concept of the slip circle (not a friction force circle) Using the slip circle concept, all tire forces at any cornering/braking combination can be predicted from the results of only two basic tests -- a free-rolling cornering test and straight-line braking test The slip circle concept has been incorporated into a subroutine called the COMBINATOR -- a piece of public domain software sponsored by SAE Cooperative Research This paper discusses the Slip Circle Model, introduces the COMBINATOR, and demonstrates effectiveness by comparison of modeling results and experimental data
Technical Paper

The BNPS Model - An Automated Implementation of the “Magic Formula” Concept

The “Magic Formula” concept is an elegant, empirical method of fitting tire data for inclusion in vehicle dynamics models. Its behavior as a function of parameter values is explained in detail in this paper. This paper presents the BNPS model, a modification of the Magic Formula concept, which has been fully automated on a personal computer. This allows the ready reduction of data into practical Magic Formula type models without any investment of engineering time. BNPS fitting example results are presented.
Technical Paper

Effects of Test Speed and Surface Curvature on Cornering Properties of Tires

The effect of test speed and surface curvature on tire force and moment properties has been investigated. Lateral force at low slip angles increases linearly 8 to 9 percent for a tenfold increase in test speed. The effect of test speed on tire force and moment properties produces only a modest change in predicted steady state vehicle handling, but a rather significant change in predicted transient vehicle handling. Surface curvature tends to reduce slip and camber generated lateral force and aligning torque, but the effect is extremely complex and no simple flat to curved surface transformation relationship exists.