Static tire properties analysis and static parameters derivation to characterising tire model using experimental and numerical solutions

Tire-ground interaction plays substantial role in determining vehicle kinetics and kinematics yet a clear understanding of such an interaction outputs is complex process. The present study aims at static analysis of tire parameters using both experimental and numerical based finite element method (FEM) solutions. To this end, tire cross section shape with different inflation pressures, vertical stiffness together with the footprint were measured using controlled apparatus and then are compared with the simulation results in order that the accuracy of the FE tire model in static condition can be validated. The 3D tire model was obtained by revolving the 2D axisymmetric tire model, and static stiffness and footprint were predicted using the 3D model. Inflation pressure analysis was presented by comparing the tire cross-section shape variation at different inflation pressures. The conclusions will serve future investigations as a concise knowledge source to develop improved tire models

A finite element based approach to characterising flexible ring tire (FTire) model for extended range of operating conditions

In order to accurately predict vehicle dynamic properties when tires impact high obstacles or large bumps, appropriate tire models need to be developed and characterised. The Flexible Ring Tire (FTire) model is one of the models for predicting the transient dynamic responses when traversing obstacles. In this thesis, a combination of experimental tests and Finite Element (FE) modelling is used in deriving FTire models for different levels of tire/road interaction severity. A FE tire model is built to characterize tire properties including static properties, steady-state rolling properties and transient dynamic rolling properties. A 235/60 R18 tire is cut in order that the tire cross-section can be captured and the tire rubber and reinforcement components can be extracted. A detailed method for the determination of geometrical and material properties of tires has been developed for tire modelling. The 2D and 3D models for static and dynamic analysis are both developed using a commercial FE code ABAQUS. The parameters of FTire model are derived based on the experimental data and FE simulation data, and different FTire models are derived under different operation conditions. Multi-body dynamic analysis is carried out using these FTire models, and the transient dynamic responses using different FTire models are compared with each other. It is shown that FE modelling can be used to accurately characterise the behaviour of a tire where limitations in experimental facilities prevent tire characterisation using the required level of input severity in physical tests

RISE-Based Integrated Motion Control of Autonomous Ground Vehicles With Asymptotic Prescribed Performance

This article investigates the integrated lane-keeping and roll control for autonomous ground vehicles (AGVs) considering the transient performance and system disturbances. The robust integral of the sign of error (RISE) control strategy is proposed to achieve the lane-keeping control purpose with rollover prevention, by guaranteeing the asymptotic stability of the closed-loop system, attenuating systematic disturbances, and maintaining the controlled states within the prescribed performance boundaries. Three contributions have been made in this article: 1) a new prescribed performance function (PPF) that does not require accurate initial errors is proposed to guarantee the tracking errors restricted within the predefined asymptotic boundaries; 2) a modified neural network (NN) estimator which requires fewer adaptively updated parameters is proposed to approximate the unknown vertical dynamics; and 3) the improved RISE control based on PPF is proposed to achieve the integrated control objective, which analytically guarantees both the controller continuity and closed-loop system asymptotic stability by integrating the signum error function. The overall system stability is proved with the Lyapunov function. The controller effectiveness and robustness are finally verified by comparative simulations using two representative driving maneuvers, based on the high-fidelity CarSim-Simulink simulation

Modeling Photosynthesis of \u3ci\u3eSpartina alterniflora\u3c/i\u3e (Smooth Cordgrass) Impacted by the Deepwater Horizon Oil Spill Using Bayesian Inference

To study the impact of the Deepwater Horizon oil spill on photosynthesis of coastal salt marsh plants in Mississippi, we developed a hierarchical Bayesian (HB) model based on field measurements collected from July 2010 to November 2011. We sampled three locations in Davis Bayou, Mississippi (30.375 degrees N, 88.790 degrees W) representative of a range of oil spill impacts. Measured photosynthesis was negative (respiration only) at the heavily oiled location in July 2010 only, and rates started to increase by August 2010. Photosynthesis at the medium oiling location was lower than at the control location in July 2010 and it continued to decrease in September 2010. During winter 2010-2011, the contrast between the control and the two impacted locations was not as obvious as in the growing season of 2010. Photosynthesis increased through spring 2011 at the three locations and decreased starting with October at the control location and a month earlier (September) at the impacted locations. Using the field data, we developed an HB model. The model simulations agreed well with the measured photosynthesis, capturing most of the variability of the measured data. On the basis of the posteriors of the parameters, we found that air temperature and photosynthetic active radiation positively influenced photosynthesis whereas the leaf stress level negatively affected photosynthesis. The photosynthesis rates at the heavily impacted location had recovered to the status of the control location about 140 days after the initial impact, while the impact at the medium impact location was never severe enough to make photosynthesis significantly lower than that at the control location over the study period. The uncertainty in modeling photosynthesis rates mainly came from the individual and micro-site scales, and to a lesser extent from the leaf scale

APPRAISAL OF TAKAGI–SUGENO TYPE NEURO-FUZZY NETWORK SYSTEM WITH A MODIFIED DIFFERENTIAL EVOLUTION METHOD TO PREDICT NONLINEAR WHEEL DYNAMICS CAUSED BY ROAD IRREGULARITIES

Wheel dynamics play a substantial role in traversing and controlling the vehicle, braking, ride comfort, steering, and maneuvering. The transient wheel dynamics are difficult to be ascertained in tire–obstacle contact condition. To this end, a single-wheel testing rig was utilized in a soil bin facility for provision of a controlled experimental medium. Differently manufactured obstacles (triangular and Gaussian shaped geometries) were employed at different obstacle heights, wheel loads, tire slippages and forward speeds to measure the forces induced at vertical and horizontal directions at tire–obstacle contact interface. A new Takagi–Sugeno type neuro-fuzzy network system with a modified Differential Evolution (DE) method was used to model wheel dynamics caused by road irregularities. DE is a robust optimization technique for complex and stochastic algorithms with ever expanding applications in real-world problems. It was revealed that the new proposed model can be served as a functional alternative to classical modeling tools for the prediction of nonlinear wheel dynamics

The effects of tyre material and structure properties on relaxation length using finite element method

This study investigates the influence of tyre structural layup and material properties on the relaxation length of a rolling tyre using finite element analysis. Relaxation length for rolling tyre under different operating conditions has been studied recently. However, the effects of tyre structural layup and material properties on relaxation length were ignored. In this present work, a finite element (FE) tyre model was built based on the material and geometry properties obtained from measurements of the tyre provided by a vehicle company. Rather than the common method (steady state rolling analysis) used for cornering behaviour simulations, ABAQUS/Explicit program was used for prediction of the cornering performance and relaxation length for a constant slip angle of the rolling tyre. Two different steer inputs were applied to the rolling tyre in terms of slip angle variation, namely step input and ramp input. The effects of various factors, including cross-section area, spacing, crown angle and strength of the tyre reinforcement cords, on relaxation length of the rolling tyre were investigated by numerical experiments using the design of experiment (DOE) method