Development and experimental validation of a real-time analytical model for different intelligent tyre concepts

In recent years, the ever-increasing interest in intelligent tyre technology has led to the formulation of different empirical models correlating deformation measurements provided by the sensors with tyre dynamics. In this paper, a real-time physical model, suitable for describing the dynamics of intelligent tyres based on measurements of strains and/or displacements of the tyre carcass, is presented. The proposed flexible ring model can reproduce the tyre dynamics for both concentrated and distributed forces by introducing a discrete approach that also allows to analyse the longitudinal dynamics of the tyre in real-time. The analytical description of the problem allows to obtain solutions in closed form and to quickly identify model parameters from experimental data. The comparison between the simulated results and the ones provided by indoor tests of two intelligent tyre concepts highlighted that the proposed tyre model can estimate with an acceptable precision both the carcass deformations and the forces acting on the tyre

Vehicle Lateral State Estimation Based on Measured Tyre Forces

Future active safety systems need more accurate information about the state of vehicles. This article proposes a method to evaluate the lateral state of a vehicle based on measured tyre forces. The tyre forces of two tyres are estimated from optically measured tyre carcass deflections and transmitted wirelessly to the vehicle body. The two remaining tyres are so-called virtual tyre sensors, the forces of which are calculated from the real tyre sensor estimates. The Kalman filter estimator for lateral vehicle state based on measured tyre forces is presented, together with a simple method to define adaptive measurement error covariance depending on the driving condition of the vehicle. The estimated yaw rate and lateral velocity are compared with the validation sensor measurements

Onset of frictional sliding of rubber-glass contact under dry and lubricated conditions

Rubber friction is critical in many applications ranging from automotive tyres to cylinder seals. The process where a static rubber sample transitions to frictional sliding is particularly poorly understood. The experimental and simulation results in this paper show a completely different detachment process from the static situation to sliding motion under dry and lubricated conditions. The results underline the contribution of the rubber bulk properties to the static friction force. In fact, simple Amontons' law is sufficient as a local friction law to produce the correct detachment pattern when the rubber material and loading conditions are modelled properly. Simulations show that micro-sliding due to vertical loading can release initial shear stresses and lead to a high static/dynamic friction coefficient ratio, as observed in the measurements.Peer reviewe

Top topography surface roughness power spectrum for pavement friction evaluation

This article deals with the most suitable calculation procedure for top topography surface roughness power spectrum (PSD). The information top PSD provides about the roughness characteristics and its practical application in tyre-road friction studies are covered. The influence of portions of top topography used for calculations on the realization these PSDs give about surface height distributions is investigated. Results of roughness PSDs generally proved to be dependent on portions of top topography used for calculations. A high correlation with an average around 0.8 was found with friction and top 20% of PSDs, but only at a short-scale surface roughness λ≤1 mm. Low correlation coefficients between friction and longer λ were discussed through the depth of the penetration of the rubber into each pavement.Peer reviewe

Multiscale physics of rubber-ice friction

Ice friction plays an important role in many engineering applications, e.g., tires on icy roads, ice breaker ship motion, or winter sports equipment. Although numerous experiments have already been performed to understand the effect of various conditions on ice friction, to reveal the fundamental frictional mechanisms is still a challenging task. This study uses in situ white light interferometry to analyze ice surface topography during linear friction testing with a rubber slider. The method helps to provide an understanding of the link between changes in the surface topography and the friction coefficient through direct visualization and quantitative measurement of the morphologies of the ice surface at different length scales. Besides surface polishing and scratching, it was found that ice melts locally even after one sweep showing the refrozen droplets. A multi-scale rubber friction theory was also applied to study the contribution of viscoelasticity to the total friction coefficient, which showed a significant level with respect to the smoothness of the ice; furthermore, the theory also confirmed the possibility of local ice melting.Peer reviewe

A surface topography analysis of the curling stone curl mechanism

The curling motion of the curling stone on ice is well-known: if a small clockwise rotational velocity is imposed to the stone when it is released, in addition to the linear propagation velocity, the stone will curl to the right. A similar curl to the left is obtained by counter-clockwise rotation. This effect is widely used in the game to reach spots behind the already thrown stones, and the rotation also causes the stone to propagate in a more predictable fashion. Here, we report on novel experimental results which support one of the proposed theories to account for the curling motion of the stone, known as the "scratch-guiding theory". By directly scanning the ice surface with a white light interferometer before and after each slide, we observed cross-scratches caused by the leading and trailing parts of the circular contact band of the linearly moving and rotating stone. By analyzing these scratches and a typical curling stone trajectory, we show that during most of the slide, the transverse force responsible for the sideways displacement of the stone is linearly proportional to the angle between these cross-scratches.Peer reviewe