Ari Tuononen

Optical position detection to measure tyre carcass deflections

Active safety systems would benefit from tyre force and friction potential information. Different sensor concepts, including, among others, the EU–funded Apollo–project developed tyre sensor based on optical position detection, are being studied. The sensor can measure tyre carcass deflections with respect to the rim. The carcass deflections can be used to calculate tyre forces and they may be exploited in the estimation of friction potential. The waveforms of the sensor signal are illustrated. The vertical and lateral force estimations are presented with unavoidable compensation parts. The tyre sensor measurements were compared to the measurement–vehicle results and good correlations achieved. Continuing activities are concerned with the estimation of friction potential and the detection of aquaplaning.

On-board estimation of dynamic tyre forces from optically measured tyre carcass deflections

Active safety systems would benefit from accurate information on tyre forces. A special sensor module has been developed for research purposes to study real-time tyre force estimation from tyre carcass displacements. The forces can be measured in vertical, lateral and longitudinal directions. The sensor measures tyre carcass movement with respect to the rim and transmits the data wirelessly to the chassis. The raw data is analysed and tyre force information is available on a CAN-bus. The sensor is calibrated in a tyre test rig and proving ground measurement results are presented. The lateral and longitudinal force estimates are accurate when compared with the vehicle accelerations, but the vertical force is difficult to estimate during heavy braking manoeuvres.

Macro- and micro-texture evolution of road pavements and correlation with friction

This article features a field experiment conducted on existing road pavements to characterise macro- and micro-texture variations at actual road conditions and to substantiate links to friction values. Three-dimensional inspections of the wearing course surface of three asphalt mixes were performed during a short period of 9 months. Several statistical texture indicators, spectral analysis and photo-simulated images of surface height maps were employed to analyse macro/micro-texture evolution and to study the physical phenomena behind it. Fractal and non-fractal parameters, with a focus on Hurst exponent (H), were used in associating texture with friction. The results of texture evolution clearly state that changes in macro/micro-scales occur within full surface profile and not solely from the polishing phenomena of a small percentage of top surface topographies. It was demonstrated that H, as an indicator of full surface profile specification, could not be employed for road texture–friction studies at actual road conditions.

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.

Measuring stud and rubber friction on ice under laboratory conditions

A linear friction tester is used to test stud and rubber friction on ice. Studs are metallic objects inserted into tyre treads to improve winter tyre performance. Special small-scale rubber specimens, with and without studs, are used in this study. To begin, the device itself is presented and described. Testing methodologies and procedures were implemented and are presented in this paper. The influence of several operational conditions, including ambient temperature, stud geometry, number of studs, normal load and sliding velocity, are investigated and discussed. In addition, modern imaging tools are used in conjunction with the linear friction tester. A thermal camera shows frictional heating in the small-scale specimens. A high-speed camera is used to visualise and analyse the contact area during the sliding.

Optical position detection sensor to measure tyre carcass deflections in aquaplaning

Information about the available friction of individual tyres is crucial for the operation of different Advanced Driver Assistance (ADAS) systems, such as collision mitigation and Adaptive Cruise Control (ACC). The information about aquaplaning is especially useful because aquaplaning severely hampers tyre-road interaction. In addition, validation tools are needed for complex physical tyre models, which are common development and research tools in the tyre industry. The optical tyre sensor is capable of accurately measuring the deformations in the inner ring of the tyre. Partial and full aquaplaning can be detected using the sensor. It also provides a research tool for understanding the phenomenon itself.

Three 3-axis accelerometers fixed inside the tyre for studying contact patch deformations in wet conditions

The tyre–road contact area was studied visually by means of a high-speed camera and three accelerometers fixed to the inner liner of the tyre carcass. Both methods show a distorted contact area in wet conditions, but interesting differences appeared. First, the contact area in full aquaplaning seems strongly distorted on a glass plate when subjected to visual inspection, while the accelerometers indicate a more even hydrodynamic aquaplaning contact length (CL) across the tyre width. Secondly, the acceleration sensors predict the clear shortening of the CL of the tyre before the critical aquaplaning speed. It can be concluded that the visual contact area and shape are heavily dependent on the transparency of the liquid and smoothness of the glass. Meanwhile, the tyre sensors can provide a CL estimate on any road surface imaginable.

Laser triangulation to measure the carcass deflections of a rolling tire

Tire sensors are powerful tools to study tire behavior and to evaluate the tire operating state. A laser tire sensor (LTS) is introduced in this paper. It is based on a laser triangulation sensor, which can measure the carcass deflections of a rolling tire. The sensor principle is explained and a special tire sensor module is introduced. The results are shown for several wheel loads and inflation pressures, which have linear influence on both the tire radius mean value and radius amplitude. Results from more complex driving situations are also covered, including soil deformation and aquaplaning. It was possible to observe tire penetration into the soft soil. An aquaplaning study shows significant influence of hydrodynamics forces on tire carcass behavior. Also the influence of inflation pressure on aquaplaning is shown.

A laser-based sensor system for tire tread deformation measurement

Optical tire sensors are powerful engineering tools that can reveal the mechanisms behind tireroad interactions. This paper presents a laser-based sensor system to measure tire-tread block deformation. The methodology and corresponding procedure for the system are introduced. Practical issues, such as tire sensor localization, are discussed. Validation experiments were conducted on a chassis dynamometer, and an asymmetric tire tread deformation along the contact patch was observed. It is proposed that asymmetric tread deformation is due to rolling resistance. The measurements under different operational conditions, including the rolling direction, wheel load, rolling velocity, and inflation pressure, were analyzed in the context of rolling resistance.

Real-time estimation of aquaplaning with an optical tyre sensor

Abstract Future active safety systems will require more accurate information about the state of a vehicle and the operating conditions of an individual tyre. Aquaplaning is a dangerous situation in which the contact between the tyre and the road is partially or completely lost. In this paper, the movements of the inner liner of the tyre during aquaplaning are measured optically and exploited to estimate aquaplaning. The results from proving-ground tests are shown and compared with those of the conventional approach of estimating aquaplaning from wheel speeds. The proposed method performs reliably in real time and can detect several different levels of aquaplaning. The results support the future development of production-capable tyre sensors. An optical tyre sensor also provides a research tool for attaining an in-depth understanding of the aquaplaning phenomenon.