Weight-in-Motion Estimation Based on Reconstruction of Tyre Footprint’s Geometry by Group of Fibre Optic Sensors

The problem of measuring road vehicle’s weight-in-motion (WIM) is important for overload enforcement, road maintenance planning and cargo fleet managing, control of the legal use of the transport infrastructure, road surface protection from the early destruction and for the safety on the roads. The fibre-optic sensors (FOS) functionality is based on the changes in the parameters of the optical signal due to the deformation of the optical fibre under the weight of the crossing vehicle. A fibre-optic sensor responds to the deformation, therefore for WIM measurements it is necessary to estimate the impact area of a wheel on the working surface of the sensor called tyre footprint. This information is used further for the estimation of the vehicle wheel’s speed, contact width, length, and, finally, axle’s weight while in motion. Recorded signals from a truck passing over a group of FOS with various speeds and known weight are used as an input data. The results of the several laboratory and field experiments with FOS, e.g. load characteristics according to the temperature, contact surface width and loading speed impact, are provided here. The method of initial signal deconvolution on symmetric and asymmetric components provides the chance to approximate geometric size of tyre surface footprint as well as calculate weight on each wheel separately. The examples of the estimation of a truck speed, tyre contact surface footprint parameters using FOS signals are discussed in this article.