Vehicle wheel load estimation with fiber optical contact patch elongation measurement
Résumé
Load estimation of wheels, especially for heavy vehicles, is of importance for several reasons. First safety imposes to respect loading limits for a given tire, but the variety of road infrastructures or bridges passed by a vehicle are defining constraints of larger scales as structure resistance or pavement durability. Moreover, multiple-wheels load estimation may be an efficient verification mean of the loading uniformity of goods inside a heavy vehicle. All these reasons are justifying the interest for a continuous estimation of load for each wheel. In this context, this work aims at contributing to the development of an intelligent tire solution, able to estimate the loading applied on a wheel from the elongation measurement of the tire-to-road contact patch. As a first step of proof of concept, without regarding durability, this measurement has been done with a tire instrumented with a longitudinal, circumferential optical fiber. Measurement on a static test wheel has shown the relevance of the method to detect slight elongation of the contact patch, surrounded by compression of nearby tire areas. The Distributed Optic Fiber (DOF) measurement, widely used in the structural health monitoring domain (SHM), has been related to the force applied to the wheel, by a near linear relation, on the experienced domain of 70mm to 110 mm for the contact length and 1.1 to 2.6 kN for the vertically applied force. As a result, demonstration is done that an intelligent tire could provide a relevant information on a given wheel load of a vehicle. The optimization of the experimental setup should lead to a robust system, usable continuously on heavy vehicles, to detect harmful loading displacements or to qualify adequacy between vehicle load and road infrastructure capacity.
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