Design and testing of fibre Bragg grating force transducers for the measurement of pantograph–catenary contact force

This paper deals with the design, development and testing of a novel force transducer based on fibre-optic technology, for the measurement of contact force between a pantograph and an overhead line. Due to the particular application, in which part of the measurement chain is at high voltage and part is at ground potential, fibre-optic technology has the advantage of making the set-up easier to install and to manage with respect to the adoption of classical electrical-based transducers. Fibre Bragg grating is used as detectors in strain-based force transducers developed for this purpose. Considering that the force transducers become part of the connection between each collector of the pan head and the suspension, a proper design matching many conflicting requirements, such as encumbrance, mass, static and fatigue strength and sensitivity, is necessary. Laboratory tests and in-line tests proved the suitability of the optical force transducers. In particular, tests demonstrated that optical transducers represent an alternative to the classical electrical-based transducers for pantograph–catenary force measurement, reducing the complexity of the complete measurement set-up