Browsing by Author "Crawley, Fregus"

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    Energy scavenging piezoelectric powered led system for use in tracer ammunition
    (Cranfield University, 2025-04) Crawley, Fregus; Luo, Jerry; Hucker, Martyn; Almond, Heather
    Fuel-oxidizer tracer ammunition is the standard technology used to produce bright light for projectile observation. However, a modern electronic tracer system has the potential to eliminate the safety risks associated with combustible materials and open flame systems by replacing them with a safer, integrated energy harvester-powered electronic light-emitting system. The goal of this research is to investigate the technologies necessary to convert kinetic energy from the bullet propulsion into electrical power and to assess whether an integrated energy harvesting system, coupled with electrical storage and an LED with the accompanying circuitry, could feasibly replace the current technology in the future. The study focuses on analysing existing mechanical-to-electrical transduction technologies, understanding their design and use limitations, and evaluating their suitability for implementation with small arms munitions that undergo high linear and rotational acceleration. Additionally, this research examines the complexity of manufacturing, construction, and adaptability of these technologies to smaller and larger of munitions. After reviewing and filtering previous system designs and technology prototypes, piezoelectric energy harvesting technology was selected due to its energy density, material and structural compatibility for withstanding large forces and lower mechanical system complexity for further development. A prototype piezoelectric system was designed and simulated using commercial software to model both structural and electrical behaviour. Experimental validation tests were conducted with high compressive loads and rotational forces experienced in real-world conditions. The research developed three novel spring structures that significantly increase the power density of linear and rotational piezoelectric energy harvesters. These spring structures feature enhanced shearing capabilities with disc spring optimisation allowing 39% energy harvesting improvement and a prototype system tuned for the 7.62 mm tracer outputting 3 V. and can be manufactured with relatively low complexity compared to other energy harvesting technologies. With the novel energy harvesting system in place, additional modelling was conducted to design the accompanying LED circuit and capacitive energy storage, thereby completing the development of the Electronic Tracer system.