Abstract:
Gallagher Group are a manufacturer of livestock management systems, developing products including electric fencing, livestock weighing systems, electronic identification and data collection. At the core of the livestock weighing system and data collection is the Gallagher load bar. Load bars form the foundation of weighing systems, measuring and transmitting animal weight data for collection. This data is used to track animal growth and advise users of the most suitable feed and drenching levels in order to maximise stock yields. The predominant failure points in the Gallagher livestock weighing system are the cables that connect the load bars to the data collection terminal. These cables are exposed and subjected to dirt, animal waste, sunlight, chemicals and physical damage; accelerating their degradation. Gallagher Group seek to develop a solution which allows for the removal of the cables from the system. The aim of this project is to develop the concept of a self-powered wireless load bar. The device must be capable of generating sufficient electrical energy to allow for the collection of animal weight samples and to wirelessly transmit this information to a nearby data collection terminal. A transduction mechanism for converting the force applied by livestock supported by the weighing system to electrical energy is presented. The transduction mechanism consists of a piezoelectric stack housed within a compliant mechanism, used to amplify the applied force. Configurations of combined load cell and the transduction mechanism are demonstrated. A comprehensive model for the coupled mechanical and electrical behaviour of the system is developed. In order to achieve the highest energy conversion efficiency, the effects of structure, materials and electrical load are considered. The accuracy of the developed model is validated under controlled test conditions and a testing platform constructed. Optimisation of the transduction mechanism is conducted, considering both the effect of design materials and the structure of the device. The performance of the device under various animal loading conditions is analysed to maximise energy transfer at suitable output voltage levels. Recommendations are then made for commercial implementation. Finally, power management circuitry is explored, covering voltage rectification, regulation and charge storage.