Power harvesting using piezomaterial in a helicopter rotor blade

摘要

Current power harvesting research has focused on bending beams and determining power output under a given excitation. For the European CleanSky – Green Rotor Craft project a tool is being developed which optimizes the piezoelectric material and placement thereof for power harvesting. It focuses on beam-like structures exhibiting more complex dynamics where the optimum configuration is not evident. In particular helicopter rotor blades are considered where strains are high and frequencies low, stepping away from typical high frequency / low strain harvesting applications. This application will allow for smart rotor blades, alleviate rotor induced vibrations, subsequently increasing comfort and possibly airframe longevity. First an uncoupled model was developed, using an airfoil shape and vibration input from industry. The blade surface is covered with piezo electric patches of which the strain during one cycle is calculated. Materials, either ceramic or piezo polymer, are selected based on a peak strain criterion and the energy of each patch is then evaluated using a specified harvesting circuit. Optimum locations are determined using a minimum desired efficiency relative to the best performing patch. For aircraft application the main performance indicator is clearly the power to weight ratio. Experiments have also been conducted which confirm the piezo polymer performance up inudthe percentage strain range where piezo ceramics fail. The harvesting performance of ceramic patches has also been evaluated. Measurements will be conducted on a complex beam shape to confirm the theoretical results as well when the theoretical model is completed. Future development encompasses dynamic coupling since the behaviour may be influenced as more energy is extracted. An iteration algorithm will need to be selected for the optimization process. Lastly electrical models will be included as this directly determines the harvesting efficiency. The final tool will be applicable on any slender structure which exhibits complex harmonic loading.