This paper presents a finite element (FE) model developed using commercial FE software COMSOL to simulate the multiphysical process of pieozoelectric vibration energy harvesting (PVEH), involving the dynamic mechanical and electrical behaviours of piezoelectric macro fibre composite (MFC) on carbon fibre composite structures. The integration of MFC enables energy harvesting, sensing and actuation capabilities, with applications found in aerospace, automotive and renewable energy. There is an existing gap in the literature on modelling the dynamic response of PVEH in relation to real-world vibration data. Most simulations were either semi-analytical MATLAB models that are geometry unspecific, or basic FE simulations limited to sinusoidal analysis. However, the use of representative environment vibration data is crucial to predict practical behaviour for industrial development. Piezoelectric device physics involving solid mechanics and electrostatics were combined with electrical circuit defined in this FE model. The structure was dynamically excited by interpolated vibration data files, while orthotropic material properties for MFC and carbon fibre composite were individually defined for accuracy. The simulation results were validated by experiments with <10% deviation, providing confidence for the proposed multiphysical FE model to design and optimise PVEH smart composite structures.
Based on the works of Yahya Rahmat-Samii, a multiobjective optimization model is developed to analyze the effects of surface errors' nonuniformity along the radius on the reflector's radiation characteristic. Through the optimization model, Pareto front for trading off the peak gain loss (PGL) and the first sidelobe level increase (SLLI) is obtained. Simulations clearly show that for the same root mean square (rms) error for the whole reflector, different distributions along the radius result in different PGLs and first SLLIs. Then, the weighting function of the rms errors is considered and the evaluation formula of PGL is successfully applied to nonuniform errors. It is concluded that besides the radius, the amplitude aperture distribution, and the ratio of focal length to diameter (F/D), errors' nonuniformity is also an important factor that should be considered in the procedure of the quality evaluation of the reflector surface.
Active phased array antennas (APAAs) can suffer from the effects of harsh thermal environments, which are caused by the large quantity of power generated by densely packed T/R modules and external thermal impacts. The situation may be worse in the case of limited room and severe thermal loads, due to heat radiation and a low temperature sink. The temperature field of the antenna can be changed. Since large numbers of temperature-sensitive electronic components exist in T/R modules, excitation current output can be significantly affected and the electromagnetic performance of APAAs can be seriously degraded. However, due to a lack of quantitative analysis, it is difficult to directly estimate the effect of temperature on the electromagnetic performance of APAAs. Therefore, this study investigated the electromagnetic performance of APAAs as affected by two key factors—the uniformly distributed temperature field and the temperature gradient field—based on different antenna shapes and sizes, to provide theoretical guidance for their thermal design.
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