Wave Compensator Design Based on Adaptive FFT Prediction Algorithm and H∞ filtering

Abstract

As the performance of the unmanned aerial vehicle (UAV) has been greatly improved with the rapid development of science and technology, the UAVs have been widely used for a broad range of applications. In recent years, the shipborne UAV has received considerable attention due to its low cost, small size, and high cost-effectiveness ratio. A key difficulty for the shipborne UAV is that due to the effect of the waves, the vertical sway, horizontal sway, and heave motions of the ships brought great challenges to the safe take-off and landing of the shipborne UAVs. To circumvent this drawback, this study proposed a wave compensation system based on the adaptive fast Fourier transform (FFT) prediction algorithm and H∞ filtering. On the one hand, in order to reduce the time delay errors caused by sensors, controllers, and other devices, the FFT was adopted to construct an adaptive wave prediction algorithm. With the help of this algorithm, the heave motion model of the waves is forecasted to compensate the waves as synchronously as possible. On the other hand, in order to improve the robustness of the system and reduce external disturbances, the H∞ filter was used to eliminate the high-frequency wave interference and make the compensation platform move more smoothly. Using the control and computation simulation software Matlab and the visual scene simulation software Vortex, based on the adaptive FFT prediction algorithm and H∞ filtering, the co-simulation platform was constructed for the take-off and landing structural platform, the three-degree-of-freedom wave simulation, and the six-degrees-of-freedom wave compensation. The examples presented demonstrated that the proposed wave compensation system has feasibility in the take-off and landing of the shipborne UAVs. The examples also verified that the adaptive FFT prediction algorithm could forecast the waves effectively, and H∞ filter has a good filtering effect in the wave compensation.