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In this article, we investigate the trajectory tracking problem of underactuated aerial vehicles with unknown mass in the presence of unknown nonvanishing disturbances using an event-triggered approach, while considering the constraint that the derivative of the reference trajectory is not available. In contrast to existing references where the derivative of the reference trajectory is needed, here we first introduce a high-gain observer to estimate the unknown derivative solely from the reference trajectory. A disturbance observer is designed to compensate for nonvanishing disturbances, such as wind. Fuzzy logic systems are used to approximate the model uncertainty arising from the unknown mass of the vehicle, and then we derive a thrust command law that follows from a desired stabilizing force. In addition, unlike traditional fixed and relative threshold strategies that rely solely on control signals, we develop a new …