Evaluation methods for PIO trend during ultra low altitude airdrop process

This paper presents the pilot-induced oscillation (PIO) problem in the airdrop stage, analyzes the main causes of the PIO in the drop stage, establishes the closed-loop system with the actuator rate limit, and deduces the PIO formula of closed loop system. Based on the synchronization and Neal-Smith pilot model and the different actuator saturation values, the descriptive function method and the GAP criterion are used to predict the PIO trend of a conveyer in the drop stage. The results show that the PIO prediction results are different for different driver models. If the PIO is caused by the driver, the driver can effectively avoid the occurrence of PIO by reducing the manipulated gain. In the reasonable and permissible range, increasing actuator limit value can avoid the occurrence of PIO to a certain extent.