Research On Pilot Induced Oscillations(PIO)

Pilot Induced Oscillation(PIO)is a series of problems brought by the instability of the closed-loop system of pilot-aircraft, and one of the most fatal factors which influence the flight safety. With a mathematical model for the closed-loop system of pilot-aircraft, this paper, based on the Neal-Smith criterion, first establishes standards in accordance with Kopper-Happer evaluation rating, calculates in the Newton iteration method, and matches the references for the above mentioned mathematical model so as to simulate and verify the rationality of the model. Based on the model, the study then focuses on the mechanism of the phenomenon of PIO, and explores from two different aspects how to avoid the negative influence aroused by PIO.From the aspect of restraining the PIO, a suppression link was added into the model——pilot-induced-oscillation suppression(PIOS)filters. The study took the Rod Displacement PIOS filters as an example to clarify the arithmetic of the PIOS filters. And then it simulated and analyzed the model using related software, which proved that the PIOS filters restrained the PIO while guaranteed the quality of the flight. Then by changing the parameters of the filter, its influence on the suppression of PIO was studies, the conclusion of which will be helpful for the further design of PIOS filters.From the aspect of avoiding and preventing the PIO, based on William Gray's Boundary Avoidance Tracking (BAT) theory, a mathematical model of the Boundary Avoidance Tracking was established. The study selected the aircraft mathematical model of the formation of a pitch tracking closed-loop system and simulated. The comparison proved that the BAT theory was beneficial to aircraft handling and stability. Meanwhile, it analyzes the relationship between the main parameters of the BAT theoretical model and Flying Quality Parameters. The result provided a roadmap for in-depth study of BAT theoretical. People can determine and analyze these parameters by testing or simulating in flight simulator, so as to carry out qualitative research on the BAT theory, and observe the impact of BAT on the successful tracking.