ALBERT ZAJDEL; MICHAŁ WELCER; CEZARY SZCZEPAŃSKI; MARIUSZ KRAWCZYK
DOI Number: 10.13009/EUCASS2023-088
This article presents an assessment of an automatic flight stabilization system that utilizes trim tabs. The system,knmvn asAST-1, was designed for the Polish military turboprop trainer aircraftPZL-130 Orlik. The AST-1 differs from traditionalautomatic flight control systems as it moves only the trim tabs of the primary control surfaces instead of the smfaces themselves. This solution offers benefits such as reduced complexity, cost, and energy consumption. The article describes the development of the AST-1 using model-based design and its evaluation through flight tests and hardware in the loop (HIL) simulations. The controller structure of the AST-1 system includes internal and external control loops with proportional-integral-derivative regulators. The system was tested in simulations at various levels of advancement, including model, software, and hardware in the loop simulations. The real flight data were com pared with hardware in the loop simulations results, where the controller software ran on the same onboard computer connected to actuators as in the actual aircraft. Flight tests were conducted to verify the control system, and various parameters were analysed to assess control quality, including step response analysis and the integral square error metric. The results of the flight tests were compared with the simulation results. The article provides detailed comparisons for the lateral control channel of the AST-1 system. Overall, the responses in real flight were stable and converged to setpoints, however they exhibited larger over/undershoots and settling times compared to the simulations. The discrepancies were attributed to factors such as air turbulence and the need for further refinement of the aerodynamic model to include asymmetrical effects. The article also suggests potentialimprovements to reduce the differences between simulationandrealflight, such as modifying the controller gains during flight and expanding the trim tab and primary control surface interaction model.