Towards the design of a pilot induced oscillation detection and mitigation scheme
Preliminary development of a real time pilot induced oscillations detection and mitigation system that consists of a detector, based on Short Time Fourier Transform and autoregressive model, and an adaptive mitigation system is presented. The system is not only capable of detecting Type I and II pilot induced oscillation characteristics but also focuses on the pilot's behavioural trend by calculating the rate of change of the open loop pilot vehicle system crossover frequency. The detection system employs a sliding Short Time Fourier Transform method to identify frequency and phase characteristics by monitoring pilot input and aircraft states. An autoregressive model with exogenous inputs was also applied to identify pilot characteristics and estimate the rate of change of the crossover frequency. After detection, a pilot induced oscillation cue is shown on the primary flight display and the adaptive controller is used to provide mitigation. The system was assessed through a series of desktop based piloted simulations where subjects conducted a number of tracking tasks. Results have shown that presenting the pilot with the state of the mitigation system via the visual PIO cue led to the opinion of reduced PIO tendencies. However, the lack of this information led to cases of over control and increased workload, which in turn resulted in higher PIO ratings. The main factor affecting the results was the inability to induce the levels of urgency in pilot control behaviour for the assessing the impact of including the rate of change of open loop PVS crossover frequency as a PIO feature. As a result only some of the test data showed its effectiveness. The real time calculation speed was constrained by the computer and the calculation algorithm.