Failure Effect Analysis of Oscillation Signal in the Active Sidestick System

The electric loading function of the active sidestick system introduces new safety risks, making the failure effects of the system uncertain. To clarify the failure effect characteristics of uncommanded oscillation signals in the active sidestick system, fault mechanism analysis and fault injection simulations were conducted. For the standalone active sidestick system, oscillation faults with different injection locations, waveforms, amplitudes, and frequencies were investigated, and their effects were evaluated from three aspects: surplus force, active sidestick deflection angle, and loading motor speed. The results show that oscillation faults cause the active sidestick deflection angle to oscillate, with the response amplitude depending on the fault injection location and signal characteristics. In addition, the pilot response to the fault was incorporated into the active sidestick system. The results show that the influence of pilot response on oscillation faults exhibits significant frequency dependent characteristics. When the fault frequency is lower than approximately 0.72 Hz, the additional pilot control force reduces the aircraft pitch angle tracking error and suppresses the oscillation fault. When the fault frequency is higher than 0.72 Hz, the pilot response increases the aircraft pitch angle tracking error, and its effect changes from a counteracting action to an amplifying action. Based on the standalone active sidestick system simulated by the experimental setup, a sinusoidal oscillation fault injection experiment was conducted at the torque sensor output. The variation trends observed in the experimental results were generally consistent with the corresponding simulation results, thereby providing indirect validation of the fault injection simulations.