Mitigating Unfavorable Pilot Interactions with Adaptive Controllers in the Presence of Failures/Damage

Abstract

As a means to enhance aviation safety, numerous adaptive control techniques have been developed to maintain aircraft stability and performance in the presence of failures or damage. The techniques apply a wide array of adaptations from simple gain scheduling to online learning algorithms. While the ready availability of low cost, reduced scale unmanned systems have allowed for many successful flight test demonstrations, applications to piloted aircraft have been more limited. Flight evaluations of various adaptive control applications conducted by NASA and others have shown great promise. In some cases, however, unfavorable pilot-vehicle interactions including pilot-induced oscillations have occurred. Susceptibility to such interactions is more likely when the pilot interacts with a highly nonlinear vehicle that may no longer have predictable response characteristics due to the intervention of the adaptive controller and/or presence of flight control system nonlinearities such as actuator rate and position limits. To address the challenge of adverse pilot interactions with an adaptive control system, the Smart Adaptive Flight Effective Cue or SAFE-Cue system is introduced. This innovative cueing system provides force feedback to the pilot via an active control inceptor with corresponding command path gain adjustments. The SAFE-Cue will alert the pilot that the adaptive control system is active, provide guidance via force feedback cues, and attenuate commands, thus ensuring pilot-vehicle system stability and performance in the presence of damage or failures. Piloted simulation results found that the SAFE-Cue system was effective at suppressing pilot-vehicle system oscillations for failure/damage scenarios, allowing the pilots to focus on the task at hand rather than simply maintaining control.