Redistributed Pseudoinverse Control Allocation for Actuator Failure on a Compound Helicopter

Abstract

The present study focuses on applying a redistributed pseudoinverse control allocation method on a 20,110 lb compound helicopter in order to utilize the redundant control effectors in feedback control pre- and post-actuator failure. A range of tolerable positions for locked-in-place actuator failures is established for the aircraft at a cruise speed of 150 knots. A model following linear dynamic inversion control system is implemented for the nonlinear simulation model. Stability margins, phase delay, and bandwidth evaluated for the longitudinal and lateral axis according to ADS-33E specifications show level 1 for most cases except minimum failed aft actuator position (level 2 stability margin) and maximum failed stabilator (level 3 stability margin). Nonlinear simulations are used to examine the control reconfiguration and the aircraft response for failure in the longitudinal axis (swashplate aft actuator and stabilator) and lateral axis (swashplate lateral actuator and ailerons) demonstrating the capability of the redistributed pseudoinverse method. For certain failures, especially for actuators locked in extreme positions, the post-failure response is considerably degraded (showing limit cycle oscillations, actuator saturation, or sluggish response), which was not evident from the handling qualities metrics evaluated from the extracted linear models.