Analysis of Controller Errors in an Asynchronous, Redundant Flight Control System

Redundancy is a common means in the design of flight control system architectures, to meet demanding safety objectives for safety-critical applications. Redundancy management provides fault tolerant system operation when introducing redundancy to the system. In an asynchronous system, inherent signal errors introduced to the system due to timing offsets can affect the excitation of signals used for failure monitoring and redundancy management. In this work, we present the frequency domain analysis of the inherent errors in redundant controller outputs that result from timing offsets in an asynchronously operating flight control system. For an abstracted redundant system, we derive the transfer functions for the controller output error excited by pilot inputs and analyze the effects of different operational sequences also considering state equalization. We present several observations and perform the analysis for the closed-loop dynamics of a large drone model. The observations are validated in time domain with numerical simulations.