Using discrete fourier transforms to detect operational environments for autonomous nonlinear systems

The proportional-integrative-derivative (PID) controller provides effective control in linear systems. However, performance is poor in nonlinear systems unless combined with a fuzzy logic controller (FLC) that modifies the PID controller gains as needed. System behavior can adapt to operational environment changes by switching different FLCs online. But that capability requires accurate operational environment identification. Identification must be done without human intervention in autonomous systems. This paper describes how Discrete Fourier Transforms can identify operational environments in an autonomous nonlinear system. Simulation results indicate the proposed method accurately identifies the environment and switches the correct FLC online to adapt the system's behavior.