Using Relay Controllers to Excite Self-Oscillations in Underwater Vehicle for Identification and Controller Tuning

This work investigates relay-based methods to reveal the frequency domain characteristics of BlueROV2 underwater vehicle. Two relay-based approaches are examined: the Modified Relay Feedback Test (MRFT) and a two-relay (twisting-type) controller. The distinguishing feature of these relay tests is their ability to capture process frequency-response data at a desired phase angle in the Nyquist plot. Approximate equivalence of these tests is also discussed. Influence of additional dynamics on oscillations for these tests is discussed and it is argued that these relay tests have capability to excite both actuator and plant dynamics simultaneously, hence provide a mean to perform full system identification and precise controller tuning. Experiment and simulations of oscillation tests are also presented.