Mixed H2/H∞ control for underwater vehicle with time delay and parameter uncertainty

A mixed H²/H^∞ controller with two-degree-of-freedom for underwater vehicle with time delay in all variables and parameter uncertainties are designed considering uncertain structure. A hydrodynamic coefficient error and scale factor error of measurement sensor (gyro and accelerometer) are modeled as parameter uncertainties. The time delays by the fin actuator model and process computing time are approximated using the Pade approximation. The approximation errors are modeled as time delay uncertainties. For the system with parameter uncertainties and time delay uncertainties, H² performance and robust H^∞ performance conditions that account for model matching of closed loop system and disturbance rejection are derived. Simulations are presented to demonstrate the achievement of good robust performance