Collision Avoidance using Mixed H2/H∞ Control for an Articulated Intervention-AUV

In this paper we consider the problem of mixed H
₂
/H
_∞
control to combine optimal and robust control for a double integrator system with nonlinear performance variables, and we apply this to control an articulated intervention autonomous underwater vehicle (AIAUV). The AIAUV has an articulated body like a snake robot, is equipped with thrusters, and can be used as a free-floating underwater manipulator. The objective is to control the joints of the AIAUV to desired setpoints without causing collisions between links or with obstacles in the environment. The mixed H
₂
/H
_∞
problem is viewed as a differential game, and a set of matrix equations is solved in order to construct an approximate solution to the problem for a system described by double integrator dynamics and with nonlinear performance variables. A feedback linearising controller is derived to obtain the double integrator dynamics for the joints of the AIAUV, and the solution found for the mixed H
₂
/H
_∞
control problem is applied to the resulting system. Simulations demonstrate that collisions between links of the manipulator are successfully avoided also in the presence of parameter uncertainties while regulating the joints to the desired setpoints, and the method can easily be extended to include collision avoidance with static and dynamic obstacles in the environment.