<h2>AAS  96-107</h2><h2>AN OPTIMAL CONTROL APPROACH TO NONLINEAR ROBUSTNESS</h2><h4>H. Seywald and R. R. Kumar, Analytical Mechanics Associates, Inc.</h4><h2> Abstract </h2>An optimal control formulation is introduced that enables the design of trajectories with reduced sensitivity to state perturbations encountered at any time along the trajectory.  Perturbations in fixed constants can be treated with this approach through a simple transformation that raises the status of the relevant parameters to that of states.  Thus, the concepts introduced in this paper include a method to achieve robustness with respect to parameter uncertainties in the solution to nonlinear optimal control problems. As a numerical example, a Zermelo-type boat path optimization problem is treated, with uncertainties in the strength of the water current.<br><br>