Optimization-based Inverse Simulation of a Helicopter Slalom Maneuver

This paper presents an inverse simulation methodology based on numerical optimization. The methodology is applied to a simplified version of the slalom maneuver in the ADS-33D helicopter handling qualities specifications. The inverse simulation is formulated as an optimization problem with trajectory and dynamic constraints, pilot inputs as design variables, and an objective function that depends on the specific problem being solved. A maximum speed solution is described in the paper. The results show that numerical optimization is a reliable and flexible tool for inverse simulation, both when the required trajectory is prescribed explicitly and when it is defined indirectly through geometric and dynamic constraints. When the trajectory is defined indirectly, there is not a single acceptable trajectory, but rather an entire family with noticeable differences in the helicopter dynamics and in the required pilot inputs. Even when the trajectory is prescribed explicitly multiple solutions exist. For handling qualities studies, the multiple solutions may provide an indication of the amount of scatter in pilot ratings to be expected for a given aircraft and a given maneuver. However, if the inverse simulation is used for simulation validation, then additional constraints may have to be placed on the solution to make it unique.