| A periodic active control scheme is presented and applied to a physical model of ground resonance in helicopters. While the equations of motion have periodic coefficients, periodic sampling leads to a constant-coefficient discrete dynamic model: a Poincare map. Control is applied to stabilize this discrete model. This discrete control consists of small, periodic perturbations in applied torque; the perturbations serve only to keep the system near an existing stable orbit. Thus, the resulting control uses very little power. After the discrete control was proven effective and robust in a numerical simulation of ground resonance, a physical system was designed and built to implement desired control torque input on the Washington University ground resonance model. An adapted asymptotic state observer is used to estimate only those states not otherwise directly measurable. |
