TY - JOUR A2 - Dixon, Warren AU - Aguilar, Luis T. PY - 2009 DA - 2009/06/15 TI - Output Feedback Nonlinear 𝐻 -Tracking Control of a Nonminimum-Phase 2-DOF Underactuated Mechanical System SP - 718728 VL - 2009 AB - Nonlinear H synthesis is developed to solve the tracking control problem restricted toa two degrees-of-freedom (DOF) underactuated mechanical manipulator where position measurements are the only available information for feedback. A local H controller is derivedby means of a certain perturbation of the differential Riccati equations, appearing in solvingthe H control problem for the linearized system. Stabilizability and detectability propertiesof the control system are thus ensured by the existence of the proper solutions of the unperturbed differential Riccati equations, and hence the proposed synthesis procedure obviates an extra verification work of these properties. Due to the nature of the approach, the resulting controller additionally yields the desired robustness properties against unknown but boundedexternal disturbances. The desired trajectory is centered at the upright position where themanipulator becomes a nonminimum-phase system. Simulation results made for a doublependulum show the effectiveness of the proposed controller. SN - 1687-9600 UR - https://doi.org/10.1155/2009/718728 DO - 10.1155/2009/718728 JF - Journal of Robotics PB - Hindawi Publishing Corporation KW - ER -