This paper treats the question of force control and stabilization of a flexible beam using a piezoceramic actuator using only output feedback. It is assumed that there exists unstructured model uncertainties including beam parameters, contact surface stiffness, and the number of vibration modes in the model, and only force measurement is used for the contact force control. The controller has the structure of an inverse (a feedback linearizing) control system. For compensating the unknown function in the inverse control law arising from the uncertainties in the model, its estimate is constructed by a high-gain observer. Simulation results are presented which show robust force trajectory control and stabilization in the closed-loop system in the presence of unstructured uncertainties.