Abstract.A class of control problems for a damped distributed parameter system governed by a system of partial differential equations with side constraints (equality and/or inequality) is considered. The proposed approach approximates each control force of the system by a Fourier-type series. In contrast to standard linear optimal control approaches, the method used here is based on the mathematical programming approach, in which the necessary condition of optimality is derived as a system of linear algebraic equations. The proposed approach is easy to apply to a large class of control problems. A vibrating beam excited by an initial disturbance is studied numerically in which the effectiveness of the control and the amount of force spent in the process are investigated in relation to the reduction to the dynamic response.