A Simple and Efficient Design of 2DOF Controllers with Application to the Speed Regulation of Electrical Motors

This paper proposes a design procedure for a two degree of freedom (2DOF) controller applied to first order plants. The feedforward controller is comprised here by a simple proportional gain, and the feedback action is provided by a proportional-integral controller. The proposed design procedure provides the control gains that allow to the closed-loop system a first order transfer function response, demanding from the control designer the choice of only one parameter: the frequency, p, of the closed-loop pole. The limit for the control signal,
$\bar{U}$
, is also taken into account in the 2DOF design, allowing operation without control signal saturation. The proposed 2DOF controller is applied to the speed regulation and current regulation of a permanent magnet synchronous motor. For a comparison, a conventional proportional-integral controller (without the feedforward action) is obtained by a specialized function in MATLAB, and the results show the superiority of the 2DOF controller, which guarantees operations without overshoot and without control signal saturation.