Design of robust controllers with constraints on the control signal application for brushless DC drives

Controller design for systems with hard constraints is a quite vivid area of research, due to the fact that most practical control problems are dominated by constraints on the control signal. The paper presents a general theoretical framework of how robust controllers can be designed, taking into account the constraint on the control signal. The systematic design of a robust controller is illustrated in case of a vector controlled brushless DC motor drive, which is identified using advanced identification techniques. In order to enhance the dynamic performances of the designed control system, in case of limitation of the control signal, a gain-scheduled control strategy is considered. The robust stability of the gain-scheduled control system, considering the variation rate of the time-varying parameter is studied by linear matrix inequalities. The proposed robust controller design approach is verified by experimental results in case of a brushless DC motor drive, when the control algorithm is implemented on a DSP board.