Synthesis of the finite controller for the servo drive with the synchronous motor

Abstract

The paper is devoted to the synthesis of a finite controller for a digital servo drive with a synchronous motor, as well as to the determination of the possibility and area of its application. A block diagram of the single-loop servo drive is considered, which contains a digital finite controller that ensures the completion of transient processes in a strictly defined number of clock cycles of the sampling period. The form of the discrete transfer function of the finite controller is proposed. The transfer function of the closed-loop electric drive with the proposed type of controller is found. The system of equations was compiled and solved, which makes it possible to determine the tuning parameters of the finite controller for the servo drive with the synchronous motor. The results of computer simulation are given, showing that the transient processes in the control and disturbing effects in the servo drive are completed in 6 clock cycles of the sampling period. A formula is obtained for calculating the output signal of a finite controller for digital technical implementation on a microcontroller. A computational model of the considered digital electric drive has been developed, taking into account the limitation of current and voltage in the power converter. At small sampling periods, a servo drive with the finite controller is shown to require current limitation at the level of 16 nominal values. At low limiting values, the drive becomes unstable. To ensure the operability of an electric drive with the finite controller, it is proposed to increase the sampling period. It is shown that, in this case the servo drive remains stable in the entire range of displacements even under current and voltage limitations at the level of nominal values. The simulation results made it possible to conclude that the developed electric drive has a high speed of response, since during the development of the control action, the entry into the zone of 1 discrete from the set value is 0.022 s. It is shown that the presence of a static positioning error, which increases with an increase in the sampling period, is a negative effect of the finite control application in the servo drive with the synchronous motor. The electric drive in question is proposed to be supplied with one more position loop with an integral controller, which allows to compensate for the static positioning error.