Discrete PI controller applied on a brushless motor with a coupled load

Abstract

Direct current motors are widely used on the actioning of the electromechanical systems. One of the reasons for that usage is due to the possibility of a precise control of its axis rotation and therefore of the actioning performed by the motor. Due to the important role of that motors, this work presents a study about the control of a direct current motor using the discrete Proportional (P) – Integral (I) control technique, that encompassed: (i) the system dynamics description through differential equation and its equivalent transfer function; (ii) the transfer function discretization; (iii) the project of a discrete PI controller for the system; (iv) the control implementation and experimental tests, considering simulations and the real system; and (v) the comparative analysis of the obtained results. The motor considered in the real experiments is one from Maxon® manufacturer, that is a brushless motor of 12V DC integrated with an encoder of 500 pulses per revolution. An arm was connected to the motor’s axis in order to represent the load. For the electronic instrumentation of the system, a data acquisition board from National Instruments, model NI-PCI-6602, was used. The data obtained from that board were processed in the Matlab/Simulink® software, in order to generate the control signal to be sent to the system. The results obtained from the simulations and from the real system show that the used control strategy is appropriate for the presented application. Furthermore, the results also support futures comparative studies, considering other control techniques to be implemented in the system described in this paper.