Comparison of incremental encoder digital signal processing techniques for the induction motor flux-torque vector control systems

Abstract

The article presents the results of a study on the effectiveness of various techniques for synchronous reference frame angular
position numerical calculation in flux-torque vector control system of induction motor. Investigation was caried out taking into
account the discrete nature of the angular speed signal obtained using an incremental encoder. In this work for investigation by
simulation used a direct torque vector control system, which, in the presence of an ideal rotor angular speed signal, ensures direct
asymptotic field orientation, asymptotic tracking of torque-flux reference trajectories, as well as asymptotic decoupling torque and
flux subsystems. The parameters of the induction motor and encoder used in the study correspond to those existing in traction
electromechanical systems of city trolleybuses. It is shown that the discrete nature of the angular speed signal, which used in
synchronous reference frame position equation of flux-torque vector control systems, introduces field orientation errors and leads to
current and torque ripples, which in a real system increase acoustic noise and can cause mechanical vibrations and resonance
phenomena. An analysis of possible ways to reduce the influence of the speed signal discreteness on flux-torque control is performed,
and a method for practical implementation of the synchronous reference frame angular position numerical calculation is proposed.
This method allows ensuring conditions for more precise field orientation and, by using an additional filter for the angular speed
signal, reducing the level of current and torque ripples to negligibly small values without affecting the field orientation processes.
The proposed solution can be used in the development of high dynamic flux-torque vector control systems for induction motors using
incremental encoders, including for electric vehicles.