Sliding-mode control of the permanent magnet synchronous motor (PMSM)

Date of Award


Degree Name

M.S. in Electrical Engineering


Department of Electrical and Computer Engineering


Advisor: Malcolm Daniels


The main objective of this thesis is to track a reference speed being applied to permanent magnet synchronous motor (PMSM). As it known, these types of motors depend on a 3-phase time-dependent voltage source (3-Phase AC supply voltages) that generates a magnetic flux in the air-gap of the machine. This generated magnetic flux interacts with the permanent magnetic flux on the rotor, to generate the required torque. The mathematical model of this motor is a non-linear time-varying system. To apply different control techniques, we transform this model to an equivalent linear time-invariant system. These transformations not only yield a linear time-varying model, but also, reduce the number of states in the model. Classical control techniques, such as PI control, can provide a speed tracking of this type of motors with some limitations. In general, the performance of the motor is limited in term of the range of speed and the range of applied load torque. Also, the performance is affected by parameter variations or the high frequency, un-modeled states. In this project, a sliding-mode controller is used due to its insensitivity to the variations of the parameters. These types of controllers employ sliding surface, passing through the origin on the system trajectories plane. Once the system trajectory hits the sliding surface, they remain on it, and exhibiting stable operation. The conventional sliding surfaces are gained by a fixed constant which makes the control input exhibit a chattering phenomena. The proposed gain in this project is a smooth function, depending on the surface value to eliminate the chattering phenomena (soft switching mechanism). The primary problem with this design is the steady state error when a full-load torque is applied motor. This is overcome by designing an observer to estimate the load torque.


Permanent magnet motors Stability, Permanent magnet motors Control systems, Electric motors, Synchronous Mathematical models, Electrical engineering; speed tracking; sliding-mode control; load torque estimation; PMSM

Rights Statement

Copyright 2013, author