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The identification and real time speed control, without reverse motion, for a series DC motor is presented. The identification is performed using the transient response analysis of the mechanical and electrical subsystems of a series DC motor. A linearized model which does not include the magnetic saturation around the operating conditions is considered. Based on this model, a PI speed controller is designed. A well-known problem arising in this type of electrical motors is the singularity at zero speed. It is shown that, in spite of this inconvenience, the PI controller, together with an antiwindup scheme, presents adequate regulation and tracking performance. It is also shown that the control system can compensate for varying loads and the counter-electromotive force with acceptable levels of current consumption.

Stator-currents control is essential for several high-performance induction motor control schemes such as field oriented control. There are numerous reports dealing with sophisticated control schemes for this subsystem. However, classical linear controllers remain widely used due to their experimental success and simplicity. Considering that the induction motor stator currents subsystem is normally represented by a fifth order non-linear multivariable model, it is remarkable that simple fixed linear controllers, such as typical proportional integral schemes, are able to provide adequate robustness and performance in practice. In fact, it is normally assumed that this subsystem is "easy" to control, and the difficulties are mostly technical. Moreover, it is common practice to consider a stable first order linear single input single output (SISO) system as a design model. On the other hand, it is widely known that stable and minimum phase uncertain SISO systems are also "easy" to control. In this article it is formally demonstrated that the stator currents subsystem of the induction motor is the multivariable equivalent of such SISO systems. That is, it is formally demonstrated that this process is "easy" to control. This result may assist with better induction motor control and may serve as an example of the evaluation of similar multivariable systems. Real time experimental results are included.