The control problem for a series dc motor is considered. Based on a nonlinear mathematical model of a seriesconnected dc motor, it is shown that the combination of a nonlinear transformation and state feedback (feedback linearization) reduces the nonlinear control design to a linear control design. To demonstrate its effectiveness, an experimental study of this controller is presented. These experimental results are also compared with a simulation of the closed-loop system. Finally, it is shown

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... that a nonlinear observer (with linear error dynamics) for speed and load torque can be constructed based only on measurements of the motor current. Experimental results of this speed and load-torque estimator are also presented.