The following chapter focuses on state estimation of a brushed motor, specifically its angular position \(\theta\) , angular velocity \(\dot{\theta }\) and armature current i using a linear Kalman filter. For a concrete example, it is assumed that the angular velocity is to be controlled, but only the angular position can be measured by an absolute rotary encoder. It is shown that the estimated angular velocity is significantly more accurate than if the angular velocity were determined by the approximated derivative of the angular position.