  As an alternative to both classical PID-type and modern model-based
approaches to solving control problems, active disturbance rejection control
(ADRC) has gained significant traction in recent years. With its simple tuning
method and robustness against process parameter variations, it puts itself
forward as a valuable addition to the toolbox of control engineering
practitioners. This article aims at providing a single-source introduction and
reference to linear ADRC with this audience in mind. A simulative study is
carried out using generic first- and second-order plants to enable a quick
visual assessment of the abilities of ADRC. Finally, a modified form of the
discrete-time case is introduced to speed up real-time implementations as
necessary in applications with high dynamic requirements.
