<div class="htmlview paragraph">The dynamic characteristics of electric power steering (EPS) systems can be characterized by the transmissibility from rack load to steering wheel torque. The transmissibility can be studied by fixing the steering wheel and calculating the frequency response from the rack load to the torque needed to hold the steering wheel. A proportion plus-derivative control is needed for EPS systems to generate desired static torque boost and avoid high transmissibility at the mid-frequency range. A pure proportion control can't satisfy both requirements at the same time.</div>