Nonlinear phenomena in the dynamic behavior of DC motors are commonly disregarded in speed regulation systems because it has a constant operation point or a reduced range of variation. Therefore, in the majority of applications, a second order linear model is enough to design the required controllers. However, in angle positioning systems involving DC-motor based actuators, deviation of linear models becomes unacceptable because the impact of non-linearities accentuates. This paper presents a method for experimental modelling of DC motor bidirectional dynamic following three main steps: i) obtaining input-output measurements from multiple experiments using chirp signals as input stimulus; ii) to produce a family of Hammerstein-Wiener type models using software tools for parametric system identification, and iii) to synthesize a unique model from superposition analysis of both the nonlinear gains and the root loci of the linear part. Validity of the obtained model is demonstrated using simulation results showing its potential application in engineering practice.