This article shows the behavior of several controllers supplemented with an Active Disturbance Rejection Control (ADRC) and their respective performance when facing a nonlinear plant with uncertainties in its parameters. In addition the performance is tested before two types of disturbances, a step disturbance which also modifies the parameters of the plant and an impulse disturbance. The comparison is made with a PI+D controller, a Sliding Mode Control (SMC) and an Integral Generalized Proportional (GPI).