Design of a nonlinear speed controller for a DC motor system wit unknown external torque based on backstepping approach

Abstract EN

A nonlinear PI controller for a system with a mismatched and unknown external disturbance is proposed in the present paper.

A Sigmoidal function is proposed to be used in the nonlinear integral element to attenuate the disturbance effect.

Formally the controller forces the state to a positively invariant set around the origin.

As an application, the nonlinear PI controller is used as a virtual controller for the upper subsystem in the frame of Backstepping control approach for the DC motor system.

In this Backstepping controller design the restriction about the disturbance form in the upper system is relaxed.

The results show the effectiveness of the nonlinear PI controller to attenuate the effect of unknown and varying disturbance torque and force the angular velocity to follow the desired reference.

Finally a reduced order observer is designed to estimate the armature current used in the designed controller for the DC motor system.