| Sumario: | bstract: In this paper, a real-time robust closed-loop control scheme for controlling the velocity
of a Direct Current (DC) motor in a compound connection is proposed. This scheme is based on
the state-feedback linearization technique combined with a second-order sliding mode algorithm,
named super-twisting, for stabilizing the system and achieving control goals. The control law is
designed to track a periodic square reference signal, being one of the most severe tests applied to
closed-loop systems. The DC motor drives a squirrel-cage induction generator which represents
the load; this generator must work above the synchronous velocity to deliver the generated power
towards the grid. A classical proportional-integral (PI) controller is designed for comparison purposes
of the time-domain responses with the proposed second-order sliding mode (SOSM) super-twisting
controller. This robust controller uses only a velocity sensor, as is the case of the PI controller, as the
time derivative of the velocity tracking variable is estimated via a robust differentiator. Therefore,
the measurements of field current and stator current, the signal from a load torque observer, and
machine parameters are not necessary for the controller design. The validation and robustness test of
the proposed controller is carried out experimentally in a laboratory, where the closed-loop system
is subject to an external disturbance and a time-varying tracking signal. This test is performed in
real time using a workbench consisting of a DC motor—Alternating Current (AC) generator group,
a DC/AC electronic drive, and a dSPACE 1103 controller board.
Keywords: compound DC motor velocity controller; feedback linearization; second-order
sliding modes
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