Susana Ortega

Discrete-time modeling and control of a boost converter by means of a variational integrator and sliding modes

Abstract This work deals with the discrete-time modeling of a boost DC-to-DC power converter by means of a discrete Lagrangian formulation based on the midpoint rule integration method. Then in the basis of this model, a discrete-time sliding mode regulator is designed in order to force the boost circuit to track a DC-biased sinusoidal signal. Simulations and experimental tests are carried on where the great performance of the proposed methodology is verified.

Super-twisting control of induction motors with core loss

A novel nonlinear affine model for the induction motor with core loss is developed in the well known (α β) stationary reference frame. The core is represented with a resistance in paralled with the magnetization inductance. Then, an optimal rotor flux modulus is calculated such that, the power loss due to stator, rotor and core resistances is minimized, and as a consequence the motor efficiency is raised. The calculated optimal flux modulus is forced to be tracked by the induction motor along with a desired rotor velocity by means of a super-twisting sliding mode controller. Using a novel Lyapunov function, the closed-loop stability of the system is demonstrated. A simulation study is carried on, where the superior performance of the proposed controller is put in evidence when compared to the same controller when not taking into account an optimal flux modulus.

Discrete-Time Modeling and Control of an Under-actuated Robotic System

In this work a discrete-time model for the Pendubot is proposed based on the symplectic Euler method. Then, a discrete-time sliding mode controller and observer are designed. A simulation study is carried on in order to verify the good performance of the proposed modeling and control scheme when compared to the case of using explicit Euler method for discrete-time modeling.

Robust Control of the Air to Fuel Ratio in Spark Ignition Engines with Delayed Measurements from a UEGO Sensor

A precise control of the normalized air to fuel ratio in spark ignition engines is an essential task. To achieve this goal, in this work we take into consideration the time delay measurement presented by the universal exhaust gas oxygen sensor along with uncertainties in the volumetric efficiency. For that purpose, observers are designed by means of a super-twisting sliding mode estimation scheme. Also two control schemes based on a general nonlinear model and a similar nonlinear affine representation for the dynamics of the normalized air to fuel ratio were designed in this work by using the super-twisting sliding mode methodology. Such dynamics depends on the control input, that is, the injected fuel mass flow, its time derivative, and its reciprocal. The two latter terms are estimated by means of a robust sliding mode differentiator. The observers and controllers are designed based on an isothermal mean value engine model. Numeric and hardware in the loop simulations were carried out with such model, where parameters were taken from a real engine. The obtained results show a good output tracking and rejection of disturbances when the engine is closed loop with proposed control methods.

Discontinuous output regulation for a DC-to-AC boost converter

This work presents the design of a discontinuous output regulator for a DC-to-AC power conversion problem on a boost converter, for asymptotic output trajectory tracking. The steady state reference signal for the inductor current is proposed as an approximated solution of the well known Francis-Isidori-Byrnes equations, then, by a proper selection of a sliding surface one can stabilize the non-minimum phase inductor current tracking variable. Finally, by means of numerical simulations one verifies the performance of the proposed control strategy.

Discrete-Time Modeling and Control of PMSM

In this work a discrete-time model for Permanent Magnet Synchronous Motors (PMSM) is proposed based on the Symplectic Euler method. Open-loop simulations predict that the discrete-time model obtained via the Symplectic Euler method performs better than the discrete-time model obtained with the classical Explicit Euler method. Then, a discrete-time sliding mode controller is designed for the model obtained via the Symplectic Euler method for the tracking of the rotor velocity. A closed-loop simulation of the continuous-time plant with the discrete-time controller is carried on for the verification of the good performance of the discrete-time model and control scheme.

Methodology for the implementation of a SIMULATOR of electric transients on FPGA

This article describes the implementation of a real time electric circuit simulator prototype on a reconfigurable device. Real time measurement are presented and validated through specialized software. The proposed architecture relies on particular hardware techniques, such as parallel design, looking to satisfy the requirements of computation time.