Juan J. Raygoza

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 sensorless control of linear induction motors

In this work, a sensorless control scheme is presented for linear induction motors. The secondary fluxes are algebraically calculated by first determining the primary fluxes, then, a super-twisitng observer for secondary fluxes is designed in order to retrieve the back-EMF components by means of the equivalent control method. Based on these components, the linear velocity is determined and used in a linear velocity and load force observer, where the estimated variables along with primary current and voltage measurements are used to control the linear induction motor for the tracking of a reference linear velocity signal and a square secondary flux modulus, all by means of a super-twisting controller. Simulations show that the proposed observer based controller scheme performs well when tracking a time varying linear velocity signal.

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.

FPGA-based startup for AC electric drives

HighlightsA startup algorithm is design for AC synchronous machine.The algorithm is implemented with a custom VHDL design.The FPGA-based solution yields to a smooth acceleration ramp for the rotor velocity in the motor.The AC synchronous machine is applied as a fan drive in a greenhouse.The AC synchronous machine presents smooth transient currents. In this work, a simplified startup method for AC synchronous machines is solved by means of a simplified algorithm based only in feeding the AC synchronous machine with stator voltages with a ramp frequency. The implementation of the algorithm along with the Space Vector Pulse Width Modulation technique is carried out by means of a Field Programmable Gate Array (FPGA) device, where Very High Speed Integrated Circuit, Hardware Description Language (VHDL) modules are custom designed. Experimental results were carried out for the ventilation of a greenhouse. The fan drive is turned on according to an existing control strategy designed for an optimal ventilation of the greenhouse. The designed algorithm with custom VHDL modules yields to a great performance for the fan drive in terms of smooth transient currents. The proposed algorithm was also implemented with an embedded microprocessor or softcore in an FPGA device for comparison purposes, yielding to same results. But in the case of optimal utilization of FPGA resources and the speed of execution of the algorithm, the VHDL modules custom design showed the best results.

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.

Super-twisting observer based on PLL technique for sensorless control of induction motors with core loss

In this paper a sensorless control scheme is presented for induction motors with core loss. First, a super-twisting sliding mode observer for stator currents is designed, where, by means of the equivalent control method one can determine the rotor fluxes, second, these fluxes are fed to a PLL stage where the rotor flux velocity is retrieved, then, by easy to follow calculations the rotor mechanical velocity is determined and filtered by a Luenberger observer. In the control part of the induction motor, a twisting controller is designed for the tracking of a desired rotor velocity signal and the tracking of an optimal rotor flux modulus that can minimize the power loss in copper and core. Simulations show that the proposed observer based control scheme performs well, also in the case of time-varying reference velocities.