Spartacus Gomáriz

Minimum time control of a buck converter by means of fuzzy logic approximation

This paper investigates the use of fuzzy logic to implement some nonlinear control laws in bidirectional power converters. The authors design a minimum time control scheme of a buck power converter by means of fuzzy logic approximation. The proposed controller is implemented by means of an analog hardware architecture which is able to efficiently implement neuro-fuzzy models. By combining the main features of digital and analog alternatives, it is possible to provide a high degree of flexibility (in terms of number of inputs, number of membership functions per input and number of fuzzy rules) when handling real world tasks. Also, the authors have created a program for validating, via software, the proposed architecture. Computer simulation results for a buck power converter structure illustrate the design and the implementation. VLSI ASIC mixed-mode implementation details are also included.

Development of a control system for an Autonomous Underwater Vehicle

Work proposes the development of a control system for an autonomous underwater vehicle dedicated to the observation of the oceans. The vehicle, a hybrid between Autonomous Underwater Vehicles (AUVs) and Autonomous Surface Vehicles (ASV), moves on the surface of the sea and makes vertical immersions to obtain profiles of a water column, according to a pre-established plan. The displacement of the vehicle on the surface allows the navigation through GPS and telemetry communication by radio-modem. The vehicle is 2300mm long by 320mm wide. It weighs 85kg and reaches a maximum depth of 30m. A control system based on an embedded computer is designed and developed for this vehicle that allows a vehicles autonomous navigation. This control system has been divided into navigation, propulsion, safety and data acquisition subsystems.

Development of a low-cost autonomous oceanographic observation vehicle

This work proposes the development of a low-cost ocean observation vehicle. This vehicle, a hybrid between Autonomous Underwater Vehicles (AUV) and Autonomous Surface Vehicles (ASV) moves on the surface of the sea and makes vertical immersions to obtain profiles of a water column according to a pre-established plan. Its design means production costs are low and efficiency is increased. Also, the vehicle is able to make high resolution space and time measurements simultaneously. GPS navigation allows the platform to move along the surface of the water while a radio-modem provides direct communication links and telemetry. The vehicle measures 1885mm by 320mm wide. It weighs 76kg. It navigates at a speed of 1.5m/s at 80% at full propulsion power and reaches a maximum depth of 20m. It is a vehicle of electrical propulsion with an autonomy of 3–5 hours. This work outlines the mechanical and electronic design of the vehicle, as well as considerations for navigational and immersion experiments.

TSK-fuzzy controller design for a PWM boost DC-DC switching regulator operating at different steady state output voltages

A Takagi-Sugeno-Kang (TSK) fuzzy controller design for a PWM boost DC-DC switching regulator operating at different steady-state voltages is presented. On the other hand, the controller assigns different linear control laws according to the steady-state voltage value and limits their application to the small-signal perturbations. On the other hand the controller assures a proper start-up to reach the desired steady-state voltage by means of properly saturating the PWM according to the sliding-mode control principles. As a result, both equalized small-signal behaviour and a controlled start-up are achieved for different steady-state voltages, thus enhancing the regulator features. Simulation results for a current-controlled boost regulator operating at different steady-state voltages are presented to validate the approach.

On the use of the describing function in fuzzy controller design for switching dc-dc regulators

In this work, the describing function technique is applied to a two-rules fuzzy controller for switching regulators, in order to establish the scaling factors boundaries for which the system presents an oscillatory behavior, thus facilitating the fuzzy controller design. Simulation results for a boost converter are presented to illustrate the method.

Virtual instrumentation for power supply harmonic measurement

The work reported here presents a virtual instrument (VI) for total harmonic distortion (THD) measurement index with a high accuracy, this is due to the use of high characteristics windows and DFT (discrete Fourier transform) interpolation algorithms are specially interesting in power switching supplies measurements. In the PWM switching regulators frequency characterization the stimulus signal amplitude has to be small enough to keep the converter in its linear region of operation, but it has to be also large enough to be distinguishable from the random noise. This VI allows the amplitude and frequency range obtention. The THD generated by a nonlinear load in the power distribution system can be measured by this VI. The THD generated in the power distribution system by a flyback DC-DC switching converters has been measured.

Generating design rules for buck converter-based fuzzy controllers

A significant performance improvement is obtained in buck converter-based fuzzy controllers using the design procedure reported in this paper. The method requires the fulfilment of two steps. First, the converter dynamics under a reference fuzzy controller are observed. Second, cause-effect relationships are identified by changing controllers parameters and analyzing the resulting variations in the output response.

Design of obstacle detection and avoidance system for Guanay II AUV

This paper presents the design of an obstacle avoidance algorithm for Guanay II AUV. The obstacle detection system disposes a SONAR and its use guarantees the safety in navigation of AUV. Obstacle avoidance is performed based on a fuzzy reactive architecture for different forward speeds of the vehicle. The simulation results obtained through the implementation of the algorithms designed in Matlab validate the designs.

Novel pulse-width-modulated current-mode analog defuzzifier for the fuzzy control of switching DC-DC converters

In this communication, the authors propose a current-mode analog circuit solution for the defuzzying step required for the fuzzy-knowledge-based control (FKBC) of switching DC-DC converters. Considering the modulation of pulse widths needed for the control of switched power plants, the division operation at the output layer of a fuzzy inference controller takes advantage of the implicit signal-to-time conversion in the PWM process. This theoretical aspect is complemented with the proposal of a high-speed current-mode division circuit, which allows a wide range of switching frequencies. The PWM division circuit is preceded by a switched-current integrator to obtain a full defuzzifier. HSPICE layout-extracted transistor-level simulations for a standard CMOS 0.8 /spl mu/m technology verify the functionality of both the proposed defuzzifying method and circuit.

Range-only underwater target localization: Path characterization

Underwater localization using acoustic signals is one of the main components in a navigation system for an AUV as a more accurate alternative to dead-reckoning techniques. While different methods based on the idea of multiple beacons have been studied, other approaches use only one beacon, which reduces the system costs and deployment complexity. The inverse approach for single-beacon navigation is to use this method for target localization by an underwater or surface vehicle. In this paper we present a method of range-only target localization using a Wave Glider™, for which simulations and sea tests have been conducted to determine optimal parameters to minimize acoustic energy use and search time and to maximize location accuracy and precision.