Felipe Espinosa

Integral system for assisted mobility

Abstract This paper presents the results of a research work carried out in the Electronics Department of the University of Alcala in the field of electronic systems for the guidance of wheelchairs for the disabled and/or the elderly. These electronic systems have been designed to meet a wide range of needs experienced by users of this type of wheelchair. One of their most important features is their modularity, thereby making them adaptable to the particular needs of each user according to the type and degree of handicap involved. The overall system includes a complete user–machine interface, motor control modules and safety and autonomous guidance systems. The project is called: “Sistema Integral de Ayuda a la Movilidad (SIAMO)” (integral system for assisted mobility).

Design of a Back-to-Back NPC Converter Interface for Wind Turbines With Squirrel-Cage Induction Generator

As the number of wind power applications with power electronic interfaces in the grid increases, it is becoming unacceptable to disconnect the generating units every time disturbances occur, especially under voltage dips, as was a common practice in the past. Keeping the converter online during unbalanced voltage, and guaranteeing the actual standards of the converter connected to the grid, is becoming a very critical issue. From these goals, the design of a robust back-to-back neutral point clamped (three levels) voltage source converter of 150 kVA is developed in this paper. The converter is divided into two main parts: the power electronic system and the control electronic system. Concerning the first part, on the one hand, the paper presents the designs of active and passive components as insulated gate bipolar transistor, free-wheeling diodes, clamping diodes, grid filter, DC-bus capacitors, etc.; and on the other hand, the converter requirements are analyzed to ride through real grid conditions, i.e., unbalanced voltage dips. Concerning the control electronic system, the chosen electronic structure and the task distribution between the two processors used are shown.

UAV Attitude Estimation Using Unscented Kalman Filter and TRIAD

A main problem in autonomous vehicles in general, and in unmanned aerial vehicles (UAVs) in particular, is the determination of the attitude angles. A novel method to estimate these angles using off-the-shelf components is presented. This paper introduces an attitude heading reference system (AHRS) based on the unscented Kalman filter (UKF) using the three-axis attitude determination (TRIAD) algorithm as the observation model. The performance of the method is assessed through simulations and compared to an AHRS based on the extended Kalman filter (EKF). The paper presents field experiment results using a real fixed-wing UAV. The results show good real-time performance with low computational cost in a microcontroller.

Current control of voltage source converters connected to the grid through an LCL-filter

The aim of this paper is to propose a current control of VSCs connected to the grid through an LCL-filter. The proposed algorithm controls the grid current using only two sensors. Other variables are obtained with a state estimator, and the possible disturbances of the system are attenuated with active damping. The control algorithm has been proved for different disturbances, such as temporal variations in the components of the model and perturbations in the grid, and also with the linear and nonlinear models.

SPLL design to flux oriented of a VSC interface for wind power applications

Accurate phase information is crucial for most of modern power electronic systems such as VSC connected to the grid. In this paper, it is proposed an algorithm software phase-locked loop (SPLL) to obtain phase and frequency information of the grid voltage. This is based in an algorithm of on-line separation of the grid voltage sequences (DSC), and a discrete traditional PLL. A criterion to tune the SPLL constants from a PLL discrete linearized model is discussed. The SPLL response is evaluated for different grid disturbances and different SPLL parameters. Besides, a VSC connected to the grid through and L filter with the SPLL obtained in this paper has been tested for different configurations of SPLL and different grid perturbations. Conclusions about where to apply the SPLL different configurations are obtained from these last tests.

Adaptive UAV Attitude Estimation Employing Unscented Kalman Filter, FOAM and Low-Cost MEMS Sensors

Navigation employing low cost MicroElectroMechanical Systems (MEMS) sensors in Unmanned Aerial Vehicles (UAVs) is an uprising challenge. One important part of this navigation is the right estimation of the attitude angles. Most of the existent algorithms handle the sensor readings in a fixed way, leading to large errors in different mission stages like take-off aerobatic maneuvers. This paper presents an adaptive method to estimate these angles using off-the-shelf components. This paper introduces an Attitude Heading Reference System (AHRS) based on the Unscented Kalman Filter (UKF) using the Fast Optimal Attitude Matrix (FOAM) algorithm as the observation model. The performance of the method is assessed through simulations. Moreover, field experiments are presented using a real fixed-wing UAV. The proposed low cost solution, implemented in a microcontroller, shows a satisfactory real time performance.

Odometry and laser scanner fusion based on a discrete extended kalman filter for robotic platooning guidance

This paper describes a relative localization system used to achieve the navigation of a convoy of robotic units in indoor environments. This positioning system is carried out fusing two sensorial sources: (a) an odometric system and (b) a laser scanner together with artificial landmarks located on top of the units. The laser source allows one to compensate the cumulative error inherent to dead-reckoning; whereas the odometry source provides less pose uncertainty in short trajectories. A discrete Extended Kalman Filter, customized for this application, is used in order to accomplish this aim under real time constraints. Different experimental results with a convoy of Pioneer P3-DX units tracking non-linear trajectories are shown. The paper shows that a simple setup based on low cost laser range systems and robot built-in odometry sensors is able to give a high degree of robustness and accuracy to the relative localization problem of convoy units for indoor applications.

Fuzzy Decentralized Control for guidance of a convoy of robots in non-linear trajectories

This article presents a control solution for the guidance of wheeled convoy units in non-linear trajectories. The proposal consists of a Mamdani fuzzy controller to solve the Decentralized Control problem as applied to a set of units following a leader, whilst guaranteeing the so called “string stability” condition of the convoy.

Optimized design of a back-to-back NPC converter to be used as interface for renewable energies

As the number of wind power with power electronics interfaces in the grid increases, it becomes unacceptable to disconnect the generating units every time a disturbance occurs, as was a common practice in the past. Keeping the converter online during unbalanced voltage and guaranteeing the actual standards of the converter connected to the grid becomes a very critical issue. From these goals, the design of a robust back-to-back NPC (three levels) converter of 100 KVA is researched in this work. The converter is divided into two main parts: the power electronics system and the control electronics system. In both designs, some important contributions are shown. Concerning the first part, the paper presents primarily the converter limitations to compensate unbalanced dips, the grid filter design and the DC-bus capacitor design. Concerning the control electronics system, the chosen electronic structure and the tasks distribution between the chosen processors are shown.

Efficient Smart CMOS Camera Based on FPGAs Oriented to Embedded Image Processing

This article describes an image processing system based on an intelligent ad-hoc camera, whose two principle elements are a high speed 1.2 megapixel Complementary Metal Oxide Semiconductor (CMOS) sensor and a Field Programmable Gate Array (FPGA). The latter is used to control the various sensor parameter configurations and, where desired, to receive and process the images captured by the CMOS sensor. The flexibility and versatility offered by the new FPGA families makes it possible to incorporate microprocessors into these reconfigurable devices, and these are normally used for highly sequential tasks unsuitable for parallelization in hardware. For the present study, we used a Xilinx XC4VFX12 FPGA, which contains an internal Power PC (PPC) microprocessor. In turn, this contains a standalone system which manages the FPGA image processing hardware and endows the system with multiple software options for processing the images captured by the CMOS sensor. The system also incorporates an Ethernet channel for sending processed and unprocessed images from the FPGA to a remote node. Consequently, it is possible to visualize and configure system operation and captured and/or processed images remotely.