J.A. Somolinos

A Tandem Active Disturbance Rejection Control for a Laboratory Helicopter With Variable-Speed Rotors

This paper introduces a laboratory helicopter with a variable-speed rotor system based on decentralized active disturbance rejection control. The new control scheme is composed of two independent stages that are utilized to achieve the precise trajectory tracking of the generalized coordinates of the system. A simplified model is proposed at each stage, which highly simplifies the controller design task. High-gain generalized proportional integral observers are considered in order to locally estimate all the disturbances affecting each subsystem online. These estimated disturbances are used in the control law of each stage to eliminate the effects of these disturbances on the system performance. Some of the advantages of the proposed control are: it only requires the knowledge of the input gain to the subsystems (minimum information required from the dynamical models to control them); the robust controller design procedure is simplified; easier and safer implementation with regard to standard controllers; and high robustness to large initial errors, unmodeled unmatched perturbations, noisy measurements, and parametric uncertainties in the model. The effectiveness of the proposed approach has been verified with real experiments conducted on a laboratory platform.

Generalized Proportional Integral Control for an Unmanned Quadrotor System

In this article, a generalized proportional integral (GPI) control approach is presented for regulation and trajectory tracking problems in a nonlinear, multivariable quadrotor system model. In the feedback control law, no asymptotic observers or time discretizations are needed in the feedback loop. The GPI controller guarantees the asymptotically and exponentially stable behaviour of the controlled quadrotor position and orientation, as well as the possibilities of carrying out trajectory tracking tasks. The simulation results presented in the paper show that the proposed method exhibits very good stabilization and tracking performance in the presence of atmospheric disturbances and noise measurements.

Dynamic Model and Control of a New Underwater Three-Degree-of-Freedom Tidal Energy Converter

There is currently a growing interest in developing devices that can be used to exploit energy from oceans. In the recent past, the search for oil and gas at ever-greater depths has led to the evolution of devices with which these resources are extracted. These devices range from those that simply rest on the seabed to those that are fully floating and anchored to it. This trend can be considered as the basis needed to understand the future evolution of devices for harnessing depth renewable resources. This paper presents a simple dynamic modeling and a nonlinear multivariable control model-based system for a new three-degree-of-freedom underwater generator with which energy from depth marine currents is harnessed when reference trajectory tracking for the emersion maneuvers needed to carry out maintenance tasks is performed. The goodness of both the model and the proposed controller has been demonstrated through the development of various simulations in the MATLAB-Simulink environment. Additionally, the validation of the control algorithms was carried out by using the dynamic model offered by the simulation environment Orcina OrcaFlex (software for the dynamic analysis for offshore marine systems) through the MATLAB-OrcaFlex interface.

A new self-calibrated procedure for impact detection and location on flat surfaces.

Many analyses of acoustic signals processing have been proposed for different applications over the last few years. When considering a bar-based structure, if the material through which the sound waves propagate is considered to be acoustically homogeneous and the sound speed is well known, then it is possible to determine the position and time of impact by a simple observation of the arrival times of the signals of all the transducers that are strategically disposed on the structure. This paper presents a generalized method for impact detection and location on a flat plate, together with a calibration procedure with which to obtain the sound speed from only one set of measurements. This propagation speed is not well known as a result of either imprecise material properties or the overlapping of longitudinal and transversal waves with different propagation velocities. The use of only three piezoelectric sensors allows the position and time of impact on the flat plate to be obtained when the sound speed is well known, while the use of additional sensors permits a larger detection area to be covered, helps to estimate the sound speed and/or avoids the wrong timing of difference measurements. Experimental results are presented using a robot with a specially designed knocking tool that produces impacts on a metallic flat plate.

Robust Decentralized Nonlinear Control for a Twin Rotor MIMO System

This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of the model, which is due to the action-reaction principle originated in the acceleration and deceleration of the motor-propeller groups. The proposed controller is composed of two nested loops that are utilized to achieve stabilization and precise trajectory tracking tasks for the controlled position of the generalized coordinates of the TRMS. The nonlinear internal loop is used to control the electrical dynamics of the platform, and the nonlinear external loop allows the platform to be perfectly stabilized and positioned in space. Finally, we illustrate the theoretical control developments with a set of experiments in order to verify the effectiveness of the proposed nonlinear decentralized feedback controller, in which a comparative study with other controllers is performed, illustrating the excellent performance of the proposed robust decentralized control scheme in both stabilization and trajectory tracking tasks.

Low-cost impact detection and location for automated inspections of 3D metallic based structures.

This paper describes a new low-cost means to detect and locate mechanical impacts (collisions) on a 3D metal-based structure. We employ the simple and reasonably hypothesis that the use of a homogeneous material will allow certain details of the impact to be automatically determined by measuring the time delays of acoustic wave propagation throughout the 3D structure. The location of strategic piezoelectric sensors on the structure and an electronic-computerized system has allowed us to determine the instant and position at which the impact is produced. The proposed automatic system allows us to fully integrate impact point detection and the task of inspecting the point or zone at which this impact occurs. What is more, the proposed method can be easily integrated into a robot-based inspection system capable of moving over 3D metallic structures, thus avoiding (or minimizing) the need for direct human intervention. Experimental results are provided to show the effectiveness of the proposed approach.

Mathematical Model Switched Reluctance Motor

This paper describes a mathematical model of switched reluctance motor (SRM). The mathematical model of the SR motor is nonparametric and can only be established with experimental data, instead of an analytical representation. Because the reluctance varies with rotor position and magnetic saturation is part of the normal operation of SR motors, there is no simple analytical expression for the magnetic field produced by the phase windings. The shape of phase current before commutation is of interest because it varies widely depending on when the phase winding is excited and what the rotor speed is. To illustrate this effect, two step response simulations were done here in Matlab/Simulink. The SR motor model used in these two simulations is a 6/4 linear magnetics model, the same structure as the experimental SR motor. For the first simulation, a step voltage is fed into phase A and the initial rotor position is set to be 1o instead of 0o so that the rotor will move in the positive direction. The results show that the rotor stops at 45o after some oscillation which is the aligned position of this phase A. For the second simulation, a step voltage is fed into phase C. The initial position is 0o. According to this, the rotor will move towards the aligned position of phase C, i.e. 15o.

Anisotropic Magnetoresistive Study in Bilayer NiFe-NiO for Sensor Applications

Related with the detection of weak magnetic fields, the anisotropic magnetoresistive (AMR) effect is widely utilized in sensor applications. Exchange coupling between an antiferromagnet (AF) and the ferromagnet (FM) has been known as a significant parameter in the field sensitivity of magnetoresistance because of pinning effects on magnetic domain in FM layer by the bias field in AF. In this work we have studied the thermal evolution of the magnetization reversal processes in nanocrystalline exchange biased Ni80Fe20/Ni-O bilayers with large training effects and we report the anisotropic magnetoresistance ratio arising from field orientation in the bilayer.

Development of an Electrochemical Maltose Biosensor

In this work, electrochemical maltose biosensors based on mutants of the maltose binding protein (MBP) are developed. A rutheniumII complex (RuII), which is covalently attached to MBP, serves as an electrochemical reporter of MBP conformational changes. Biosensors were made through direct attachment of RuII complex modified MBP to gold electrode surfaces. The responses of some individual mutants were evaluated using square wave voltammetry. A maltose-dependent change in Faradic current and capacitance was observed. It is therefore demonstrated that biosensors using generically this family of bacterial periplasmic binding proteins (bPBP) can be made lending themselves to facile biorecognition element preparation and low cost electrochemical transduction.

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented.