José Manuel Andújar

Augmented Reality for the Improvement of Remote Laboratories: An Augmented Remote Laboratory

Augmented reality (AR) provides huge opportunities for online teaching in science and engineering, as these disciplines place emphasis on practical training and unsuited to completely nonclassroom training. This paper proposes a new concept in virtual and remote laboratories: the augmented remote laboratory (ARL). ARL is being tested in the first and second years of the new degrees in industrial engineering and computer engineering, respectively, at the School of Engineering, University of Huelva, Huelva, Spain. By means of augmented reality techniques, ARL allows the student to experience sensations and explore learning experiences that, in some cases, may exceed those offered by traditional laboratory classes. The effectiveness of this methodology for remote laboratory work is evaluated by comparing it to practical sessions in the laboratory at the university itself with the same group of students. Students completed a questionnaire after having experienced both types of practicals, and the results show that the use of ARL improves student outcomes. As discussed in the paper, the potential of AR to configure different experiments from the same physical configuration is virtually limitless.

A methodology to design stable nonlinear fuzzy control systems

The stability of nonlinear systems has to be investigated without making linear approaches. In order to do this, there are several techniques based on Lyapunov’s second method. For example, Krasovskii’s method allows to prove the sufficient condition for the asymptotic stability of nonlinear systems. This method requires the calculation of the Jacobian matrix. In this paper, an equivalent mathematical closed loop model of a multivariable nonlinear control system based on fuzzy logic theory is developed. Later, this model is used to compute the Jacobian matrix of a closed loop fuzzy system. Next, an algorithm to solve the Jacobian matrix is proposed. The algorithm uses a methodology based on the extension of the state vector. The developed algorithm is completely general: it is independent of the type of membership function that is chosen for building the fuzzy plant and controller models, and it allows the compound of different membership functions in a same model. We have developed a MATLAB’s 1 function that implements the improved algorithm, together with a series of additional applications for its use. The designed software provides complementary functions to facilitate the reading and writing of fuzzy systems, as well as an interface that makes possible the use of all the developed functions from the MATLAB’s environment, which allows to complement and to extend the possibilities of the MATLAB’s Fuzzy Logic Toolbox. An example with a fuzzy controller for a nonlinear system to illustrate the design procedure is presented. The work developed in this paper can be useful for the analysis and synthesis of fuzzy control systems.

A Methodology for Sizing Backup Fuel-Cell/Battery Hybrid Power Systems

Hybridization of fuel cells and batteries combines the advantages of both power sources. This paper proposes the use of fuel-cell/battery hybrid power systems as backup power systems and develops a methodology for sizing both fuel cell and battery bank, according to a minimum lifecycle cost criterion, from any defined hourly load profile and any defined backup time. For this purpose, an existing power-system-sizing computer tool has been used, but its initial capabilities have been extended. The developed methodology allows decisions to be taken before any investment is made. As a practical application, the methodology is used for the sizing of a backup power system for a telecommunication system.

Analog Current Control Techniques for Power Control in PEM Fuel-Cell Hybrid Systems: A Critical Review and a Practical Application

This paper presents a prototype of a proton exchange membrane (PEM) fuel-cell hybrid system, with a bus connection set by a dc battery bank and all the power electronics and control needed to manage the system. The system power control is based on analog current control. To choose the topology of the controller, a critical review of all the topologies of analog current controllers for dc/dc converters has been done. This review was necessary because there is no literature found that shows a similar compilation. In the experimental part, the proper functioning of the controlled hybrid system is reflected on one hand and the way to solve the known problem of starvation on the other hand. A very important aspect of the system is its scalability. It can be developed in parallel to implement a whole system that handles power levels higher than the rate power of each single fuel-cell system.

Comparative analysis of buck-boost converters used to obtain I–V characteristic curves of photovoltaic modules

In this paper, the usefulness of several topologies of DC-DC converters for measuring the characteristic curves of photovoltaic (PV) modules is theoretically analyzed. Eight topologies of DC-DC converters with step-down/step-up conversion relation (buck-boost single inductor, CSC (canonical switching cell), Cuk, SEPIC (single-ended primary inductance converter), zeta, flyback, boost-buck-cascaded, and buck-boost-cascaded converters) are compared and evaluated. This application is based on the property of these converters for emulating a resistor when operating in continuous conduction mode. Therefore, they are suitable to implement a system capable of measuring the I-V curve of PV modules. Other properties have been taken into account: input ripple, devices stress, size of magnetic components and input-output isolation. The study determines that SEPIC and Cuk converters are the most suitable for this application mainly due to the low input current ripple, allow input-output insulation and can be connected in parallel in order to measure PV modules o arrays with greater power. CSC topology is also suitable because it uses fewer components but of a larger size. Experimental results validate the comparative analysis.

Stability analysis and synthesis of multivariable fuzzy systems using interval arithmetic

Abstract This paper deals with the design of stable rule-based fuzzy control systems. Interval analysis is applied to design a stable fuzzy Takagi–Sugeno–Kang controller using a robust condition to ensure the stability. The presented methodology starts with a state model of the plant, finds a candidate fuzzy controller and uses an interval arithmetic algorithm to verify the stability of closed-loop fuzzy model. It is important to emphasize the generality of the presented methodology for fuzzy controller synthesis since there are no constraints in the state vector nor in the control vector. This methodology can also be used with nonlinear plant models. In previous works we showed the applicability of the interval analysis to design a controller that ensures the stability of first order nonlinear system. In this paper, we extend the analysis and the synthesis of stable fuzzy control system to the multivariable case. An example with a fuzzy controller for a nonlinear system is presented to illustrate the design procedure.

Multivariable fuzzy control applied to the physical–chemical treatment facility of a Cellulose factory

Abstract Feedback linearization is a well-known technique in nonlinear control in which known system nonlinearities are canceled by the control input leaving a linear control problem. Feedback linearization requires an exact model for the system. Fundamental and advanced developments in neuro-fuzzy synergy for modeling and control are used to apply the feedback linearization control law on second-order plants. In the models that are used, the nonlinear plant is decomposed on six fuzzy systems necessary to apply the control signal to allow the following of a reference value. A practical application is also presented using a waste water plant. This method can be extended to multiple input–multiple output (MIMO) plants based on input–output data pairs collected directly from the plant.

Different methods to obtain the I–V curve of PV modules: A review

In order to characterize photovoltaic devices a procedure to measure I–V curves is required. The main methods used to perform this task are reviewed. It is shown that at least six distinct methods have been reported in the literature with many variations in implementation. A detailed comparison taking into account typical parameters for measuring systems is accomplished. This paper could be used as a reference for future work on photovoltaic module characterization.

A New and Inexpensive Pyranometer for the Visible Spectral Range

This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

A new approach to obtain I-V and P-V curves of photovoltaic modules by using DC-DC converters

The achievement of I-V and P-V curves of photovoltaic modules gives the possibility of obtaining their characteristic parameters: the short-circuit current (I/sub sc/), the open-circuit voltage (V/sub oc/), the maximum power point (MPP) and the fill factor (FF). These values are significant for the design of a photovoltaic system. These curves depend on the global irradiance (G), the temperature (T) and the spectral distribution of the solar irradiation. In this paper, a new methodology to determine the afore mentioned curves by using DC-DC converters is proposed. This methodology allows carrying out the complete sweep of the voltage and the current (including V/sub oc/ and I/sub sc/). Regarding the traditional methods, this new one provides the following advantages: a) minimum power loss with regard to the systems that operate in lineal zone (active zone); this implies several advantages in size and cost; and b) this new method allows an automatic adaptation of the interpolation interval.