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The current flat-plate solar collectors perform best when their absorbers rotate around their axis. However, with their concentrators, reflectors, and tracking mechanisms, they take up a lot of space and are thus commercially speaking, not the best solutions. This paper proposes a novel solar collector design which employs the (relative) rotation of absorbers, but strives to combine the benefits of fixed and (absolute) tracking solar systems, i.e. volume occupancy from the former and thermal performance from the latter. The findings of our numerical analysis show that, the solar irradiance efficiency of this novel design is 20% higher than that of a fixed flat-plate collector during clear-sky days, and it is equally lower than that of an absolute tracking collector. This paper also introduces a new criterion for describing single-axis tracking solar collectors which should be included in the classifications of solar collectors. Finally, the article, which represents a continuation of our research in the field of solar energy utilization, can contribute to the future development of solar technologies and solve some of the current challenges. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators are widely used in structural systems for active vibration control with the aim to enhance the performance of systems. The developed system of active vibration control consists of active structure, controller and high voltage amplifier. In this paper, the composite beam is host structure for sensor platform (strain gages) and actuator platform (dual layer PZT piezoelectric actuator). In order to improve the dynamic characteristics of active system, the coefficients of PID controller are changed. The effectiveness of active vibration control system at mode of interest can be improved with change of PID coefficients, but the stability of system can be reduced. The instability of the active structure is often perturbed by spillover effect. In this paper the importance of considering spillover effects in closed loop of piezoelectric active structures is demonstrated and shown the importance of change the PID coefficients in stability of active vibration control system. Experimental results which correspond to the developed active vibration control system are presented and affirmed stability on proposed active structure.

This paper presents two methods (theoretical and numerical) for the thermal analysis of the previously experimentally installed solar collector construction at the Faculty of Engineering in Kragujevac -- a fixed flat-plate solar collector with Sn-Al2O3 selective absorber and gravity water flow. The theoretical research was based on the application of a specific calculation algorithm with a triple iterative procedure, i.e. with a three-stage check of all important performance indicators of the fixed flat-plate solar collector. In the numerical phase of the research, simple linear regression was applied to experimentally measured values of solar radiation intensity and experimentally determine values of heat power to form simple equations that could be used to predict the thermal performance of similar solar structures in the future. The results of theoretical and numerical studies showed agreement with experimental studies, because in the first case, the absolute measurement error was less than 10%, while in the second case, the determination coefficient was greater than 90%, so the authors hope that this work will be useful to the wider scientific community. [ABSTRACT FROM AUTHOR]

This paper presents a design, development and experimental verification of an active vibration control system of aluminum plate. The active structure consists of an aluminum rectangular plate as the host structure, strain gages as the sensor element and a piezoceramic patch as the actuation element. Based on characteristics of the integrated elements with use of the fuzzy optimization strategy based on the pseudogoal function the optimal orientation of piezoelectric actuator is found, and the whole active vibration control system is designed and developed. The active vibration control system is controlled by proportional-integral-derivative (PID) control strategy. Control algorithm was implemented on the PIC32MX440F256H microcontroller platform. In order to prevent it from negative occurrences from derivative and integral terms in a PID controller, the first-order low-pass filters are implemented in the derivative action and in the feedback of integral action. The experiment considers active damping control under periodic excitation. Experiments are conducted to verify the effectiveness of the vibration suppression and to compare the damping effect with different adjustment of PID gains. Experimental results corresponding to the developed active vibration control system are presented. The system suppresses more than 90% of vibration amplitude, which confirms the high level of effectiveness in vibration active damping at the proposed active structure. [ABSTRACT FROM AUTHOR]

This paper presents experimental verification of the active vibration control of a smart cantilever composite beam using a PID controller. In order to prevent negative occurrences in the derivative and integral terms in a PID controller, first-order low-pass filters are implemented in the derivative action and in the feedback of the integral action. The proposed application setup consists of a composite cantilever beam with a fiber-reinforced piezoelectric actuator and strain gage sensors. The beam is modeled using a finite element method based on third-order shear deformation theory. The experiment considers vibration control under periodic excitation and an initial static deflection. A control algorithm was implemented on a PIC32MX440F256H microcontroller. Experimental results corresponding to the proposed PID controller are compared with corresponding results using proportional (P) control, proportional–integral (PI) control and proportional–derivative (PD) control. Experimental results indicate that the proposed PID controller provides 8.93% more damping compared to a PD controller, 14.41% more damping compared to a PI controller and 19.04% more damping compared to a P controller in the case of vibration under periodic excitation. In the case of free vibration control, the proposed PID controller shows better performance (settling time 1.2 s) compared to the PD controller (settling time 1.5 s) and PI controller (settling time 2.5 s). [ABSTRACT FROM AUTHOR]