There are actually several solutions for two axis solar tracking systems using electromechanical devices, in which a controller detects the Sun apparent position, and controls the position of the structure supporting ...There are actually several solutions for two axis solar tracking systems using electromechanical devices, in which a controller detects the Sun apparent position, and controls the position of the structure supporting the panels toward the sun by enabling the engines movement. This work studies the solution of two axis solar tracking system based on solar maps, which can predict the exact apparent position of the Sun, by the latitude's location, thereby avoiding the need to use sensors or guidance systems. To accomplish this, it is used a low-power microcontroller, suitably programmed, to control two electric motors to ensure that the panels supporting structure is always oriented towards the sun.展开更多
Field studies were conducted in Lebanon to investigate the effect of solarization with/without cover crop green manure on weed population in subsequent planting of cabbage. Cover crops (alfalfa, barley, clover, lathr...Field studies were conducted in Lebanon to investigate the effect of solarization with/without cover crop green manure on weed population in subsequent planting of cabbage. Cover crops (alfalfa, barley, clover, lathrus and vetch) or crushed olive pulp were planted/added in i 8 m2 plots 75 days prior to planting cabbage. Crops and crushed olive pulps were ploughed under (CCGM) and then half the plots in each treatment were solarized (Biofumigation) by covering each plot with a clear polyethylene sheet for 40 days. Solarization with or without biofumigation significantly reduced weed population in subsequent cabbage planting as compared to nonsolarized CCGM or to the control. Solarization and biofumigation significantly increased fresh weight of cabbage as compared to the control and to nonsolarized CCGM treatments. Optimal weed control was observed in plots which were biofumigated with clover as a CCGM,展开更多
This paper presents a model and analysis for a flexible link with non-collocations of sensors and actuators. It shows the changes in the system dynamics and the appearance of zeroes in the right-plan complex, turning ...This paper presents a model and analysis for a flexible link with non-collocations of sensors and actuators. It shows the changes in the system dynamics and the appearance of zeroes in the right-plan complex, turning the system a non-minimum phase system. The performance of the PID (proportional-integral-derivative) and LQR (linear quadratic regulator) controller are discussed considering the zero dynamics of the system in three points of special interest: (I) the collocated case, when the sensor is in the base of the link; (2) the critical case, where the system starts to present zeroes in the right-plan complex and (3) the limit case, when the sensors are in the end point of the flexible link. Investigation for a simple rigid-flexible model with one mode, in the three cases, the PID and LQR controller performance are damage. To deal with this kind of problem, new control techniques should be developed.展开更多
The MPPT (maximum power point tracking) is one of the most important features of a regulator system that processes the energy produced by a photovoltaic generator. It is necessary, in fact, to design a controller th...The MPPT (maximum power point tracking) is one of the most important features of a regulator system that processes the energy produced by a photovoltaic generator. It is necessary, in fact, to design a controller that is able to set the output value of the voltage and ensure the working within the maximum power point. In this paper, we propose the application of the robust sliding mode control technique to a DC-DC buck converter which is combined with a classical P & O (perturbation and observation) algorithm to enhance the solar system efficiency. Dynamic equations describing the boost converter are derived and a sliding mode controller for a buck converter is designed. It is shown that, this control approach gives good results in terms of robustness toward load and input voltage variations. The effectiveness of the proposed work is verified by the simulation results under PowerSim environment.展开更多
文摘There are actually several solutions for two axis solar tracking systems using electromechanical devices, in which a controller detects the Sun apparent position, and controls the position of the structure supporting the panels toward the sun by enabling the engines movement. This work studies the solution of two axis solar tracking system based on solar maps, which can predict the exact apparent position of the Sun, by the latitude's location, thereby avoiding the need to use sensors or guidance systems. To accomplish this, it is used a low-power microcontroller, suitably programmed, to control two electric motors to ensure that the panels supporting structure is always oriented towards the sun.
文摘Field studies were conducted in Lebanon to investigate the effect of solarization with/without cover crop green manure on weed population in subsequent planting of cabbage. Cover crops (alfalfa, barley, clover, lathrus and vetch) or crushed olive pulp were planted/added in i 8 m2 plots 75 days prior to planting cabbage. Crops and crushed olive pulps were ploughed under (CCGM) and then half the plots in each treatment were solarized (Biofumigation) by covering each plot with a clear polyethylene sheet for 40 days. Solarization with or without biofumigation significantly reduced weed population in subsequent cabbage planting as compared to nonsolarized CCGM or to the control. Solarization and biofumigation significantly increased fresh weight of cabbage as compared to the control and to nonsolarized CCGM treatments. Optimal weed control was observed in plots which were biofumigated with clover as a CCGM,
文摘This paper presents a model and analysis for a flexible link with non-collocations of sensors and actuators. It shows the changes in the system dynamics and the appearance of zeroes in the right-plan complex, turning the system a non-minimum phase system. The performance of the PID (proportional-integral-derivative) and LQR (linear quadratic regulator) controller are discussed considering the zero dynamics of the system in three points of special interest: (I) the collocated case, when the sensor is in the base of the link; (2) the critical case, where the system starts to present zeroes in the right-plan complex and (3) the limit case, when the sensors are in the end point of the flexible link. Investigation for a simple rigid-flexible model with one mode, in the three cases, the PID and LQR controller performance are damage. To deal with this kind of problem, new control techniques should be developed.
文摘The MPPT (maximum power point tracking) is one of the most important features of a regulator system that processes the energy produced by a photovoltaic generator. It is necessary, in fact, to design a controller that is able to set the output value of the voltage and ensure the working within the maximum power point. In this paper, we propose the application of the robust sliding mode control technique to a DC-DC buck converter which is combined with a classical P & O (perturbation and observation) algorithm to enhance the solar system efficiency. Dynamic equations describing the boost converter are derived and a sliding mode controller for a buck converter is designed. It is shown that, this control approach gives good results in terms of robustness toward load and input voltage variations. The effectiveness of the proposed work is verified by the simulation results under PowerSim environment.