Using three actuators, in this article, we construct a control system for rubber-tired gantry (RTG) cranes to track three actuated outputs and stabilize two unactuated outputs. The controller is ...designed by utilizing the fast-terminal sliding mode, fractional calculus, and backstepping. Considering that RTG cranes encounter with uncertainties and random winds, an adaptive mechanism is constituted using neural networks to estimate uncertain parameters and unknown winds. A neural observer that reduces the number of sensors by half is also proposed for approximating feedback velocities. By applying these advanced techniques, the control system is endowed with adaptive and robust features. The quality and effectiveness of the control system are investigated by simulation and experimentation.
Nuclear power sources can offer a potential solution to some of the challenges related to space applications, such as the use of photovoltaics in opaque atmospheres or in a dark environment for a ...long time. Thanks to their high energy densities, certain isotopes are capable of generating considerable amounts of heat for long periods of time, independently of insolation levels; this heat can then be converted into electrical power, or used to keep suitable temperatures inside the spacecraft.
However, the presence of radioactive material implies new sets of requirements, to properly manage all the aspects related to safety (heat source design, risk assessments, launch approval process etc.).
This paper provides an overview of the international agreements, the existing NASA/US and Russian policies for the management of space nuclear power systems, as well as some updates and recent considerations for the ESA Radioisotope Power Systems (RPS) programme, which aims to provide a European capability for the independent design, management and launch of RPS.
A significant amount of programmatic effort in many domains and by different entities will be required in order to create a common European safety framework, but the long and wide-ranging experience of other countries in dealing with space nuclear power systems could be an appropriate starting point. Recommendations are also made which could lead to an international standard linked to key stages of the mission lifecycle.
•A new mathematical model for rubber–tyred gantry cranes is developed considering the elastic structure.•Two advanced sliding mode controls are proposed to validate dynamic model.•Experiment shows ...the sufficient accuracy and effective application of modeling and control to cranes.
A gantry crane holds strict underactuation and elastic multibody structure, and thus faces challenges in control system design. For model–based control, we develop a three–dimensional dynamic model of rubber–tyred gantry cranes considering the distributed mass and bending deformation of gantry. Such modelling hybridises the lumped model of trolley–bridge–payload motions and continuous model of gantry vibration. We consider a complex operation in which three motors composed of travelling trolley, pushing bridge and hoisting container run simultaneously. We propose two versions of the robust controller, namely, dynamic sliding mode and fast terminal sliding mode for tracking the three motions, eliminating swings of container, and reducing the bending vibration of elastic gantry. Simulation and experiment reveal precision and effective application of our crane modelling to control approaches. The control system effectively tracks and stabilises all outputs and achieves robustness when a crane suffers from the structural and parametric uncertainties.
Nitrogen is one of the most important essential nutrient sources for biogenic activities. Regulation of nitrogen metabolism in microorganisms is complicated and elaborate. For this review, the yeast
...was chosen to demonstrate the regulatory mechanism of nitrogen metabolism because of its relative clear genetic background. Current opinions on the regulation processes of nitrogen metabolism in
, including nitrogen sensing, transport, and catabolism, are systematically reviewed. Two major upstream signaling pathways, the Ssy1-Ptr3-Ssy5 sensor system and the target of rapamycin pathway, which are responsible for sensing extracellular and intracellular nitrogen, respectively, are discussed. The ubiquitination of nitrogen transporters, which is the most general and efficient means for controlling nitrogen transport, is also summarized. The following metabolic step, nitrogen catabolism, is demonstrated at two levels: the transcriptional regulation process related to GATA transcriptional factors and the translational regulation process related to the general amino acid control pathway. The interplay between nitrogen regulation and carbon regulation is also discussed. As a model system, understanding the meticulous process by which nitrogen metabolism is regulated in
not only could facilitate research on global regulation mechanisms and yeast metabolic engineering but also could provide important insights and inspiration for future studies of other common microorganisms and higher eukaryotic cells.
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•A comprehensive modeling and simulation of the GPHS-RTG in space is realized.•The simulation results are validated by reports with error less than 1.6 %.•The conservative application ...range of the GPHS-RTG in the solar system is revealed.•Several methods to expend the application range of the GPHS-RTG are summarized.•The GPHS-RTG’s axial and circumferential thermal distributions in space are analyzed.
The radioisotope thermoelectric generator relies solely on radioactive decay for its energy and generates power through the thermoelectric effect. The General-Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) represents the RTG with the largest power and highest conversion efficiency ever built, and its energy supply supported four daring interplanetary missions (Galileo, Ulysses, Cassini, New Horizons). To explore the use potential of the GPHS-RTG in the solar system, its conservative application range and performance should be determined. In this work, a comprehensive model of the GPHS-RTG was developed, and its calculated results agreed well with Lockheed Martin’s test report (temperature relative error < 1 %). The study demonstrates that within the Earth orbit, the distance of the mission area from the sun and the angle of incidence sunlight significantly affect the thermoelectric performance and hot-junctions’ temperature. Moreover, conservative application ranges and their extending methods (changing coating material, thermal loading, and operational voltage) for GPHS-RTG at different attitudes in the solar system were determined for the first time by comparing the proportion of the hot-junction over-temperature area. The temperature distribution and its cause of formation in the axial and circumferential directions of the GPHS-RTG during solar system missions were revealed in the end. This work is valuable for future RTG design and mission planning.
The art of solving a structure from powder diffraction data has developed rapidly over the last ten years to the point where numerous crystal structures, both organic and inorganic, have been solved ...directly from powder data. However, it is still an art and, in contrast to its single crystal equivalent, is far from routine. The art lies not only in the correct application of a specific experimental technique or computer program, but also in the selection of the optimal path for the problem at hand.
Analysis of energy usage for RTG cranes Papaioannou, Vicky; Pietrosanti, Stefano; Holderbaum, William ...
Energy (Oxford),
04/2017, Letnik:
125
Journal Article
Recenzirano
Odprti dostop
The purpose of this paper is to study and analyse the energy that is used by the various motors of a crane of the Rubber Tyred Gantry type. For this reason a single Rubber Tyred Gantry (RTG) crane ...has been instrumented at port of Felixstowe and data has been collected during normal operation for eight days. This data has been analysed in terms of active and idle modes and also in terms of energy usage by the various motors. From this analysis it is possible to determine that on average about half of the energy consumed is potentially recoverable. It is also estimated that the recovery of this proportion of energy could lead to savings of 32,600 L of fuel and 8100 tonnes of CO2 per year at Port of Felixstowe.
•The RTG crane in Port of Felixstowe is only active about 50% of the time.•60% of the energy is used by the hoist and 30% by the gantry motor.•The average percentage of recoverable hoist energy ranges from 70% to 80%.•The average percentage of recoverable gantry energy ranges from 3% to 5%.•The average total percentage of recoverable energy ranges from 50% to 57%.
Silicon–Germanium is an excellent and well-proven alloy with wide application in the transistor technology and space industries because of its meritorious features such as easy to form both n- and ...p-type depending on the dopant, environment friendliness, highly abundant material on earth's crust, high mechanical strength etc. This review article highlights the status, potential, and challenges associated with thermoelectric applications. In spite of the fact that Si–Ge exhibits a complex phase diagram due to the wide separation between the solidus and liquidus line, solid-state synthesis could overcome the difficulties associated with the homogeneity and is an epitome to achieve single-phase alloy. Moreover, the beauty of the method is that the yield of the product is very high. This review article also encompasses the strategies involved to reduce the thermal conductivity of the alloy which is otherwise essential to have high figure-of-merit (zT). It also highlights the importance of bulk nanostructuring, which still embraces the title of highest ever reported zT of both n- and p-type bulk Si–Ge alloy. Towards the end, the review opens up a new avenue for exploring methods to reduce the internal resistance of the Si–Ge unicouple and fabrication of DC-DC booster circuit so that the demand for higher voltage can be realized.
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•Superiority of the Si–Ge alloy in contrast to elemental Si in thermoelectric and transistor technology was reviewed.•All the solid-state synthesis methods were discussed in detail in order to obtain homogeneous alloy.•Strategies to reduce the thermal conductivity and enhance the zT of the alloy were discussed.•Fabrication of unicouple and the technological challenges involved at various electrical contacts were reviewed.•Towards the end, article highlights the global status of the thermoelectric modules and its future prospect in market size.
•A Monte Carlo ARIMAX forecasts is developed to predict the stochastic nature of crane demand.•SMPC utilising on DP is developed to increase cost saving and peak reduction for network of cranes.•SMPC ...and MPC with variable horizons are investigated to improve energy management performance of ESS compared to set-point controller.•A comparison analysis for different ESS location scenarios and the economic implications are conducted to evaluate the proposed models.
An Energy Storage System (ESS) is a potential solution to increase the energy efficiency of low voltage distribution networks whilst reinforcing the power system. In this article, energy management systems have been developed for the control of an ESS connected to a network of electrified Rubber Tyre Gantry (RTG) cranes. Considering the highly volatile crane demand behaviour and uncertainty in the RTG crane demand prediction as a nonlinear optimisation problem, this paper presents and verifies an optimal energy control strategy based on a Stochastic Model Predictive Control (SMPC) algorithm. The SMPC controller aims to improve the reliability and economic performance of a network of RTG cranes, under a given ESS and network specification. A specific case, using different ESS locations, is presented and the results of the proposed SMPC and MPC control models are compared to a set-point controller using data collected from an instrumented electrified RTG cranes at the Port of Felixstowe, UK. The results indicate that the SMPC controller successfully reduce electrical energy costs, the peak demand and outperforms each of the presented control techniques.
Rubber tyred gantry (RTG) cranes are an important piece of transport equipment in ship and rail container terminals. They have a diversified power demand, for example, peak powers of 292-kW driving, ...178 kW regenerating, and 7-kW idle power. The high peak power demand determines the system prime mover (internal combustion engine) rating, which is highly over-rated for the crane average energy requirements. Such a variation in peak to idle power demand favors a hybrid power solution which, given appropriate design, can yield significant gains in fuel or energy usage and, importantly, reductions in local emissions, thus improving air-quality. In this study, a hybrid energy source for an RTG crane is presented. The hybrid energy source comprises of a lithium battery and a down-sized diesel-generator connected to the dc link through an active front end unit. While other systems have been previously proposed, the system presented here utilizes a smaller diesel-generator, thus reducing plant and fuel consumption. In addition, the battery connects directly to the dc link reducing system power electronics while improving battery response and efficiency. Experimental results from a full-size evaluation system are presented showing a 57% reduction of fuel consumption compared to a conventional RTG crane system.
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