Event-triggered formation control of n-link networked stochastic robotic manipulators

This article proposes an event-triggered control framework to satisfy the tracking formation performance for a group of uncertain non-linear n-link robotic manipulators. The robotic manipulators are configured as a multi-agent system and they communicate over a directed graph (digraph). Furthermore, the non-linear robotic manipulator-multi-agent systems are subject to stochastic environmental loads. By introducing extra virtual controllers in the final step of the backstepping design, a total number of n event-triggering mechanisms are introduced independently for each link of all the robotic manipulator agents to update the control inputs in a fully distributed manner. More precisely, the actuator of each link of a particular agent is capable of being updated independent of other link actuator updates. A rigorous proof of the convergence of all the closed-loop signals in probability is then given and the Zeno phenomenon is excluded for the control event-triggered architectures. The simulation experiments finally quantify the effectiveness of proposed approach in terms of reducing the number of control updates and handling the stochastic environmental loads.

Minimum Structure for Well Appraisal in Marginal Fields at 35m Water Depth without Jacket & Mudline Suspension System

ABSTRACT This paper proposes a minimum structure for drilling two appraisal wells. Conductors will be driven into seabed by a crane vessel or drilling-rig crane through a pre-installed lightweight guide-frame placed on seabed. After driving the conductors to required depth, the frame is raised and joined to the conductors at appropriate elevation by bolted and grouted connections. Six tie members connected between the frame and seabed by specially-designed small mat foundations will ensure stability of the structure against environmental loads. A small deck will be installed on the top of conductors to provide space for essential equipment required for prolonged well testing after departure of drilling rig. The platform will be accessed by small boats through a boat landing and ladder. In case of positive drilling outcome, a riser and flexible pipeline will be added to connect with the nearest subsea tie-in point. A detailed structural design of the minimum facility is performed to withstand omnidirectional environmental loads due to 10.0m high wave along with associated wind and current loads. Susceptibility of the structure against dynamic effect of wave loads is also investigated. Demonstration of structural adequacy against wave-induced fatigue loads and reserve strength against extreme environmental loads show the robustness of the minimum structure to perform against design environmental loads.

Houses with public functions at Lake Baikal

The lack of recommendations for establishment of a sustainable architectural environment at Lake Baikal predetermines a haphazard approach to territory development. The growing tourist flow increases anthropogenic environmental loads. These issues require the development of the necessary architectural tools for the implementation of local projects. The article focuses on the particular properties of the spatial solutions for detached houses with public functions.

Recent Advances in Vibration Control Methods for Wind Turbine Towers

Wind power is a substantial resource to assist global efforts on the decarbonization of energy. The drive to increase capacity has led to ever-increasing blade tip heights and lightweight, slender towers. These structures are subject to a variety of environmental loads that give rise to vibrations with potentially catastrophic consequences, making the mitigation of the tower’s structural vibrations an important factor for low maintenance requirements and reduced damage risk. Recent advances in the most important vibration control methods for wind turbine towers are presented in this paper, exploring the impact of the installation environment harshness on the performance of state-of-the-art devices. An overview of the typical structural characteristics of a modern wind turbine tower is followed by a discussion of typical damages and their link to known collapse cases. Furthermore, the vibration properties of towers in harsh multi-hazard environments are presented and the typical design options are discussed. A comprehensive review of the most promising passive, active, and semi-active vibration control methods is conducted, focusing on recent advances around novel concepts and analyses of their performance under multiple environmental loads, including wind, waves, currents, and seismic excitations. The review highlights the benefits of installing structural systems in reducing the vibrational load of towers and therefore increasing their structural reliability and resilience to extreme events. It is also found that the stochastic nature of the typical tower loads remains a key issue for the design and the performance of the state-of-the-art vibration control methods.

Dynamic response of the mooring system in the floating photovoltaic power station

The floating photovoltaic power (FPV) station becomes popular to decrease carbon emission. However, limited research has been done on the dynamic response of the mooring lines of the FPV array. Based on a typical 2.14MW FPV array, this study investigates the displacement of the array and the mooring tension of the mooring lines. The numerical model of the FPV array is built through three-dimensional potential theory with 124 mooring lines. Firstly, the effect of the environment on the response is investigated under wave-only, current-only and wind-only conditions. Then, the tension and motion in the combined environmental loads are analyzed. It is found that the wind load has the greatest influence on the motion and mooring tension on the FPV power station, the effect of wave and current on the response is very limited.

Assessing Extreme Environmental Loads on Offshore Structures in the North Sea from High-Resolution Ocean Currents, Waves and Wind Forecasting

The fast development of the offshore energy industry becomes an essential component of resilient economies in most of the countries around the North Sea, addressing an increasing demand for cost-efficient and environmentally safe energy sources. Offshore wind farms are planned to be installed further away from the coasts to ensure stronger and more stable wind resources in this region. Oil and gas extraction infrastructures are also planned to move into deeper areas of the continental shelf and continental shelf slopes to explore new fields. These deeper areas of the ocean are characterised by harsh environmental conditions: stronger winds, larger waves and strong shelf slope currents, inducing considerably larger loads on offshore structures. This study brings together operational physical oceanography and the mathematics of fluid-structure interactions to estimate the likelihood of extreme environmental loads on offshore structures in the North Sea. We use the state-of-the-art Met Office high resolution ocean forecasting system, which provides high-frequency data on ocean and tidal currents, wave heights and periods and winds at a ~7 km horizontal resolution grid, spanning the North–West European Shelf. The Morison equation framework is used to calculate environmental loads on various types of offshore structures that are typically employed by the offshore industries in the North Sea. We use hourly data for a 2-year period to analyse the spatio-temporal variability of mean and extreme hydrodynamic loads and derive the relative contributions of currents, waves and winds in the region. The results indicate that waves dominate extreme hydrodynamic forces on the shallow shelf, whereas the current contribution is important at the shelf break and in the English Channel.

How to Аssess Еnvironmental Safety?

The analysis of the main approaches to the assessment of environmental safety is presented. The requirements for environmental safety measurement are justified. The relationship between safety and development, safety and danger are revealed. The approach to the environmental safety methodology is proposed. The goals of environmental safety are justified. The article analyzes life expectancy as the indicator of environmental safety and its dependence on other priorities of the state development, such as the cost of childbirth and raising children, support for pregnant and nursing mothers, care for pensioners (the size of pensions, their indexation, retirement age), the cost of ensuring industrial and transport safety, etc. The indicators that determine the quality (state) of the natural environment as maximum permissible environmental loads and the degree of proximity of the ecosystem state to the border of its stability are considered in the article. The possibility and advantages of using the assessment of the photosynthetic organisms (photosynthetics) state as the indicator of environmental safety are substantiated. The possibility of using the other integral biota state indicators to assess environmental safety is shown in the article.