Multi-connected System Research Articles

Assessing the dynamic behavior of multiconnected offshore floating photovoltaic systems under combined wave-wind loads: A comprehensive numerical analysis

Floating photovoltaic (FPV) systems have garnered considerable interest due to their numerous benefits. However, the mechanical design of these systems remains underexplored in existing literatures, necessitating further investigation before they can be commercially deployed in ocean environments. In this study, a novel modular offshore FPV solution was proposed, and numerical modeling and hydrodynamic coupling analysis of multi-body FPV systems were conducted to assess the relative behavior of multi-connected FPV modules under combined wave-wind conditions. Initially, the multi-connected system was modeled, taking into account fixed and hinged connection boundary conditions (BC). Utilizing frequency-domain analysis, the hydrodynamic coefficients essential for time-domain analysis were derived. Subsequently, the overall hydrodynamic performance and behavioral characteristics of various FPV platform types were evaluated. In addition, the strength of connectors under extreme conditions were assessed. Lastly, we compared the motion responses of the multi-body platform under different connection BCs and wave headings. It has been proven that the joint of the hinged connector will generate additional moments, which will affect the dynamic response of the platform as an excitation load. Moreover, the connector's structural responses were mainly dominated by the motion response of the FPV platforms. Furthermore, for the multi-body FPV systems, 0° wave heading should be avoided for installation to reduce the motion responses and structural responses. This study provides valuable insights into the mechanical design of FPV systems for ocean deployment.

Wave-induced structural response analysis of the supporting frames for multiconnected offshore floating photovoltaic units installed in the inner harbor

In this study, a hydrodynamics-based structural response analysis procedure of supporting frames for multiconnected offshore floating photovoltaics (FPVs) is suggested. Based on the suggested simulation methodology, the dynamic behavioral characteristics of the system were investigated. First, rational mooring types for FPVs installed in the inner harbor were studied based on the analysis results. Subsequently, extensive parametric studies have been conducted to determine a rational design strategy for dynamic response mitigation. In this study, the effects of the initial configuration and axial stiffness of taut mooring lines, arrangement angles of FPV systems, and floater dimensions on the static and dynamic responses of supporting frames under irregular waves in the inner harbor were studied. The corner module in the multiconnected system showed critical responses among others, the investigation of which is required for safety evaluation. Furthermore, it was observed that the mooring stiffness governed the overall stiffness of the system, which was proportional to the mitigation of the dynamic responses. Finally, the unsupported length of the frame, which was defined by the floater size, was found to be the key parameter for the mitigation of structural responses.

Construction of a mathematical model of the dynamics of an autonomous mobile robot of variable configuration

This paper considers the construction of a mathematical model of the movement of an autonomous mobile robot (AMR) in variable configuration, taking into account the relationship of the dynamic parameters of a mechanical system. As an example, the design of AMR with a manipulator is considered. The object of this study is the dynamics of AMR with a manipulator. The peculiarities of the dynamics of AMR with the manipulator are due to the change in the position of the center of mass of the system with the relative movement of the manipulator and the commensurate non-diagonal and diagonal elements of the inertia tensor calculated relative to the axes of the base coordinate system. The construction of the mathematical model was carried out according to the Nyton-Euler method. The resulting mathematical model contains: – an equation of motion of the center of mass of the AMR system of variable configuration along the trajectory in the inertial coordinate system; – an equation of angular motion of AMR in variable configuration in the inertial coordinate system; – an equation of motion of the manipulator with respect to AMR. In a general case, the center of mass of the AMR platform moves in a horizontal plane. Establishing the relationship of dynamic parameters of the mechanical system will make it possible to maintain functionality and ensure the orientation of AMR in vertical planes despite the movement of the manipulator. As an object of control, AMR with a manipulator is a multi-connected system with a cross-internal connection of control channels, which is formed by the dynamic parameters of a mechanical system. Based on the results of mathematical modeling using the proposed model, it is possible to develop algorithms for adaptive control using cross-connection of channels. This will make it possible to identify reserves to reduce energy consumption, increase stability, improve the efficiency and survivability of AMR in variable configuration during autonomous work under extreme conditions.

Optimal adaptive control of electromechanical oscillations modes in power systems

The paper proposes methods and algorithms for optimal tuning of power system stabilizers (PSS). The methods are based on the representation of the power system in the form of a graph and the construction for the graph of the power system of an equivalent multi-connected system of automatic control of modes of electromechanical oscillations. The node dynamics is represented by a simplified model of an oscillator together with a proportional-differential regulator, which is fair for describing a real generator with a PSS only in the region of low frequencies of dangerous oscillations. The problem of optimal tuning PSS parameters is formulated and methods for its solution based on heuristic intelligence algorithms and the method of tuning with implicit reference model are proposed. The effectiveness of the proposed methods is demonstrated on the model of a modified classical two-area Kundur test system with tuning parameters of PSS of three generators.

Quasi-Terminal Controllers Synthesis

In the class of linear algorithms of linear stationary multi-connected plants control the subclass is distinguished of quasi-terminal algorithms with implicit aiming at the boundary conditions moving along the program of the required change of the state vector coordinates and being at a fixed interval from the current time. Aiming is realized by calculating the programs of changing the future control vector components in the form of power series segments that depend on the future time and provide a solution of the two-point boundary value problem. In idealized model conditions of the complete controllability and the availability of an accurate information about the control plant state and equations, as well as of the instantaneous and accurate implementation of the calculated commands, the quasi-terminal algorithm provides the asymptotic stability of a closed multi-connected system and as high pre-set rate of transients convergence as needed, regardless of whether the control plant model is stable. The relatively simple and easy to implement in Matlab non-optimization method of algorithm synthesis is suggested based on the use of the matrix representation of the control plant model in the state space and of the apparatus of exponential functions of matrices. Quasi-terminal algorithms can be used in multiconnected stabilization systems and, in particular, in stabilization systems of mobile terminal plants with respect to trajectories calculated by the terminal control system.

Analysis of separate channels in a multi-connected control system

The object of research is the control system of an autonomous mobile robot equipped with an anthropomorphic manipulator with four degrees of mobility. When a mobile robot of variable configuration moves along a given route, the control system must ensure a minimum deviation of the center of mass of the platform from a given trajectory. In this case, the control moments are directed along the axes of the coordinate system associated with the platform of the autonomous mobile robot. With relative movements of the manipulator, the tensor of inertia of the system of bodies in the coordinate system associated with the platform becomes off-diagonal and non-stationary, which determines the interconnection of control channels. The number of control actions: when moving the trajectory – four (for each wheel), when the manipulator is working – four (for each generalized coordinate). Thus, the control system is multidimensional, the connection between control channels is carried out due to the physical properties of the control object.The paper presents the results of the first stages of the development of a multi-connected control system: study of separate control channels, synthesis of a separate controller, adjustments of the controller and analysis of the quality of the created control system. The research is carried out using matrix transfer functions; Besekersky formulas are applied to determine the parameters of the desired transfer function. During the analysis, logarithmic and amplitude frequency characteristics were constructed for each separate channel, a block diagram was chosen, and a transfer function was compiled. The quality assessment of the synthesized separate channel is carried out according to the following criteria: accuracy, speed, oscillation, transient time, overshoot, amplitude and phase distortions, stability margins. The properties of the synthesized separate channel in terms of accuracy, speed and oscillation correspond to the conditions.Further research and synthesis of multi-connected control systems of a mobile robot with a manipulator will increase its survivability and efficiency in autonomous operation. Since a mobile robot with a manipulator is an example of an «autonomous mobile robot of variable configuration» object class, the results obtained can be applied to all objects of this class.

Issues of Multi-Motor Electric Drive Dynamics through the Example of Converter Tilting Mechanism

Many heavy machines and mechanisms of mining and metallurgical industry, for example, basic-oxygen converters (BOCs), are equipped with multi-motor electric drive. Reducing the influence of the disadvantages characteristic of a branched multi-connected system is possible by creating control systems based on mathematical models of the considered electromechanical systems (EMS). The full mathematical model takes into account the number of EMS motors, gear backlashes, elasticity of shafting, the effect of dissipative forces, etc. Disadvantage of this approach is complexity of such models, which leads to high computational costs and time expenditure for their implementation. To analyze dynamic processes arising under acceleration and deceleration conditions of the electromechanical system of the converter tilting mechanism, it is proposed to use a simplified equivalent simulation model, which would take into account changing the EMS natural oscillation frequency for any operation conditions based on process and design features. Based on the simulation model analysis, it was concluded that it is necessary to assess mechanical loads in the system by comparing their current and basis values, as well as taking into account the damping properties of the electric drive. To reduce dynamic loads, it is proposed to form a law of changing the control voltage using an intensity generator, which reduces the risks of occurrence of elastic moments, significantly exceeding those permissible for this class of mechanisms. The results of thermal and vibration diagnostics for assessing malfunctions of key units of the converter tilting mechanism, as well as assessing the system behavior based on the Matlab Simulink model with varying shafting elasticity and normalized gear backlashes, showed significant effect of the latters on the dynamic loads.

Stabilization of a multiconnected controlled continuous discrete system with non-overlapped decompositions with respect to part of variables

This paper considers a multi-connected controllable system with non-overlapping decompositions. Given that most of the control laws are implemented on digital controllers, the control of the system is implemented as a piecewise-constant function. Multiconnectivity of the system, in turn, makes it impossible to use centralized control. Every isolated subsystem must work stably, and intersystem connections can have a destabilizing effect. In this case, piecewise-constant control is constructed as two-level, i.e. in the form of a sum of local and global control. Local control stabilizes the equilibrium positions of individual linear subsystems. Global control acts on intersystem connections. Conditions are obtained under which local control stabilizes linear subsystems, and the equilibrium position of the original multi-connected system is asymptotically stable in part of variables.

Methodological aspects of research into the stress-strain state of panel-frame vertical load-bearing systems

Aim . To analyse the possibilities of various computational methods (primarily numerical) in terms of investigating the stress-strain state of complex multi-dimensional vertical loadbearing systems. Methods . The fundamental essence of the finite-difference method (grids) and the finite element method is revealed, their advantages and disadvantages are described in terms of solving the plane problem of elasticity theory, in particular, in calculating the stress-strain state of panelframe structures united in a single vertical multi-connected system. Results . The obtained results can be used to optimize the methodology of theoretical stress-strain state analysis of complex multiconnected systems, taking into account available computer equipment and licensed software packages for automated calculation of building structures. Conclusion . The conducted analysis shows that, provided there is a sufficiently powerful computer, the finite element method is the most versatile and effective method. This method was the basis of a large number of software packages permitting analysis of the stress-strain state of any designs characterized by the complexity of form, topology, load, etc.

A composite control design for suppressing mutual interference of interconnected systems

This paper presents a new disturbance decoupling and rejection method for a multi-connected system, and introduces the composite controller based on disturbance compensator and the state feedback control. While in action, a developed dynamic model of a 2DOF robot system was studied and analyzed. The movement of one joint affects the motion of the other, which brings the control performance down. In order to compensate and keep the desired control performances, we designed a double active control system which can effectively reject the direct mutual disturbances. These disturbances are considered the known uncertainties and can be experimentally determined. The designed control system consists of two controllers, the first one is an inner loop controller and works as a disturbance compensator that attenuates the known disturbances. And the second one, on the other hand, is an outer loop controller, which was designed based on H∞ control theory to maintain the system stability and a robust control performance under the unpredictable uncertainties. In this paper, simulation and experiments were conducted using a PID controller, and the designed control system, as well as changing the payload attached to the end-effector in order to test the control performance. Finally, the results show that the proposed system suppresses and rejects the mutual disturbances effectively with enhanced tracking performances.

Representation of multi-connected system of Fuzzy State Space Modeling (FSSM) in potential method based on a network context

The complexity of a system of Fuzzy State Space Modeling (FSSM) is the reason that leads to the main objective of this research. A multi-connected system of Fuzzy State Space Model is made up of several components, each of which performs a function. These components are interconnected in some manner and determine how the overall system operates. In this study, we study the concept of graph, network system and network projections which are the requisite knowledge to potential method. Finally, the multi-connected system of FSSM of type A namely feeder, common feeder and greatest common feeder are transformed into potential method using various method of transformation.

Case study of the distribution system planning for a multi-divided and multi-connected system

Case study of the distribution system planning for a multi-divided and multi-connected system

An electrical feed drive-control system for a cold reducing mill

Methods of control synthesis with the selection of parameters of the electrical-power equipment of a cold reducing mill using the example of the Chelyabinsk Pipe-Rolling Plant have been proposed. The proposed methods of a multiconnected system based on the minimum-error criterion for positioning of a movable element, and it is different in that the selection of the control structure is determined by the frequency ratio of the contour cutoff “unchangeable part” of the electric drive and electromagnetic-torque control loop. The task of control synthesis was divided into three stages. The first stage is the search for the optimal curve of movable-element variable speed based on the criterion of minimum electric losses. The second stage is parametric optimization of the electric-power-system parameters. Finally, the third stage is selection of the structure and parameters of the control-system corrective links. Control measures in systems with subordinate regulation and modal control with a change of the frequency ratio of the contour cutoff “unchangeable part” of the system and torque control were compared during research. The developed control-synthesis methods for the positioning electric drive may be recommended for any technological facilities of steel production in which an electric drive provides motion for a movable element with a high level of accuracy.

Analytical synthesis of robust controllers of the given accuracy under external perturbations

An approach that allows finding a set of robust statistic feedback controllers that ensure the given control accuracy for the controlled parameters in a multiconnected control system under bounded parametric and external perturbations of various classes is proposed. To describe the set of controllers of the given accuracy, the results of analytically solving the matrix equations based on matrix canonization and parametrization of the Lyapunov equation are used. The solvability conditions of the synthesis problem ensure the robustness and optimal suppression of the perturbations. They are homogeneously represented as linear matrix inequalities obtained based on the Lyapunov functions. A methodological example is given.

Exponential stability of serially connected thermoelastic system of type II with nodal damping

In this paper, we consider a serially connected thermoelastic rods of type II, where the heat conduction is described by the theories of Green and Naghdi. Using the frequency domain method, together with multiplier techniques, we show that the energy of this multi-connected system decays to zero exponentially in the presence of boundary and joint damping, by estimating the uniform boundedness of the norm of the resolvent operator along the imaginary axis.

Experimental Research of Variable Operating Performance on Water Source Multi-Connected Air-Conditioning System with Digital Scroll Compressor

In this study, we study the water source heat pump and digital scroll compressor and experimentally in the multi-connected air-conditioning system. Variable performance is developed when the unit operates in refrigerating and heating mode. The maximum of refrigerating capacity is 36519.95W when inlet water temperature of the condenser is 30°C and dry-bulb temperature of indoor air is 32°C, at the same time the maximum of EER is 4.33 when inlet water temperature of the condenser is 20°C and dry-bulb temperature of indoor air is 27°C. The unit operates in heating mode, the maximum of heating capacity and EER is 33275.73W and 3.86 when inlet water temperature of the condenser is 30°C and dry-bulb temperature of indoor air is 20°C.

Comparison and Selection of HVAC Schemes for Weihai Baidu City

The second phase of Weihai Baidu City project plans to become a three-star certificated program which is labled by China’s enviromental building evaluation. Heating and ventilated air conditioning program is one of the most important aspects in evaluation of energy saving. Feasibility study on GSHP, GWHP, air-source heat pump, seawater source heat pump were carried out, it’s confirmed that the most energy-saving and reliable way is that using municipal pipe networks for heating in winter and using split air conditioning or multi-connected air-conditioning system in summer. Summer air-conditioning adopts the new idea “part of time, part of space", representative the latest concept of energy efficiency in buildings in China.

Dynamics and control of multi-connected satellites aligned along local horizontal

The paper presents dynamics and control of multi-connected satellites aligned along an unstable local horizontal configuration. The satellites are modeled as point masses and they are connected through cables. The cables are assumed to be flexible but massless. The governing equations of motions of the system moving in an elliptic orbit are obtained through a Lagrangian approach. The control laws are developed and the cable deployment and retrieval laws are stated for an N-body system. Results of numerical simulations of the nonlinear governing equations of motion of two- and three-body systems and approximate closed-form solutions indicate the feasibility of controlling multi-connected satellites along the local horizontal. Finally, the effects of various system parameters as well as the cable deployment and retrieval on the system response have been investigated. It is important to mention that the multi-connected satellites system outperforms the free flyer multi-satellite system and the controller only requires force in the order of a Millinewton for multi-satellites in geostationary orbit with a desired inter-satellite separation distance of 100 m.

Formation of required transfer zero location in the multiconnected dynamic system

A method for providing the required location of a transfer zero set in the linear multiconnected dynamic system with an equal number of inputs and outputs is considered.

Converter configurations and switching frequency for a GTO reactive power compensator

This paper compares two converter configurations for a multi-10 MVA gate-turn-off (GTO) reactive power compensator (STATCOM) from the viewpoints of converter connection and switching frequency. One is a single-bridge system consisting of a three-phase bridge converter unit and a transformer. Its pulsewidth modulation (PWM) frequency varies from 450 to 1800 Hz, and its line frequency is 50 Hz. The other is a multiconnected converter system consisting of plural, single-, or three-phase converter units and transformers. Its switching frequencies are chosen to be the lowest possible. The evaluated items are harmonic distortion, power loss, GTO utilization factor, and control response. Our simulation study shows that the multiconnected converter system with the lowest switching frequency is superior to the single-bridge system with the higher switching frequency in every case, even when there are severe line faults requiring very quick response. A new control strategy is adopted for obtaining quick response.