Complex Transmission Systems Research Articles

Accuracy Analysis of Complex Transmission System with Distributed Tooth Profile Errors

Tooth profile errors are the internal excitations that cause gear meshing errors, which are critical error factors affecting gear transmission accuracy. In existing studies, it is usually regarded as a constant or random distribution function. However, the actual machined tooth profile error is not a constant, so this estimation is inconsistent with the actual situation, resulting in an inaccurate evaluation of transmission accuracy. This paper proposes a method for representing tooth profile errors using distribution errors (including systematic and random errors), and a mathematical model of distributed tooth profile errors is presented. The contact stresses of the complex transmission system were compared with those obtained by formulas, proving that tooth profile errors increase contact stress. A method for calculating gear meshing error is proposed to evaluate the actual output accuracy of the complex transmission system. Compared with the test, the output accuracy is reduced by 13.8% under the temperature environment and distributed tooth profile errors. The proposed methods can accurately predict the transmission accuracy of precision transmission systems at the design stage and provide theoretical support for reducing systematic and random errors at the gear machining stage.

Assembly accuracy prediction method of planetary gear train considering bolt-bearing-shaft-gear coupling effects

Planetary gear train (PGT) is a complex transmission system composed of gears, shafts, bearings and bolted joints, of which the assembly accuracy affects the transmission accuracy and dynamic behavior. In this paper, a new assembly accuracy prediction method is proposed for PGT considering gear-shaft-bearing-bolt coupling effects. The new method is formulated by establishing three models for bolt assembly, shaft error motion and assembly accuracy (transmission error) of PGT. The model for bolt assembly is an original FE-analytical model to analyze the bolt assembly effect on elastic deformation of bearing cap, which is developed by finite element (FE) method and analytical method for addressing the elastic effect of bearing cap and elastic interaction between bolts. The models for shaft error motion and assembly accuracy are performed by the three-dimensional contact analysis with errors and preload of bearing cap based on analytical method and kinematic geometry relationship. Combining the three models, the assembly accuracy can be predicted by simulations. The simulations indicate that the proper bolt assembly parameters can alleviate the influence of manufacturing errors on assembly accuracy. The assembly accuracy tests of PGT are conducted. The results well agree with the simulations’, and the assembly accuracy is improved by the proper bolt assembly parameters.

A parallel approach for ultra-fast state estimation in large power system using graph partitioning theory

This paper introduces a novel approach for multi-area state estimation in large transmission networks through the application of graph partitioning theory. By harnessing the eigenvalues and eigenvectors of the Laplacian matrix, a large-scale transmission network is partitioned into manageable sections. Within these partitions, state estimation processes run in parallel, markedly improving efficiency compared to conventional methods. Linear state estimation is employed within each area, expediting computations and making it adaptable to large-scale networks, which traditionally pose computational challenges. The method's efficacy is demonstrated through comprehensive validation, commencing with small networks and extending to real-world applications on the IEEE 118-bus test system and the 9241-bus European high-voltage transmission network. In comparison to the integrated network method, our approach has achieved state estimation answers with reduced computation time. The partitioning of the integrated network into multi areas has effectively mitigated computational loads, showcasing its potential for enhancing operational efficiency and reliability in complex power transmission systems. This approach not only offers a robust solution for state estimation but also represents a significant stride toward advancing the field of state estimation, promising to bolster the stability and performance of modern power grids.

Research on Gear Synthesis of Automatic Transmission

Abstract The lever method facilitates a straightforward analysis of the motion dynamics of an automatic transmission under various gear settings, offering a simple and intuitive approach to examining planetary gear transmissions. Specifically, the equivalent lever diagram for a parallel-double planetary gear transmission comprises four component points. From a control perspective, a transmission system with two planetary rows can accommodate up to two reduction gears, one direct gear, one overdrive gear, and one reverse gear. In contrast, the equivalent lever diagram for a parallel three-planetary gear transmission includes five component points, with such systems typically supporting up to three reduction gears, one direct gear, two overdrive gears, and two reverse gears. This methodological approach underscores the lever diagram’s utility in delineating the functional capabilities of complex transmission systems.

Design and Characteristics of Shape Memory Alloy Bidirectional Torsional Actuator

To overcome the problems of the low power/weight ratio of traditional servo motors, complex transmission systems, and large space occupied by hydraulic drive systems, this paper designs a bidirectional torsional actuator using the shape memory effect of Ti-Ni shape memory alloy (SMA) wire, which aims to realize the folding and unfolding of the wings of flying cars. The model of the designed actuator was established and the theoretical calculation was analyzed, based on which the experimental verification was carried out. It is found that when the heating current is 1.6 A, the mechanism can take into account the economy under the premise of meeting a certain folding speed. When the pre-stretching amount of SMA wire is 3%, the residual strain corresponding to the wire is small, about 0.577%, and it can provide driving torque and torsion angle to meet the design requirements of the actuator. This verifies the feasibility of the actuator and obtains the driving characteristics of the actuator. Finally, the shortcomings and improvement measures of the actuator are analyzed briefly.

A modeling method for the DC side simplified impedance of line commutated converter based on the simplified switching function

With a large amount of new energy access and the wide application of high voltage direct current (HVDC) transmission technology based on line commutated converter (LCC), it is of great significance to study the impedance frequency characteristics of the converter to analyze the stability of the LCC-HVDC system. Due to the complexity and inefficiency of the existing modeling techniques, in this paper, a simplified impedance modeling method for the DC side of LCC based on the simplified switching function is proposed. Firstly, the commutation process of LCC is deduced according to the converter valve opening sequence and circuit principle, and the simplified switching function of LCC is proposed. Next, based on the dynamic phasor method, through the analysis and calculation of harmonic transmission between the AC and DC sides of LCC, the simplified impedance of the DC side of LCC is obtained. Then, a simulation model is established in PSCAD, and the impedance scanning results of the simulation model show that the error is small between the method proposed in this paper and the method without simplification, which verifies the validity of the proposed model. The proposed method can reduce modeling complexity and provide a fast calculation model of the DC side impedance of LCC for analyzing the stability of large complex transmission systems.

Numerical Simulation of Hydrodynamic Performance of Podded Propulsion under Maneuvering Condition

Podded propulsion offers excellent maneuverability without the need for mechanically complex transmission systems. However, the hydrodynamic performance of podded propulsion under maneuvering conditions has not yet been adequately investigated. This study proposes a Reynolds-averaged Navier–Stokes (RANS)-based method to investigate the hydrodynamic performance of pod thrusters under maneuvering conditions. The accuracy of the numerical method is verified based on a comprehensive convergence analysis and experimental comparison. A comparative analysis of the difference in thrust, moment and their coefficients between maneuvering and steady-state conditions is performed. Additionally, the impact of the advance number on the propeller hydrodynamic performance under maneuvering conditions is examined. The results demonstrate that the thrust coefficient and the torque coefficient of the propeller at positive and negative oblique flow angles exhibit asymmetry owing to the influence of the incoming flow velocity. Furthermore, the thrust and torque under maneuvering conditions increase significantly compared with those under the steady-state condition.

State of the art, challenges and prospects of wide-area event identification on transmission systems

The proliferation of advanced metering devices such as phasor measurement units (PMUs) along with communication systems readiness has opened new horizons for centralized protection and control of transmission systems. Wide-area event identification (WAEI) is considered an indispensable enabling block to these advanced applications. This paper is aimed at scrutinizing existing WAEI methods and discussing their prospects and shortcomings in improving the situational awareness of complex transmission systems. The disturbances of interest are those that significantly impact system operation and stability, namely short-circuit faults, line outages, and generation outages. The reluctance of system operators to entrust WAEI methods is discussed and linked to the inability of existing methods to deal with real-world challenges such as communication latencies, temporarily incomplete network observability, and the loss of the time synchronization signal. The superimposed-circuit concept is detailed and promoted as a powerful methodology with great unleashed potential for addressing these problems. The paper ends with remarks on the remaining research gaps that need to be addressed to fulfill the needs of power system operators, thus facilitating the uptake of WAEI methods in practice.

G-Reactor at Micro-Plan

The stirrer reactor govern the industrial pharmaceutical productions up to the present, however the complex transmission systems may increase the costs exponentially with the power rates and the hermetic rector sealing. G-reactor improves the analogous reactors with simple pneumatic power device to heavy duty performances at high technological risks by pathogens and per substitution of complex transmissions by own-design; a single compression unit produces the sterile air to the power input of micro-plants and the oxygen of aerobic processes; important economic technical profits is foreseen; microplants distinguishes by small installations for compressed air and the services with overall automatic control available; the reliable performance for the human health, variable speed and standard impeller system, simple sterilization, safe sampling and supplies, foam-breaks to avoiding chemicals and simple automatic flow control distinguish the installations. The mathematical simulation of G-reactor performances to the mixing operations at gas-liquid systems to mass-transfer is shown; a solved example to a specific process illustrates the calculus fundamentals; the software enables the calculus of consumption parameters to the reactor scale-up and micro-plants of maximum capacity; the descriptive data analysis is discussed for the primary technical evaluations and general conclusions. The innovation is proposed for the small production scale of drugs and the unit operations of the chemical industry; a brief technical description of micro-plants and the production of sterile air may lead to the process engineering and the preliminary analysis of costs. The prophylactic treatment of the residual gas flow is shown.

Research on Vibroactivity of Toothed Gears with Highly Flexible Metal Clutch under Variable Load Conditions

The article provides a discussion on a methodology intended for testing of power transmission systems featuring an innovative highly torsionally flexible metal clutch patented by the co-authors of this paper. What this methodology takes into account is the amplitude and frequency analyses discussed in the article, as well as a sensing system based on diverse piezoelectric and magnetic phenomena, the Doppler effect, etc. Both contact and non-contact (laser measurement) methods were used during the tests. The purpose of the tests conducted at the stand, originally designed by the authors in accordance with the methodology proposed, was to evidence that using the innovative and patented, highly torsionally flexible metal clutch makes it possible to reduce the vibrations of multi-stage toothed gears, consequently reducing the forces affecting the gear bearings and those acting at the tooth space, which is to enable the service life of individual components of the power transmission systems intended for mining scraper conveyors to be significantly extended. Based on the studies and analyses performed by the authors, one can observe and conclude that the methodology proposed in the paper makes it possible to use an example of a relatively complex power transmission system in order to examine the relationships between the processes at work, i.e., the decline of the linear vibrations of the gear housing (which is undoubtedly positive in power transmission systems) at the expense of increasing torsional vibrations of the innovative clutch, the latter not to be considered unfavourable to users in the case analysed.

Functional brain imaging and central control of the bladder in health and disease.

Central control of the bladder is a complex process. With the development of functional imaging technology and analysis methods, research on brain-bladder control has become more in-depth. Here, we review previous functional imaging studies and combine our latest findings to discuss brain regions related to bladder control, interactions between these regions, and brain networks, as well as changes in brain function in diseases such as urgency urinary incontinence, idiopathic overactive bladder, interstitial cystitis/bladder pain syndrome, urologic chronic pain syndrome, neurogenic overactive bladder, and nocturnal enuresis. Implicated brain regions include the pons, periaqueductal grey, thalamus, insula, prefrontal cortex, cingulate cortex, supplementary motor area, cerebellum, hypothalamus, basal ganglia, amygdala, and hippocampus. Because the brain is a complex information transmission and processing system, these regions do not work in isolation but through functional connections to form a number of subnetworks to achieve bladder control. In summarizing previous studies, we found changes in the brain functional connectivity networks related to bladder control in healthy subjects and patients involving the attentional network, central executive network or frontoparietal network, salience network, interoceptive network, default mode network, sensorimotor network, visual network, basal ganglia network, subcortical network, cerebella, and brainstem. We extend the working model proposed by Griffiths et al. from the brain network level, providing insights for current and future bladder-control research.

OPTIMIZATION OF CONTROL OF OPERATING MODES OF GAS TRANSPORT SYSTEM USING UGS

The Soyuz, Urengoy-Pomary-Uzhhorod and Progress gas pipeline systems form the basis of the trans-Ukrainian trans-Ukrainian pipeline system. The complex gas transmission system contains a number of gas pipelines forming a linear part and several compressor stations. The amount of capacity of pipelines depends on the number and characteristics of compressor stations. Reliability of work, regulation of transit flows and ensuring uninterrupted gas supply is carried out with the help of underground gas storage facilities, which are an integral part of the GTS of Ukraine. The use of underground storage facilities is considered to be one of the most efficient ways of gas supply, improving the quality of gas supplies to consumers and the efficiency of gas sales within the country and abroad. With the use of storage, you can reduce the unevenness of seasonal consumption and ensure security of supply. The use of underground storage facilities is an integral part, as during the year the maximum daily gas extraction exceeds the minimum more than three times, and the supply of gas through the main gas pipelines is almost constant. The maximum storage capacity cannot be represented as the sum of the absolutely free flow rates of all production wells. This is explained by the fact that the productivity of the underground gas storage during the extraction period is affected by the hydraulic resistance of the gas collection system to the underground storage and its technical condition, which is determined by the coefficient of hydraulic efficiency of loops and collectors.
 Studies show that the location of gas storages in the system has an impact on the amount of energy consumption. Therefore, the strategy of rational use of underground gas storage facilities in pipeline transport (in terms of minimizing energy consumption) is based on the study of the impact of their location in the gas transmission system. The principle of energy efficiency of the use of underground gas storage facilities for long-distance transportation (in order to equalize the unevenness of gas consumption) is based on the sequence: the most remote UGS should be used first. These are the objects that are located at the end points of the GTS route and whose location corresponds to the proximity to consumers.

Rational modes of operation of complex gas transmission systems

The principles of formation of mathematical models for the choice of rational modes of operation of complex gas transmission systems with multi-shop compressor stations equipped with different types of gas pumping units are given. It is proposed to optimize the modes on the basis of the use of energy-economic characteristics of the gas transmission system, which are built on the basis of the parameters of the gas transmission system taking into account the technical condition of its elements and economic performance for a certain period. This approach ensures compliance with the principle of operation of the gas transmission system in the field of permissible modes and maximum energy consumption on the one hand and minimizing the cost of gas transportation on the other. If it is possible to use the actual data on the actual technical condition of the equipment and gas pipelines of the system, this method allows to evaluate and take into account in the further procedure the parameters of gas supply reliability. An important requirement for the optimization procedure is the stability of energy efficiency characteristics, which means that in any practical changes of non-basic regime parameters, the energy efficiency characteristic should not be shifted beyond the allowable error. The problem of optimal load distribution in a complex gas transmission system is considered based on their minimum total energy costs at a given volume of gas supply and other planning and technological constraints. The task of optimizing a multiparameter object is to find the extremum of the goal function by selecting a vector of control effects that would satisfy the constraint. The distribution of loads at the highest hierarchy for the system of main gas pipelines is obtained by finding the minimum total cost of gas compression for each pipeline. The method of construction of such characteristics and the procedure of establishing their stability are shown, which allows the formalization of the construction of the criterion dependence of the regime parameters on energy economic factors. The stated basic decisions allow to formalize the function of the purpose for a choice of a rational mode of operation of gas transmission system in the conditions of its incomplete loading.

Demonstration of a fiber optical communication system employing a silica microsphere-based OFC source.

The fabrication of microsphere resonators and the generation of optical frequency combs (OFC) have achieved a significant breakthrough in the past decade. Despite these advances, no studies have reported the experimental implementation and demonstration of silica microsphere OFCs for data transmission. In this work, to the best of our knowledge, we experimentally for the first time present a designed silica microsphere whispering-gallery-mode microresonator (WGMR) OFC as a C-band light source where 400 GHz spaced carriers provide data transmission of up to 10 Gbps NRZ-OOK modulated signals over the standard ITU-T G.652 telecom fiber span of 20 km in length. A proof-of-concept experiment is performed with two newly generated carriers (from 7-carrier OFC) having the highest peak power. The experimental realization is also strengthened by the modeling and simulations of the proposed system showing a strong match of the results. The demonstrated setup serves as a platform for the future experimental implementation of silica microsphere WGMR-OFC in more complex WDM transmission system realizations with advanced modulation schemes.

CALCULUL CÂMPULUI ELECTRIC ASOCIAT UNUI CUPLOR INDUCTIV DESTINAT TRANSFERULUI DE PUTERE WIRELESS

"Contactless or wireless power transmission has become a widespread disruptive technology. Although known for more than 100 years, it is the result of the unprecedented development of microelectronics and power electronics in recent decades. Numerous technical solutions for near-field energy transmission at different power and frequency levels are currently established: capacitive electric field transmission (CPT), inductive magnetic field transmission (IPT), multi-coil transmission and simultaneous transmission via electric field and magnetic field as a combination of the first two. The materialization of the contactless transmission is achieved in theory and practice through different types of contactless coupling circuits, generically called ""contactless couplers"". The inductive coupler can be considered as an electrical transformer in air or with open magnetic circuit in which the primary (Tx) and the secondary winding (Rx) can occupy different positions from each other depending on the application [1]. It is considered a representative element for WPT (Wireless Power Transfer) systems currently used from transferred powers of several watts to tens or hundreds of kilo-watts. To increase the transfer efficiency, the coupler works at high frequencies, of the order of kHz or MHz and in some cases has planar windings, of different shapes, made of litz wire and usually has magnetic flux concentrators [2]. Any inductive coupler is integrated into a complex transmission system, consisting of many other components [3]. In addition to the electromagnetic calculation widely presented in other works, open magnetic circuit construction produces electric and magnetic scattering fields that have a negative effect on both electrical and electronic equipment in the vicinity and on human health if the exposure exceeds certain thresholds. These thresholds are indicated by international standards and requirements [4-5] achieved by applying the precautionary principle [6] so that they can be reviewed periodically and are not mandatory unless they are taken over in national law. In this paper we analyze by the finite element method, in approximate 2D, the electric field produced by an inductive coupler in various simplified construction variants and calculate certain related quantities of practical importance such as: electric field distribution in the field of calculation, electric field strength in the vicinity of the inductive coupler, equipotential lines, reactive power, equivalent capacities."

Dynamic behavior of a power re-circulating gear test rig including periodic variation of mesh stiffness and static transmission error

We characterized the dynamic behavior of a pair of high performance aeronautical gears which are part of a complex transmission system. The gear pair was tested using a mechanical recirculating power test rig designed to simulate the severe operating conditions of transmitted torque and angular speed. The test rig and the most important phenomena that influence its dynamic behavior are described. A (static) finite element model, developed to calculate the input parameters for the dynamic analysis of the tested gears, is also presented. Using the results of the FE model, we developed a lumped dynamical model with which it is possible to reproduce the most significant dynamic phenomena of the test rig. We characterized the behavior of the test rig focusing on the actual loads transmitted by the tested gears. The dynamic model was validated by comparing its results with the experimental outcomes in various test conditions. The comparison highlights the limitations of the design procedures based on common standards for assessing the dynamic overload experienced by heavy-duty gear transmission systems.

Industrial Archaeology Applied to the Study of an Ancient Harvesting Machine: Three-Dimensional Modelling and Virtual Reconstruction

This article shows the three-dimensional (3D) modelling and virtual reconstruction of an ancient harvesting machine developed at the beginning of the 19th century. SolidWorks software is employed to obtain the 3D model of this historical invention and its geometric documentation. The original material for the research is available on a farm located in the province of Cádiz (Spain). Thanks to the three-dimensional modelling performed, both its operation and the final assembly of this invention can be explained in detail in a coherent way. Having carried out the functional analysis, it can be verified that the machine combines well-performed chain-sprocket transmissions, which, together with complex gearboxes with parallel and bevel gears, make this reaper a very reliable machine. Furthermore, the inclusion of elements such as gimbal joints on shafts with possible misalignments, and clutches to adapt the operation of the machine to the needs of the operator, makes it highly versatile and functional without over-exerting the mechanics. From a technical point of view, the complex transmission systems, the perfect synchronization achieved between all its parts, and the combination of continuous oscillatory movements, such as that of sheaf compactors with intermittent movements as complex as that of the knotting system, are all worthy of note, and reveal the great work of engineering involved in this historical invention.

GPU parallel acceleration of transient simulations of open channel and pipe combined flows

Simulating the transient processes in complex water transmission system is time-consuming, and improving computational efficiency by means of parallelization on CPU clusters or even faster GPU platform is demanded. This paper proposes an approach to accelerate the transient simulations of open channel and pipe combined flows on single GPU chip. The Saint-Venant equations for open channel flows is solved by using the method of characteristics (MOC), whose inherent parallelism can be well exploited by GPU implementations in the thread-level parallelism structure of Compute Unified Device Architecture (CUDA). The sub-processes, including open channel computation, pipe flow computation and connecting boundary treatment, are implemented by different kernels. The procedures are first verified by analyzing the parallel computation efficiency of hydraulic transient processes in an open channel. Then the transient processes of a practical engineering project, which involves both open channel flow and pressurized pipe flow, are simulated. The GPU kernels are found to be memory bandwidth bounded, and the proposed single chip GPU parallel can achieve up to hundreds of speedup ratios compared to the sequential counterpart on single CPU chip.

Identification of system vulnerabilities in the Ethiopian electric power system

The Ethiopian Electric Power (EEP) has been operating and managing the national interconnected power system with dispersed and geographically isolated generators, a complex transmission system and loads. In recent years, with an increasing load demand due to rural electrification and industrialization, the Ethiopian power system has faced more frequent, widely spread and long lasting blackouts. To slash the occurrence of such incidents, identifying the system vulnerabilities is the first step in this direction. In this paper, the vulnerability assessment is performed using indices called active power performance index (PIp) and voltage performance index (PIv). These indices provide a direct means of comparing the relative severity of the different line outages on the system loads and voltage profiles. Accordingly, it is found that the most severe line outages are those lines that interconnect the high load centered (Addis Ababa and Central regions) with the rest of the regional power systems. In addition, the most vulnerable buses of the network in respect of voltage limit violations are mainly found at the high load centers.

Research on vibration characteristics of multistage gears transmission system driven by internal and external excitation

In order to accurately describe the complex transmission systems and clarify the effects of internal and external excitation on the vibration characteristics for large complex transmission systems, a dynamics model considering gear meshing error and time-varying meshing stiffness is established at two-stage planetary gears systems. The coupling model is established by matrix set method for two-stage planetary gears and multistage spur gears transmission systems. The random load excitation verified by experiments is the external excitation in the system, and the excitation caused by the time-varying meshing stiffness and meshing error is the internal excitation. The research on the response of the vibration systems shows that the internal excitation caused by gear meshing stiffness and gear meshing error has important influence on the dynamic load behavior of spur gears transmission in complex systems. For the planetary system with heavy external load, the dynamic behavior mainly depends on the external load, and the influence of internal excitation on the dynamic meshing force is less than that of the external excitation for the planetary system. The external excitation mainly affects the low-frequency region of the dynamic meshing force for the system, and the internal excitation affects the high-frequency region of the dynamic force for the system. The frequency influence interval of the internal excitation is much larger than that of the external excitation.