Series-parallel Structure Research Articles

A new model for reliability optimization of series-parallel systems with non-homogeneous components

In discussions related to reliability optimization using redundancy allocation, one of the structures that has attracted the attention of many researchers, is series-parallel structure. In models previously presented for reliability optimization of series-parallel systems, there is a restricting assumption based on which all components of a subsystem must be homogeneous. This constraint limits system designers in selecting components and prevents achieving higher levels of reliability. In this paper, a new model is proposed for reliability optimization of series-parallel systems, which makes possible the use of non-homogeneous components in each subsystem. As a result of this flexibility, the process of supplying system components will be easier. To solve the proposed model, since the redundancy allocation problem (RAP) belongs to the NP-hard class of optimization problems, a genetic algorithm (GA) is developed. The computational results of the designed GA are indicative of high performance of the proposed model in increasing system reliability and decreasing costs.

Superiority of Dual-Mechanical-Port-Machine-Based Structure for Series–Parallel Hybrid Electric Vehicle Applications

Appropriate structure is the first key issue that a designer of an efficient hybrid vehicle should pay attention to. This paper presents three different structures for the concept of series-parallel structure in hybrid electric vehicles (HEVs) and compares them with each other for the application of Toyota Prius 2004 as a well-known case study. The first structure consisting of one electric motor, one electric generator, and one power split device is the conventional structure as one existing in Toyota Prius 2004 and called THS-II in the literature. The second and third structures are based on two special electric machines named transmotor-based structure (TBS) and dual-mechanical-port (DMP) machine-based structure (DMPBS), respectively. The three structures are compared by considering different aspects such as weight, occupied volume, and overall efficiency. A surface-mounted fractional-slot concentrated winding DMP machine is designed, and the design is verified by applying the finite-element analysis. Simulation results have been presented to support the accomplished comparison of the structures under study. Simulation results show that all structures have approximately equal weight, volume, and efficiency, but DMPBS is a compact, efficient, and simple way to convert the existing fossil-fuel cars into an HEV. One DMP machine prototype has been implemented, and experimental results have been included.

Reconfiguration of Urban Photovoltaic Arrays Using Commercial Devices

A recent approach to mitigate the adverse effects of photovoltaic (PV) arrays operating under mismatching conditions is the dynamic electrical reconfiguration of the PV panels. This paper introduces a procedure to determine the best configuration of a PV array connected in a series-parallel structure without using complex mathematical models. Such a procedure uses the experimental current vs. voltage curves of the PV panels, which are composed of multiple PV modules, to construct the power vs. voltage curves of all of the possible configurations to identify the optimal one. The main advantage of this method is the low computational effort required to reconstruct the power vs. voltage curves of the array. This characteristic enables one to implement the proposed solution using inexpensive embedded devices, which are widely adopted in industrial applications. The proposed method, and its embedded implementation, were tested using a hardware-in-the-loop simulation of the PV system. Finally, the real-time operation and benefits of the proposed solution are illustrated using a practical example based on commercial devices.

Research on the Pose Detection and Control Methods of Robot with Series-Parallel Structure

Aiming at the load requirements, positioning accuracy and workflow of building panels installed robot, developed a 6 DOF of a series-parallel hybrid structure installed robot. According to the structural features of parallel mechanism to the installation manipulator, designed a robot attitude sensing system based on the inclination and laser ranging sensor information feedback; according to the characteristics of the building environment, proposed the position detection method of panels to be installed based on the structured light vision; constructed the control system of the installation manipulator, and used teaching mode to achieve robot control and system calibration. The experimental data prove that, the control and sensing systems of panels installed robot, overcome the complexity of the building environment and the diversity of installation object, and can achieve the automated installation of building panels.

Design and Research of a Construction Robot Based on Series Parallel Structure

Aiming at the difficulty and low automation in installing slabstone under dry-hanging technology which is heavy and large in size, a slabstone dry-hanging installation robot system was developed. According to the working requirements such as load, installing precision and process, we researched a 6-DOF of series-parallel manipulator, analyzed its structural and completed the inverse solution. The inverse position equation of the robot was derived based on the kinematical theory. Mathematical relation between the Position-Orientation parameters and the direction cosine matrix was established. Experiments show that the robot can achieve slabstone auto- installing, and solve the problems in the dry-hanging installing.

Non-inductive modular circuit of dislocated synchronization of fractional-order Chua's system and its application

In this paper, from the stability theory of fractional-order chaotic system, a kind of dislocated projective synchronization for fractional-order Chua's system is successfully completed through a nonlinear controller. Meanwhile, the fractional-order unit circuit is designed, according to the series-parallel structure of resistor-capacitor and the approximate linear transfer function expression for the complex frequency domain. Thus, non-inductive modular circuit of dislocated projective synchronization of fractional-order Chua's system is realized. The circuit simulation results prove the feasibility of the scheme. Furthermore, the method can be applied in secure communication through the improved chaotic masking. The information signal can be concealed and recovered. Numerical simulation results show the effectiveness of the proposed method.

Dynamic maintenance decision-making for series–parallel manufacturing system based on MAM–MTW methodology

Proper maintenance schedule is required to improve manufacturing systems’ profitability and productivity. A novel dynamic maintenance strategy is thus developed to incorporate both the single-machine optimization and the whole-system schedule for series–parallel system. Firstly, multiple attribute value theory and maintenance effects are considered in the single-machine optimization. A developed multi-attribute model (MAM) is used to determine the optimal maintenance intervals. Then, a series–parallel structure of the system is investigated in terms of the whole-system schedule. Maintenance time window (MTW) programming is presented to make a cost-effective system schedule by dynamically utilizing maintenance opportunities. The maintenance scheme achieved by using the proposed MAM–MTW methodology is demonstrated through a case study in a hydraulic steering factory. It is concluded that proper consideration of maintenance effects and time window leads to a significant cost reduction.

Grid-Interfacing Converter Systems With Enhanced Voltage Quality for Microgrid Application—Concept and Implementation

Grid-interfacing converter systems with enhanced voltage quality are proposed for microgrid applications in this paper. By adapting the conventional series-parallel structure, a group of grid-interfacing system topologies are proposed for the purpose of interfacing local generation/microgrid to the grid, or interconnecting microgrids. The functionality of the proposed systems is also reconfigured in order to ease the control design and to improve overall system performance, differing from existing series-parallel structure-based systems. Experiments with a concrete laboratory system are given to detail the proposed concepts and to demonstrate the practical implementations. Two three-phase four-leg inverters, together with dc microsources and nonlinear loads, are employed to construct a general series-parallel grid-interfacing system. Through the introduction of multilevel control objectives, it is illustrated that the proposed system could ride through voltage disturbances and continue the power transfer between the local generation and the grid, while a high-quality voltage is maintained for the local loads. The system also shows the possibility to achieve auxiliary functions such as voltage unbalance correction and harmonic current compensation. The main design aspects of the controllers are specified, and the entire system is effectively validated on a laboratory setup.

Regulated Peak Power Tracking (RPPT) System Using Parallel Converter Topologies

Regulated peak power tracking (RPPT) systems such as the series structure and the series-parallel structures are commonly used in satellite space power systems. However, these structures process the solar array power or the battery power to the load through two cascaded regulators during one orbit cycle, which reduces the energy transfer efficiency. Also the battery charging time is increased due to placement of converter between the battery and the solar array. In this paper a parallel structure has been proposed which can improve the energy transfer efficiency and the battery charging time for satellite space power RPPT systems. An analogue controller is used to control all of the required functions, such as load voltage regulation and solar array stabilization with maximum power point tracking (MPPT). In order to compare the system efficiency and the battery charging efficiency of the proposed structure with those of a series (conventional) structure and a simplified series-parallel structure, simulations are performed and the results are analyzed using a loss analysis model. The proposed structure charges the battery more quickly when compared to the other two structures. Also the efficiency of the proposed structure has been improved under different modes of solar array operation when compared with the other two structures. To verify the system, experiments are carried out under different modes of solar array operation, including PPT charge, battery discharge, and eclipse and trickle charge.

Service Life Predicting of Dam Systems with Correlated Failure Modes

The 50-year design reference period is coming to an end for many dam projects in China. In the last decade, it has become clear that remaining service life analysis of existing dams must be used to optimally manage the growing number of aging and deteriorating structures. The uncertainties associated with deteriorating dams require the use of probabilistic methods to properly assess their lifetime performance. A dam system involves multiple failure modes; however, conventional assessment and prediction models often neglect the correlations among failure modes. As a result, the remaining service life predicted by these methods is relatively rough. First, in this paper, conventional lifetime distribution functions are introduced. The influences of the correlations among failure modes on series, parallel, or series-parallel structure are discussed, respectively, and the approach for calculating correlation coefficients is proposed. Second, on the basis of the analysis of dam failure causes, failure modes of concrete gravity dams are defined, and the concrete gravity dam is reviewed as a series system with parallel subsystems. Third, the limit state functions for failure modes are given, and quantified progressive deterioration functions for various random variables to describe the aging process of gravity dams are obtained. Based on the correlation analysis and time-varying theory, a prediction model of remaining service life for gravity dam systems is finally proposed. An existing concrete gravity dam is investigated. Failure modes and deterioration mechanisms are studied. The results can be used to better predict the remaining service life of deteriorating dams.

Multi-Body Model Identification of Vehicle Semi-Active Suspension Based on Genetic Neural Network

A multi-body vehicle dynamics model was established using ADAMS and a multilayer feed forward neural network of series parallel structure was built by Matlab in this study. The weights and threshold of neural networks which has built was optimizes by GA. This method was used in identifying multi-body vehicle dynamics model. The results show that the maximum error of identification is less than 0.05% and the network convergence rapidly. The designed genetic neural network could replace the vehicle semi-active suspension systems using in neural network adaptive control which can avoid the difficulty of establishing accurately mathematical model and the poor effective of traditional identification methods for the vehicle semi-active suspension.

“Product Partition” and related problems of scheduling and systems reliability: Computational complexity and approximation

Problem Product Partition differs from the NP-complete problem Partition in that the addition operation is replaced by the multiplication operation. Furthermore it differs from the NP-complete problem Subset Product in that it does not contain the product value B in its input. We prove that problem Product Partition and several of its modifications are NP-complete in the strong sense. Our results imply the strong NP-hardness of a number of scheduling problems with start-time-dependent job processing times and a problem of designing a reliable system with a series–parallel structure. It should be noticed that the strong NP-hardness of the considered optimization problems does not preclude the existence of a fully polynomial time approximation scheme (FPTAS) for them. We present a simple FPTAS for one of these problems.

Percolation Effect on the Conductivity of Single-Walled Carbon Nanotube Network

In this paper, we report that the resistance of the SWNT network grown by chemical vapor deposition has a close relationship with the applied current in the range of microampere to milliamperes. At the temperature of 1.5 K, the resistance of SWNT network will decrease with an increasing current. When the applied current is larger than 1 mA, the resistance tends to saturate gradually. At temperature of 100 K, the resistance remains stable and does not depend on the current. The mechanism of this phenomenon is attributed to the series-parallel connection structure of SWNT network, which forms a conducting network with the percolation probability modulated by the applied current. At low temperature, the resistance of the SWNT network will decrease because the percolation probability becomes large with an increasing current. While at high temperature, the percolation probability remains constant due to thermally assisted transfer effect and thus the resistance is not affected by the applied current.

Upward Spirality and Upward Planarity Testing

A digraph is upward planar if it admits a planar drawing where all edges are monotone in the upward direction. It is known that the problem of testing a digraph for upward planarity is NP-complete in general. This paper describes an $O(n^4)$-time upward planarity testing algorithm for all digraphs that have a series-parallel structure, where $n$ is the number of vertices of the input. This significantly enlarges the family of digraphs for which a polynomial-time testing algorithm is known. Furthermore, the study is extended to general digraphs, and a fixed parameter tractable algorithm for upward planarity testing is described, whose time complexity is $O(d^t \cdot t \cdot n^3 + d \cdot t^2 \cdot n + d^2 \cdot n^2)$ where $t$ is the number of triconnected components of the digraph and $d$ is an upper bound on the diameter of any split component of the digraph. Our results use the new notion of upward spirality that, informally speaking, is a measure of the “level of winding” that a triconnected component of a digraph $G$ can have in an upward planar drawing of $G$.

Re-Design and Realization of Automatic Control for the Compressor Station of the 2 kW Helium Cryoplant

A large-scale compressor set of a 2 kW helium cryoplant, as one of the subsystems of EAST (the experimental advanced superconducting tokamak), is arranged in a two-stage series-parallel structure. A fully automatic control system used to handle the compressors' on/off/scheduling and the pressures' adjustment was developed. To reduce the long time lag and the uncertainty with the energy slide valves effectively, expert rules in combination with proportional-integral-derivative (PID) algorithms were applied. Safety protection and status analysis mechanisms were built up to reinforce its stability and robustness. The new system has been applied to the EAST operations and is operated stably. The problems in the previous semi-automatic system, such as the big overshoot of pressure and complexity of the operations, were solved.

Approximate methods for convex minimization problems with series–parallel structure

Consider a problem of minimizing a separable, strictly convex, monotone and differentiable function on a convex polyhedron generated by a system of m linear inequalities. The problem has a series–parallel structure, with the variables divided serially into n disjoint subsets, whose elements are considered in parallel. This special structure is exploited in two algorithms proposed here for the approximate solution of the problem. The first algorithm solves at most min{ m, ν − n + 1} subproblems; each subproblem has exactly one equality constraint and at most n variables. The second algorithm solves a dynamically generated sequence of subproblems; each subproblem has at most ν − n + 1 equality constraints, where ν is the total number of variables. To solve these subproblems both algorithms use the authors’ Projected Newton Bracketing method for linearly constrained convex minimization, in conjunction with the steepest descent method. We report the results of numerical experiments for both algorithms.

A Nonlinear Hybrid Fault Detection, Isolation and Estimation using Bank of Neural Parameter Estimators

Abstract This paper presents two novel hybrid schemes for component fault diagnosis in a general nonlinear system. Unlike most fault diagnosis techniques, the proposed solution detects, isolates, and identifies the severity of faults in the system within a single integrated framework. The proposed technique is based on a bank of adaptive neural parameter estimators (NPE) and a set of parameterized fault models. At each instant of time, the NPEs provide estimates of the unknown fault parameters (FP) that are used for fault diagnosis. Two structures of NPE, namely series-parallel and parallel, are proposed with their respective fault isolation policies. While the series-parallel structure possesses fast convergence, the parallel scheme is extremely robust to measurement noise. Although, it has a more complex isolation policy, the parallel structure exhibits a more robust fault isolation capability. The parameter estimation for both architectures is based on an on-line minimization of instantaneous output estimation error. Simple network architecture and straightforward weight adaptation laws make our proposed technique appropriate for real-time implementation. Simulation results presented in this paper for detection, isolation, and identification of faults in nonlinear reaction wheel actuators of a 3-axis stabilized satellite in the presence of disturbances and noise demonstrate the effectiveness of our proposed fault diagnosis schemes.

An optimization method for solving mixed discrete-continuous programming problems

This paper presents a heuristic approach for minimizing nonlinear mixed discrete-continuous problems with nonlinear mixed discrete-continuous constraints. The approach is an extension of the boundary tracking optimization that was developed by the authors to solve the minimum of nonlinear pure discrete programming problems with pure discrete constraints. The efficacy of the proposed approach is demonstrated by solving a number of test problems of the same class published in recent literature. Among these examples is the complex problem of minimizing the cost of a series–parallel structure with redundancies subject to reliability constraint. All tests conducted so far show that the proposed approach obtains the published minima of the respective test problems or finds a better minimum. While it is not possible to compare computation time due to the lack of data on the test problems, for all the tests the minimum is found in a reasonable time.

Stability Analysis of Nonlinear System Identification via Delayed Neural Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this brief, the identification problem for time-delay nonlinear system is discussed. We use a delayed dynamic neural network to do on-line identification. This neural network has dynamic series-parallel structure. The stability conditions of on-line identification are derived by Lyapunov–Krasovskii approach, which are described by linear matrix inequality. The conditions for passivity, asymptotic stability and uniform stability are established in some senses. We conclude that the gradient algorithm for updating the weights of the delayed neural networks is stable to any bounded uncertainties. </para>

05/02141 Transmission reliability cost allocation method based on market participants' reliability contribution factors

System reliability has become one of the most important design specifications for present day systems. Many of the practical systems lead to non-series-parallel reliability logic diagrams. One of the important problems in the reliability design of a system is to allocate the reliability values to various constituent units of the system. Any improvement in the unit reliability is associated with the requirement of additional effort. It is, therefore, imperative to evolve techniques for reliability allocation amongst various units of a system with minimum effort. The existing techniques for this exercise make unrealistic and unduly restrictive assumptions, such as a series-parallel structure, similarity of all units in a system, etc.In this paper, a general method for reliability allocation has been presented which can be applied to any system structure that has identical or non-identical components. The evolved procedure is implemented on computer and tested for several practical structures. The suggested program is based on the analytical-numerical method developed and has been illustrated by several examples.