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New Publications are available now online for this publication.
Please follow the links to view the publication.Process model of vehicle body-in-white welding assembly based on polychromatic sets
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1314
Based on Polychromatic Sets theory, the process model for body-in-white welding assembly is introduced. Firstly, the assembly relation model is built to describe the assembly relation of parts. By analyzing connection relation and interference relation, a new algorithm is proposed to generate the welding assembly sequence. Secondly, On the basis of generated assembly sequence, the process requirement of the assembly sequence is gotten by operating in the process requirement contour matrix. Finally, Equipment contour matrix are constructed to express the association of requirements and equipments. The process equipments to satisfy the requirements are obtained by searching in the contour matrix. This model provides a new way to design the vehicle body-in-white welding assembly process with high computational efficiency.Product generation model for remanufacturing and reuse based on polychromatic sets
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0415
A product generation model (PGM) integrates information from several different generations of a product to facilitate remanufacturing and eventual reuse, by storing all the information from each product generation. Using this method, a new or remanufactured component is checked for compatibility with the existing system before it is installed. New PGM architecture based on polychromatic sets uses sets and Boolean matrices to manage the logical relationships between the different generations of product data and is a highly efficient data management system to control multiple lifecycles of a product. The implementation process of this system for remanufacturing and reuse based on the product generation model is analyzed in this paper.Research of missile assembly process based on ant colony algorithm
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1270
Assembly process directly affects quality and performance of the product. In this paper, the model of the missile's cabin is built under its structure design. According to the constrained relationship among parts, the integrated interference matrix of the missile's cabin is defined, the digraph of the assembly relations among parts of the missile cabin is provided, and the assembly precedence relation is received. Planning processes and calculation procedure of assembly process are given based on ant colony optimization. The result shows that the algorithm is adequate to the assembly process planning of the complex cabin structure.Study on disassembly sequence decision making for products recycling and remanufacturing systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0446
The disassembly sequence decision-making for used products is extremely important for recycling and reuse of components. In order to calculate the analysis difficulty of disassembly path in deciding on the disassembly sequence of products, a decision-making model of product disassembly sequence with Fuzzy Reasoning Petri Nets (FRPN) is proposed. Combined with the matrix operation, a formalization reasoning algorithm is adopted to calculate the disassembly sequences. The result shows that the model of decision-making has strong parallel operation ability in the disassembly process sequence, and can make intelligent decisions based on the product information from each disassembly step. It also realize the automatic clustering identification and decrease the complexity of product disassembly.Development of a novel three-axis force sensor
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1440
A novel three-axis force sensor is presented in this paper. It uses strain gauge as sensing element for the detection of force. The elastic body is a thin cylinder on which four holes are opened evenly in two levels. There are three Wheatstone bridges on the beams to detect the force in three directions. The mathematic model of the sensor is analyzed, and strength check, stiffness design and the linearity of the sensor were studied with FEA. Finally, the transmission matrix is calculated. As indicated by the calculations and experiments, this sensor is not only of high sensitivity and adequate rigidity in the three directions, but also of fairly small cross sensitivities. (4 pages)Inverse kinematics computation in robotics using conformal geometric algebra
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1527
Conformal geometric algebra is a kind of new geometric representation and geometric computation tool. In this paper, an approach to the inverse kinematics of a serial manipulator is presented based on the conformal geometric algebra. First, the basics of the conformal geometric algebra are introduced. Then, an algorithm for the inverse kinematics of a 5-dof serial manipulator is presented, which can be able to comprehend without prior knowledge of geometric algebra. (5 pages)Assessment on green degree of biodegradable packaging material based on LCA and FAHP methodology
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1494
In this paper, the indexes system of green degree of biodegradable packaging materials is built and the fuzzy analytical hierarchy process (FAHP) methodology based on life cycle assessment (LCA) is employed to analyze and assess this system. The qualitative assessment is gained by the survey and the statistics theory is employed to deal with the qualitative data. The judgment matrix is built and the maximum characteristic root and vector are computed by the sum and product method. Then the relative importance degree of every influence factor is computed and the comprehensive importance degree of every influence factor is gained. The membership function of every influence factor is established by logical reasoning assignment method, then the membership degree is gained. According to the comprehensive importance degree and the membership degree of every influence factors, the green degree of biodegradable packaging materials is generally assessed. The green degree of biodegradable packaging materials is compared with that of plastic material, and the result is that the biodegradable packing materials have higher green degree then that of plastic material. (5 pages)Design of wheelset vibration diagnosis based on UKF
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1977
Vibration parameter of the train wheelset is a key technology of the estimated fault prediction and diagnosis of train. According to the nonlinear problem for the state signal of wheelset vibration diagnostic system, unscented transformation is introduced into Kaman filter. The UKF method could be applied to addresses the estimation inaccuracy of linear Kalman filter and the filtering divergence problem caused by error covariance matrix non-positive in general unscented Kalman filter. The results obtained from trail vertical irregularity simulation show that, UKF features rapid convergence, higher stability and accuracy, making it become an efficient estimation of diagnosis method for Vibration Diagnostic of train's wheelset.Binary decision diagrams applied to fault tree analysis
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080314
Fault tree analysis (FTA) is employed in remote condition monitoring for detecting and identifying faults. FTA model is a graphical representation of logical relationships between events. In this paper a binary decision diagram (BDD) approach is used in order to provide an alternative to the traditional cutest-based methods for FTA. BDD could be defined as a method which determines the output value of the function by examining the inputs. The BDD method does not analyse the fault tree directly, but converts the tree to a BDD that represents the Boolean equation for the top event. The conversion process from FTA to BDD presents several problems. The variable ordering scheme chosen for the construction of the BDD and has a crucial effect on its resulting size. In order to facilitate improvement efforts and resource deployment in an existing system, proper and accurate prioritisation of the basic events is necessary. This paper evaluates different methods. They are and criterion, Structural Heuristic, Weigh, top-down left-right, Fussell-Vesley, depth first search and Birnbaum. (5 pages)Research on a novel approach to multi-axis line contact milling
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061003
The principle of a novel multi-axis milling is presented. Peripheral edges of a cutter are in contact with the theoretical profile of a work-piece, and rotation of spindle drum imitates turning. Thus, the theoretical profile can be achieved with the minimum reciprocating movements of the cutter and the shortest cutter path length. It is a novel efficient numerical control (NC) machining approach that combines the high efficiency of line contact machining with low roughness of turning. A whole developable ruled surface can be processed with only one NC code by lifting, swinging, shifting, and rotating of the spindle drum. Two rotating movements adjust the vector of the cutter axis. The lifting of the spindle drum makes the tangent point of the cutter moves along the drive curve of surfaces while the peripheral edges of the cutter are tangent to the theoretical surfaces. The milling methods, efficiency and machining precision to process various curved surfaces are contrasted. Comparing the efficiency and machining accuracy in the approach with those of 5-coordinate point contact machining and 5-coordinate line contact machining, the results show that the approach excels the others.Research of input-output energy decoupling in tension system
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061112
The input-output energy decoupling is put forth for the complex electromechanical tension system problem including strong coupling, multi-variance, uncertainties, etc. The aim is that an energy of any input controls mainly the energy of a corresponding output and influences the energy of the other as weakly as possible. After the looper height and tension control system has been modeled, a H<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">∞</sub> robust control algorithm based on input-output energy decoupling is proposed in terms of the solution of linear matrix inequalities (LMI). Finally, the input-output energy decoupling algorithm is applied to the tension system, and the simulation results show that the method has satisfactory decoupling performance. The validity of the designed controller is validated.A vector projection method to evaluating machine tool alternatives for green manufacturing
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060838
Machine tool selection for green manufacturing is a practical approach for reducing the resource consumption and negative environmental impact in mechanical processes. On the other hand, selecting the best machine tool from its increasing number of existing alternatives in market are multiple-criteria decision making problem in the presence of many quantitative and qualitative attributes. Therefore, in this paper, a reference index system is setup for the machine tool selection by the consideration of resource consumption and environmental impact. A machine tool selection model is established, and a methodology so called vector projection method is developed to justify machine tool alternatives. Lastly, an example is discussed.An improved algorithm for inverse kinematics solution of redundant modular robots
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061116
It is difficult to get solutions that can meet the requirements of high positioning accuracy and real time control simultaneously among the infinite solutions of a redundant robot. Based on weighted least-norm method (WLNM), an optimized algorithm for inverse kinematics solution of redundant modular robots, with which the joint limits can be avoided, is presented in this paper. According to the characteristic of robot global wrist organ, the position and pose of the robot tag end can be resolved separately, therefore the computing time is reduced without decreasing the solution accuracy. Recently, an Intravehicular Robot Service System's Ground Demonstration for Space Station has been built in the Space Robot Lab of Bupt, and the operation object of the demonstration is a 9-DOF modular reconfigurable robot. Through the experiments of pulling drawers and pressing buttons by the 9-DOF robot, the accurate and real-time solutions are given to show the applicability and effectiveness of the proposed algorithm. The experiment results demonstrate that the positioning accuracy is up to ±2.0 mm and single-step computing time is less than 1 ms.A machine learning based approach of robust parameter design
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060802
Dual response surface methodology (DRSM) and nonparametric methodology (NPM) are main approaches used to achieve robust parameter design (RPD) of industrial processes and products. When the relationship between influential input factors and output quality characteristic of a process is very complex, both approaches have their limitations. For DRSM, it fails to fit the real response surfaces of process mean and variance by using the second order polynomial models. For NPM, it is hard to optimize parameters of fitting equation, and it needs more experiments as well. From a machine learning perspective, this paper generalizes RPD as a restricted active learning problem and proposes a new approach to achieve it. It fits process mean and variance responses by support vector machines (SVM), and then optimizes levels of design parameters by genetic algorithm. In order to reduce experiment times, the influence of priori knowledge on generalized error of fitting model is studied. Then a prior knowledge based experiment design is developed. Moreover, the approach selects the form of kernel function and optimizes parameters in SVM by comparing the upper bounds of generalized error of different SVM models without extra samples. The example given in the paper shows that, the generalized error and the experiment times of the approach decrease by no less than 45% and 39% respectively, compared with traditional approaches. All these results demonstrate the adaptability and superiority of the approach proposed in the paper.Research on assembly modeling and sequence planning based on features
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060795
To take full advantage of CAD models information of product for assembly sequence planning (ASP), a product hierarchy model based on assembly features was presented. In this model, both single parts and subassemblies were united as a basic assembly unit (AU) to form a product. By constructing the assembly feature matrixes (AFM), the information of degree of freedom (DOF) for an AU could be found out by analyzing the AFM and the probability of removing this AU from assembly could be also ascertained. Based on the hypothesis that an AU can be disassembled then be assembled, the disassembly heuristic rules, the global disassembly direction and the connecting relations of different AU were analyzed. With these analyses the disassembly/assembly sequence of an assembly was acquired. Considering the selecting principle of basic AU, the parallel degree of assembly sequence and the number of reorientation in assembling process, the assembly sequence was optimized by fusing these factors. Taking a ball-valve model as example, these theories and its achieve process was described.Kinematics analysis of active reflector supporting mechanism for FAST
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061084
In the application of active reflector units supporting mechanism for a large spherical radio telescope (five-hundred meter aperture spherical radio telescope: FAST), a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees rotation and one degree translation is investigated. In this paper, the mechanism is described in detail and its inverse kinematics solutions are derived. The parasitic motion of this mechanism is analyzed, and the relationships between the parasitic motions and independent motions of the mechanism are illustrated, followed by the Jacobian matrix of the velocity equation. The distribution of conditioning index on the workspace of the mechanism is obtained. And the workspace of the mechanism is numerically generated. The analysis results prove that the parasitic motion is neglectable compared to the independent motion in this application and the mechanism can be used as the supporting mechanism of spherical radio telescope.Undirected graph model of product family architecture for mass customization
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060799
The reasonable model of product family architecture is a premise for effectively implementing product family design. Two kinds of vertexes are defined in product fundamental modules with graph theory. Based on the relationships between the defined vertexes, three kinds of constraints are defined, which include fundamental composing constraints, differentiation customizing constraints and differentiation matching constraints. On the basis of the above-defined, an undirected graph model of product family architecture is proposed, and then the relation matrix and the customization algorithm are developed. Finally, the proposed model and algorithm are validated by taking the wheel loader as an example. The results show that not only can the model rationally express customization of individual products and effectively filter redundancy information, but also the customization algorithm can improve the customization efficiency and reduce the customization work.Research on real-time error measurement in curve grinding process based on machine vision
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060841
A machine vision image measurement system for online monitoring of the wheel wear degree during the curve grinding process is designed and developed. The measurement apparatus and its principle of operation are introduced in detail. Real-time image of work piece and wheel in the grinding zone is gathered by CCD camera installed in the grinder. For the purpose of increasing the measurement precision, a new edge detection approach combining Zernike moments operator with Prewitt operator is proposed. The edge of the finished work piece is located with sub-pixel level accuracy, and then the machining error of the work piece is calculated on-line by comparing with the theoretical curve of the work piece. An application of its validity and the experimental results are also given. Experimental results demonstrate the proposed measurement method in this paper is effective, and its detection precision and results are reasonable.Semantic net knowledge model in auto-reasoning process plan
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060930
In process planning, how to use manufacturing features to obtain an optimal process planning is the essential of computer-aided process planning (CAPP) system. The main goal of CAPP system is to translate the manufacturing features into machining operations and sequence the machining operations of the part in a feasible (by some technological constraints) and effective (by some economical standards) order. In this paper, we construct a process-planning model (PP model), which consists of three parts: the features framework, the precedent relation net and the sequencing mathematical model. The features framework makes a mapping from manufacturing features into machining operations. A semantic net named the precedence-relations-net reflects the precedence relationships among the machining operations. And we employ the vectors and the matrixes to construct a mathematical sequencing model. Firstly, a part is decomposed into several basic geometrical units, namely, U1,U2,...UN. For each unit - Ui, two vectors, named Fi and Pi represents the features and machining operations of Ui. Finally, a matrix named PP is used to memorize the process plan, and a matrix; namely, PO (performing objects) represents the object of machining operations.Architecture singularity analysis for a class of parallel manipulators
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061097
The present investigates the architecture singularity of a class of parallel manipulators. In general, singularity of parallel manipulators can be categorized into inverse and forward kinematic singularities. Based on the kinematics, the inverse Jacobian matrix of the parallel manipulator is factorized into three parts as: limb length diagonal matrix, structure parameter matrix and the motion parameter matrix so that the singularity analysis becomes convenient. Because each limb length is not zero, there does not exist inverse singularity. Only forward kinematic singularity exists in the parallel manipulators. The forward kinematic singularity is divided into architecture singularity and motion singularity. Architecture singularity is global and results in no solutions for forward kinematics. It should be avoided at the design stage. The class of parallel manipulators becomes architecture singularity as long as their six vertices of the platform are placed in a quadratic curve. Since the architecture singularity can be algebraically expressed, the constraints to avoid the undesired effects of the architecture singularity can be straightforwardly implemented for the design of the parallel manipulators and the planning of workspace and trajectory.Kinematics and dynamics analysis of maintenance manipulator
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061082
A new approach is developed to model dynamic behaviors of robot manipulator. The process is realized through equivalent elements and the equivalent system of forces. Firstly, the concept of element pseudo-mass matrix is proposed based on the equivalent principle of elements, then establishes pseudo-mass matrix of the equivalent system through assembling units normatively, based on finite element thought. Secondly, dynamical modeling equations are produced base on the generalized dynamic equation and concepts of the equivalent system and vector of force. The expression is concise, standard and convenient for using with computer normatively. At last, the approach is used to generate the dynamic equations of five-DOF maintenance manipulator, and the dynamic response of the manipulator is obtained. The results of simulation are the same as those of ADAMS.Analysis of the tool-chip contact length incorporating the effects of shear strain
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060973
In metal cutting, it has been acknowledged that the tool-chip contact length significantly affects many aspects of machining, such as chip formation, cutting temperatures, cutting forces, tool wear and tool life. As a result, it has great influence on finished surface quality and accuracy. A slip-line model of tool-chip contact length with two rake faces tool is simplified in this paper, and based on Dewhurst and Collins's matrix technique for numerically solving slip-line problems and Powell's algorithm of nonlinear optimization, the mathematical formulation of the tool-chip contact length is resolved. Because of the variation of the work material's shear strain, it must be taken into account the effect of the shear strain on the tool-chip contact length. From the formulation of the tool-chip contact length, it can be seen that tool geometry, cutting conditions and the stress boundary conditions have great influence on the tool-chip contact length. In addition, the predicted ratio of tool-chip contact length L/t is in good agreement with theoretical and experimental results gained by other researchers.Fuzzy decoupling control of melt temperature and melt pressure for plastic electromagnetism dynamic extruder
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061076
The plastic electromagnetism dynamic extruder has gained wide applications because of its novel structure and fine engineering performance. In the polymer processing, melt temperature and melt pressure control is crucial to the quality of the extruded product. A new fuzzy decoupling control algorithm of melt temperature and melt pressure for the novel extruder is introduced in the transfer function matrix system, which is obtained through the experimental data with system identification. The control system is implemented on programmable computer controller. Experimental results show melt temperature and melt pressure can be successful individually controlled by the heater power and the screw speed. The good system performance verifies the control strategy's validity.A new 3D ray-tracing propagation model
http://dl-live.theiet.org/content/conferences/10.1049/cp_20020389
Various ray-tracing methods have been developed for wireless propagation predication. Most of them are hybrid 2D and 3D models (see Athanasiadou, G.E. and Nix, A.R., IEEE Trans. Veh. Technol., vol.49, no.4, p.1152-68, 2000; Liang, G. and Bertoni, H.L., IEEE Trans. Antennas Propagat., vol.46, no.6, p.853-63, 1998). They assume the walls are vertical, roofs and ceilings are horizontal and the ground is flat. These assumptions are not always true. This paper presents a new 3D ray-tracing method based on 3D geometry and vector calculations. Propagation path concepts of triangular reflection pyramid ray-tubes and diffraction hollow cones have been developed. This method applies to different terrains and both indoor and outdoor environments. Virtual reality (VR) is used to visualise the environments and line-of-sight (LOS) and non-LOS signal paths and allows us to verify the methods we used.Worksheet-based “keep on trying” tests for foundation mathematics
http://dl-live.theiet.org/content/conferences/10.1049/ic_20010032
The worksheet-and-test approach has proved a useful tool in improving students' basic algebra. It encourages continued practice. Advantages have been: relatively low staffing time required after initial setup; can easily be tailored to provide support for other modules; self-timed approach is popular with students; and the worksheets are useful revision material for other students. The main problem has been the necessity to bar students who already have A-level mathematics from taking the module as an easy option. (5 pages)A direct method for frequency stability assessment of power systems
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000408
A direct method for frequency stability assessment of power systems is proposed in this paper, which is based on the latest Jacobian matrix of the Newton-Raphson load flow calculation. The method can directly calculate the final system frequency after the last switching without step-by-step integral, and the system frequency stability can be determined. The proposed method has been applied to the New England 68-bus system, and the results show that the method is of good accuracy and the fine prospect of online application.Using temporal information in input features of neural networks
http://dl-live.theiet.org/content/conferences/10.1049/cp_19991153
In many applications neural networks use temporal information, i.e. any kind of information related to a time series. Temporal information can be either represented within a network using a dynamic network paradigm or embodied in the input features of a network. The paper presents two methods for an explicit use of temporal information in input features. A least-squares approximation of signals with orthogonal polynomials is used to infer information about trends in a signal (average, increase, curvature, etc.). Input information about the length of a time series up to a certain point in time may act as a decreasing threshold making the network more and more sensible to changes in other input features. The advantages of the two methods are demonstrated by means of a real-world application example, tool wear monitoring in turning.Computer-aided quality control of radiological systems
http://dl-live.theiet.org/content/conferences/10.1049/ic_19981041
The problem of quality control of radiological systems is discussed in relation to the management and quantitative tools normally applied to it. An alternative approach is to consider the problem in terms of a control loop in which the sets of quality control measurements are compared with their previous values in the context of a numerical model of the system to produce quantitative corrections. A preliminary study of the method applied to mammographic quality control is discussed. By modelling the system with an appropriate set of simultaneous linear equations relating changes in the controlled parameters to the quality control measurements obtained, it is possible to identify quantitative changes in the controlled parameters from measured quality control data using the inverse of the model in matrix form. This method essentially encapsulates knowledge about the system in the form of the linear model. This is distinct from current work attempting to apply artificial intelligence knowledge-based techniques to the problem. (4 pages)Exact algebraic pole-zero cancellation using symbolic mathematical computation
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980212
Modern symbolic computational systems which perform automated manipulation of mathematical variables offer insights during modelling and problem solving which remain otherwise partially or wholly obscured to the analyst. The classic inverted pendulum model is re-visited, and previous work concerning the systems controllability is investigated. In particular, the ability of the software to factorise complicated multivariable polynomials is exploited to identify, in fully general form, the anticipated pole-zero term cancelling throughout the transfer functions of the system when it is in a state of un-controllability. All three balancing problems associated with the two link pendulum are treated, and the phenomenon of non-controllability is examined in this way along the entire `curve of non-controllability' which, within the approximation of linearity, theoretically exists for each when damping is present.An LMI-based machining logic fusion
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980283
Discusses the issues of robust machining process controller synthesis. In practical cases, operating conditions have strong effects on the process dynamics, and it is very difficult to use a fixed controller to achieve a satisfactory performance. Here, a fuzzy logic inference mechanism is introduced to adjust the controller according to the online measurements of operating variables which define the operating conditions or operating points of the processes, and a linear matrix inequality (LMI) based hybrid approach is developed to achieve robust properties against modelling errors, uncertainties, disturbances, and inaccuracy of online measurements. The simulation results of a design example (an end milling process control) shows that robust stability and satisfactory performance have been achieved.Implementation of balanced realization algorithms in a symbolic environment
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980420
Calculation of controllability and observability Gramians, and the determination of balanced realizations are considered in a symbolic framework. Two different approaches to balancing transformations are explained step by step, and more efficient, simple and numerically stable algorithms based on these two approaches have been implemented. An example taken from the literature is presented in order to illustrate the superiority of the symbolic implementations.Nonlinear identification of a turbogenerator by local model networks
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980445
Local model (LM) networks are applied to the identification of the global nonlinear dynamics of a turbogenerator excitation loop. A hybrid algorithm is used to optimise the learning process. Extensive use of plant `a priori' information is used to form an initial estimate for the nonlinear interpolation regions. The resulting model was found to describe the behaviour of the nonlinear generator-exciter system over its entire operating range.Fault isolation using inverse sensitivity analysis
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980359
In this paper, a new fault isolation method is proposed. This method is based on the inverse sensitivity analysis. The idea is to identify input command and parameter perturbations using the information provided by the output trajectory deviation and the sensitivity matrices. The estimated perturbation is then used for fault isolation and possibly system reconfiguration. The proposed fault isolation method has been applied to a simulated aircraft control system and the results confirm the effectiveness of this sensitivity analysis approach.A frequency domain toolbox using interval arithmetic
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980376
In linear control theory the frequency domain approach and the state-space approach are equivalent. But for the implementation of numerical algorithms the use of state-space equations is preferred. To avoid the numerical problems caused by a polynomial arithmetic, the use of an interval arithmetic with variable length of the mantissa is suggested. Some basic algorithms for polynomial and transfer-function matrices implemented in interval arithmetic are stated. A control example shows the feasibility of this method.Secondary measurement selection and scaling sensitivity
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980380
Often in process control, it is necessary to use extra measurements, or so-called secondary outputs for monitoring processes. Traditionally, the selection of these outputs is based on criteria which need to be calculated scheme-by-scheme resulting in a combinatorial problem. In this work, it is shown that these secondary outputs can be selected using an efficient measure, the output effectiveness (OE) when the outputs are scaled in a special way. This method does not need any scheme-by-scheme calculation so that the combinatorial problem is avoided. Since the OE measure is dependent on output scaling, its sensitivity to this scaling is also discussed. A scaling sensitivity matrix is derived for the designer to quickly determine the effect of different choices of scaling factors on the OE measure. This information can then be used for efficient output selection. This is demonstrated on a distillation example.Symbolic algebra toolbox for the design of dynamical adaptive backstepping controllers
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971293
The backstepping control design algorithms described by Krstic et al. (1995) provide a systematic framework for the design of regulating strategies suitable for large classes of nonlinear uncertain systems. However, the equations arising at the successive steps are usually too complicated to be computed by hand. We consider here a symbolic toolbox which implements a general algorithm for the design of dynamic adaptive controllers following the basic ideas of backstepping with tuning functions without transformation into canonical forms. This algorithm is applicable to observable minimum phase systems not necessarily in triangular form and also to uncertain nonlinear systems in triangular forms. Additionally the control can be generated by a sliding mode approach. (3 pages)Local model networks for nonlinear system identification
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970785
Local model networks represent a nonlinear dynamical system by a set of locally valid submodels across the operating range. Training such feedforward structures involves the combined estimation of the submodel parameters and those of the interpolation functions. The paper describes a new hybrid learning approach for local model networks that uses a combination of singular value decomposition and second order gradient optimization. A new nonlinear internal model control scheme is proposed which has the important property that the controller can be derived analytically. Simulation studies of a pH neutralization process confirm the excellent modelling and control performance using the local model approach. (3 pages)Parallel transient stability analysis on distributed memory message passing multiprocessors
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971849
This paper presents a new parallel-in-space algorithm for power system transient stability simulations. The nonlinear differential equations are discretized by applying the trapezoidal rule and solved together with the nonlinear algebraic equations for each time step. A network partitioning scheme, which is based on the subdivision of the factorization path tree of the network matrix, is proposed to exploit the parallelism-in-space of the transient stability problem. The parallel version of the very dishonest Newton (VDHN) method, in which the parallel algorithm for solving large sparse network matrix equations is incorporated, is developed and tested on a distributed memory message passing multicomputer. Test results on a sample power system are presented to show the performance of the proposed algorithm.Analytical determination and simulation of frequency response functions of a structure with a rotating component for the purpose of system identification for condition monitoring of machinery
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970192
This paper outlines the method of obtaining the frequency response functions of a rotor system with strong gyroscopic effect and simulating it using MATLAB. The rotating effect causes unsymmetry in the system matrices, resulting in complexity in decoupling the mathematical models of the system for the purpose of modal analysis. A different method is therefore required, which can handle general system matrices rather than symmetrical matrices, which is normal for passive structures. In this paper the mathematical model of an overhung rotor system with two degrees of freedom is expressed. This model is then used to extract the right and left eigenvalues/vectors and subsequently the frequency response functions are extracted and simulated. MATLAB is used to carry out such simulation, since it has good capability for eigen analysis and also good graphical facility. The reflection of splitting of critical speeds of a rotating rotor on the frequency response functions are shown.Input screening method for disturbance rejection
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960602
The control structure selected has a strong effect on the performance of a closed loop system with respect to its disturbance rejection capability. But the methods used for its selection usually result in a combinatorial problem. To overcome this difficulty, an input pre-screening criterion, the input-disturbance alignment (IDA) measure, is proposed. Some important features of the new indicator and its relationship with other well-known controllability measures are presented. The case study included shows that the IDA can be used for efficient selection of manipulated variables from a large number of candidate inputs. These then form the best control structure for disturbance rejection.Numerical simulation of power static converters: diagonalization method of the dynamical matrix
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960966
The authors propose a method of simulation of static power converters which uses the diagonalization technique of the dynamical matrix to decrease simulation time. This technique leads to a simple analytical solution, allowing a reduction in calculation time. This method allows new independent state variables, and a reduction in the system order. The authors verify that for the structures analyzed, they have observed, on average, a gain in calculation time of the matrix exponential of about 97% using the matrix diagonalization method. The developed algorithm is shown to be a powerful, efficient and, in certain cases, an essential tool for the study of applications in power electronics.A fault isolation method based on parity equations with application to a lathe-spindle system
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960572
A robust fault isolation method is proposed in this paper, which uses state-space parity equations to isolate structured faults. Numerically robust calculations are used to find certain matrices. A workable sufficient condition is given for high threshold isolability. The method is applied to a lathe-spindle system which demonstrates the effectiveness of the method.New developments in batch process input profile optimisation
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960651
A novel algorithm for solving nonlinear discrete time optimal control problems with model-reality differences is presented. The technique uses dynamic integrated system optimisation and parameter estimation (DISOPE) which achieves the correct optimal solution in spite of deficiencies in the mathematical model employed in the optimisation procedure. A new method for approximating some Jacobian trajectories required by the algorithm is introduced. It is shown that the iterative procedure associated with the algorithm naturally suits applications to batch chemical processes.Symbolic CAD system for algebraic approach on MATLAB - Symbolic Control Toolbx
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960747
This paper has dealt with the prototype symbolic manipulation CAD system-Symbolic Control Toolbox-running on MATLAB. The functions are implemented in the conventional numerical CAD system. Compared with numerical CAD our system has the following advantages: there exists no roundoff or truncated error; the adopted algorithms are so systematic and well-defined that functions are implemented easily over various rings corresponding to control theories by using the symbolic computation; and the results of the system can be extended easily to n-dimensional system theories.The use of symbolic computation for the problem of stabilisation via small order feedback controllers
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960516
The problem of stabilising a MIMO plant via output feedback controllers of a given degree was recently tackled via linearisation around some special degenerate compensators. This can be numerically implementated as an ɛ-perturbation method. The solution is in the form of a perturbation series which can be constructed by repetitively solving a set of linear equations, coming from the expansions (in ɛ and s) of the original pole placement equations. This expansion can be done almost trivially in any symbolic language using standard symbolic commands. The code is only a few lines long and can be done by the nonexpert. There is no need to understand the algebra of the problem, which involves tensor, polynomial algebra and some combinatorics since the load of the expansion is taken solely by the symbolic package. (4 pages)Controllability of SVD control structures for ill-conditioned plants
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960605
A conventional diagonal controller can be designed from very limited process information. In the SVD control structure, a diagonal controller is applied to orthogonal sums and differences of the inputs and outputs. In this work, the process knowledge needed for the design of an SVD controller is analyzed. In contrast to conventional decentralized controllers, the SVD controller can compensate for the process directionality of ill-conditioned processes. The dual composition control problem of distillation columns is of particular interest, since reliable models for these columns are quite hard to obtain.Quartz oscillators: deriving oscillation condition by symbolic calculus
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960092
This paper presents the method used to derive the oscillation condition by using symbolic calculus. The program is based on the full nonlinear Barkhausen criterion method. The behaviour of an oscillator is described by a complex polynomial called the characteristic polynomial. This polynomial enables us to calculate the steady state features of the oscillation as well as the differential equation for transient analysis in the time domain. The literal determination of this characteristic polynomial involves lengthy algebraic calculations and cannot be done by hand as the electronic oscillator circuit involves too many components. We recently developed a formal calculus program allowing to automatically obtain all necessary equations for oscillation analysis. We propose new methods to calculate them in an optimal form.TLM time-domain modelling and the use of windowing profiles for frequency-domain transformations applied to microwave cavity resonators
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960213
This paper presents developments made to the TLM method in the time to frequency-domain transformation of the impulse response solution. An improvement to the technique by which the three-dimensional TLM time-domain method is post-processed is presented. It is shown that the selective choice of a particular data windowing profile plays a significant role in the accuracy of the results, clarity of output response and the extraction of the S-parameters.Analysis and measurement of the ‘Hartley effect’ in HF curtain arrays
http://dl-live.theiet.org/content/conferences/10.1049/ic_19951269
This paper describes a method for predicting the operating performance of an array (input match, power split between the stacks and the voltages on components) based on a 4-port S-parameter measurement and on a model of the array's bay feeder network. The measured S-parameters are converted to an admittance matrix (Y-parameters) and used to terminate an equivalent circuit of the array's bay feeder. The resulting network is analysed using a method based on chain matrices. The correlation between measurement and prediction of the arrays performance in the straight ahead condition, and at small slew angles is good. However, this deteriorates as the angle of the slew is increased. The model is based on a balanced network and it is thought the errors between measurement and prediction, at large slew angles, can be attributed to unbalanced currents in the array. (7 pages)Robust multivariable feedback design for an extractive distillation column
http://dl-live.theiet.org/content/conferences/10.1049/cp_19940369
In this paper, multivariable quantitative feedback theory (QFT) techniques are used to synthesize a robust feedback system for an extractive distillation column with a vaporous sidestream. The simplified state space model of Gilles and Retzbach (1983) for an extractive distillation column exhibiting sharp temperature profiles is adopted here. Large uncertainty of +20% is assumed in three key matrix elements of this model. The feedback design problem is to find the controller and prefilter matrices such that the stated tracking specifications are met, over the entire range of model parametric uncertainty. The fourth MIMO QFT technique of Yaniv and Horowitz (1986) is used to solve the design problem. The design is verified through extensive simulations in both frequency and time domains, for several plants picked from the plant uncertainty set. In all cases, the results obtained are quite satisfactory.