- Sort by:
- Newest first
- Titles A to Z

### Filter by subject:

- Computer and control engineering [135]
- Systems and control theory [135]
- Mechanical and production engineering [135]
- General topics in manufacturing and production engineering [135]
- General support functions [135]
- Engineering mathematics and numerical techniques [135]
- Algebra [135]
- Mathematical techniques [133]
- Algebra [129]
- Electrical and electronic engineering [70]
- [69]
- http://iet.metastore.ingenta.com/content/subject/b0200,http://iet.metastore.ingenta.com/content/subject/b0210,http://iet.metastore.ingenta.com/content/subject/c3000,http://iet.metastore.ingenta.com/content/subject/c1300,http://iet.metastore.ingenta.com/content/subject/c3300,http://iet.metastore.ingenta.com/content/subject/e1000,http://iet.metastore.ingenta.com/content/subject/c7000,http://iet.metastore.ingenta.com/content/subject/c7400,http://iet.metastore.ingenta.com/content/subject/e1500,http://iet.metastore.ingenta.com/content/subject/a,http://iet.metastore.ingenta.com/content/subject/a0000,http://iet.metastore.ingenta.com/content/subject/a0200,http://iet.metastore.ingenta.com/content/subject/a0210,http://iet.metastore.ingenta.com/content/subject/c1310,http://iet.metastore.ingenta.com/content/subject/c1340,http://iet.metastore.ingenta.com/content/subject/e1550,http://iet.metastore.ingenta.com/content/subject/e2000,http://iet.metastore.ingenta.com/content/subject/c4000,http://iet.metastore.ingenta.com/content/subject/c1320,http://iet.metastore.ingenta.com/content/subject/e2200,http://iet.metastore.ingenta.com/content/subject/c7410,http://iet.metastore.ingenta.com/content/subject/e0210l,http://iet.metastore.ingenta.com/content/subject/c1160,http://iet.metastore.ingenta.com/content/subject/c1200,http://iet.metastore.ingenta.com/content/subject/c1330,http://iet.metastore.ingenta.com/content/subject/e0210e,http://iet.metastore.ingenta.com/content/subject/c1180,http://iet.metastore.ingenta.com/content/subject/c4100,http://iet.metastore.ingenta.com/content/subject/e0210g,http://iet.metastore.ingenta.com/content/subject/c3100,http://iet.metastore.ingenta.com/content/subject/c7420,http://iet.metastore.ingenta.com/content/subject/c3120,http://iet.metastore.ingenta.com/content/subject/c4130,http://iet.metastore.ingenta.com/content/subject/e3000,http://iet.metastore.ingenta.com/content/subject/e3600,http://iet.metastore.ingenta.com/content/subject/b0250,http://iet.metastore.ingenta.com/content/subject/b0290,http://iet.metastore.ingenta.com/content/subject/b8000,http://iet.metastore.ingenta.com/content/subject/c3350,http://iet.metastore.ingenta.com/content/subject/c1140,http://iet.metastore.ingenta.com/content/subject/c1340k,http://iet.metastore.ingenta.com/content/subject/c3355,http://iet.metastore.ingenta.com/content/subject/c3390,http://iet.metastore.ingenta.com/content/subject/e0210j,http://iet.metastore.ingenta.com/content/subject/b0290f,http://iet.metastore.ingenta.com/content/subject/c1220,http://iet.metastore.ingenta.com/content/subject/c3360,http://iet.metastore.ingenta.com/content/subject/c7410b,http://iet.metastore.ingenta.com/content/subject/b8100,http://iet.metastore.ingenta.com/content/subject/c6000,http://iet.metastore.ingenta.com/content/subject/c6100,http://iet.metastore.ingenta.com/content/subject/e1520,http://iet.metastore.ingenta.com/content/subject/e2100,http://iet.metastore.ingenta.com/content/subject/e2230,http://iet.metastore.ingenta.com/content/subject/b0260,http://iet.metastore.ingenta.com/content/subject/b8110,http://iet.metastore.ingenta.com/content/subject/c3120c,http://iet.metastore.ingenta.com/content/subject/c3200,http://iet.metastore.ingenta.com/content/subject/c4200,http://iet.metastore.ingenta.com/content/subject/c5000,http://iet.metastore.ingenta.com/content/subject/c7420d,http://iet.metastore.ingenta.com/content/subject/e0400,http://iet.metastore.ingenta.com/content/subject/e0410,http://iet.metastore.ingenta.com/content/subject/e1525,http://iet.metastore.ingenta.com/content/subject/b0240,http://iet.metastore.ingenta.com/content/subject/b1000,http://iet.metastore.ingenta.com/content/subject/c1140z,http://iet.metastore.ingenta.com/content/subject/c1340b,http://iet.metastore.ingenta.com/content/subject/c4240,http://iet.metastore.ingenta.com/content/subject/c5200,http://iet.metastore.ingenta.com/content/subject/c3390m,http://iet.metastore.ingenta.com/content/subject/c7410d,http://iet.metastore.ingenta.com/content/subject/b1100,http://iet.metastore.ingenta.com/content/subject/b1130,http://iet.metastore.ingenta.com/content/subject/b1130b,http://iet.metastore.ingenta.com/content/subject/b6000,http://iet.metastore.ingenta.com/content/subject/c1290,http://iet.metastore.ingenta.com/content/subject/c1340e,http://iet.metastore.ingenta.com/content/subject/c4240c,http://iet.metastore.ingenta.com/content/subject/e2210,http://iet.metastore.ingenta.com/content/subject/e2220,http://iet.metastore.ingenta.com/content/subject/b0100,http://iet.metastore.ingenta.com/content/subject/b0170,http://iet.metastore.ingenta.com/content/subject/b0240z,http://iet.metastore.ingenta.com/content/subject/b1200,http://iet.metastore.ingenta.com/content/subject/c1120,http://iet.metastore.ingenta.com/content/subject/c1230,http://iet.metastore.ingenta.com/content/subject/c1340g,http://iet.metastore.ingenta.com/content/subject/c3360l
- b0200,b0210,c3000,c1300,c3300,e1000,c7000,c7400,e1500,a,a0000,a0200,a0210,c1310,c1340,e1550,e2000,c4000,c1320,e2200,c7410,e0210l,c1160,c1200,c1330,e0210e,c1180,c4100,e0210g,c3100,c7420,c3120,c4130,e3000,e3600,b0250,b0290,b8000,c3350,c1140,c1340k,c3355,c3390,e0210j,b0290f,c1220,c3360,c7410b,b8100,c6000,c6100,e1520,e2100,e2230,b0260,b8110,c3120c,c3200,c4200,c5000,c7420d,e0400,e0410,e1525,b0240,b1000,c1140z,c1340b,c4240,c5200,c3390m,c7410d,b1100,b1130,b1130b,b6000,c1290,c1340e,c4240c,e2210,e2220,b0100,b0170,b0240z,b1200,c1120,c1230,c1340g,c3360l
- [69],[66],[51],[50],[49],[48],[42],[42],[40],[38],[38],[38],[36],[35],[31],[31],[27],[25],[22],[22],[21],[21],[20],[19],[19],[19],[18],[18],[18],[16],[16],[15],[15],[15],[14],[13],[13],[13],[13],[12],[12],[12],[12],[12],[11],[11],[11],[11],[10],[10],[10],[10],[10],[10],[9],[9],[9],[9],[9],[9],[9],[9],[9],[9],[8],[8],[8],[8],[8],[8],[7],[7],[6],[6],[6],[6],[6],[6],[6],[6],[6],[5],[5],[5],[5],[5],[5],[5],[5]
- /search/morefacet;jsessionid=28ttaob3l39fs.x-iet-live-01
- /content/searchconcept;jsessionid=28ttaob3l39fs.x-iet-live-01?option1=pub_concept&facetOptions=2+3&option2=pub_concept_facet&sortField=prism_publicationDate&pageSize=50&sortDescending=true&facetNames=pub_concept_facet+pub_concept_facet&value1=e0210a&operator2=AND&value2=c1000&operator3=AND&option3=pub_concept_facet&value3=
- See more See less

### Filter by content type:

### Filter by publication date:

- 1997 [9]
- 2015 [9]
- 1996 [8]
- 1998 [8]
- 2012 [8]
- 2013 [8]
- 2002 [7]
- 2006 [7]
- 2017 [7]
- 1995 [5]
- 2009 [5]
- 2018 [4]
- 1994 [3]
- 2010 [3]
- 2014 [3]
- 2016 [3]
- 2019 [3]
- 1988 [2]
- 2007 [2]
- 1978 [1]
- 1983 [1]
- 1990 [1]
- 1992 [1]
- 1993 [1]
- 1999 [1]
- 2000 [1]
- 2001 [1]
- 2005 [1]
- 2008 [1]
- See more See less

### Filter by author:

- Yang Liu [3]
- Ai-Guo Wu [2]
- D. Rossiter [2]
- G. Lightbody [2]
- G.W. Irwin [2]
- H. Wang [2]
- Hamid Reza Karimi [2]
- J.-S. Hong [2]
- Mohammed Chadli [2]
- N. Munro [2]
- Y. Cao [2]
- A. Mahmood [1]
- A. Moeini [1]
- A. Nacaroğlu [1]
- A. Van Londersele [1]
- A. Zolghadri [1]
- A.C. Zambroni de Souza [1]
- A.D. Hope [1]
- A.G. Wills [1]
- A.K. Swain [1]
- A.M. Al-Ahmari [1]
- A.M. Al-Kandari [1]
- A.M. Leite da Silva [1]
- A.R. Wood [1]
- A.S. Morris [1]
- A.S.I. Zinober [1]
- A.Y. Zomaya [1]
- Ahmed Alsaedi [1]
- Alessandro Della Bona [1]
- Ali Javadi [1]
- Amin Nobakhti [1]
- B. Açıkmeşe [1]
- B. Baran [1]
- B. De Deckere [1]
- B. Sick [1]
- Baixiang Luo [1]
- Baoli Ma [1]
- Bei Chen [1]
- Biao Wang [1]
- Biao Zhang [1]
- Bin Hu [1]
- Bin Jiang [1]
- Boming Zhang [1]
- Boris Almonacid [1]
- Bowen Li [1]
- Broderick Crawford [1]
- C. Hong [1]
- C. Vinatoru [1]
- C.A. Woodham [1]
- C.C. Fung [1]
- C.J. Kotre [1]
- C.K. Cheung [1]
- C.M. Shen [1]
- Chao Li [1]
- Chen Renren [1]
- Chen Yushu [1]
- Cheng Tan [1]
- Chiou-Yng Lee [1]
- Chiu-Chin Wu [1]
- Chuanda Qi [1]
- Chun-Sheng Yang [1]
- Chunqi Chang [1]
- Congzhi Huang [1]
- Cui Nan [1]
- Cui Qing'an [1]
- D. De Zutter [1]
- D. Owens [1]
- D. Vande Ginste [1]
- D.L. Ma [1]
- D.M. Falcao [1]
- D.N. Shields [1]
- D.P. Atherton [1]
- D.P. Scharf [1]
- D.Y. Chao [1]
- D.Z. Fang [1]
- Daizhan Cheng [1]
- Dandan Xu [1]
- Derui Ding [1]
- Dingli Yu [1]
- Dongpu Cao [1]
- Dounia Saifia [1]
- E. Fuchs [1]
- E. Iancu [1]
- E. Kaszkurewicz [1]
- Elena Ficara [1]
- Eugenio Alcala [1]
- F. Cazaurang [1]
- F.Y. Hadaegh [1]
- Fabián Aspée [1]
- Fang Liu [1]
- Fang Minglun [1]
- Fei Han [1]
- Fei Hao [1]
- Fei He [1]
- Feng Yan [1]
- Francesca Malpei [1]
- Francisco Palacios-Qui nonero [1]
- Fuad Alsaadi [1]
- FuadE. Alsaadi [1]
- G. Fisher [1]
- See more See less

### Filter by access type:

The lifting methodology can be used for simplifying the closed-loop stability study of a system in which the measurement data are acquired at different frequencies. This is because the lifting operators allow treating this kind of systems as if there is only one control frequency, which reduces the complexity of the problem in a very important way. The four-rotor microhelicopter designed by the authors, whose control is faced, is a nonlinear plant with sensors operating at two different frequencies. First, the system is linearised cancelling the rotors dynamics. Then, the authors implement a model reference adaptive control structure for identifying the gains of the linear reference plant and performing the adaptive control of the microhelicopter. At this point, the system stability study is carried out by just computing the eigenvalues of the closed-loop states matrix thanks to the lifting operators.

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)

This part reviews complex-variable algebra.

Computation of elementary siphons proposed by Li *et al.* is essential for deadlock control and expensive since complete siphon enumeration of the Petri net is needed, and the number of strict minimal siphons (SMS) grows quickly and exponentially with the size of the net. They assumed that the siphon constructed from each resource circuit is an elementary one and proposed a polynomial algorithm to compute elementary siphons. However, the author demonstrates a counter example where there may be an exponential number of resource circuits. Hence, constructing elementary siphons from resource circuits will result in an exponential number of elementary siphons, which is wrong. The author then develops a polynomial algorithm to find elementary siphons, which also constructs all SMS on the way. This is because, in the method proposed by Li *et al.*, a linear algebraic expression must be established for each dependent siphon, which implies, all SMS must be located. However, all elementary siphons with polynomial complexity can be located.

Motivated from some practical industrial processes, an optimal fault tolerant control (FTC) scheme is studied for stochastic continuous dynamic systems with time delays using output probability density functions (PDFs). Different from the classical FTC problems, the measured information is the PDFs of system output rather than its value, where the B-spline expansion technique is applied so that the output PDFs can be formulated in terms of the dynamic weightings. For the established weighting system with nonlinearities, uncertainties and time delays, the concerned FTC problem is investigated by using robust optimisation techniques. A linear matrix inequality (LMI) based feasible FTC method is presented to ensure that the fault can be well estimated and compensated, where the generalised *H*_{∞} performance is optimised for the time-delayed systems with the non-zero initial condition and the truncated norms. Simulations for a model in the paper-making process are given to demonstrate the efficiency of the proposed approach.

A formulation of stability for formation flying spacecraft is presented. First, a formation is defined via control interactions between the spacecraft. Then, stability is formulated on the basis of input-to-output stability with respect to a partitioning of the formation dynamics. The particular form of input-to-output stability used here is based on the peak-to-peak gain of a system from its input to its output. This formulation of stability is shown to be useful in characterising disturbance propagation in the formation as a function of the partition interconnection topology, and also in analysing the robustness of sensing, communication and control topologies. Stability analysis results are presented for hierarchical, cyclic and disturbance attenuating formations in terms of the input-to-output gains of the partitions in the formation. Finally, Lyapunov stability analysis results are provided in terms of linear matrix inequalities for a general class of formations.

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.

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.

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.

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.

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.

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.

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_{∞} 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 controller based on first-order decoupled equations of motion for application to rigid serial manipulators is presented. The equations result from a modification of equations expressed in generalised velocity components form. It is shown that using the proposed quasi-velocities i.e. normalised generalised velocity components (NGVCs) leads to differential equations that contain the identity mass matrix (instead of a diagonal matrix). Using the proposed controller and equations written in terms of NGVCs it is possible to obtain information on the system dynamics. The considered controller is stable in the Lyapunov sense. Experimental results obtained on a two-degree-of-freedom manipulator illustrate the effectiveness of the proposed technique.

Transient conditions such as switching operations and faults cause the generation of travelling waves on power transmission lines. Spatial current and voltage distributions on the transmission line are computed in the time domain using the state-space technique. The state-space representations of the transmission lines for short- and open-circuit faults and for various types of terminations are given. The results obtained by the method are compared with the solutions obtained in the frequency domain.

The authors analyse the steady-state behaviour of a class of cross-directional controllers that are pertinent to general web-forming processes. Their analysis is framed in terms of the controllable space prescribed by the interaction matrix and general discrete orthonormal basis descriptions of both the input and output space under the assumption of closed-loop stability. The specific choice of controller defines (whether explicitly or implicitly) an additional assumed controlled space. It is well known that the controllable space determines a lower bound on output variation. They examine the implications of integral action and provide sufficient conditions for the steady-state output variation to achieve this lower bound. They confirm some intuitive results that connect the optimal constrained and unconstrained steady-state solutions for model-based control with no model mismatch. Model mismatch is usually detrimental to steady-state performance. This effect is interpreted in terms of leakage between the controllable and assumed controlled spaces, as well as their respective orthogonal complements.

A

It is of practical interest to identify which processes will benefit significantly from the use of constrained control algorithms such as model predictive control, and which will not. Explicit conditions are derived that identify whether a particular process may benefit from constraint handling. These conditions are also useful for understanding the interactions between design and control for a particular system, especially for actuator placement and selection. The conditions are computable for a large-scale system directly from its transfer function model, a simulation model (e.g. defined by a set of ordinary/partial-differential equations and algebraic conditions), or experimental input–output data. The formulation considers the effects of measurement noise, process disturbances, model uncertainties, plant directionality and the quantity of experimental data. The conditions are illustrated by application to a paper-machine model constructed from industrial data.

Although the full radix-4 CORDIC algorithm is efficient compared to the standard radix-2 version, the scale-factor overhead causes its improvement to be limited. In this work, an algorithm and its associated architecture have been proposed for parallel compensation of the scale factor for the radix-4 CORDIC algorithm in the rotation mode. The proposed method, which makes no prior assumptions about the elementary angles of rotation, reduces the latency from *n* to (*n*/2)+3, where *n* is the precision length in bits, at the cost of a reasonable increase in hardware complexity. The architecture presented relates to the redundant signed-digit number system. The architecture has been modelled in VHDL and simulated to establish its functional validity.

The speed of simulation of power system dynamics has been one of the topics most concerned with on-line security assessment. This paper proposes a new method for forming the constant Jacobian matrix for enhancing the speed of system simulation. By using the constant Jacobian matrix approach in system simulations, both for post-fault and fault-on duration, simulation efficiency is greatly enhanced. Techniques for speeding up the constant Jacobian matrix approach are discussed. Theoretical analysis is presented to demonstrate how the constant Jacobian matrix approach can be extended to a power system with generator controls. Simulation results with the constant Jacobian matrix approach in the 10-generator New England test system and the North China power system are compared with the results obtained by the use of commercial software BPA.

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.

Obtaining the steady-state operation of a power electronic device by means of brute force computer simulation is not feasible in many practical cases. Fast steady-state algorithms that formulate the steady-state problem as a boundary problem and solve it using Newton's method have been proposed to overcome this difficulty. These algorithms are known as shooting algorithms. An extension of the shooting algorithm for piecewise linear circuits is provided. The complete Jacobian matrix that takes into account the switching instants variation is analytically derived for a state variable formulation of the steady-state problem of a piecewise linear circuit. A computer program PWiseSS based on this algorithm is used to solve a previously proposed test circuit of difficult convergence as well as to solve a realistic six-pulse converter of interest to the power electronics engineer.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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)

Sparse-matrix solution is a dominant part of execution time in simulating VLSI circuits by a detailed simulation program such as SPICE. The paper develops a parallel-block partitionable sparse-matrix-solution algorithm which exploits sparsity at the matrix block level as well as within a nonzero block. An efficient mapping scheme to assign different matrix blocks to processors is developed which maximises concurrency and minimises communication between processors. Associated reordering and efficient sparse storage schemes are also developed. Implementation of this parallel algorithm is carried out on a transputer processor array which plugs into a PC bus. The sparse matrix solver is tested on matrices generated from a transistor-level expansion of ISCAS-85 benchmark logic circuits. Good acceleration is obtained for all benchmark matrices up to the number of transputers available.

The capabilities of computer algebra extend well beyond the bounds of mathematics. The author describes some of the less obvious ways in which these powerful software packages can come to the help of the busy engineer in many fields, including text processing, graphics etc.

A method of controlling certain types of nonlinear dynamical systems whose dynamics can be modelled by a multilayer neural network is proposed. The control algorithm assumes that the plant equations are not known but the dimension of the system is known. The control input is derived by inversion of a forward neural network via the Newton Raphson method. During inversion of the multilayer neural network some optimal control senses are resolved. To suppress the control error due to the modelling error of the forward neural network, the inversion controller with a conventional feedback controller is proposed, which provides a better performance than a pure inversion controller. The proposed algorithm shows various advantages, and computer experiments on a bioreactor prove the effectiveness of this algorithm.

A new design method of discrete-time model reference adaptive control for nonminimum phase systems is presented, with disturbances using approximate inverse systems obtained from the long division method. It is assumed that the disturbances are described by a polynomial function of time with known degree and unknown coefficients. The proposed scheme uses only input and output data, and the existence of bounds for all signals is proved. This scheme also assures that plant output converges to the reference model output. The results of computer simulation are also presented to illustrate the effectiveness of the proposed method.

The A-function method is extended to analyse a relay feedback control system with additional nonlinearities in the feedback loops. The situation considered is where the output of the plant and/or its successive derivatives are fed back to the input through nonlinearities that are assumed to be of polynomial type. An example is also given to show that, in some cases, the method can be used in systems with saturation or a linear segmented nonlinearity in the feedback path.

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.

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.

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)

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)

Geometrical symmetry often occurs in computational electromagnetics. However, it is generally not taken into account when the excitations do not share this symmetry. A rationale is required, and group theory gives the only valuable tool for this purpose. It provides a symmetric decomposition of any problem that allows its study on a reduced part of the initial geometry. This way of treating field problems generally leads to substantial computational savings. The symmetry concept is applied in the paper to 3-D linear eddy-current analysis, where the numerical scheme used is a mixed FEM–BEM method. Detailed examples are presented to demonstrate the efficiency of the use of symmetry.

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.

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.

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)

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.

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.

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.

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.

This paper reports the use of a general technique to combine several different methods to solve complex systems of algebraic equations in the context of load flow calculations of electrical power networks. Such a combinations of methods, referred to as 'team algorithms', seem specially well suited to be used with distributed memory computer systems, in an asynchronous environment. Experimental results solving example problems in a commercially available parallel computer system show that a 'synergetic effect' with considerable speedup can be obtained using these 'team algorithms'.