http://www.ifac-papersonline.net/ en Copyright 05:34 PM Tuesday 07, 2012 IFAC-PapersOnline http://www.ifacpapersonline.com 05:34 PM Tuesday 07, 2012 05:34 PM Tuesday 07, 2012 ET webmaster@ifac-papersonline.net webmaster@ifac-papersonline.net http://www.ifac-papersonline.net/Detailed/29014.html 04:00 PM Wednesday 31, 1969 Robust stability and performance of an induction machine controlled with Indirect Self Control (ISC) are examined through µ-analysis. The analysis indicates poor robust performance at higher rotor speeds. Using reasonable parameter deviations between plant and controller, the predicted bad performance is however hard to verify through simulations. The tested parameter variations seem not to generate the worst case model errors. In simulations, the ISC therefore outperforms linear controllers optimized with respect to the robust performance criterion (at dispense of nominal performance). The large predicted sensitivity to model errors however explains the large impact on performance due to seemingly small differences in the implementation of the ISC control. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/27337.html 04:00 PM Wednesday 31, 1969 An algorithm to identify the parameters of a 3D model of a building subjected to two orthogonal components of seismic excitation is presented. A convenient reparameterization is proposed for a least-squares algorithm that allows an important reduction in the order of the covariance matrix, when compared with the standard formulation. This reduction facilitates real time implementation of the algorithm. Simulation results for a three stories building, that confirm analytical findings, are presented. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28545.html 04:00 PM Wednesday 31, 1969 In this paper, a novel method to determine the shape of a 3D object is proposed. Instead of a flexible conventional touch probe, a high-stiffness vibration touch sensor was developed. The proposed sensor consisted of a piezo-electric device and thin probe, and generated feedback voltage according to the relative distance from the object. The structure of this sensor is simple, so that it can withstand high rates of acceleration during the measurement process. A nonlinear synchronous multi-axis control algorithm is also proposed. The effectiveness of our proposed sensor and control algorithm is demonstrated through experiments and simulations. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29345.html 04:00 PM Wednesday 31, 1969 This paper addresses the path-following problem of steering an autonomous vehicle along a desired path, while tracking a predefined velocity profile. The presented solution relies on the definition of a path-dependent error space to express the dynamic model of the vehicle, which is specially suited for a D-methodology controller implementation. The error space exhibits a high-degree of directionality accuracy in the definition of velocity references. The proposed strategy guarantees asymptotic stability of the closed-loop system about trimming paths, and has the particular feature of eliminating the need to feedforward trimming values for both actuation and vehicle orientation. The effectiveness of the technique is assessed in simulation with the full nonlinear model of a model-scale helicopter. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/27390.html 04:00 PM Wednesday 31, 1969 The challenging issue of identifying a closed-loop system from short and/or non-informative data records is addressed. A bayesian approach is developed within this framework. It is shown that accurate estimates and realistic confidence intervals can be obtained by taking into account prior knowledge on the system. The performances of the proposed method are illustrated with a simulation example. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28359.html 04:00 PM Wednesday 31, 1969 The biological world has often offered inspirations to novel approaches to solving engineering problems. This paper presents an engineering analogy of the human immune system, known as the artificial immune system (AIS) for the strategic control of multi-agent based systems such as fleet of autonomous guided vehicles or a multi-jointed manipulator. The human immune system is a complex, adaptive and highly distributed system that exhibits the behaviors of autonomy, self-organizing, distributivity, fault tolerance, robustness, learning and memory, which is underpinned by a set of theories including the immune discrimination and specificity theories. A distributed control framework is developed based on the conceptual framework of the immune system. The AIS-based multi-agent control paradigm is studied via two key mechanisms in the generalized control hierarchy, namely, detection of events and the activation of control actions. Simulation and experimental study using a fleet of autonomous guided vehicles in a material handling system to illustrate the effectiveness of the proposed framework. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28746.html 04:00 PM Wednesday 31, 1969 The purpose of this study is to propose a new branch-and-bound algorithm for a class of scheduling problems to minimize total tardiness on identical parallel machines. In this algorithm, Lagrangian decomposition is applied to obtain better lower bounds. In addition, the job dominance conditions for the single machine tardiness problem are utilized for both restricting branches and improving the lower bounds. As will be shown by computational experiments, instances with up to 25 jobs and any number of machines are optimally solved within acceptable computational times. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/27790.html 04:00 PM Wednesday 31, 1969 This work proposes a methodology to deal with full decentralized controller synthesis in the case of open loop stable plants in the discrete time domain. The results are based on a convenient characterization of the set of all stabilizing decentralized controllers and lead to a closed form one. Sufficient and necessary conditions for the stability of the resulting closed loop are established and the method is illustrated with examples. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28869.html 04:00 PM Wednesday 31, 1969 Stirred tank reactors are widely used in the chemical process industry and in many of them there are problems and constraints related to the temperature control. In order to achieve a model suitable for temperature control of such a system a number of ad hoc assumptions and approximations are generally made. Here, a method to systematically evaluate the validity of such simplifications based on the resulting performance of the controlled closed loop system is proposed. The method is applied to a twocompartment model of a reactor with an exothermic reaction. It is then shown that many standard assumptions are reasonable but some assumptions are clearly not advisable because of possibly deteriorated closed loop performance. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28179.html 04:00 PM Wednesday 31, 1969 This paper presents the optimal regulator for a linear system with multiple state delays and a quadratic criterion. The optimal regulator equations are obtained using the maximum principle. Performance of the obtained optimal regulator is verified in the illustrative example against the best linear regulator available for linear systems without delays. Simulation graphs demonstrating better performance of the obtained optimal regulator with respect to the criterion value are included. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28685.html 04:00 PM Wednesday 31, 1969 In the disassembling process context, the supervision and control system assumes very large dimensions, represented by the need to automatically plan the disassembly process of the end-of-life product, including generation of product model, identification of the best sequence of operations, planning the actors (persons and machines) and programming the machines used to perform this task. This paper describes supervision architecture by analysing the supervision and control system of a disassembling process, and proposes two types of supervision architecture. It also describes a structure of decision-making system within global supervisory level. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29206.html 04:00 PM Wednesday 31, 1969 In this paper we introduce a new collision warning system which permits to warn the driver with sufficient anticipation about some inter-vehicular distance danger. The warning system is based on the future predictions from a 5-DOF (Degree Of Freedom) vehicle dynamics. The future inter-distance and the future relative velocity are compared with respect to certain safe conditions which are calculated from a dynamic inter-distance reference model. Some simulations with real measure data illustrate the behavior of the proposed driver assistance system. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28817.html 04:00 PM Wednesday 31, 1969 The use of XML as a description language has become state of the art within the automation and control domain. Use cases and application scenarios are manifold, resulting in heterogeneous XML document structures. However, a common basic model for XML Applications is still lacking. This paper describes requirements and principle structures for such a common model, which has been developed for use within PROFIBUS and PROFINET systems. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28198.html 04:00 PM Wednesday 31, 1969 This paper focuses on the application of stochastic (genetic algorithms, simulated annealing) and deterministic (sequential quadratic programming) optimization methods for the Integrated Design of processes considering dynamical non-linear models. Moreover, a hybrid methodology that combines both types of methods is proposed, showing an improvement on performance. Controllability indexes such as disturbance sensitivity gains, the Hα norm, and the ISE were considered to obtain optimum disturbance rejection. In order to illustrate and validate our proposal, an activated sludge process with PI schemes is taken. The problem is stated as a multiobjective non-linear optimization problem with non-linear constraints. The application of the mentioned strategies is discussed. The results are encouraging for future application of these techniques to solve synthesis MINLP problems. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29494.html 04:00 PM Wednesday 31, 1969 A comparative study of software sensors using Multiway Partial Least Squares and Extended Kalman Filters in an application to a fed-batch yeast fermentation process is presented. The MPLS theory is introduced firstly and then applied to a yeast fed-batch fermentation process to provide soft-sensing facilities. The soft-sensing capabilities of the MPLS approach are found to compare favourably with the results using EKF. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/27917.html 04:00 PM Wednesday 31, 1969 The aim of this study is to offer a comparison of the numerical procedures for an important problem, the determination of purely imaginary characteristic roots of LTITime Delayed Systems (LTI-TDS). This problem, in fact, has a crucial role in assessing the stability of the general class of vector LTI-TDS x = Ax + Bx(t -τ). There are many procedures discussed in the literature for this purpose. Those, which are exact, first determine the complete set of imaginary characteristic roots of the dynamics, as they constitute the only points where stability switching can take place. These approaches are, in fact, some variations of the five main methods, which may demand numerical procedures of different complexity and they may result in different precisions in finding the roots. There is, however, no comparative case study known to the authors to demonstrate the strengths and weaknesses of these methods. This document is prepared primarily for this purpose. We first present an overview of each of the five methods and then compare their numerical performances over an example case study. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29517.html 04:00 PM Wednesday 31, 1969 This paper examines some performance measures to be considered as an alternative of the Sharpe Ratio. More specifically, we analyze allocation problems taking into consideration portfolio selection models based on different performance ratios. For each allocation problem, we compare the maximum expected utility observing all the portfolio selection approaches proposed here. We also discuss an ex-post multiperiod portfolio selection analysis in order to describe and compare the sample path of the final wealth processes. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28306.html 04:00 PM Wednesday 31, 1969 This paper compares two different linear matrix inequality (LMIs) algorithms for the static Hα loop shaping synthesis problem. One effective and popular algorithm to solve fixed-order control problems is the so-called Cone Complementary Linearization algorithm (CCL). The CCL algorithm is guaranteed to produce, at each iteration, a reduced order controller. The algorithm proposed in this paper is quite different in its nature as it is based on sufficient, potentially conservative, LMI conditions. Our algorithm is compared to the Cone Complementary algorithm on a collection of plants taken from the benchmark library COMPleib. The numerical experiments indicate that our algorithm is computationally more attractive and more efficient than the cone complementary algorithm. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28133.html 04:00 PM Wednesday 31, 1969 The wave reflection phenomenon that appears when actuator and plant are connected through long cables is studied in this paper. In several applications, the perturbation induced by the presence of these reflected waves is non-negligible and seriously degrades the performance of the control and the operativity of the system. Standard compensation schemes are based on matching impedances at specific frequencies (possibly infinity) and are realized with the addition of linear RLC filters. Impedance matching is clearly ineffective if there is no single dominant frequency in the system and-or the plant is highly uncertain. In a recent paper the authors proposed a novel compensator design framework, based on the scattering representation of the transmission line, that is applicable for the latter scenario. In contrast with the standard schemes the compensators are active and require for their implementation regulated sources placed either on actuator or plant side. The use of active compensators raises the issue of ensuring stability of the design, a point left open in our previous work, that is fully solved in the present note.We propose a family of compensators that requires only knowledge of cable characteristics and-under some practically reasonable assumptions-guarantees transient performance improvement and asymptotic tracking for all (unknown) plants with passive impedance. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28785.html 04:00 PM Wednesday 31, 1969 In this paper, an aggregate production planning problem is formulated as a chance-constrained stochastic control problem under imperfect information of states (i.e., the inventory levels). Using the Kalman filter device, the mean and covariance of state variables are estimated. Then the certainty equivalence principle is applied, resulting in a deterministic problem that is equivalent to the original formulation. In order to provide a sequential optimal solution to the equivalent problem, the Naive Feedback Controller (NFC) approach is used. It provides a revised sub-optimal production policy to the stochastic problem. An example illustrates the applicability of this approach. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29241.html 04:00 PM Wednesday 31, 1969 A control architecture for executing multi-vehicle search algorithms is presented. The proposed hierarchical structure consists of three control layers: maneuver controllers, vehicle supervisors and team controllers. The system model is described as a dynamic network of hybrid automata in the programming language Shift and allows reasoning about specification and dynamical properties in a formal setting. The particular search problem that is studied is that of finding the minimum of a scalar field using a team of autonomous submarines. As an illustration, a coordination scheme based on the Nelder-Mead simplex optimization algorithm is presented and illustrated through simulations. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/27778.html 04:00 PM Wednesday 31, 1969 Precise manipulation of payloads is difficult with large cranes. Oscillation can be induced into the lightly damped system by motion of the overhead support point, or from environmental disturbances. A combined feedback and input shaping controller is presented here. The controller uses feedback to detect and compensate for positioning error in the overhead support unit (e.g. the bridge or trolley), and input shaping is used to negate motion-induced oscillation in the payload. The controller is implemented on a 10-ton bridge crane at the Georgia Institute of Technology. The controller generates simple on-off commands, suitable for typical cranes that employ on-off, relay-driven motors. The controller achieves good positioning accuracy, and significant payload sway reduction. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29572.html 04:00 PM Wednesday 31, 1969 This paper presents a conversational interface that uses the speech recognition and synthesis and animation abilities of two Microsoft software agents in order to assure a more natural and efficient interface with an autonomous robot. The interface is used in the robotics educational process. The basic commands to be given by voice (back, right, etc.) and the control of the agents are implemented in Visual Basic. More complex control programs can be implemented and tested in Matlab and after that executed with a simple voice command. This program is used as a part of an integrated educational strategy in autonomous robotics and was evaluated by a group of students. First experimental results related to the use of this conversational interface compared to traditional robot simulation environments and control of real robots are presented in this paper with related discussions. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/28286.html 04:00 PM Wednesday 31, 1969 Contrary to the standard H2 problem, the so-called insensitive H2 problem makes use of a criterion that takes explicitly into account the parametric sensitivity of the closed loop system. This problem has already been re-formulated as a structured H2 problem that is known to be equivalent to a specific BMI optimization problem when assuming full order controller. This paper presents a new formulation leading to a convex optimization problem. This is obtained thanks to the Youla parameterization and using the specific structure of the problem. The use of a finite dimensioned orthonormal basis for the structured Youla parameter leads to an LMI-based algorithm solving the insensitive H2 problem. Its interest is shown by comparison with existing algorithms. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/29229.html 04:00 PM Wednesday 31, 1969 Marine environments offer suggestive scenarios for Automatic control and Cooperation strategies to be applied. The present paper focus on a particular one: Two ships towing together an off-shore oil retaining boom. Basic dynamical equations are presented for the combined displacement of both ships plus the boom. Computer simulation of basic manoeuvres works out the basic control implications of the problem and suggests cooperation among the ships as a more reliable technique to fulfil ships goals and minimize boom strain. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif