A. Pouliezos

An integrated DSS for financing firms by an industrial development bank in Greece

Abstract This paper presents an integrated DSS for the analysis and financing of firms by an industrial development bank in Greece. Firstly, the system evaluates the financial performance of firms (financial ratios of profitability, managerial performance, solvency) during a 5-year period and allows inferences about their development tendencies. Furthermore, multivariate statistical techniques (discriminant analysis, principal components analysis) are available to aid in the identification of the most significant financial ratios and in the grouping of the firms in coherent categories. Finally, a multi-criteria method is used, which ranks the firms from the most dynamic to the bankrupt and in this way dynamic to the bank to select the less risky for financing. The capabilities of the system are illustrated with actual data provided by the bank.

Optimal Robot Speed Trajectory by Minimization of the Actuator Motor Electromechanical Losses

This paper considers the control problem of a robotic manipulator with separately excited dc motor drives as actuators. An innovative method is proposed which achieves robot speed-control requirements, with simultaneous minimization of total electromechanical losses, while the drives follow the desired speed profiles of the robot joints under various loads and random load disturbances. If there is no demand for a specific speed profile, the optimal speed trajectory is determined by minimizing an electromechanical losses criterion. Controllable energy losses, such as armature copper losses, armature iron losses, field copper losses, stray load losses, brush load losses, friction and windage losses, can be expressed proportionally to the squares of the armature and the field (exciting) currents, the angular velocity and the magnetic field flux. The controllable energy loss term is also included in the optimal control integral quadratic performance index, defined for the whole operation period. Thus the appropriate control signals required for following the desired trajectory by simultaneous energy loss minimization for the whole operation interval are achieved. Two case studies of optimal robot control with and without minimization of actuator energy losses are presented and compared, showing the energy savings that can be achieved by the proposed methodology.

Fault detection for quality control of household appliances by non-invasive laser Doppler technique and likelihood classifier

This paper addresses the problem of developing an on-line diagnostic system for mechanical quality control of household appliances. The selection of a suitable measurement technique for feature extraction is discussed; the choice of a laser Doppler vibrometer technique and a laboratory measurement station for washing machines is presented. Vibration velocity and displacement are measured over a grid of points on the machine surface and data are stored in a database suitable for processing, both with good appliances and with defect ones with known defects. Features from the vibration velocity spectrum are used as the input to a likelihood classifier, which is shown to achieve very good classification scores.

Intelligent on-line quality control of washing machines using discrete wavelet analysis features and likelihood classification

Abstract This paper presents a method for extracting features in the wavelet domain from the vibration velocity signals of washing machines, focusing on the transient (non-stationary) part of the signal. These features are then used for classification of the state (acceptable-faulty) of the machine. The performance of this feature set is compared to features obtained through standard Fourier analysis of the steady-state (stationary) part of the vibration signal. Minimum distance Bayes classifiers are used for classification purposes. Measurements from a variety of defective/non-defective washing machines taken in the laboratory as well as from the production line are used to illustrate the applicability of the proposed method.

Fast fault diagnosis for industrial processes applied to the reliable operation of robotic systems

Fault detection, identification and monitoring play a primary role in systems engineering. This also holds for advanced processes, such as robotic systems, with highest demands on reliability and safety. A method is presented for fast fault detection and location, due to the data deweighting in the identification procedure of the monitored process parameters and the iterative on-line calculation of the statistics of the fault detection scheme. This method has many advantages for microcomputer applications and guarantees a very early process fault detection. Application of the method to the fast fault detection of the de motor actuators of a robotic system is described.

Developing a control algorithm for CEN indoor environmental criteria - Addressing air quality, thermal comfort and lighting

In this specific paper a control algorithm for serving CENs indoor environmental input parameters in building energy management systems is presented. In the proposed control system, techniques of natural ventilation and daylight penetration are exploited. Electric lighting as well as mechanical cooling and heating are used supplementary to the techniques mentioned above. This fairly simple controller works quite satisfactory on the given input levels reducing the need for high-energy solutions.

Fatigue life prediction using a new moving window regression method

Abstract A simple method to assess the safety of metallic structures in the presence of crack-like defects is considered. Linear regression techniques are used to fit fatigue-crack growth (FCG) laws of exponential type with respect to the number of cycles, in FCG experimental results. A moving window regression method is used to accurately predict whether or not the critical crack length region is reached. The probability of fast failure at any time (number of cycles) is formulated in terms of a characteristics defect size exceeding a critical value. The concept of conditional probability of failure is also employed here in order to evaluate the failure rate used in reliability practice. As an illustrative example, an analytical closed-form solution for the failure probability of structures is presented and evaluated using experimental FCG data.

A decision support system for the development of voyage and maintenance plans for ships

The waterborne sector faces nowadays significant challenges due to several environmental, financial and other concerns. Such challenges may be addressed, among others, by optimising voyage plans, and diagnosing as early as possible engine failures that may lead to performance degradation. These two issues are addressed by the decision support system (DSS) presented herein, which focuses on the operation of merchant ships. For the development of voyage plans, a multicriteria decision problem is developed and handled with the PROMETHE method, while a multivariable control chart is used for the fault diagnosis problem. A MATLAB-based software implementation of the DSS has been developed adopting a modular architecture, while, in order to provide a generic software solution, the required input data are retrieved from dedicated web-services, following specific communication and data exchange protocols.

Intelligent online quality control using discrete wavelet analysis features and likelihood classification

This paper presents a method for extracting features in the wavelet domain of vibration velocity transient signals of washing machines, that are then used for classification of the state (acceptable-faulty) of the product. The Discrete Wavelet Transform in conjunction with Statistical Digital Signal Processing techniques are used for feature extraction. The performance of this feature set is compared to features obtained through standard Fourier analysis of the stationary part of the signal. Minimum distance Bayes classifiers are used for classification purposes. Measurements from a variety of defective/non-defective washing machines taken in the laboratory as well as from the production line are used to illustrate the applicability of the proposed method.

Innovation in Active Vibration Control Strategy of Intelligent Structures

Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.