Journal of Mechanical Engineering 51 (2005) 9

 

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A Combined System for Off-Line Optimization and Adaptive Adjustment of the Cutting Parameters During a Ball-End Milling Process

Corresponding author - Uroš Župerl

Authors - Franci Čuš - Edi Kiker - Matjaž Milfelner

Abstract

This paper discusses the use of combining the methods of neural networks, fuzzy logic and PSO evolutionary strategy in modelling and adaptively controlling the process of ball-end milling. An overall procedure for the hybrid modelling of the cutting process (ANfis-system) used for working out the CNC milling simulator has been prepared. On the basis of the hybrid process modelling, off-line optimization and feed-forward neural control scheme (UNKS) the combined system for off-line optimization and adaptive adjustment of the cutting parameters is built. This is an adaptive control system controlling the cutting force and maintaining the constant roughness of the surface being milled by digital adaptation of the cutting parameters. In this way it compensates for all the disturbances during the cutting process: tool wear, non-homogeneity of the workpiece material, vibrations, chatter etc. The basic control principle is based on a control scheme (UNKS) consisting of two neural identificators of the process dynamics and the primary controller. The CNC milling simulator tests the system stability and tunes the control-scheme parameters. The approach was successfully applied to a Heller CNC milling machine. Experiments have confirmed the efficiency of the adaptive control system, which was reflected in improved surface quality and decreased tool wear.

Keywords - machining, force control, adaptive control systems, optimization, ball-end mill

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)9, 542-559
UDC 621.914:681.51

A Combined System for Off-Line Optimization and Adaptive Adjustment of the Cutting Parameters During a Ball-End Milling Process (pdf)

 

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Viscously Damped Transverse Vibrations of an Axially-Moving String

Corresponding author - Nikola Jakšić
Authors - Miha Boltežar

Abstract

In this paper the linear viscous-damping mechanism acting on an axially-moving string is analyzed. The analyzed damping model is in the form . The equation of motion, i.e., the linear partial differential equation, of the free, transverse vibrations of the string’s span is solved first. Then the influence of the coefficients b1 and b2 on the natural frequencies and the free responses is studied. It was found that the values of the coefficients should be carefully selected in order to avoid physically unrealistic responses.

Keywords - partial differential equations, hyperbolic equations, free damped vibrations, moving string systems

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)9, 560-569
UDC 534.01:517.9

Viscously Damped Transverse Vibrations of an Axially-Moving String (pdf)

 

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Efficient Shape Optimization of Space Trusses

Corresponding author - Boštjan Harl
Authors - Marko Kegl

Abstract

This paper describes an approach to the optimization of statically loaded space trusses. The cross-sectional properties of individual elements, the shape of the whole structure as well as the support locations depend on the design variables. The variable structural shape and the support locations are addressed by employing the design-element technique and an appropriate design element – the Bézier body. The variable cross-sectional properties of the individual truss elements are handled in the usual way. Kinematically nonlinear truss elements are employed as the finite elements. The optimization problem is defined in the form of a general nonlinear problem of mathematical programming. Since the design variables are all assumed to be continuous, a gradient-based optimization procedure is proposed. Two numerical examples of space-truss optimization are presented in detail to illustrate the use of the proposed approach.

Keywords - space trusses, shape optimization, mathematical programming, parametrization

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)9, 570-588
UDC 524.074.5:519.85

Efficient Shape Optimization of Space Trusses (pdf)

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Measuring-System Analysis for Quality Assurance in a Six-Sigma Process

Corresponding author - Mirko Soković

Authors - Duško Pavletić - Romeo Matković

Abstract

To maintain market share, suppliers to the automotive industry must be involved in the continuous improvement of their processes. They have to strive to perfect their processes as well as their overall business. Therefore, the search for appropriate improvement methods is ongoing, whether these methods are well known or completely new, e.g., six-sigma (6s) methods. This paper explains the analysis of measuring systems as a part of a six-sigma methodology.

Keywords - measurement systems, variance, six sigma methodology,  gauge repeatability and reproducibility (R&R) study

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)9, 589-599
UDC 658.562:53.08

Measuring-System Analysis for Quality Assurance in a Six-Sigma Process (pdf)

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Statistical Analysis of the Equivalent Design Rainfall

Corresponding author - Jože Panjan

Authors - Marija Bogataj - Boris Kompare

Abstract

Statistical analyses of rainfall data are used for the design of sewerage systems and pump-stations, for the evaluation of the duration and the frequency of overflow in runoff detention facilities, for the determination of the critical influence on a municipal wastewater-treatment plant or for the protection of watercourses from storm-water runoff (e.g., from highways). The basic data in this calculation are the intensity and the duration of a rainstorm. Different procedures used in the analysis of Equivalent Design Rainfall (EDR) in Slovenia and abroad are described. The stochastic model used is presented in more detail because of its applicability for the determination of the probability of the occurrence of partial rainfalls of higher frequencies and the determination of the lower limit of rainfall evaluation. Computation procedures and the results of the evaluation of rainfall data according to the stochastic model are presented for Ljubljana.

Keywords - rainfall statistics, rainfall intensity, rainfall frequency, rainfall duration, regression analysis

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)9, 600-611
UDC 556.16:551.577

Statistical Analysis of the Equivalent Design Rainfall (pdf)

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